CoFish: co-designing citizen science between fishers and scientists to monitor the phosphorus distribution across two Lake Geneva basins

CoFish: co-designing citizen science between fishers and scientists to monitor the phosphorus distribution across two Lake Geneva basins | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article CoFish: co-designing citizen science between fishers and scientists to monitor the phosphorus distribution across two Lake Geneva basins Tania Jenkins, Laura Fayet, Alexandre Fayet, Daniel Chollet, Yves Depraz, and 13 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6170350/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background Eutrophication, followed by re-oligotrophication during lake restoration, in many peri-alpine lakes has caused important changes to the functioning and biodiversity of freshwater ecosystems. In Lake Geneva, total phosphorus (TP) concentration has been reduced since the eutrophic years, and is now close to the upper value of the target range of 10-15 µg/L. For over 60 years the lake has been monitored at SHL2, the central and deepest point in the Eastern basin, complemented by data from GE3 in the Western basin. Selection of these reference points was based on a lake-wide analysis of TP in the 1950s. Fishers have for some time expressed concerns that further reductions in TP could damage the sustainability of their livelihoods. They have called for a re-evaluation of the historical sampling points to determine whether SHL2 and GE3 can still be considered representative in terms of nutrient concentration of the lake. Results Here, we present the scientific and societal impacts of CoFish, a co-designed research project between scientists and fishers of Lake Geneva. To reassess the spatial variability of TP we applied a low-cost method to collect integrated water samples across the lake, using stoppered hosepipes as a collection instrument. In this article, we present four key messages: i) There is spatial variation in phosphorous levels, and in most cases the two points fall withinan acceptable range of variability; ii) The concentrations of phosphorus are generally low across the lake in ranges that could have an impact for plankton development. iii) Citizen science can complement long-term monitoring, allowing for instance for better spatial coverage of environmental data; iv) The co-design process resulted in community empowerment, a willingness to further collaborate. Conclusions The management implications of this work are that using a single reference station as being representative for the lake as a whole is not straightforward. In the discussion we advocate for a re-evaluation of the TP targets, given radical changes in the lake`s physical structure and food web. We further highlight the important role of engaging fishers in citizen science, which resulted in bridging existing gaps between lake management, science and fisheries, providing a broader basis for lake conservation. phosphorus fisheries citizen science co-design lake spatial variation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Background Peri-alpine lakes and their services Peri-alpine lakes are ecologically important habitats for a range of aquatic communities ( 1 ). They provide crucially important services for humans ranging from the provisioning of drinking water, fisheries and recreational activities. Optimal lake management that ensures the continuation of these services in times of environmental change, requires stakeholder engagement and balancing of priorities. Lake eutrophication in the 20th century caused important changes in the functioning and biodiversity of peri-alpine lakes, with the development of anoxia in deeper parts. Problems due to low oxygen have returned in recent years, this time linked to climate change, which is preventing full lake overturn in winter, creating a deep isolated layer, cut-off from the atmosphere ( 2 ) and the layers where oxygen is produced by photosynthesis. Warming is often claimed to create more favorable conditions for blooms of (toxic) cyanobacteria – “blooms like it hot”, see ( 3 ) for Lake Geneva, however, also see ( 4 , 5 ) for a contrasting opinion. In peri-alpine lakes, the dominant cyanobacterium Planktothrix rubescens seems to benefit from warm autumns and mild winters rather than hot summers ( 4 ). Moreover, these peri-alpine lakes are impacted by invasive species like the quagga mussel, Dreissena bugensis ( 6 ), which threatens to change the trophic structure and ecological functioning ( 7 ). Setting the optimal nutrient levels requires to balance the needs for safe drinking water, i.e. prevention of toxic algal blooms, with those for sustainable fisheries. To a certain extent, controlling eutrophication benefits both, e.g. Bninska ( 8 ) showed how in Poland the fisheries yield for coregonids was substantially higher in lakes with good, than with poor water quality. The reduction of phosphorus levels has been a key strategy to restore water quality in eutrophic lakes, controlling blooms and enhancing biodiversity, e.g. ( 9 , 10 ), while it also helped to mitigate negative effects of nutrient enrichment on coregonids and fisheries ( 11 ). However, for a set of peri-alpine lakes a reduction in total fish catches – dominated by coregonids and perch - have been reported below 20 µg/L ( 12 ), with minimal catches below 10 µg/L. A study by Alexander and Seehausen ( 13 ) gives a different perspective, with maximal coregonids biomass at TP levels below 10 µg/L. However, coregonids of small size seem to dominate in lakes of low TP, whereas for fisheries larger individuals are crucial ( 12 ). At lower levels of TP, balancing the different interests becomes more of a challenge. For example, in Lake Geneva, the present long-term TP goal of 10–15 µg/L, lowered from 20–30 µg/L in 2011, is based upon the consideration of various lake services, including fisheries. Yet, disagreements, rooted in different opinions about optimal TP-levels for different lake services remain. Sinclair et al. ( 14 ) concur that an optimum – intermediate - nutrient level which can support both good water quality and high fishery yields may not exist, in particular if fisheries target species that differ in their sensitivity to lake productivity, like for perch and coregonids, the main species for Lake Geneva. Particularly relevant for large lakes, is whether all parts of a lake have the same nutrient level, support the same productivity, pose similar risks for cyanobacterial blooms or see comparable fish catches ( 15 ). There is a sizeable literature on spatial variation in the sources of TP, both internal, i.e. nutrient release from lake sediments, e.g. ( 16 , 17 ) or external sources, (e.g. ( 18 , 19 ) (Johnson and Nicholls, 1989; Zong et al., 2023). However, data on the spatial variation of dissolved phosphorus and TP in the water across a lake are surprisingly scarce, possibly due to the specific logistical and economic constraints of sampling a large lake over its full surface on a single day. Sometimes spatial variation in TP is visualized by looking at Chla patterns in a lake ( 20 ) or derived from satellite images using algorithms that link in situ TP to reflectance data from “visible” lake parameters ( 21 )or by using water-quality 3D models ( 22 ). Given the known large spatial variability in large lakes, several publications provide advice on where best to locate a routine sampling point through use of satellite images or modeling ( 23 – 25 ). For Lake Geneva, Soulignac et al. ( 22 ) also addressed this question through 3D modeling. The Soulignac study confirms that, despite strong spatial gradients in ecological quality (expressed as nutrients and Chla ), the most representative point for the pelagic zone of Lake Geneva as a whole is situated in the central part of Grand Lac, not far from the reference station SHL2 (see Fig. 1 ). Yet spatially explicit data on nutrient concentrations like TP that could have been used for direct validation of the model output, were not available. Citizen science could be one answer to allow wide scale lake sampling and thus capture some of the spatial variation as in situ data, to help with interpretation of satellite images and model output. Citizen science, broadly defined as the public’s participation in scientific research and knowledge production ( 26 ) and has been advocated as a way to gather vast amounts of environmental and ecological data whilst involving societal actors in the research process ( 27 ). Despite the promise of the approach to promote community participation in conservation efforts, several ethical issues have been voiced (reviewed in ( 28 ), relating to the potential of masking exploitation and unremunerated labor under a shield of “democratisation” of science ( 29 ). This has led to a call and a drive to a more meaningful engagement with research in all parts of the research cycle ( 30 ). Indeed, the co-production of knowledge, where citizens are involved in key parts of the research cycle, such as the formulation of the research and communication of results, has been recognized as a tool to help address some of the key sustainability issues of our time ( 31 ). Place-based community projects, centered around a locally rooted issue, and often co-designed to align with the community’s needs, have been highlighted as playing an important role to maximise the impact of the research, resulting in better environmental management and community action ( 32 ). In the case of water-based research, stakeholder engagement and co-design approaches have a long tradition ( 33 ) and have resulted in the long-term monitoring of freshwater systems ( 32 ) and collaborative water management of river catchments for example ( 34 ). Participatory management, with anglers in particular, is reported to have led to long-lasting learning outcomes ( 35 ) as well as better environmental monitoring, conservation and advocacy ( 36 ). Collaboration with commercial fishers has further improved fisheries population models (e.g. crab fisheries of South Devon, UK), resulting in improved relations and trust between fishers and scientists ( 37 ). In Switzerland and France, the transdisciplinary Fischnetz network (1998–2004) was a very productive research partnership between administration, the chemical industry, fisheries associations and academic researchers, that resulted in 77 research projects and had a policy level impact that improved the state of Swiss watercourses( 38 ). Co-design of research and participatory fisheries management therefore can have a meaningful societal impact. In this article, we propose that citizen science and in particular co-designed citizen science, can provide a useful tool for monitoring of water quality of large lakes, as well as for the empowerment of fishers as citizen scientists. We illustrate this with CoFish, a co-designed research project between fishers and scientists on Lake Geneva. Though citizen science and participatory research are often cited to lead to a greater societal impact, the outcomes - other than the scientific output of the citizen science research itself - are not often measured reviewed in ( 39 ). This is problematic, especially given the institutionalisation of citizen science in some countries, e.g. UK, Austria, Germany that rely on evaluation and impact assessment for the continuity of particular funding schemes (40) as well as the importance of developing a more reflective approach to inform future programs. Several impact assessment frameworks, e.g.( 39 – 41 ) break down the impact of a project into five dimensions: science and technology, societal, environmental, political and economic. However, societal impacts are rarely reported alongside the scientific results. The CoFish project, that ran from 2021–2024 and was funded by the Swiss National Science Foundation, was initiated to in part to gain a better understanding of the lake ecosystem, but also to bridge academic with the local knowledge of commercial and recreational fishers, and in doing so the CoFish project also further brokered relations between local scientists, policy-makers, lake management and fishers. The project`s two main goals were therefore (i) to co-design an original research project with the fishers of Lake Geneva, and (ii) to evaluate the learning outcomes both for fishers and scientists. Methods Lake Geneva: situating the co-designed CoFish research project Lake Geneva, Switzerland and France, is the largest and deepest lake in Western Europe and is an important source of drinking water for 900,000 people. It provides opportunities for recreational activities such as swimming, sailing, angling, hiking and biking around the lake, and it helps to attract tourists to the region. There is evidence of fishing activity in the lake since the Neolithic ( 42 ), and to this day, 129 commercial fishers depend on the lake for their livelihoods, whilst it attracts a further 1000 recreational fishers. Yearly catches of the commercial fisheries amount from close to 1000 tons of whitefish as recent as 2013/2014 to less than 200 tons in the most recent years. For the other main target species, perch, catches decreased from nearly 1250 tons in the 1970s to ca. 1000 tons in the 1990s to some 250–500 tons this century, though this Figurecould partially reflect a shift in changing fishing efforts ( 43 ) and may not fully reflect the size of the fish populations. Following a period of eutrophication in the 1950s – 1970s where the nutrient levels, phosphorus and nitrogen rose steeply, causing environmental problems like phytoplankton blooms and decrease in whitefish and arctic char catches, CIPEL, (International Commission for the Protection of the Waters of Lake Geneva), a Franco-Swiss intergovernmental body, that coordinates the water policies in the Lake Geneva watershed and monitors the water quality was created in 1963. CIPEL conducts bi-weekly to monthly sampling at the single sampling point, SHL2 (46.45270°N,6.58872°E, depth 309 m, Fig. 1 ). This point was chosen because it overlies the deepest point, and therefore samples could be collected to cover the entire depth of the water column. In addition, being central in the Central Lake Basin, Grand Lac, it was sufficiently far from the lake shore to not be overly affected by pollution coming from the land (Monod, 1983). Additionally, Canton Geneva monitors the lake at GE3 (46.29721°N,6.21994°E, depth 72 m,) in the Petit Lac, the Eastern lake basin. Over several decades the water quality, at least in terms of phosphorous concentrations, has improved and is now approaching the upper end of the long-term objective of an annual mean of C ( 10–15 µg/L):: $$\:C=\:{\Sigma\:}\frac{\left(Ci\:.\:Vi\right)}{V}$$ Where C is the weighted average of TP concentrations; Ci = concentration of TP in a depth layer; Vi = the volume of this layer, and V = the total volume of Grand Lac (86 km 3 ). Co-design process Researchers at the University of Geneva initiated this project, motivated by the fact that as the lake has issues under the impact of a changing environment and there is an interest of fishers in participating in the project in a participatory research project that addressed this broad issue. The organisation of recreational fishers, FIPAL (Fédération Internationale des Pêcheurs Amateurs du Léman) became a partner in the project, already during the application stage. Firstly, presidents of the fishing clubs or unions were contacted for consultation and feedback. The CoFish goals were presented at local meetings where fishers were invited to contribute, which also resulted in the recruitment of commercial fishers via their own union, SIPPL (Syndicat Intercantonal des Pêcheurs Professionnels du Léman). Subsequent recruitment was led by the initially engaged fishers via their networks (social media, newsletters, presentations at local meetings). It is worth noting that in some instances this resulted in other lake users, e.g. lake police, contributing to some sampling campaigns. To prepare for the project, there were informal exchanges and interviews conducted to assess learning outcomes (Jenkins et al, in prep.). Some fishers indicated that they had contributed to scientific research in the past, yet they felt disappointed as there had been a lack of feedback on scientific results that were obtained. Commercial fishers sometimes distrusted science as they feared that scientific results may result in further fishing restrictions. In addition, they felt disempowered and lacking a voice in political discussions that have an impact on their fishing practices. Furthermore, they consider themselves to have detailed local knowledge and the potential to act as sentinels of the ecosystem. Therefore, developing a more collaborative approach and involving fishers in the monitoring of the lake could go a long way to remediate the relationships between diverse stakeholders. A kick-off workshop took place on October 15th, 2021 where actors from both science and practice (recreational, commercial fishers, lake managers, NGOs) were invited to brainstorm about the future of the lake`s fish populations and the sustainability of the fisheries. We followed a 7-step Participatory Action Research process ( 44 ) to co-design the research through a series of workshops and interviews ( see SI Table 1 ), inspired by methods in the td-net toolbox ( 45 ). By the third workshop, fishers shared a growing concern that the lake may become too oligotrophic and therefore less able to support fish populations and lake fisheries. Fishers wondered whether the two reference points, SHL2 and GE3 (Fig. 1 ) monitored by CIPEL and Canton Geneva respectively were indeed still representative, decades after they were first selected (a period during which the lake underwent important changes in its environmental drivers, functioning and usage). They also questioned whether the 10–15 µg/L long term TP objective may already have been attained, at least in parts of the lake, for which there is no information given that monitoring is restricted to two locations only. The co-design process resulted in the following two coupled research questions: To what extent do we observe spatial variation in total phosphorus (TP) and the biologically available form of phosphorus, orthophosphate (P-PO 4 ) in the critical concentration range of 10–20 µg/L - for both phytoplankton biomass and fish stocks - in the productive layer of Lake Geneva? To what extent are SHL2 in Grand Lac and GE3 in Petit Lac, i.e. the long-term reference sampling points, representative locations for basin-wide levels of TP and P-PO 4 ?. Sampling To answer the research questions, we decided to go back to the original points that were used by CIPEL to monitor Lake Geneva water in the 1950s (Fig. 1 ). We divided the lake into 9–10 zones and each fisher team was given between 2–5 points to cover, close to the location of their usual fishing grounds. The fishers used their own fishing boats and guidance from Google Maps on mobile phones to navigate to the exact coordinates (Fig. 1 , SI Table 2 ). Where required, members of the CoFish team joined to help individual fishers. To collect samples, we constructed 18m long integrated water sampler out of a garden hose, fitted with a cork stopper at one end and a 5kg weight at the other (see Fig. 2 ), following a design used in the European Multi Lake Survey ( 46 ). We chose 18m as we aimed to get an integrated sample of the productive part of the Lake Geneva water column- defined by us as the sum of epi- and metalimnion- and this was estimated to be 18 m after consulting the platform alplakes.ch prior to campaign 1. While not the central objective of the study, we also measured lake transparency and trained fishers to use self-made Secchi disks. Average Secchi depths were calculated as the mean of the depth at which the Secchi disk was no longer visible and the depth that it starts to be visible again, once bringing it back up to the surface. The material was first tested by members of the core team and training videos and protocols were made in order to train the fishers in correct usage. Hands-on training took place when the sampling kits were distributed among the participants. A workshop before the sampling allowed for final troubleshooting and adjustments. Sampling occurred on the following dates to capture seasonal variation in physical structure of the water column and typical succession patterns of phytoplankton in deep lakes, following the PEG model ( 48 ): Campaign 1 (September 26, 2022): end of summer, maximum stratification strength, seasonal minimum in mixing depth, second annual peak in phytoplankton productivity. Campaign 2 (January 31, 2023): middle of winter, minimum stratification strength, deep winter mixing, low phytoplankton biomass. Campaign 3 (April 5, 2023): early lake stratification, time of spring phytoplankton bloom, typically the first annual peak in primary production. Campaign 4 (September 25, 2023): go full circle, comparison with September 2022 On the sampling day, the integrated sampler and all materials (e.g. bottles, buckets) were provided by the university, and were rinsed once with lake water prior to use and fishers then sampled the water, poured it into a clean bucket, and used to fill two pre-labelled bottles, which were stored on ice in the dark. Lake transparency was measured as Secchi depth. Samples were collected from the respective fishers by members of the CoFish team and returned to the laboratory at the University of Geneva laboratory within 24 hours for processing. Lab analyses Methods were chosen to correspond to those used by the CIPEL for their long-term monitoring of the lake’s two reference points according to a reaction of acidic molybdate in the presence of antimony (EPA 365.3). All 36 stations were sampled in all four campaigns except CRG10 that was not sampled at the first campaign due to windy conditions. Orthophosphate measurements were conducted within 48 hours of sample collection. In the Geneva lab, samples were analysed for TP and P-PO 4 using a Seal Analytical AQ2, following protocols EPA 119-A-Rev. 7 and EPA 155-A, which is also based on a reaction of acidic molybdate in the presence of antimony. The limits of quantification were 3µg/L for both with a range of application 10-1000µg/L for TP and 3-300 µg/L for P-PO 4 . A second bottle was sent to Eawag, in a frozen state, where the measurements for total P and orthophosphate were repeated, initially to serve as an inter-laboratory comparison. The method also involved a spectrophotometric determination of TP and P-PO 4 after the reaction to phosphorus molybdenum blue complex,according to ( 49 ) using the Spectrophotometer Agilent Cary 60. Their method was more sensitive (range of application for TP 3-100µg/L and LOQ = 3µg/L and for P-PO 4 1-100µg/L and LOQ = 1µg/L). In order to check whether our methods and labs produced similar results to those of the CIPEL, 10 samples from points in the French part of the lake were sent to the Observatoire des Lacs Alpins (OLA) at INRAE-CARRTEL, which is the laboratory that routinely runs the monitoring for CIPEL (see SI3). Analysis of spatial variability We visualise the distribution of measurements across the four sampling campaigns and compare where the standard points lie in relation to the mean and standard deviation of the distribution for that part of the lake basin on that day. Assessment of societal impacts of the project For a parallel study on the learning outcomes of the fishers (Jenkins et al. in prep), semi-structured interviews were conducted with ten participants, five who participated in data collection and co-creation, and five only in data collection. Of these, five interviewees were commercial fishers and five were recreational. The interviews were adapted from ( 50 ) ( 51 , 52 ) (see SI 3) to measure dimensions of engagement and learning. Participants were subject to ethical procedures of the University of Geneva and informed consent to participate was obtained, with the right to withdraw their data at any time. The identities of interviewees were anonymised. Interviews were transcribed with the aid of the online software Happyscribe (Happy Scribe Ltd.) We used the Action Framework ( 41 ) to categorise the individual parts of the transcripts into the five societal sub-dimensions that they identify: (i) community building and empowerment; (ii) social inclusion; (iii) researcher growth; (iv) knowledge skills and competences; (v) changes in ways of thinking, attitude and values, (vi) behavioural change. Results Profile and engagement of participants We brought together 13 commercial (11 Swiss/2 French) and 19 recreational (15 Swiss/4 French) fishers, as well as 22 scientists from surrounding institutions such as the University of Geneva, UMRR CARRTEL (INRAE), Maison de la Rivière, the University of Lausanne, the Geneva Museum, and a consultancy firm and public open lab, Hackuarium, to participate in one or more of the co-design workshops as co-researchers (Table 2 ), with a smaller proportion (23–31%) belonging to the highly engaged sub-group, who attended more than half of the workshops. During the four sampling campaigns 9–10 teams went out to sample and the effort was collectively shared amongst a total of 19 fishers, 1 fishing guard, 1 member of the lake police, 1 scuba diver and 5 scientists. Engagement numbers were greater for the data collection than for the codesign workshops, with over 60% of recreational fishers contributing to at least three sampling campaigns. Though the numbers of commercial fishers contributing to the sampling were lower, their engagement was high, with all fishers contributing to all four sampling campaigns. Scientists and other stakeholders were involved in the co-creation workshops in consulting roles at different time points. The lower engagement number of scientists by the end of the project reflects the fact that the project ended up taking a specific research line that was less relevant for the other scientists. Some scientists stayed on as part of the process despite this and almost half scientists that attended the kick-off attended the closing meeting to find out about the outcomes of the project. Table 2 The profile, number and engagement of participants in CoFish Profile Number attending co-design workshops Engagement Number attending more than 4 out of 8 workshops (% of total) Number participants in data collection Engagement Number contributing to at least 3 campaigns (% of total) commercial fishers 13 3(23) 6 6 (100) Recreational fishers 19 6(31.5) 14 9 (64.2) Others 5 0 3 0 Scientists 22 3 (13.6) 6 3 ( 50 ) How variable is TP across the lake? To answer the first research question, we report phosphorus measurements from the Eawag lab as the method was more sensitive to low phosphorus concentrations, although overall agreement between the University of Geneva, Eawag and INRAE measurements was acceptable (not shown). At the first sampling campaign, TP at CRG5 was 513 µg/L, which was > 20 times higher than all other values, which ranged from below the detection limit (< 3 µg/L) to almost 24 µg/L. This sample was also high in the Geneva lab. The reason for this high value is not known, possibly due to its proximity to wastewater treatment plants or due to a contamination in storing the water sample. Therefore, this point was excluded as an outlier from further analysis. There was substantial variation in lake phosphorus concentration across the lake and between the different sampling periods (Fig. 3 , SI4 ). In campaign 1 , the concentration of TP ranged from 6.5 to 23.4 µg/L. Concentrations at GE3 and SHL2 were similar at 19.3 and 17.7 µg/L, respectively. Both were approximately 6–7 µg/L higher than the means of 12.5 and 10.9 µg/L for Petit and Grand Lac, falling well outside +/-1 SD of the mean (Figs. 3 a and b , Fig. 4 a). In campaign 2 , the concentration of TP ranged from 4.7 to 16.8 µg/L, with mean concentrations of 7.2 µg/L (Petit Lac) and 8.4 µg/L (Grand Lac). Concentration was highest at GE3, 3µg/L higher than the mean for Petit Lac falling outside the + 1 SD, whereas SHL2 was almost exactly the same as the mean ( Figs. 3 c and d , Fig. 4 b ) . In campaign 3 , the concentration of TP ranged from 6.2 to 21.6 µg/L. GE3 was 2.3µg/L lower than the mean of 9.3 µg/L, placing it just 1SD below the mean for Petit Lac. TP at SHL2 was 5.5 µg/L higher than the mean for Grand Lac (12.2 µg/L), above 1 SD of the mean (Grand Lac) ( Figs. 3 e and f , Fig. 4 c ) . In campaign 4 , the concentration of TP ranged from 3.4 to 34.7 µg/L. The means for Petit and Grand were similar (11.1 vs 11.4). TP at GE3 was very close to the mean for Petit Lac, while TP at SHL2 was almost 3µg/L lower, but well within 1 SD of the mean ( Figs. 3 g and h , Fig. 4 d ) . Orthophosphate across the four sampling campaigns The range of values for orthophosphate was less variable than TP with most values being between 3–8 µg/L with a couple of values around 13µg/L (Fig. 4 , SI5). In campaign 1 concentrations ranged from 3.1 to 6.6 µg/L. In SHL2 and GE3 the concentrations were almost identical around 6µg/L, and higher than the mean values (4.7 and 3.9 µg/L in Petit and Grand Lac respectively, lying outside the + 1 SD of the distribution (Figs. 5 a and b , Fig. 6 a). In Campaign 2 P-PO4 concentrations ranged from 3.6 to 8.8 µg/L. Concentrations recorded at GE3 and SHL2 were close to the mean values 5.4 and 5.5 µg/L, being slightly higher for GE3 in Petit Lac and lower for SHL2, but well in the +/- 1SD of the mean of the distribution (Figs. 5 c and d , Fig. 6 b). Campaign 3 P-PO4 concentrations ranged from 3–13 µg/L. The concentration at GE3 was 0.6µg/L higher than the mean for Petit Lac (4.6 µg/L) and the concentration SHL2 was very close to the mean of 4.7 µg/L. Both fell within the + 1/- 1SD of the distribution (Fig. 5 e and f , Fig. 6 c). Campaign 4 P-PO4 concentrations ranged from 3.9–13.1 µg/L. The values at both reference stations were very close to the mean 4.6 and 4.7 µg/L for Petit Lac and Grand Lac, respectively (Fig. 5 g and h , Fig. 6 d). Secchi disk readings Lake transparency, measured as Secchi disk depth, varied between stations and over the seasons and ranged more or less from a minimum of 5 m to a maximum of 15 m. It is worth noting that GE1 at the Rade de Genève (Petit Lac) is only 1.6m deep and so consistently gives a lower Secchi depth than other parts of the Lake, always with bottom visibility. In campaign 1 , Secchi depths ranged from 5 to 8.5 m, and the observed values at the reference points were very close to the means of 6.2 and 6.9 m respectively, Figure SI5 a,b, SI6a . In campaign 2 , Secchi depths ranged from 7 to 15.25 m. The Secchi depth at the reference points was close to the mean in Petit Lac and approximately 3 m deeper than the mean in Grand Lac, see Figure SI5c,d, SI6b . In campaign 3 Secchi depths ranged from 4.75 to 15.25 m. The mean Secchi depth in Petit Lac was about 1m less than the depth recorded at GE3, whereas for Grand Lac the Secchi depth was very close to the mean close to 9m, see Figure SI5e,f, SI6c . In campaign 4 , Secchi depths were shallow, ranging from 3.8–6.9 m across the lake, with the depth at GE3 being 1.3m deeper than the mean and that at SHL2 a bit shallower than the average of 5m for Grand Lac, see Figure SI5 g,h, SI6d . Societal impacts of CoFish Out of the ten participants, one commercial fisher did not reply to a request for the final interview - we therefore omitted this person from the analysis. Analysis of the transcriptions of the nine interviews gave us insights into two out of the five dimensions of the Action Framework ( 41 ) namely: (i) community building and empowerment; (ii) changes in knowledge skills and competences. The second was less surprising given the interview was designed to study learning outcomes (Jenkins et al, in prep). Seven out of nine interviewees expressed views of community empowerment, equally seven out of nine reported a change in knowledge, skills or competence as a result of CoFish (Table 3 for exemplary quotes). Furthermore, participants were willing to engage in future scientific research. Through the CoFish approach, the project results were more broadly communicated and made accessible, than would have been the case through a routine academic report or publication. For example, all participants communicated some project results within their communities informally (e.g. social circles), at general assemblies, on social media (e.g. videos of lab analyses with up to 2000 views), and standard news media (2 news stories), indicating the multiplier effect of the project. The closing meeting also was attended by authorities responsible for the water sampling: CIPEL and Swiss cantons, offering the opportunity to further bridge the gap between science and policy. Discussion We co-designed a research study to investigate a question in response to concerns voiced by the commercial and recreational fishers that the two long term monitoring stations of Lake Geneva may no longer be representative of the lake as a whole in terms of total phosphorus and the biologically available form of phosphorus, orthophosphate (P-PO 4 ). This concern clearly plays out against a backdrop in which fishers are worried that the lake is becoming too oligotrophic to sustain fish populations and therefore fisheries. By collaborating with commercial and recreational fishers on the same day across four campaigns, we were able to – for the first time since the 1950s – create empirical maps of TP and P-PO 4 distribution in Lake Geneva. This gave us three key scientific results: (i) that there is variability in phosphorus, both TP and P-PO 4 concentrations across the lake (3.4–34.9 µg/L observed across campaigns); (ii) that in most cases, except for campaign 1, TP from SHL2 and GE3 fell within +/- 1SD of the mean, or very close to it, indicating that the values for these reference monitoring stations are mostly representative iii) for a great majority of stations the TP was less than 20 µg/L, many below 15 µg/L; this means that concentrations are mostly below threshold values of 15–20 µg/L where TP can be expected to bring down phytoplankton biomass in peri-alpine lakes ( 53 ). Concentrations of P-PO4 are always below 10µg/L indicating that phosphorus may be limiting for many species ( 54 ).Furthermore, in some locations, the concentrations can reach 3 µg/L which is reported to be the threshold below which phosphorus can cause severe reduction in algal growth ( 55 ). We discuss these findings of the sampling campaign alongside the equally important societal outcomes of the project of greater empowerment of the fishers. Our empirical results show variability in TP, and to a lesser extent orthophosphate across Lake Geneva. There are few studies that have empirically investigated spatial variability in nutrient levels in a lake. A study based on remote sensing data of Lake Chaohu in China by Gao et al. (2015) showed spatial variability in TP, derived from reflectance data. They further show how the representativeness of a reference station improved when TP data are used solely for the specific lake basin where i is located, rather than for the lake as a whole. This would seem to be true for Lake Geneva too, GE3 being the reference station for Petit Lac and SHL2 for Grand Lac, rather than either one for Lake Geneva as a whole. In fact, the two lake basins behave differently and have a distinct history of eutrophication and re-oligotrophication, as is evident in CIPEL data. So, SHL2 and GE3 both remain key locations to evaluate temporal changes in the lake basins. We ask the question to which extent SHL2 and GE3 are representative for their respective lake basins as a whole. For our purposes, we define representativity in statistical terms as being +/- 1SD of the mean. The results of campaign 1 indicate that GE3 and SHL2 are not representative for Petit and Grand Lac, as TP levels were much higher than the basin average. We hypothesise that the reason behind the high concentration at SHL2 during this first campaign may in part be due to position of the thermocline of the lake on this day. The depth of the thermocline at SHL2 matched with the depth of the integrated water sample. Typically, in deep stratified lakes, phosphorous concentrations increase in the hypolimnion, data show several fold higher concentrations of both P-PO4 and TP in the hypo- compared to epilimnion of Lake Geneva in recent years ( 56 ). The results of 3D model of Lake Geneva, see ( 22 ) for this day show that the position of the thermocline in Grand Lac was dome-shaped, with it being positioned higher in the water column in the center of the lake, where SHL2 is positioned, than closer to the shore. This then resulted in sampling closer to the hypolimnion at the reference station than in other stations, which could help explain the higher TP level recorded. In many large thermally stratified lakes, the thermocline tends to develop a dome shape, showing shallower thermocline depths in the center than in nearshore waters, e.g. described for Lake Erie by Beletsky et al. ( 57 ). In the other three campaigns, the TP and P-PO 4 values for SHL2 and GE3 were much closer to the basin-wide averages, in these cases suggesting that these reference stations can correctly inform us about the lake as a whole. Soulignac et al. ( 22 ) studied the representativeness of SHL2 and GE3 for the ecological status of Lake Geneva (expressed as parameters like TP, NO 3 , NH 4 , Chla or Secchi disk). They took the median of the ecological status of all grid cells of the Delft 3D model they ran. An individual grid cell – like SHL2 – was then deemed representative if the ecological status was identical to the theoretical value for the lake as a whole. Clearly when using our measured data, we have a much coarser spatial distribution than the fine grid cells of a computer model. When looking at this uneven distribution of stations across the lake (Fig. 1 ), a station like SHL2 in the middle of Grand Lac represents a much larger volume of Lake Geneva than a littoral station like VD4, since closer to the shore the sampling stations are closer together while widely spaced apart in the middle of the lake. Also, one would expect, and we see evidence for this in some of our littoral zone data, that given their proximity to the inflow of P from the land, TP or PO4 levels would be higher for near-shore stations than for open water. To obtain a lake mean for TP that truly represents the lake as a whole weighing the volumes of water represented by each station would be needed, comparable to what is done to get a weighted average with lake depth (see formula in Introduction). Data from CoFish will be very usfull for future modeling works as those data can be used to calibrate or validate the models.Given that there is spatial heterogeneity in large lakes like Lake Geneva – as clearly visible in for instance sentinel images - no point in the lake can be truly representative. So, for monitoring purposes with a limited budget, lake managers usually try to localise the “most representative” point of a specific lake area or basin, and this point is used as a reference. Is P limiting lake productivity? Given that the key research question in CoFish is clearly inspired by the fishers’ apprehension that fish production is increasingly limited by low P-availability, we discuss several aspects of this. Almost all of the TP measurements in our data are below 20 µg/L, which according to Müller et al. ( 53 ) should limit phytoplankton biomass in Lake Geneva. It is worth noting that our samples come from the euphotic zone and not the entire water column and so may not be directly comparable to the CIPEL annual average, presently for TP, presently at 16.9 µg/L, getting very close to the upper limit of the long-term target of 10–15 µg/L. Actually, since the lake does not fully mix, the CoFish data show that limiting concentrations for phytoplankton growth are already reached early in spring in the productive – upper – part of the water column of the lake. Over the past years, Lake Geneva has provided good quality drinking water and abundant fish biomass. Such an “ideal” setting was thanks to a decrease in TP concentrations after a period of eutrophication in the 1960-70s. When P-levels are brought down to restore lakes from eutrophication, the fish community composition changes, so that salmonids and piscivorous species like pike increased, see for example ( 12 ). However, at the time of writing of Gerdeaux et al. ( 12 ), it was expected that the overall fish production would decrease when phosphorus concentrations would start to drop below 20 µg/L. A sensitive, but important question to ask now becomes whether a further reduction of TP, to perhaps 10 µg/L, is required to safeguard the lake against future blooms, likely at the expense of a reduced fish biomass? Additionally, there is increasingly strong variation in the concentration of TP over depth. As outlined in the Introduction, a lack of winter overturn is locking-away the elevated P-levels in the deeper parts of the lake, which do no longer become available for primary production through deep winter mixing. Salmaso et al. ( 58 ) speak of oligotrophication of the euphotic layer. Therefore, it becomes all the more important to consider hydrodynamic processes, which are changing under impact of climate-warming for the identification of nutrient levels that balance lake usages. Whereas the risks of blooms under a warming climate remain real, augmented by extreme events in precipitation or temperature, as witnessed by the Uroglena bloom in Lake Geneva in 2021 ( 59 ), further re-oligotrophication may result in further – already ongoing - depletion of biological communities, like zooplankton, and lead to a potentially impoverished lake ecosystem. To enter into a bit more detail, the major arguments for controlling P in deep lakes that have suffered from eutrophication are to: (i) avoid anoxia in deeper layers, (ii) reduce the risk of blooms of nuisance / harmful algae, cyanobacteria in particular and (iii) to support lake biodiversity. Are these historical arguments that set the control of phosphorus into motion in the 1970s still valid in our time? Hypoxia is once again a problem in Lake Geneva, like in the eutrophic years, and the legal limit of 4 mg O 2 per L is no longer met in the deepest parts of the lake; however reducing TP further will probably not solve hypoxia, since phosphorus is not its leading cause ( 2 ). In deep lakes, oxygen concentrations are strongly driven by water mixing processes, in particular a lack of full winter overturn and increased duration of the period of thermal stratification ( 58 , 60 ). Blooms of cyanobacteria clearly increase with nutrient levels, and risks of nuisance or harmful levels of cyanobacteria at the long-term TP level of 10–15 µg/L would indeed be much reduced ( 61 ). However, blooms, defined here as a period in which levels of phytoplankton are elevated above the long-term average causing discoloration of the lake, are part of the normal functioning of lakes, and will continue to occur, even in oligotrophic systems ( 5 ). It may therefore not be realistic to avoid blooms altogether. Optimal P levels to conserve biodiversity is a tricky, multi-faceted issue. Based upon long term data from 11 peri-alpine lakes, the optimum TP-level for whitefish seems to be between 20–30 µg/L ( 12 ). When re-oligotrophication continues and TP drops to values below 10–20 µg/L, coregonid catches may decrease significantly, albeit still higher than during the most eutrophic years. On the other hand, perch catches peaked in the eutrophic years, likely due to reduced competition for zooplankton. At levels below 20–30 µg/L TP, however catches of perch became much reduced. Overall, Gerdeaux et al. ( 12 ) state that where total fish biomass decreases below 10 µg/L TP, biomass increases at TP levels between 10–15 µg/L, while further increases above 20 µg/L do not further enhance fish biomass. Conversely, what is the risk of blooms of nuisance or harmful algae at TP levels between 15–20 µg/L, a concentration that seems fairly optimal for fisheries? If we focus on the main toxic species in peri-alpine lakes, the metalimnetic red cyanobacterium Planktothrix rubescens , it is hard to find critical TP levels below which this cyanobacterium disappears. Clearly factors other than TP play a role, in particular climate change impacts. For example, Suarez et al. ( 62 ) studied Lake Hallwil and showed that Planktothrix was absent during the eutrophic period. With re-oligotrophication Planktothrix returned and peaked around TP levels of 50 µg/L. Further reduction of TP did bring Planktothrix down, but the species is still present, albeit now at a position well below the metalimnion. Planktothrix did not show a real presence in Lake Constance until recently when TP levels had dropped below 10 µg/L( 63 ) (Fournier et al., 2021). In contrast, for Lake Bourget (France) controlling phosphorus levels (TP reduction from 33 to 14 µg/L) was a key factor in the disappearance of Planktothrix blooms from the lake ( 64 ). Knapp et al ( 65 ) discuss how, under the impact of climate warming, seasonal patterns in the physical structure of the water column of Lake Zurich (Switzerland) are changing and how this can have both positive (shallower lake winter overturn) and negative (instability in the thermocline during spring) effects on Planktothrix , which remains a dominant species in this lake. The impact of the participatory approach There were several benefits of adopting a participatory approach both in terms of scientific findings and societal outcomes. First of all, we would not have had this type of information on lake wide variation in TP. In order to gather this type of data on the same day, a citizen science approach was required, as it would have been impossible for a single, or even a few researchers to visit this many stations in one day. Our simple hosepipe method – not our invention, see ( 46 ) could be a useful technique for further citizen water science, being cheap and effective. The main societal impacts of the participatory approach were the formation of an engaged community of lake stewards. These people had felt disempowered and sometimes disappointed by previous experiences in scientific projects. They expressed a great sense of allegiance to the group and in interviews expressed empowerment and the feeling they could achieve action towards an “ecological transition”. They felt more confident in participating and even more empowered to use the results in policy relevant processes, therefore also leaning towards a more policy level impact, often included as part of the societal impact in other frameworks, e.g.( 39 ). There were multiple learning outcomes that are further explored elsewhere (Jenkins et al. in prep). As with any approach, there were several shortcomings to our interviews. The questions were designed to focus on engagement and learning outcomes rather than all dimensions of societal impact. It is therefore possible that there are other impacts that we did not measure and that remain unreported. Results were disseminated actively by fishers themselves indicating ownership and pride in the quality of the data meaning that the results of the study were communicated effectively outside the strictly academic circles. One participant, in particular, who had not previously contributed to scientific research has since contributed to several other projects, and some have since become partners on future projects. The results were presented to CIPEL, who participated and contributed to the final workshop. Several collaborations are planned with fishers in the future: one project is already under way. However, the lack of funding to sustain citizen science efforts is a perennial issue. Several lessons were learned regarding the -codesign process, summarised in ( 66 ). Briefly, these involve the time it takes to successfully run a co-design process, the need for good and neutral communication, and the need for having the trust of both ambassadors anchored in the community but also the benefits of being perceived as a neutral outsider. Important discussions for project planners are whether participants are renumerated for their work. These fit into larger debates guiding citizen science research and the benefits and pitfalls of financial rewards ( 67 ). Conclusions Our data broadly support Soulignac et al.’s model-based conclusion ( 22 ), that the use of the reference stations is an acceptable compromise, in particular for the large open water spaces of the lake. However, monitoring of the littoral zones, whose renaturation is one the key action points for CIPEL may require additional efforts, that could be complemented by a citizen science approach. Generally, among the authors of this paper, who represent academic scientists and fishers, there is an agreement that with the present TP levels further reduction may risk further impoverishment of zooplankton and a number of commercially important fish species. It is further encouraging that cyanotoxin levels in Lake Geneva are at a low level, which does not pose public health risks ( 68 ). In addition, with the ongoing invasion of quagga mussels in the lake, the P-cycling and availability of P for the pelagic food web is under increasing pressure, see ( 69 ), requiring in itself re-evaluation of the role of phosphorous in the pelagic food web. Setting optimal TP levels therefore remains challenging. Finally, we report empowerment of the community of fishers by the co-design process. Perhaps most importantly however is the longer-term effect of a community of scientifically engaged fishers, contributing to the conservation of the lake. We further advocate for citizen science projects to measure and report societal outcomes of projects alongside the scientific results. Declarations Ethics approval and consent to participate all procedures were approved by the University of Geneva Ethical Board (CUREG-2021-08-82). Participants signed informed consent forms and their identities were anonymised. Interviews were transcribed with the aid of the online software Happyscribe (Happy Scribe Ltd.) and transcripts were deleted from the cloud after use. Ethical approval is not required to sample water from the lake and we do not conduct or report on experiments on human participants. Consent for publication this manuscript does not contain personal data. Availability of data and materials The dataset TP and P-PO4 dataset is currently being reviewed in Dryad https://doi.org/10.5061/dryad.73n5tb379. Anonymised interview transcripts are available on request from the corresponding author. Competing interests The authors state no competing interests. Funding CoFish was an SNSF funded COST project - IZCOZ0_198179 awarded to B.J.S and B.W.I.. The kick-off workshop was co-funded by a grant awarded to T.J. by the Mercator Foundation. Author contributions T.J., B.J.S. and B.I. conceived the idea behind CoFish. T.J. and E.R. designed the co-creation methodology; D.C., L.F., A.F., Y.D., M.D., N.R., L.L., B.I., T.J., E.R., M.A.,O.A. co-designed the research question and the sampling methodology. O.A. gave input on the historical sampling of SHL2. D.C., L.F., A.F., Y.D., M.D., N.R., P.A., M.A., M.G., collected the data; R.F., M.A. ,Y.M.,P.A. conducted the lab analysis. M.K.T. provided input on data analysis. T.J., B.W.I. and O.A. wrote the manuscript. All authors contributed critically to the drafts and gave final approval for publication. Acknowledgements Several people supported this work at various stages of the project with discussions,: Adrian Aeschlimann, Marc Babut, Isabel Blasco Costa, Tom Boersen, Jakob Broedersen, Till Bruckermann, Egle Butkeviciene, Jonas Bylemans, Franck Cattaneo, Joelyn de Lima, Nicole Gallina, Rudolf Gerber, Christian Gillet, Chloé Goulon, Jean Guillard, Frédéric Hofmann, Dimitri Jaquet, Kostas Kampourakis, Sylvain Kramer, , Alexandre Lemopoulos, Jean-Daniel Morel, Ilan Page, Theres Paulsen, Alexandra Sa Pinto, Baptiste Paquereau, Peter Ehrensperger, Guy-Charles Monney, Pierre Marle, Maxime Prevedello, Livio Riboli Sasco, Alexandre Richard, Tiina Stämpfli, Jean-Jacques Steiner, Hugues Würsten, Daniel Wüthrich, Candice Yvon, Bernard Carridroit, Henri-Daniel Champier, René Luthi. td-net (Sibylle Studer, Theres Paulsen) is acknowleged for its consultancy on co-design and transdisciplinary research principles. We are grateful to the following for data collection Laurent Charenton, Jean Jacquier, Jean-Claude Doriot, Morgane Lefévère, Natalino Lucchetta, Michel Picotin, Yannick Rosset, Jet Osmankaq, Patrice Valentin, la Brigade du Lac, Sébastian Leblanche, Cedric Henry. Phosphorus concentrations at SHL2 are contributed by the Observatory of alpine Lakes (OLA), © SOERE OLA-IS, AnaEE-France, INRAE at Thonon-les-Bains and CIPEL We thank the Musée du Léman and Anne-Sophie Deville for hosting several of our workshops. Author information This article is the outcome of a joint collaboration between fishers L.F., A.F., D.C., Y.D., M.D., N.R., L.L. and researchers at academic instiutions T.J., O.A., P.A. ,M.A., R.F., M.G., Y.M., M.K.T, B.J.S., E.R., B.W.I. References Rapin F, Blanc P, Pelletier JP, Balvay G, Gerdeaux D. Impacts humains sur les systèmes lacustres: exemple du Léman. 1995; Soares L, Desgué‐itier O, Barouillet C, Casenave C, Domaizon I, Frossard V, et al. Unraveling Lake Geneva’s hypoxia crisis in the Anthropocene [Internet]. Limnology and Oceanography Letters. Wiley; 2024. Available from: https://hal.inrae.fr/hal-04727996 Huisman J, Codd GA, Paerl HW, Ibelings BW, Verspagen JM, Visser PM. Cyanobacterial blooms. Nat Rev Microbiol. 2018;16(8):471–83. Anneville O, Domaizon I, Kerimoglu O, Rimet F, Jacquet S. Blue-Green Algae in a “Greenhouse Century”? New Insights from Field Data on Climate Change Impacts on Cyanobacteria Abundance. Ecosystems [Internet]. 2015 Apr 1;18(3):441–58. Available from: https://doi.org/10.1007/s10021-014-9837-6 Reinl KL, Harris TD, North RL, Almela P, Berger SA, Bizic M, et al. Blooms also like it cold. Limnol Oceanogr Lett [Internet]. 2023 Aug 1 [cited 2025 Feb 11];8(4):546–64. Available from: https://doi.org/10.1002/lol2.10316 Kraemer BM, Boudet S, Burlakova LE, Haltiner L, Ibelings BW, Karatayev AY, et al. An abundant future for quagga mussels in deep European lakes. Environ Res Lett [Internet]. 2023 Nov 7;18(12):124008. Available from: https://dx.doi.org/10.1088/1748-9326/ad059f Karatayev AY, Burlakova LE. What we know and don’t know about the invasive zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels. Hydrobiologia [Internet]. 2022 Oct 13; Available from: https://doi.org/10.1007/s10750-022-04950-5 Bninska M. Commercial fisheries versus water quality in lakes with special reference to coregonid management. Fish Manag Ecol [Internet]. 2000 Feb 1 [cited 2024 Dec 3];7(1–2):105–14. Available from: https://doi.org/10.1046/j.1365-2400.2000.00199.x Ibelings BW, Fastner J, Bormans M, Visser PM. Cyanobacterial blooms. Ecology, prevention, mitigation and control: Editorial to a CYANOCOST Special Issue. Aquat Ecol [Internet]. 2016 Sep 1;50(3):327–31. Available from: https://doi.org/10.1007/s10452-016-9595-y Lepori F, Capelli C. Effects of phosphorus control on primary productivity and deep-water oxygenation: insights from Lake Lugano (Switzerland and Italy). Hydrobiologia [Internet]. 2021 Feb 1;848(3):613–29. Available from: https://doi.org/10.1007/s10750-020-04467-9 Eckmann R, Gerdeaux D, Muller R, Rösch R. Re-oligotrophication and whitefish fisheries management - a workshop summary. In: 9 International Symposium on the Biology and Management of Coregonid Fishes [Internet]. Olsztyn, Poland; 2005. Available from: https://hal.inrae.fr/hal-02832476 Gerdeaux D, Anneville O, Hefti D. Fishery changes during re-oligotrophication in 11 peri-alpine Swiss and French lakes over the past 30 years. Acta Oecologica. 2006;30(2):161–7. Alexander T, Seehausen O. Diversity, distribution and community composition of fish in perialpine lakes. Proj Lac» Synth Rep. 2021;282. Sinclair JS, Fraker ME, Hood JM, Reavie ED, Ludsin SA. Eutrophication, water quality, and fisheries: a wicked management problem with insights from a century of change in Lake Erie. Ecol Soc [Internet]. 2023;28(3). Available from: https://www.ecologyandsociety.org/vol28/iss3/art10/ Lesht BM, Scofield AE, Bockwoldt KA. Lake-wide measurements of primary productivity in Lake Erie. Aquat Ecosyst Health Manag [Internet]. 2024 Jan 1 [cited 2024 Nov 25];27(1):30–45. Available from: https://doi.org/10.14321/aehm.027.01.30 Gao Y, Gao J, Chen J. Spatial variation of surface soil available phosphorous and its relation with environmental factors in the Chaohu Lake watershed. Int J Environ Res Public Health. 2011;8(8):3299–317. Wu T, Qin B, Brookes JD, Yan W, Ji X, Feng J. Spatial distribution of sediment nitrogen and phosphorus in Lake Taihu from a hydrodynamics-induced transport perspective. Sci Total Environ [Internet]. 2019 Feb 10;650:1554–65. Available from: https://www.sciencedirect.com/science/article/pii/S0048969718335897 Johnson MG, Nicholls KH. Temporal and Spatial Variability in Sediment and Phosphorus Loads to Lake Simcoe, Ontario. J Gt Lakes Res [Internet]. 1989 Jan 1;15(2):265–82. Available from: https://www.sciencedirect.com/science/article/pii/S0380133089714817 Zong Y, Chen SS, Kattel GR, Guo Z. Spatial distribution of non-point source pollution from total nitrogen and total phosphorous in the African city of Mwanza (Tanzania). Front Environ Sci [Internet]. 2023;11. Available from: https://www.frontiersin.org/articles/10.3389/fenvs.2023.1084031 Ostrovsky I, Yacobi YZ. Temporal evolution and spatial heterogeneity of ecosystem parameters in a subtropical lake. In 2009. Gao Y, Gao J, Yin H, Liu C, Xia T, Wang J, et al. Remote sensing estimation of the total phosphorus concentration in a large lake using band combinations and regional multivariate statistical modeling techniques. J Environ Manage [Internet]. 2015 Mar 15;151:33–43. Available from: https://www.sciencedirect.com/science/article/pii/S0301479714005775 Soulignac F, Danis PA, Bouffard D, Chanudet V, Dambrine E, Guénand Y, et al. Using 3D modeling and remote sensing capabilities for a better understanding of spatio-temporal heterogeneities of phytoplankton abundance in large lakes. J Gt Lakes Res [Internet]. 2018 Aug 1;44(4):756–64. Available from: https://www.sciencedirect.com/science/article/pii/S0380133018300807 Dabrowski T, Berry A. Use of numerical models for determination of best sampling locations for monitoring of large lakes. Sci Total Environ [Internet]. 2009 Jul 1;407(14):4207–19. Available from: https://www.sciencedirect.com/science/article/pii/S0048969709002502 Karabork H. Selection of appropriate sampling stations in a lake through mapping. Environ Monit Assess [Internet]. 2010 Apr 1;163(1):27–40. Available from: https://doi.org/10.1007/s10661-009-0813-0 Li J, Tian L, Wang Y, Jin S, Li T, Hou X. Optimal sampling strategy of water quality monitoring at high dynamic lakes: A remote sensing and spatial simulated annealing integrated approach. Sci Total Environ [Internet]. 2021 Jul 10;777:146113. Available from: https://www.sciencedirect.com/science/article/pii/S0048969721011803 Strasser BJ, Baudry J, Mahr D, Sanchez G, Tancoigne E. “Citizen Science”? Rethinking Science and Public Participation. Sci Technol Stud. 2019;52–76. Fraisl D, Hager G, Bedessem B, Gold M, Hsing PY, Danielsen F, et al. Citizen science in environmental and ecological sciences. Nat Rev Methods Primer. 2022;2(1):64. Tauginienė L, Hummer P, Albert A, Cigarini A, Vohland K. Ethical challenges and dynamic informed consent. Sci Citiz Sci. 2021;397. Mirowski P. The future(s) of open science. Soc Stud Sci [Internet]. 2018 Apr 1 [cited 2024 Apr 9];48(2):171–203. Available from: https://doi.org/10.1177/0306312718772086 Haklay M. Citizen science and volunteered geographic information: Overview and typology of participation. In: Crowdsourcing geographic knowledge. Springer; 2013. p. 105–22. Norström AV, Cvitanovic C, Löf MF, West S, Wyborn C, Balvanera P, et al. Principles for knowledge co-production in sustainability research. Nat Sustain [Internet]. 2020 Mar 1;3(3):182–90. Available from: https://doi.org/10.1038/s41893-019-0448-2 van Noordwijk T, Bishop I, Staunton-Lamb S, Oldfield A, Loiselle S, Geoghegan H, et al. Creating positive environmental impact through citizen science. Sci Citiz Sci. 2021;373–95. Conallin JC, Dickens C, Hearne D, Allan C. Chapter 7 - Stakeholder Engagement in Environmental Water Management. In: Horne AC, Webb JA, Stewardson MJ, Richter B, Acreman M, editors. Water for the Environment [Internet]. Academic Press; 2017. p. 129–50. Available from: https://www.sciencedirect.com/science/article/pii/B9780128039076000073 Collins JP. Gene drives in our future: challenges of and opportunities for using a self-sustaining technology in pest and vector management. BMC Proc [Internet]. 2018;12(Suppl 8):9. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6069294/ Fujitani M, McFall A, Randler C, Arlinghaus R. Participatory adaptive management leads to environmental learning outcomes extending beyond the sphere of science. Sci Adv. 2017;3(6):e1602516. Granek EF, Madin EM, Brown MA, Figureueira W, Cameron DS, Hogan Z, et al. Engaging recreational fishers in management and conservation: global case studies. Conserv Biol. 2008;22(5):1125–34. Pearson E, Hunter E, Steer A, Arscott K, Hart PJ. Fishermen and scientists in the same boat. A story of collaboration in the UK South Devon crab fishery. Collab Res Fish Co-Creat Knowl Fish Gov Eur. 2020;27–41. Holm P, Hadjimichael M, Mackinson S, Linke S. Bridging Gaps, Reforming Fisheries. In: Collaborative Research in Fisheries. Springer; 2020. p. 279–303. Wehn U, Gharesifard M, Ceccaroni L, Joyce H, Ajates R, Woods S, et al. Impact assessment of citizen science: state of the art and guiding principles for a consolidated approach. Sustain Sci [Internet]. 2021 Sep 1;16(5):1683–99. Available from: https://doi.org/10.1007/s11625-021-00959-2 Kieslinger B, Schäfer T, Heigl F, Dörler D, Richter A, Bonn A. Evaluating citizen science. Citiz Sci Innov Open Sci Soc Policy Bonn Hecker Haklay M Bowser Makuch Z Vogel J Eds. 2017;81–96. Passani A, Janssen A, Hölscher K, Di Lisio G. A participatory, multidimensional and modular impact assessment methodology for citizen science projects. Fteval J Res Technol Policy Eval. 2022;(54):33–42. Baulaz Y. Chroniques de la pêche française au Léman. 2019 Jan 18; CIPEL. Tableau de Bord [Internet]. Nyon: CIPEL: Commission internationale pour la protection des eaux du Léman; 2023. Available from: https://www.cipel.org/wp-content/uploads/2024/01/tb-cipel-2023.pdf Cohen L, Manion L, Morrison K. Research methods in education. routledge; 2017. Pohl C, Wuelser G. Methods for Coproduction of Knowledge Among Diverse Disciplines and Stakeholders. In: Hall KL, Vogel AL, Croyle RT, editors. Strategies for Team Science Success: Handbook of Evidence-Based Principles for Cross-Disciplinary Science and Practical Lessons Learned from Health Researchers [Internet]. Cham: Springer International Publishing; 2019. p. 115–21. Available from: https://doi.org/10.1007/978-3-030-20992-6_8 Mantzouki E, Campbell J, Van Loon E, Visser P, Konstantinou I, Antoniou M, et al. A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins. Sci Data. 2018;5(1):1–13. Monod, R. Le Léman: synthèse des travaux de la Commission internationale pour la protection des eaux du Léman contre la pollution. Lausanne: CIPEL: Commission internationale pour la protection des eaux du Léman; 1984 p. 67. Sommer U, Adrian R, De Senerpont Domis L, Elser JJ, Gaedke U, Ibelings B, et al. Beyond the Plankton Ecology Group(PEG) Model: Mechanisms Driving Plankton Succession. Annu Rev Ecol Evol Syst. 2012;43(429):2012. Vogler P. Beiträge zur Phosphatanalytik in der Limnologie. Die Bestimmung des gelösten Orthophosphates. Fortschr Wasserchem Grenzgeb 109-119. 1965;2:109–19. Phillips TB, Ballard HL, Lewenstein BV, Bonney R. Engagement in science through citizen science: Moving beyond data collection. Sci Educ [Internet]. 2019 May 1 [cited 2020 Mar 30];103(3):665–90. Available from: https://doi.org/10.1002/sce.21501 Lederman NG, Abd‐El‐Khalick F, Bell RL, Schwartz RS. Views of nature of science questionnaire: Toward valid and meaningful assessment of learners’ conceptions of nature of science. J Res Sci Teach. 2002;39(6):497–521. Lederman JS, Lederman NG, Bartos SA, Bartels SL, Meyer AA, Schwartz RS. Meaningful assessment of learners’ understandings about scientific inquiry—The views about scientific inquiry (VASI) questionnaire. J Res Sci Teach. 2014;51(1):65–83. Müller B, Steinsberger T, Stöckli A, Wüest A. Increasing Carbon-to-Phosphorus Ratio (C:P) from Seston as a Prime Indicator for the Initiation of Lake Reoligotrophication. Environ Sci Technol [Internet]. 2021 May 4;55(9):6459–66. Available from: https://doi.org/10.1021/acs.est.0c08526 Sas H. Lake restoration by reduction of nutrient loading: Expectations, experiences, extrapolations. SIL Proc 1922-2010 [Internet]. 1990 Dec 1;24(1):247–51. Available from: https://doi.org/10.1080/03680770.1989.11898731 Suttle CA, Harrison PJ. Ammonium and phosphate uptake rates, N: P supply ratios, and evidence for N and P limitation in some oligotrophic lakes 1. Limnol Oceanogr. 1988;33(2):186–202. Rasconi S., Rimet F., Perney, P. Rapports sur les études et recherches entreprises dans le bassin Lémanique, campagne 2023. [Internet]. Nyon: CIPEL: Commission internationale pour la protection des eaux du Léman; 2024. Available from: htttp//www.cipel.org Beletsky D, Hawley N, Rao YR. Modeling summer circulation and thermal structure of Lake Erie. J Geophys Res Oceans [Internet]. 2013 Nov 1 [cited 2024 Nov 25];118(11):6238–52. Available from: https://doi.org/10.1002/2013JC008854 Salmaso N, Anneville O, Straile D, Viaroli P. European large perialpine lakes under anthropogenic pressures and climate change: present status, research gaps and future challenges. Hydrobiologia [Internet]. 2018 Nov 1;824(1):1–32. Available from: https://doi.org/10.1007/s10750-018-3758-x Irani Rahaghi A, Odermatt D, Anneville O, Sepúlveda Steiner O, Reiss RS, Amadori M, et al. Combined Earth observations reveal the sequence of conditions leading to a large algal bloom in Lake Geneva. Commun Earth Environ [Internet]. 2024 May 1;5(1):229. Available from: https://doi.org/10.1038/s43247-024-01351-5 Anneville O, Beniston M, Gallina N, Gillet C, Jacquet S, Lazzarotto J, et al. L’empreinte du changement climatique sur le Léman. Arch Sci. 2013;66:157–72. Chorus I, Fastner J, Welker M. Cyanobacteria and cyanotoxins in a changing environment: Concepts, controversies, challenges. Water. 2021;13(18):2463. Suarez EL, De Ventura L, Stöckli A, Ordóñez C, Thomas MK, Ibelings BW, et al. The emergence and dominance of Planktothrix rubescens as an hypolimnetic cyanobacterium in response to re‐oligotrophication of a deep peri‐alpine lake. Limnol Oceanogr. 2023;68(6):1346–59. Fournier C, Riehle E, Dietrich DR, Schleheck D. Is Toxin-Producing Planktothrix sp. an Emerging Species in Lake Constance? Toxins. 2021;13(9). Jacquet S, Kerimoglu O, Rimet F, Paolini G, Anneville O. Cyanobacterial bloom termination: the disappearance of Planktothrix rubescens from Lake Bourget (France) after restoration. Freshw Biol [Internet]. 2014 Dec 1 [cited 2024 Nov 25];59(12):2472–87. Available from: https://doi.org/10.1111/fwb.12444 Knapp D, Fernández Castro B, Marty D, Loher E, Köster O, Wüest A, et al. The Red Harmful Plague in Times of Climate Change: Blooms of the Cyanobacterium Planktothrix rubescens Triggered by Stratification Dynamics and Irradiance. Front Microbiol [Internet]. 2021;12. Available from: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.705914 Jenkins T, Jenkins T, participants C. Guide de bonnes pratiques des sciences participatives avec les pêcheurs et pêcheuses du Léman. University of Geneva. 2024. Rutten M, Minkman E, van der Sanden M. How to get and keep citizens involved in mobile crowd sensing for water management? A review of key success factors and motivational aspects. WIREs Water [Internet]. 2017 Jul 1 [cited 2024 Oct 9];4(4):e1218. Available from: https://doi.org/10.1002/wat2.1218 Niveen Ismail and Paul Seguin and Lola Pricam and Elisabeth Janssen and Tamar Kohn and Bas Ibelings and Anna Carratala. Seasonality of cyanobacteria and eukaryotes in Lake Geneva and the impacts of cyanotoxins on growth of the model ciliate Tetrahymena pyriformis. 2025 Jan 25;279. Available from: https://infoscience.epfl.ch/handle/20.500.14299/246362 Vanni MJ. Invasive mussels regulate nutrient cycling in the largest freshwater ecosystem on Earth. Proc Natl Acad Sci [Internet]. 2021 Feb 23 [cited 2025 Feb 27];118(8):e2100275118. Available from: https://doi.org/10.1073/pnas.2100275118 Table 3 Table 3 is available in the Supplementary Files section. Supplementary Files SupplementaryInformationlegends.docx SupplementaryTableS1Cocreationworkshops.docx SITableS2.xlsx SI3.docx SI4.Interviewprotocols.docx SI5Secchihistograms.pdf SI6compositesecchi.png Table3.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 09 Jul, 2025 Reviews received at journal 03 Jul, 2025 Reviewers agreed at journal 28 Apr, 2025 Reviews received at journal 25 Apr, 2025 Reviewers agreed at journal 01 Apr, 2025 Reviewers invited by journal 18 Mar, 2025 Editor assigned by journal 17 Mar, 2025 Submission checks completed at journal 17 Mar, 2025 First submitted to journal 17 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6170350","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":449247597,"identity":"fdf56236-7709-42c3-9048-4404e7a3d3a8","order_by":0,"name":"Tania Jenkins","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/klEQVRIiWNgGAWjYJCCAwwMbAwMPIwNDAwVQC4zcwNe5TyoWs6AtDAS1oJgMbaBWAS02LOfPXjgBwOfnDnP4baHP+fVRvO3A7X8qNiG2xaevISDPQxsxpa9je3GvNuO5844zNjA2HPmNh6H5Rgc4GFgS9xwnrFNmnHbsdwGoBZmxjY8WvjfGBz8w8BWD9Ii+XPOsdz5BLVI5BgcBtqSYHC2sU2Ct6EmdwNBLTfeGByWMWAz3HDmYJs0z7EDuRuBWg7i8wt7f47xxzcVx+QNzqQ/k/xRU5c77/zhgw9+VODWAgEGx2Csw2DyAAH1IFADY9QRoXgUjIJRMApGGgAAcp1ZyEGoEDoAAAAASUVORK5CYII=","orcid":"","institution":"Section of Biology, Faculty of Science, Sciences III, University of Geneva, 30 Quai Ernest Ansermet, 1205, Geneva Switzerland","correspondingAuthor":true,"prefix":"","firstName":"Tania","middleName":"","lastName":"Jenkins","suffix":""},{"id":449247598,"identity":"2a3c7a9e-b833-4eeb-9ce3-f5eaf2a959a2","order_by":1,"name":"Laura Fayet","email":"","orcid":"","institution":"Pêcherie de la Dullive, Chemin de la Dullive 4, 1196 Gland, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Laura","middleName":"","lastName":"Fayet","suffix":""},{"id":449247599,"identity":"ad18622f-0f89-4194-b952-6a656eb9a4c5","order_by":2,"name":"Alexandre Fayet","email":"","orcid":"","institution":"Pêcherie de la Dullive, Chemin de la Dullive 4, 1196 Gland, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Alexandre","middleName":"","lastName":"Fayet","suffix":""},{"id":449247600,"identity":"93c749ff-3684-48da-9f86-df54ea68c6b4","order_by":3,"name":"Daniel Chollet","email":"","orcid":"","institution":"FIPAL, c/o Lydia Lucchetta, Av. Pictet de Rochemont 27, 1207 Geneva, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Daniel","middleName":"","lastName":"Chollet","suffix":""},{"id":449247601,"identity":"23d6f36a-2984-4ad7-bf96-6660c4f8dead","order_by":4,"name":"Yves Depraz","email":"","orcid":"","institution":"Amicale des Pêcheurs amateurs de Sciez, 650 route du port, 74140 Sciez, France","correspondingAuthor":false,"prefix":"","firstName":"Yves","middleName":"","lastName":"Depraz","suffix":""},{"id":449247602,"identity":"a1129a79-62fe-43ec-922b-d6a421bb47ff","order_by":5,"name":"Michaël Dumaz","email":"","orcid":"","institution":"Micapeche, 1 bis avenue Anna de Noailles, 74500, Evian, France","correspondingAuthor":false,"prefix":"","firstName":"Michaël","middleName":"","lastName":"Dumaz","suffix":""},{"id":449247603,"identity":"69374a36-9df8-43b7-8641-e4c5118aac85","order_by":6,"name":"Neal Ricci","email":"","orcid":"","institution":"Pêcherie Neal Ricci, Chemin du Vieux Port 20, 1290, Versoix, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Neal","middleName":"","lastName":"Ricci","suffix":""},{"id":449247604,"identity":"41ac2007-42f1-4293-9933-20c56e8f257c","order_by":7,"name":"Lydia Lucchetta","email":"","orcid":"","institution":"FIPAL, c/o Lydia Lucchetta, Av. Pictet de Rochemont 27, 1207 Geneva, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Lydia","middleName":"","lastName":"Lucchetta","suffix":""},{"id":449247605,"identity":"2fe3a0cd-9067-4d77-b283-440ef0848ebe","order_by":8,"name":"Orlane Anneville","email":"","orcid":"","institution":"Université Savoie Mont Blanc, INRAE, UMR CARRTEL FR 75 bis venue de Corzent, CS 50511, 74203 Thonon les Bains, France","correspondingAuthor":false,"prefix":"","firstName":"Orlane","middleName":"","lastName":"Anneville","suffix":""},{"id":449247606,"identity":"a8d232b6-bfe6-4c27-8b84-71f4252dc34c","order_by":9,"name":"Philippe Arpagaus","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Philippe","middleName":"","lastName":"Arpagaus","suffix":""},{"id":449247607,"identity":"e6bc15e1-f10b-4790-962e-063312e44186","order_by":10,"name":"Maria Almada","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"","lastName":"Almada","suffix":""},{"id":449247608,"identity":"411e7a82-d782-4231-9d49-977dda560f18","order_by":11,"name":"Roxane Fillion","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Roxane","middleName":"","lastName":"Fillion","suffix":""},{"id":449247609,"identity":"3d537b44-87d4-44ac-9e34-ef8ace80d604","order_by":12,"name":"Matteo Gios","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Matteo","middleName":"","lastName":"Gios","suffix":""},{"id":449247610,"identity":"7017e2c9-10db-41a0-ac26-30036777ffad","order_by":13,"name":"Yasmine Moftizadeh","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Yasmine","middleName":"","lastName":"Moftizadeh","suffix":""},{"id":449247611,"identity":"a7c6e922-e3ef-43bc-b03e-380a660439ef","order_by":14,"name":"Mridul K. Thomas","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Mridul","middleName":"K.","lastName":"Thomas","suffix":""},{"id":449247612,"identity":"29e165cd-b41c-4d04-9210-0a93d41960ac","order_by":15,"name":"Bruno J. Strasser","email":"","orcid":"","institution":"Section of Biology, Faculty of Science, Sciences III, University of Geneva, 30 Quai Ernest Ansermet, 1205, Geneva Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Bruno","middleName":"J.","lastName":"Strasser","suffix":""},{"id":449247613,"identity":"47fd1289-0141-4c6a-a0d8-ca06bea935e9","order_by":16,"name":"Elisa Radosta","email":"","orcid":"","institution":"Section of Biology, Faculty of Science, Sciences III, University of Geneva, 30 Quai Ernest Ansermet, 1205, Geneva Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Elisa","middleName":"","lastName":"Radosta","suffix":""},{"id":449247614,"identity":"f1ab92c2-9179-43fc-990c-da7989bfbb25","order_by":17,"name":"Bastiaan W Ibelings","email":"","orcid":"","institution":"Department F. A Forel for Environmental and Aquatic Sciences, University of Geneva, 66 Boulevard Carl-Vogt, 1211 Geneva 4, Switzerland","correspondingAuthor":false,"prefix":"","firstName":"Bastiaan","middleName":"W","lastName":"Ibelings","suffix":""}],"badges":[],"createdAt":"2025-03-06 12:08:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6170350/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6170350/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82141006,"identity":"e0fe88ea-4248-4c58-bd37-cd3cf7b0392d","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":571257,"visible":true,"origin":"","legend":"\u003cp\u003eSampling sites CoFish redrawn from the historical CIPEL map (47).\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/d557378a641c922540ec49c1.png"},{"id":82143452,"identity":"a16d2775-0d02-4e97-b11f-7baca5dc15bb","added_by":"auto","created_at":"2025-05-07 06:41:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1029341,"visible":true,"origin":"","legend":"\u003cp\u003eOperation instructions for self-made water sampling device made of a garden hose, which was 18m long with a rope double the length. The weights were 5Kg and waterproof tape was used to join the parts.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/c8b1b447291508d6170c427e.png"},{"id":82144981,"identity":"0eb5746d-dc85-4d3f-ab2e-f5eb792990b3","added_by":"auto","created_at":"2025-05-07 06:49:33","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":284745,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHistogram plots of the concentration of TP (total phosphorus) in μg/L in the productive part of the Lake Geneva watercolumn (0-18 m).\u003c/strong\u003e The frequency indicates the number of measurements. Bar plots in the left-hand panels indicate measurements from Petit Lac, while bar plots in the right-hand plots are from Grand Lac. Panels \u003cstrong\u003ea and b \u003c/strong\u003ecorrespond to\u003cstrong\u003e, \u003c/strong\u003ecampaign 1, \u003cstrong\u003ec and d \u003c/strong\u003eto campaign 2; \u003cstrong\u003ee and f \u003c/strong\u003etocampaign 3 and \u003cstrong\u003eg and h \u003c/strong\u003eto campaign 4. For campaign 4, point SHL6 had a concentration of 34.7 μg/L and is therefore not depicted for graphical purposes here as it is out of range. \u003cstrong\u003eSolid vertical lines\u003c/strong\u003e indicate the mean of all sampling points for that lake basin, while the \u003cstrong\u003edashed lines\u003c/strong\u003e indicate the value at the standard point GE3 for Petit Lac and SHL2 for Grand Lac. The shaded boxes indicate the \u003cu\u003e+\u003c/u\u003e 1 SD of mean of the distribution. The long-term goal for TP in Lake Geneva is set at 10-15 µg/L.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/acebefa2606989b6763c02c4.png"},{"id":82141013,"identity":"db850d2d-a727-402d-a732-9b93c7d23832","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":234177,"visible":true,"origin":"","legend":"\u003cp\u003eThe reference points SHL2 for Grand Lac and GE3 for Petit Lac are marked in bold on all maps. Panel \u003cstrong\u003ea, \u003c/strong\u003ecampaign 1, September 26\u003csup\u003eth\u003c/sup\u003e 2022 (34/36 points depicted, CRG5 was much higher than the typical range- see main text - so is not shown, and CRG10 was not sampled due to windy conditions at the time of sampling, late in the day); \u003cstrong\u003eb, \u003c/strong\u003ecampaign 2, January 31 2023; \u003cstrong\u003ec, \u003c/strong\u003ecampaign, 3 April 5\u003csup\u003eth\u003c/sup\u003e 2023; \u003cstrong\u003ed, \u003c/strong\u003ecampaign 4 ,September 25, 2023. SHL6 is marked here as its concentration was 34.6 μg/L far higher than the rest of the values. Values below the analytical detection limit are marked in grey. Values of P-PO\u003csub\u003e4\u003c/sub\u003e are often taken as being limiting for phytoplankton growth.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/4aac51af701a2fc1b6dbca44.png"},{"id":82144983,"identity":"3706752f-3c66-494d-bdb7-60d073e5df89","added_by":"auto","created_at":"2025-05-07 06:49:33","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":264794,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHistogram plots of the concentration of P-PO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e orthophosphate in μg/L.\u003c/strong\u003e Bars in the left-hand panels indicate measurements from Petit Lac and bars in the right-hand plots from Grand Lac. Figure \u003cstrong\u003ea and b, \u003c/strong\u003eCampaign 1 \u003cstrong\u003ec and d. \u003c/strong\u003ecampaign 2; \u003cstrong\u003ee and f: \u003c/strong\u003ecampaign 3, \u003cstrong\u003eg and h: \u003c/strong\u003ecampaign 4. \u003cstrong\u003eSolid vertical lines\u003c/strong\u003e indicate the mean of all sampling points for that lake basin, while the \u003cstrong\u003edashed lines\u003c/strong\u003e indicate the value at the standard point GE3 for Petit Lac and SHL2 for Grand Lac, which are further included along with the percentile of the distribution (%). The shaded boxes indicate the \u003cu\u003e+\u003c/u\u003e 1 standard deviation of mean of the distribution.\u0026nbsp;\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/e422a44040f3ab9a5c6ca810.png"},{"id":82144985,"identity":"2a25106c-15a4-4d01-83db-dc0f001d0184","added_by":"auto","created_at":"2025-05-07 06:49:33","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":243593,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe concentration of P-PO4 (orthophosphate) in μg/L across stations. \u003c/strong\u003eThe reference points SHL2 for Grand Lac and GE3 for Petit Lac are marked in bold on all maps. Panel \u003cstrong\u003ea, \u003c/strong\u003eCampaign 1, September 26\u003csup\u003eth\u003c/sup\u003e 2022 (34/36 points depicted, CRG5 was much higher than the typical range, it is not shown and CRG10 was not sampled due to windy conditions; \u003cstrong\u003eb, \u003c/strong\u003ecampaign 2, January 31 2023; \u003cstrong\u003ec, \u003c/strong\u003ecampaign 3 April 5\u003csup\u003eth\u003c/sup\u003e 2023, and\u003cstrong\u003e d, \u003c/strong\u003ecampaign 4, September 25 2023. SHL6 is marked in c and d. and had a value of 13μg/L.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/96272cc1f87035a928223524.png"},{"id":82147945,"identity":"25276afc-ec8b-4e06-bd3f-d222d0903cd8","added_by":"auto","created_at":"2025-05-07 07:05:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3403648,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/7564918a-0e5c-4010-b6d5-3d6ba86137e6.pdf"},{"id":82141005,"identity":"3fd0a7b1-e0fe-4daa-a60f-87a155cc1ff6","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":14957,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformationlegends.docx","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/29c40ece8683fcf26c9d179c.docx"},{"id":82146896,"identity":"856a3ea6-923a-4825-b125-129e405394a2","added_by":"auto","created_at":"2025-05-07 06:57:33","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":219963,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryTableS1Cocreationworkshops.docx","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/596120c3868597f370958abb.docx"},{"id":82141009,"identity":"3a4a6b20-982c-438f-bbc9-1cd450ef4ad7","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":11816,"visible":true,"origin":"","legend":"","description":"","filename":"SITableS2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/2bffe3f280f09dd96a0f315c.xlsx"},{"id":82141011,"identity":"11696123-84f5-4cdb-8f5b-a8abe6da23f3","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":20271,"visible":true,"origin":"","legend":"","description":"","filename":"SI3.docx","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/e8cf9937226dcc1808c417e2.docx"},{"id":82141024,"identity":"29188a4a-b800-4d93-b121-17eafb27ea22","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":220877,"visible":true,"origin":"","legend":"","description":"","filename":"SI4.Interviewprotocols.docx","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/a0e5bf13a2bd9652c6123132.docx"},{"id":82143455,"identity":"e6ff6ee0-897a-41aa-b6ef-21d4c24ef873","added_by":"auto","created_at":"2025-05-07 06:41:33","extension":"pdf","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":262323,"visible":true,"origin":"","legend":"","description":"","filename":"SI5Secchihistograms.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/6413c559ef8d21a343db2a78.pdf"},{"id":82143461,"identity":"e7b0397c-0b09-4429-933a-a9318e3c41d0","added_by":"auto","created_at":"2025-05-07 06:41:33","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":1746987,"visible":true,"origin":"","legend":"","description":"","filename":"SI6compositesecchi.png","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/0feec15711bd928ea035af62.png"},{"id":82141021,"identity":"c7833ab3-17d2-4790-bbb5-23df989f6506","added_by":"auto","created_at":"2025-05-07 06:33:33","extension":"docx","order_by":8,"title":"","display":"","copyAsset":false,"role":"supplement","size":17595,"visible":true,"origin":"","legend":"","description":"","filename":"Table3.docx","url":"https://assets-eu.researchsquare.com/files/rs-6170350/v1/87445adb282e7292acd2d7c3.docx"}],"financialInterests":"","formattedTitle":"\u003cp\u003eCoFish: co-designing citizen science between fishers and scientists to monitor the phosphorus distribution across two Lake Geneva basins\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003ePeri-alpine lakes and their services\u003c/h2\u003e \u003cp\u003ePeri-alpine lakes are ecologically important habitats for a range of aquatic communities (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). They provide crucially important services for humans ranging from the provisioning of drinking water, fisheries and recreational activities. Optimal lake management that ensures the continuation of these services in times of environmental change, requires stakeholder engagement and balancing of priorities.\u003c/p\u003e \u003cp\u003eLake eutrophication in the 20th century caused important changes in the functioning and biodiversity of peri-alpine lakes, with the development of anoxia in deeper parts. Problems due to low oxygen have returned in recent years, this time linked to climate change, which is preventing full lake overturn in winter, creating a deep isolated layer, cut-off from the atmosphere (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) and the layers where oxygen is produced by photosynthesis. Warming is often claimed to create more favorable conditions for blooms of (toxic) cyanobacteria – “blooms like it hot”, see (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) for Lake Geneva, however, also see (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) for a contrasting opinion. In peri-alpine lakes, the dominant cyanobacterium \u003cem\u003ePlanktothrix rubescens\u003c/em\u003e seems to benefit from warm autumns and mild winters rather than hot summers (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Moreover, these peri-alpine lakes are impacted by invasive species like the quagga mussel, \u003cem\u003eDreissena bugensis\u003c/em\u003e (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e), which threatens to change the trophic structure and ecological functioning (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSetting the optimal nutrient levels requires to balance the needs for safe drinking water, \u003cem\u003ei.e.\u003c/em\u003e prevention of toxic algal blooms, with those for sustainable fisheries. To a certain extent, controlling eutrophication benefits both, e.g. Bninska (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e) showed how in Poland the fisheries yield for coregonids was substantially higher in lakes with good, than with poor water quality. The reduction of phosphorus levels has been a key strategy to restore water quality in eutrophic lakes, controlling blooms and enhancing biodiversity, e.g. (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e), while it also helped to mitigate negative effects of nutrient enrichment on coregonids and fisheries (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). However, for a set of peri-alpine lakes a reduction in total fish catches – dominated by coregonids and perch - have been reported below 20 µg/L (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), with minimal catches below 10 µg/L. A study by Alexander and Seehausen (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) gives a different perspective, with maximal coregonids biomass at TP levels below 10 µg/L. However, coregonids of small size seem to dominate in lakes of low TP, whereas for fisheries larger individuals are crucial (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). At lower levels of TP, balancing the different interests becomes more of a challenge. For example, in Lake Geneva, the present long-term TP goal of 10–15 µg/L, lowered from 20–30 µg/L in 2011, is based upon the consideration of various lake services, including fisheries. Yet, disagreements, rooted in different opinions about optimal TP-levels for different lake services remain. Sinclair et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) concur that an optimum – intermediate - nutrient level which can support both good water quality and high fishery yields may not exist, in particular if fisheries target species that differ in their sensitivity to lake productivity, like for perch and coregonids, the main species for Lake Geneva.\u003c/p\u003e \u003cp\u003eParticularly relevant for large lakes, is whether all parts of a lake have the same nutrient level, support the same productivity, pose similar risks for cyanobacterial blooms or see comparable fish catches (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). There is a sizeable literature on spatial variation in the sources of TP, both internal, i.e. nutrient release from lake sediments, e.g. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e) or external sources, (e.g. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) (Johnson and Nicholls, 1989; Zong et al., 2023). However, data on the spatial variation of dissolved phosphorus and TP in the water across a lake are surprisingly scarce, possibly due to the specific logistical and economic constraints of sampling a large lake over its full surface on a single day. Sometimes spatial variation in TP is visualized by looking at \u003cem\u003eChla\u003c/em\u003e patterns in a lake (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) or derived from satellite images using algorithms that link \u003cem\u003ein situ\u003c/em\u003e TP to reflectance data from “visible” lake parameters (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e)or by using water-quality 3D models (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGiven the known large spatial variability in large lakes, several publications provide advice on where best to locate a routine sampling point through use of satellite images or modeling (\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e–\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). For Lake Geneva, Soulignac et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e) also addressed this question through 3D modeling. The Soulignac study confirms that, despite strong spatial gradients in ecological quality (expressed as nutrients and \u003cem\u003eChla\u003c/em\u003e), the most representative point for the pelagic zone of Lake Geneva as a whole is situated in the central part of Grand Lac, not far from the reference station SHL2 (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Yet spatially explicit data on nutrient concentrations like TP that could have been used for direct validation of the model output, were not available. Citizen science could be one answer to allow wide scale lake sampling and thus capture some of the spatial variation as \u003cem\u003ein situ\u003c/em\u003e data, to help with interpretation of satellite images and model output.\u003c/p\u003e \u003cp\u003eCitizen science, broadly defined as the public’s participation in scientific research and knowledge production (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) and has been advocated as a way to gather vast amounts of environmental and ecological data whilst involving societal actors in the research process (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e). Despite the promise of the approach to promote community participation in conservation efforts, several ethical issues have been voiced (reviewed in (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e), relating to the potential of masking exploitation and unremunerated labor under a shield of “democratisation” of science (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). This has led to a call and a drive to a more meaningful engagement with research in all parts of the research cycle (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). Indeed, the co-production of knowledge, where citizens are involved in key parts of the research cycle, such as the formulation of the research and communication of results, has been recognized as a tool to help address some of the key sustainability issues of our time (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). Place-based community projects, centered around a locally rooted issue, and often co-designed to align with the community’s needs, have been highlighted as playing an important role to maximise the impact of the research, resulting in better environmental management and community action (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the case of water-based research, stakeholder engagement and co-design approaches have a long tradition (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e) and have resulted in the long-term monitoring of freshwater systems (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e) and collaborative water management of river catchments for example (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). Participatory management, with anglers in particular, is reported to have led to long-lasting learning outcomes (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e) as well as better environmental monitoring, conservation and advocacy (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). Collaboration with commercial fishers has further improved fisheries population models (e.g. crab fisheries of South Devon, UK), resulting in improved relations and trust between fishers and scientists (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). In Switzerland and France, the transdisciplinary Fischnetz network (1998–2004) was a very productive research partnership between administration, the chemical industry, fisheries associations and academic researchers, that resulted in 77 research projects and had a policy level impact that improved the state of Swiss watercourses(\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). Co-design of research and participatory fisheries management therefore can have a meaningful societal impact.\u003c/p\u003e \u003cp\u003eIn this article, we propose that citizen science and in particular co-designed citizen science, can provide a useful tool for monitoring of water quality of large lakes, as well as for the empowerment of fishers as citizen scientists. We illustrate this with CoFish, a co-designed research project between fishers and scientists on Lake Geneva. Though citizen science and participatory research are often cited to lead to a greater societal impact, the outcomes - other than the scientific output of the citizen science research itself - are not often measured reviewed in (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). This is problematic, especially given the institutionalisation of citizen science in some countries, e.g. UK, Austria, Germany that rely on evaluation and impact assessment for the continuity of particular funding schemes (40) as well as the importance of developing a more reflective approach to inform future programs. Several impact assessment frameworks, e.g.(\u003cspan additionalcitationids=\"CR40\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e–\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e) break down the impact of a project into five dimensions: science and technology, societal, environmental, political and economic. However, societal impacts are rarely reported alongside the scientific results.\u003c/p\u003e \u003cp\u003eThe CoFish project, that ran from 2021–2024 and was funded by the Swiss National Science Foundation, was initiated to in part to gain a better understanding of the lake ecosystem, but also to bridge academic with the local knowledge of commercial and recreational fishers, and in doing so the CoFish project also further brokered relations between local scientists, policy-makers, lake management and fishers. The project`s two main goals were therefore (i) to co-design an original research project with the fishers of Lake Geneva, and (ii) to evaluate the learning outcomes both for fishers and scientists.\u003c/p\u003e \u003c/div\u003e"},{"header":"Methods","content":"\u003ch2\u003eLake Geneva: situating the co-designed CoFish research project\u003c/h2\u003e\u003cp\u003eLake Geneva, Switzerland and France, is the largest and deepest lake in Western Europe and is an important source of drinking water for 900,000 people. It provides opportunities for recreational activities such as swimming, sailing, angling, hiking and biking around the lake, and it helps to attract tourists to the region. There is evidence of fishing activity in the lake since the Neolithic (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e), and to this day, 129 commercial fishers depend on the lake for their livelihoods, whilst it attracts a further 1000 recreational fishers. Yearly catches of the commercial fisheries amount from close to 1000 tons of whitefish as recent as 2013/2014 to less than 200 tons in the most recent years. For the other main target species, perch, catches decreased from nearly 1250 tons in the 1970s to ca. 1000 tons in the 1990s to some 250–500 tons this century, though this Figurecould partially reflect a shift in changing fishing efforts (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e) and may not fully reflect the size of the fish populations. Following a period of eutrophication in the 1950s – 1970s where the nutrient levels, phosphorus and nitrogen rose steeply, causing environmental problems like phytoplankton blooms and decrease in whitefish and arctic char catches, CIPEL, (International Commission for the Protection of the Waters of Lake Geneva), a Franco-Swiss intergovernmental body, that coordinates the water policies in the Lake Geneva watershed and monitors the water quality was created in 1963. CIPEL conducts bi-weekly to monthly sampling at the single sampling point, SHL2 (46.45270°N,6.58872°E, depth 309 m, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This point was chosen because it overlies the deepest point, and therefore samples could be collected to cover the entire depth of the water column. In addition, being central in the Central Lake Basin, Grand Lac, it was sufficiently far from the lake shore to not be overly affected by pollution coming from the land (Monod, 1983). Additionally, Canton Geneva monitors the lake at GE3 (46.29721°N,6.21994°E, depth 72 m,) in the Petit Lac, the Eastern lake basin. Over several decades the water quality, at least in terms of phosphorous concentrations, has improved and is now approaching the upper end of the long-term objective of an annual mean of C ( 10–15 µg/L)::\u003c/p\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:C=\\:{\\Sigma\\:}\\frac{\\left(Ci\\:.\\:Vi\\right)}{V}$$\u003c/div\u003e\u003c/div\u003e\u003cp\u003eWhere C is the weighted average of TP concentrations; \u003cem\u003eCi\u003c/em\u003e = concentration of TP in a depth layer; \u003cem\u003eVi\u003c/em\u003e = the volume of this layer, and V = the total volume of Grand Lac (86 km\u003csup\u003e3\u003c/sup\u003e).\u003c/p\u003e\u003ch3\u003eCo-design process\u003c/h3\u003e\u003cp\u003eResearchers at the University of Geneva initiated this project, motivated by the fact that as the lake has issues under the impact of a changing environment and there is an interest of fishers in participating in the project in a participatory research project that addressed this broad issue. The organisation of recreational fishers, FIPAL (Fédération Internationale des Pêcheurs Amateurs du Léman) became a partner in the project, already during the application stage. Firstly, presidents of the fishing clubs or unions were contacted for consultation and feedback. The CoFish goals were presented at local meetings where fishers were invited to contribute, which also resulted in the recruitment of commercial fishers via their own union, SIPPL (Syndicat Intercantonal des Pêcheurs Professionnels du Léman). Subsequent recruitment was led by the initially engaged fishers via their networks (social media, newsletters, presentations at local meetings). It is worth noting that in some instances this resulted in other lake users, e.g. lake police, contributing to some sampling campaigns. To prepare for the project, there were informal exchanges and interviews conducted to assess learning outcomes (Jenkins et al, in prep.). Some fishers indicated that they had contributed to scientific research in the past, yet they felt disappointed as there had been a lack of feedback on scientific results that were obtained. Commercial fishers sometimes distrusted science as they feared that scientific results may result in further fishing restrictions. In addition, they felt disempowered and lacking a voice in political discussions that have an impact on their fishing practices. Furthermore, they consider themselves to have detailed local knowledge and the potential to act as sentinels of the ecosystem. Therefore, developing a more collaborative approach and involving fishers in the monitoring of the lake could go a long way to remediate the relationships between diverse stakeholders.\u003c/p\u003e\u003cp\u003eA kick-off workshop took place on October 15th, 2021 where actors from both science and practice (recreational, commercial fishers, lake managers, NGOs) were invited to brainstorm about the future of the lake`s fish populations and the sustainability of the fisheries. We followed a 7-step Participatory Action Research process (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e) to co-design the research through a series of workshops and interviews (\u003cb\u003esee SI Table\u0026nbsp;1\u003c/b\u003e), inspired by methods in the td-net toolbox (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e). By the third workshop, fishers shared a growing concern that the lake may become too oligotrophic and therefore less able to support fish populations and lake fisheries. Fishers wondered whether the two reference points, SHL2 and GE3 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) monitored by CIPEL and Canton Geneva respectively were indeed still representative, decades after they were first selected (a period during which the lake underwent important changes in its environmental drivers, functioning and usage). They also questioned whether the 10–15 µg/L long term TP objective may already have been attained, at least in parts of the lake, for which there is no information given that monitoring is restricted to two locations only.\u003c/p\u003e\u003cp\u003eThe co-design process resulted in the following two coupled research questions:\u003c/p\u003e\u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eTo what extent do we observe spatial variation in total phosphorus (TP) and the biologically available form of phosphorus, orthophosphate (P-PO\u003csub\u003e4\u003c/sub\u003e) in the critical concentration range of 10–20 µg/L - for both phytoplankton biomass and fish stocks - in the productive layer of Lake Geneva?\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eTo what extent are SHL2 in Grand Lac and GE3 in Petit Lac, i.e. the long-term reference sampling points, representative locations for basin-wide levels of TP and P-PO\u003csub\u003e4\u003c/sub\u003e?.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e\u003ch3\u003eSampling\u003c/h3\u003e\u003cp\u003eTo answer the research questions, we decided to go back to the original points that were used by CIPEL to monitor Lake Geneva water in the 1950s (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). We divided the lake into 9–10 zones and each fisher team was given between 2–5 points to cover, close to the location of their usual fishing grounds. The fishers used their own fishing boats and guidance from Google Maps on mobile phones to navigate to the exact coordinates (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, SI Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Where required, members of the CoFish team joined to help individual fishers.\u003c/p\u003e\u003cp\u003eTo collect samples, we constructed 18m long integrated water sampler out of a garden hose, fitted with a cork stopper at one end and a 5kg weight at the other (see Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), following a design used in the European Multi Lake Survey (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e). We chose 18m as we aimed to get an integrated sample of the productive part of the Lake Geneva water column- defined by us as the sum of epi- and metalimnion- and this was estimated to be 18 m after consulting the platform alplakes.ch prior to campaign 1. While not the central objective of the study, we also measured lake transparency and trained fishers to use self-made Secchi disks. Average Secchi depths were calculated as the mean of the depth at which the Secchi disk was no longer visible and the depth that it starts to be visible again, once bringing it back up to the surface.\u003c/p\u003e\u003cp\u003eThe material was first tested by members of the core team and training videos and protocols were made in order to train the fishers in correct usage. Hands-on training took place when the sampling kits were distributed among the participants. A workshop before the sampling allowed for final troubleshooting and adjustments.\u003c/p\u003e\u003cp\u003eSampling occurred on the following dates to capture seasonal variation in physical structure of the water column and typical succession patterns of phytoplankton in deep lakes, following the PEG model (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e):\u003c/p\u003e\u003cul\u003e \u003cli\u003e \u003cp\u003eCampaign 1 (September 26, 2022): end of summer, maximum stratification strength, seasonal minimum in mixing depth, second annual peak in phytoplankton productivity.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eCampaign 2 (January 31, 2023): middle of winter, minimum stratification strength, deep winter mixing, low phytoplankton biomass.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eCampaign 3 (April 5, 2023): early lake stratification, time of spring phytoplankton bloom, typically the first annual peak in primary production.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eCampaign 4 (September 25, 2023): go full circle, comparison with September 2022\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e\u003cp\u003eOn the sampling day, the integrated sampler and all materials (e.g. bottles, buckets) were provided by the university, and were rinsed once with lake water prior to use and fishers then sampled the water, poured it into a clean bucket, and used to fill two pre-labelled bottles, which were stored on ice in the dark. Lake transparency was measured as Secchi depth. Samples were collected from the respective fishers by members of the CoFish team and returned to the laboratory at the University of Geneva laboratory within 24 hours for processing.\u003c/p\u003e\u003ch3\u003eLab analyses\u003c/h3\u003e\u003cp\u003eMethods were chosen to correspond to those used by the CIPEL for their long-term monitoring of the lake’s two reference points according to a reaction of acidic molybdate in the presence of antimony (EPA 365.3). All 36 stations were sampled in all four campaigns except CRG10 that was not sampled at the first campaign due to windy conditions. Orthophosphate measurements were conducted within 48 hours of sample collection.\u003c/p\u003e\u003cp\u003eIn the Geneva lab, samples were analysed for TP and P-PO\u003csub\u003e4\u003c/sub\u003e using a Seal Analytical AQ2, following protocols EPA 119-A-Rev. 7 and EPA 155-A, which is also based on a reaction of acidic molybdate in the presence of antimony. The limits of quantification were 3µg/L for both with a range of application 10-1000µg/L for TP and 3-300 µg/L for P-PO\u003csub\u003e4\u003c/sub\u003e. A second bottle was sent to Eawag, in a frozen state, where the measurements for total P and orthophosphate were repeated, initially to serve as an inter-laboratory comparison. The method also involved a spectrophotometric determination of TP and P-PO\u003csub\u003e4\u003c/sub\u003e after the reaction to phosphorus molybdenum blue complex,according to (\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e) using the Spectrophotometer Agilent Cary 60. Their method was more sensitive (range of application for TP 3-100µg/L and LOQ = 3µg/L and for P-PO\u003csub\u003e4\u003c/sub\u003e 1-100µg/L and LOQ = 1µg/L).\u003c/p\u003e\u003cp\u003eIn order to check whether our methods and labs produced similar results to those of the CIPEL, 10 samples from points in the French part of the lake were sent to the Observatoire des Lacs Alpins (OLA) at INRAE-CARRTEL, which is the laboratory that routinely runs the monitoring for CIPEL (see SI3).\u003c/p\u003e\u003ch2\u003eAnalysis of spatial variability\u003c/h2\u003e\u003cp\u003eWe visualise the distribution of measurements across the four sampling campaigns and compare where the standard points lie in relation to the mean and standard deviation of the distribution for that part of the lake basin on that day.\u003c/p\u003e\u003ch3\u003eAssessment of societal impacts of the project\u003c/h3\u003e\u003cp\u003eFor a parallel study on the learning outcomes of the fishers (Jenkins et al. in prep), semi-structured interviews were conducted with ten participants, five who participated in data collection and co-creation, and five only in data collection. Of these, five interviewees were commercial fishers and five were recreational. The interviews were adapted from (\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e) (\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e) (see SI 3) to measure dimensions of engagement and learning. Participants were subject to ethical procedures of the University of Geneva and informed consent to participate was obtained, with the right to withdraw their data at any time. The identities of interviewees were anonymised. Interviews were transcribed with the aid of the online software Happyscribe (Happy Scribe Ltd.) We used the Action Framework (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e) to categorise the individual parts of the transcripts into the five societal sub-dimensions that they identify: (i) community building and empowerment; (ii) social inclusion; (iii) researcher growth; (iv) knowledge skills and competences; (v) changes in ways of thinking, attitude and values, (vi) behavioural change.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eProfile and engagement of participants\u003c/h2\u003e \u003cp\u003eWe brought together 13 commercial (11 Swiss/2 French) and 19 recreational (15 Swiss/4 French) fishers, as well as 22 scientists from surrounding institutions such as the University of Geneva, UMRR CARRTEL (INRAE), Maison de la Rivi\u0026egrave;re, the University of Lausanne, the Geneva Museum, and a consultancy firm and public open lab, Hackuarium, to participate in one or more of the co-design workshops as co-researchers (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e), with a smaller proportion (23\u0026ndash;31%) belonging to the highly engaged sub-group, who attended more than half of the workshops. During the four sampling campaigns 9\u0026ndash;10 teams went out to sample and the effort was collectively shared amongst a total of 19 fishers, 1 fishing guard, 1 member of the lake police, 1 scuba diver and 5 scientists. Engagement numbers were greater for the data collection than for the codesign workshops, with over 60% of recreational fishers contributing to at least three sampling campaigns. Though the numbers of commercial fishers contributing to the sampling were lower, their engagement was high, with all fishers contributing to all four sampling campaigns. Scientists and other stakeholders were involved in the co-creation workshops in consulting roles at different time points. The lower engagement number of scientists by the end of the project reflects the fact that the project ended up taking a specific research line that was less relevant for the other scientists. Some scientists stayed on as part of the process despite this and almost half scientists that attended the kick-off attended the closing meeting to find out about the outcomes of the project.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe profile, number and engagement of participants in CoFish\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProfile\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber attending\u003c/p\u003e \u003cp\u003eco-design workshops\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEngagement\u003c/p\u003e \u003cp\u003eNumber attending more than 4 out of 8 workshops (% of total)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNumber participants in\u003c/p\u003e \u003cp\u003edata collection\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEngagement\u003c/p\u003e \u003cp\u003eNumber contributing to at least 3 campaigns (% of total)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ecommercial fishers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3(23)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6 (100)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRecreational fishers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6(31.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9 (64.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOthers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eScientists\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (13.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eHow variable is TP across the lake?\u003c/h2\u003e \u003cp\u003eTo answer the first research question, we report phosphorus measurements from the Eawag lab as the method was more sensitive to low phosphorus concentrations, although overall agreement between the University of Geneva, Eawag and INRAE measurements was acceptable (not shown). At the first sampling campaign, TP at CRG5 was 513 \u0026micro;g/L, which was \u0026gt;\u0026thinsp;20 times higher than all other values, which ranged from below the detection limit (\u0026lt;\u0026thinsp;3 \u0026micro;g/L) to almost 24 \u0026micro;g/L. This sample was also high in the Geneva lab. The reason for this high value is not known, possibly due to its proximity to wastewater treatment plants or due to a contamination in storing the water sample. Therefore, this point was excluded as an outlier from further analysis. There was substantial variation in lake phosphorus concentration across the lake and between the different sampling periods (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, \u003cb\u003eSI4\u003c/b\u003e).\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 1\u003c/b\u003e, the concentration of TP ranged from 6.5 to 23.4 \u0026micro;g/L. Concentrations at GE3 and SHL2 were similar at 19.3 and 17.7 \u0026micro;g/L, respectively. Both were approximately 6\u0026ndash;7 \u0026micro;g/L higher than the means of 12.5 and 10.9 \u0026micro;g/L for Petit and Grand Lac, falling well outside +/-1 SD of the mean (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea \u003cb\u003eand b\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 2\u003c/b\u003e, the concentration of TP ranged from 4.7 to 16.8 \u0026micro;g/L, with mean concentrations of 7.2 \u0026micro;g/L (Petit Lac) and 8.4 \u0026micro;g/L (Grand Lac). Concentration was highest at GE3, 3\u0026micro;g/L higher than the mean for Petit Lac falling outside the +\u0026thinsp;1 SD, whereas SHL2 was almost exactly the same as the mean \u003cb\u003e(\u003c/b\u003eFigs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec \u003cb\u003eand d\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 3\u003c/b\u003e, the concentration of TP ranged from 6.2 to 21.6 \u0026micro;g/L. GE3 was 2.3\u0026micro;g/L lower than the mean of 9.3 \u0026micro;g/L, placing it just 1SD below the mean for Petit Lac. TP at SHL2 was 5.5 \u0026micro;g/L higher than the mean for Grand Lac (12.2 \u0026micro;g/L), above 1 SD of the mean (Grand Lac) \u003cb\u003e(\u003c/b\u003eFigs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee \u003cb\u003eand f\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 4\u003c/b\u003e, the concentration of TP ranged from 3.4 to 34.7 \u0026micro;g/L. The means for Petit and Grand were similar (11.1 vs 11.4). TP at GE3 was very close to the mean for Petit Lac, while TP at SHL2 was almost 3\u0026micro;g/L lower, but well within 1 SD of the mean \u003cb\u003e(\u003c/b\u003eFigs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg \u003cb\u003eand h\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eOrthophosphate across the four sampling campaigns\u003c/h2\u003e \u003cp\u003eThe range of values for orthophosphate was less variable than TP with most values being between 3\u0026ndash;8 \u0026micro;g/L with a couple of values around 13\u0026micro;g/L (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, SI5).\u003c/p\u003e \u003cp\u003e \u003cb\u003eIn campaign 1\u003c/b\u003e concentrations ranged from 3.1 to 6.6 \u0026micro;g/L. In SHL2 and GE3 the concentrations were almost identical around 6\u0026micro;g/L, and higher than the mean values (4.7 and 3.9 \u0026micro;g/L in Petit and Grand Lac respectively, lying outside the +\u0026thinsp;1 SD of the distribution (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea \u003cb\u003eand b\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003e \u003cb\u003eIn Campaign 2\u003c/b\u003e P-PO4 concentrations ranged from 3.6 to 8.8 \u0026micro;g/L. Concentrations recorded at GE3 and SHL2 were close to the mean values 5.4 and 5.5 \u0026micro;g/L, being slightly higher for GE3 in Petit Lac and lower for SHL2, but well in the +/- 1SD of the mean of the distribution (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec \u003cb\u003eand d\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003cb\u003eCampaign 3\u003c/b\u003e P-PO4 concentrations ranged from 3\u0026ndash;13 \u0026micro;g/L. The concentration at GE3 was 0.6\u0026micro;g/L higher than the mean for Petit Lac (4.6 \u0026micro;g/L) and the concentration SHL2 was very close to the mean of 4.7 \u0026micro;g/L. Both fell within the +\u0026thinsp;1/- 1SD of the distribution (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee \u003cb\u003eand f\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003cb\u003eCampaign 4\u003c/b\u003e P-PO4 concentrations ranged from 3.9\u0026ndash;13.1 \u0026micro;g/L. The values at both reference stations were very close to the mean 4.6 and 4.7 \u0026micro;g/L for Petit Lac and Grand Lac, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg \u003cb\u003eand h\u003c/b\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eSecchi disk readings\u003c/h2\u003e \u003cp\u003eLake transparency, measured as Secchi disk depth, varied between stations and over the seasons and ranged more or less from a minimum of 5 m to a maximum of 15 m. It is worth noting that GE1 at the Rade de Gen\u0026egrave;ve (Petit Lac) is only 1.6m deep and so consistently gives a lower Secchi depth than other parts of the Lake, always with bottom visibility.\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 1\u003c/b\u003e, Secchi depths ranged from 5 to 8.5 m, and the observed values at the reference points were very close to the means of 6.2 and 6.9 m respectively, \u003cb\u003eFigure SI5 a,b, SI6a\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 2\u003c/b\u003e, Secchi depths ranged from 7 to 15.25 m. The Secchi depth at the reference points was close to the mean in Petit Lac and approximately 3 m deeper than the mean in Grand Lac, see \u003cb\u003eFigure SI5c,d, SI6b\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 3\u003c/b\u003e Secchi depths ranged from 4.75 to 15.25 m. The mean Secchi depth in Petit Lac was about 1m less than the depth recorded at GE3, whereas for Grand Lac the Secchi depth was very close to the mean close to 9m, see \u003cb\u003eFigure SI5e,f, SI6c\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eIn \u003cb\u003ecampaign 4\u003c/b\u003e, Secchi depths were shallow, ranging from 3.8\u0026ndash;6.9 m across the lake, with the depth at GE3 being 1.3m deeper than the mean and that at SHL2 a bit shallower than the average of 5m for Grand Lac, see \u003cb\u003eFigure SI5 g,h, SI6d\u003c/b\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eSocietal impacts of CoFish\u003c/h2\u003e \u003cp\u003eOut of the ten participants, one commercial fisher did not reply to a request for the final interview - we therefore omitted this person from the analysis.\u003c/p\u003e \u003cp\u003eAnalysis of the transcriptions of the nine interviews gave us insights into two out of the five dimensions of the Action Framework (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e) namely: (i) community building and empowerment; (ii) changes in knowledge skills and competences. The second was less surprising given the interview was designed to study learning outcomes (Jenkins et al, in prep). Seven out of nine interviewees expressed views of community empowerment, equally seven out of nine reported a change in knowledge, skills or competence as a result of CoFish (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e3\u003c/span\u003e for exemplary quotes). Furthermore, participants were willing to engage in future scientific research.\u003c/p\u003e \u003cp\u003eThrough the CoFish approach, the project results were more broadly communicated and made accessible, than would have been the case through a routine academic report or publication. For example, all participants communicated some project results within their communities informally (e.g. social circles), at general assemblies, on social media (e.g. videos of lab analyses with up to 2000 views), and standard news media (2 news stories), indicating the multiplier effect of the project. The closing meeting also was attended by authorities responsible for the water sampling: CIPEL and Swiss cantons, offering the opportunity to further bridge the gap between science and policy.\u003c/p\u003e "},{"header":"Discussion","content":"\u003cp\u003eWe co-designed a research study to investigate a question in response to concerns voiced by the commercial and recreational fishers that the two long term monitoring stations of Lake Geneva may no longer be representative of the lake as a whole in terms of total phosphorus and the biologically available form of phosphorus, orthophosphate (P-PO\u003csub\u003e4\u003c/sub\u003e). This concern clearly plays out against a backdrop in which fishers are worried that the lake is becoming too oligotrophic to sustain fish populations and therefore fisheries. By collaborating with commercial and recreational fishers on the same day across four campaigns, we were able to \u0026ndash; for the first time since the 1950s \u0026ndash; create empirical maps of TP and P-PO\u003csub\u003e4\u003c/sub\u003e distribution in Lake Geneva. This gave us three key scientific results: (i) that there is variability in phosphorus, both TP and P-PO\u003csub\u003e4\u003c/sub\u003e concentrations across the lake (3.4\u0026ndash;34.9 \u0026micro;g/L observed across campaigns); (ii) that in most cases, except for campaign 1, TP from SHL2 and GE3 fell within +/- 1SD of the mean, or very close to it, indicating that the values for these reference monitoring stations are mostly representative iii) for a great majority of stations the TP was less than 20 \u0026micro;g/L, many below 15 \u0026micro;g/L; this means that concentrations are mostly below threshold values of 15\u0026ndash;20 \u0026micro;g/L where TP can be expected to bring down phytoplankton biomass in peri-alpine lakes (\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e). Concentrations of P-PO4 are always below 10\u0026micro;g/L indicating that phosphorus may be limiting for many species (\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e).Furthermore, in some locations, the concentrations can reach 3 \u0026micro;g/L which is reported to be the threshold below which phosphorus can cause severe reduction in algal growth (\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e). We discuss these findings of the sampling campaign alongside the equally important societal outcomes of the project of greater empowerment of the fishers.\u003c/p\u003e \u003cp\u003eOur empirical results show variability in TP, and to a lesser extent orthophosphate across Lake Geneva. There are few studies that have empirically investigated spatial variability in nutrient levels in a lake. A study based on remote sensing data of Lake Chaohu in China by Gao et al. (2015) showed spatial variability in TP, derived from reflectance data. They further show how the representativeness of a reference station improved when TP data are used solely for the specific lake basin where i is located, rather than for the lake as a whole. This would seem to be true for Lake Geneva too, GE3 being the reference station for Petit Lac and SHL2 for Grand Lac, rather than either one for Lake Geneva as a whole. In fact, the two lake basins behave differently and have a distinct history of eutrophication and re-oligotrophication, as is evident in CIPEL data. So, SHL2 and GE3 \u003cem\u003eboth\u003c/em\u003e remain key locations to evaluate temporal changes in the lake basins.\u003c/p\u003e \u003cp\u003eWe ask the question to which extent SHL2 and GE3 are representative for their respective lake basins as a whole. For our purposes, we define representativity in statistical terms as being +/- 1SD of the mean. The results of campaign 1 indicate that GE3 and SHL2 are not representative for Petit and Grand Lac, as TP levels were much higher than the basin average. We hypothesise that the reason behind the high concentration at SHL2 during this first campaign may \u003cem\u003ein part\u003c/em\u003e be due to position of the thermocline of the lake on this day. The depth of the thermocline at SHL2 matched with the depth of the integrated water sample. Typically, in deep stratified lakes, phosphorous concentrations increase in the hypolimnion, data show several fold higher concentrations of both P-PO4 and TP in the hypo- compared to epilimnion of Lake Geneva in recent years (\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e). The results of 3D model of Lake Geneva, see (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e) for this day show that the position of the thermocline in Grand Lac was dome-shaped, with it being positioned higher in the water column in the center of the lake, where SHL2 is positioned, than closer to the shore. This then resulted in sampling closer to the hypolimnion at the reference station than in other stations, which could help explain the higher TP level recorded. In many large thermally stratified lakes, the thermocline tends to develop a dome shape, showing shallower thermocline depths in the center than in nearshore waters, e.g. described for Lake Erie by Beletsky et al. (\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e). In the other three campaigns, the TP and P-PO\u003csub\u003e4\u003c/sub\u003e values for SHL2 and GE3 were much closer to the basin-wide averages, in these cases suggesting that these reference stations can correctly inform us about the lake as a whole.\u003c/p\u003e \u003cp\u003eSoulignac et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e) studied the representativeness of SHL2 and GE3 for the ecological status of Lake Geneva (expressed as parameters like TP, NO\u003csub\u003e3\u003c/sub\u003e, NH\u003csub\u003e4\u003c/sub\u003e, \u003cem\u003eChla\u003c/em\u003e or Secchi disk). They took the median of the ecological status of all grid cells of the Delft 3D model they ran. An individual grid cell \u0026ndash; like SHL2 \u0026ndash; was then deemed representative if the ecological status was identical to the theoretical value for the lake as a whole. Clearly when using our measured data, we have a much coarser spatial distribution than the fine grid cells of a computer model. When looking at this uneven distribution of stations across the lake (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), a station like SHL2 in the middle of Grand Lac represents a much larger volume of Lake Geneva than a littoral station like VD4, since closer to the shore the sampling stations are closer together while widely spaced apart in the middle of the lake. Also, one would expect, and we see evidence for this in some of our littoral zone data, that given their proximity to the inflow of P from the land, TP or PO4 levels would be higher for near-shore stations than for open water. To obtain a lake mean for TP that truly represents the lake as a whole weighing the volumes of water represented by each station would be needed, comparable to what is done to get a weighted average with lake depth (see formula in Introduction). Data from CoFish will be very usfull for future modeling works as those data can be used to calibrate or validate the models.Given that there is spatial heterogeneity in large lakes like Lake Geneva \u0026ndash; as clearly visible in for instance sentinel images - no point in the lake can be truly representative. So, for monitoring purposes with a limited budget, lake managers usually try to localise the \u0026ldquo;most representative\u0026rdquo; point of a specific lake area or basin, and this point is used as a reference.\u003c/p\u003e \u003cp\u003eIs P limiting lake productivity?\u003c/p\u003e \u003cp\u003eGiven that the key research question in CoFish is clearly inspired by the fishers\u0026rsquo; apprehension that fish production is increasingly limited by low P-availability, we discuss several aspects of this. Almost all of the TP measurements in our data are below 20 \u0026micro;g/L, which according to M\u0026uuml;ller et al. (\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e) should limit phytoplankton biomass in Lake Geneva. It is worth noting that our samples come from the euphotic zone and not the entire water column and so may not be directly comparable to the CIPEL annual average, presently for TP, presently at 16.9 \u0026micro;g/L, getting very close to the upper limit of the long-term target of 10\u0026ndash;15 \u0026micro;g/L. Actually, since the lake does not fully mix, the CoFish data show that limiting concentrations for phytoplankton growth are already reached early in spring in the productive \u0026ndash; upper \u0026ndash; part of the water column of the lake. Over the past years, Lake Geneva has provided good quality drinking water and abundant fish biomass. Such an \u0026ldquo;ideal\u0026rdquo; setting was thanks to a decrease in TP concentrations after a period of eutrophication in the 1960-70s. When P-levels are brought down to restore lakes from eutrophication, the fish community composition changes, so that salmonids and piscivorous species like pike increased, see for example (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). However, at the time of writing of Gerdeaux et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), it was expected that the overall fish production would decrease when phosphorus concentrations would start to drop below 20 \u0026micro;g/L.\u003c/p\u003e \u003cp\u003eA sensitive, but important question to ask now becomes whether a further reduction of TP, to perhaps 10 \u0026micro;g/L, is required to safeguard the lake against future blooms, likely at the expense of a reduced fish biomass? Additionally, there is increasingly strong variation in the concentration of TP over depth. As outlined in the Introduction, a lack of winter overturn is locking-away the elevated P-levels in the deeper parts of the lake, which do no longer become available for primary production through deep winter mixing. Salmaso et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e) speak of oligotrophication of the euphotic layer. Therefore, it becomes all the more important to consider hydrodynamic processes, which are changing under impact of climate-warming for the identification of nutrient levels that balance lake usages. Whereas the risks of blooms under a warming climate remain real, augmented by extreme events in precipitation or temperature, as witnessed by the \u003cem\u003eUroglena\u003c/em\u003e bloom in Lake Geneva in 2021 (\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e), further re-oligotrophication may result in further \u0026ndash; already ongoing - depletion of biological communities, like zooplankton, and lead to a potentially impoverished lake ecosystem.\u003c/p\u003e \u003cp\u003eTo enter into a bit more detail, the major arguments for controlling P in deep lakes that have suffered from eutrophication are to: (i) avoid anoxia in deeper layers, (ii) reduce the risk of blooms of nuisance / harmful algae, cyanobacteria in particular and (iii) to support lake biodiversity. Are these historical arguments that set the control of phosphorus into motion in the 1970s still valid in our time? Hypoxia is once again a problem in Lake Geneva, like in the eutrophic years, and the legal limit of 4 mg O\u003csub\u003e2\u003c/sub\u003e per L is no longer met in the deepest parts of the lake; however reducing TP further will probably not solve hypoxia, since phosphorus is not its leading cause (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). In deep lakes, oxygen concentrations are strongly driven by water mixing processes, in particular a lack of full winter overturn and increased duration of the period of thermal stratification (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e). Blooms of cyanobacteria clearly increase with nutrient levels, and risks of nuisance or harmful levels of cyanobacteria at the long-term TP level of 10\u0026ndash;15 \u0026micro;g/L would indeed be much reduced (\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e). However, blooms, defined here as a period in which levels of phytoplankton are elevated above the long-term average causing discoloration of the lake, are part of the normal functioning of lakes, and will continue to occur, even in oligotrophic systems (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). It may therefore not be realistic to avoid blooms altogether.\u003c/p\u003e \u003cp\u003eOptimal P levels to conserve biodiversity is a tricky, multi-faceted issue. Based upon long term data from 11 peri-alpine lakes, the optimum TP-level for whitefish seems to be between 20\u0026ndash;30 \u0026micro;g/L (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). When re-oligotrophication continues and TP drops to values below 10\u0026ndash;20 \u0026micro;g/L, coregonid catches may decrease significantly, albeit still higher than during the most eutrophic years. On the other hand, perch catches peaked in the eutrophic years, likely due to reduced competition for zooplankton. At levels below 20\u0026ndash;30 \u0026micro;g/L TP, however catches of perch became much reduced. Overall, Gerdeaux et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e) state that where total fish biomass decreases below 10 \u0026micro;g/L TP, biomass increases at TP levels between 10\u0026ndash;15 \u0026micro;g/L, while further increases above 20 \u0026micro;g/L do not further enhance fish biomass.\u003c/p\u003e \u003cp\u003eConversely, what is the risk of blooms of nuisance or harmful algae at TP levels between 15\u0026ndash;20 \u0026micro;g/L, a concentration that seems fairly optimal for fisheries? If we focus on the main toxic species in peri-alpine lakes, the metalimnetic red cyanobacterium \u003cem\u003ePlanktothrix rubescens\u003c/em\u003e, it is hard to find critical TP levels below which this cyanobacterium disappears. Clearly factors other than TP play a role, in particular climate change impacts. For example, Suarez et al. (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e) studied Lake Hallwil and showed that \u003cem\u003ePlanktothrix\u003c/em\u003e was absent during the eutrophic period. With re-oligotrophication \u003cem\u003ePlanktothrix\u003c/em\u003e returned and peaked around TP levels of 50 \u0026micro;g/L. Further reduction of TP did bring \u003cem\u003ePlanktothrix\u003c/em\u003e down, but the species is still present, albeit now at a position well below the metalimnion. \u003cem\u003ePlanktothrix\u003c/em\u003e did not show a real presence in Lake Constance until recently when TP levels had dropped below 10 \u0026micro;g/L(\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e) (Fournier et al., 2021). In contrast, for Lake Bourget (France) controlling phosphorus levels (TP reduction from 33 to 14 \u0026micro;g/L) was a key factor in the disappearance of \u003cem\u003ePlanktothrix\u003c/em\u003e blooms from the lake (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e). Knapp et al (\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e) discuss how, under the impact of climate warming, seasonal patterns in the physical structure of the water column of Lake Zurich (Switzerland) are changing and how this can have both positive (shallower lake winter overturn) and negative (instability in the thermocline during spring) effects on \u003cem\u003ePlanktothrix\u003c/em\u003e, which remains a dominant species in this lake.\u003c/p\u003e \u003cp\u003eThe impact of the participatory approach\u003c/p\u003e \u003cp\u003eThere were several benefits of adopting a participatory approach both in terms of scientific findings and societal outcomes. First of all, we would not have had this type of information on lake wide variation in TP. In order to gather this type of data on the same day, a citizen science approach was required, as it would have been impossible for a single, or even a few researchers to visit this many stations in one day. Our simple hosepipe method \u0026ndash; not our invention, see (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e) could be a useful technique for further citizen water science, being cheap and effective.\u003c/p\u003e \u003cp\u003eThe main societal impacts of the participatory approach were the formation of an engaged community of lake stewards. These people had felt disempowered and sometimes disappointed by previous experiences in scientific projects. They expressed a great sense of allegiance to the group and in interviews expressed empowerment and the feeling they could achieve action towards an \u0026ldquo;ecological transition\u0026rdquo;. They felt more confident in participating and even more empowered to use the results in policy relevant processes, therefore also leaning towards a more policy level impact, often included as part of the societal impact in other frameworks, e.g.(\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). There were multiple learning outcomes that are further explored elsewhere (Jenkins et al. in prep).\u003c/p\u003e \u003cp\u003eAs with any approach, there were several shortcomings to our interviews. The questions were designed to focus on engagement and learning outcomes rather than all dimensions of societal impact. It is therefore possible that there are other impacts that we did not measure and that remain unreported. Results were disseminated actively by fishers themselves indicating ownership and pride in the quality of the data meaning that the results of the study were communicated effectively outside the strictly academic circles. One participant, in particular, who had not previously contributed to scientific research has since contributed to several other projects, and some have since become partners on future projects. The results were presented to CIPEL, who participated and contributed to the final workshop. Several collaborations are planned with fishers in the future: one project is already under way. However, the lack of funding to sustain citizen science efforts is a perennial issue.\u003c/p\u003e \u003cp\u003eSeveral lessons were learned regarding the -codesign process, summarised in (\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e). Briefly, these involve the time it takes to successfully run a co-design process, the need for good and neutral communication, and the need for having the trust of both ambassadors anchored in the community but also the benefits of being perceived as a neutral outsider. Important discussions for project planners are whether participants are renumerated for their work. These fit into larger debates guiding citizen science research and the benefits and pitfalls of financial rewards (\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOur data broadly support Soulignac et al.\u0026rsquo;s model-based conclusion (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e), that the use of the reference stations is an acceptable compromise, in particular for the large open water spaces of the lake. However, monitoring of the littoral zones, whose renaturation is one the key action points for CIPEL may require additional efforts, that could be complemented by a citizen science approach.\u003c/p\u003e \u003cp\u003eGenerally, among the authors of this paper, who represent academic scientists and fishers, there is an agreement that with the present TP levels further reduction may risk further impoverishment of zooplankton and a number of commercially important fish species. It is further encouraging that cyanotoxin levels in Lake Geneva are at a low level, which does not pose public health risks (\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e). In addition, with the ongoing invasion of quagga mussels in the lake, the P-cycling and availability of P for the pelagic food web is under increasing pressure, see (\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e), requiring in itself re-evaluation of the role of phosphorous in the pelagic food web. Setting optimal TP levels therefore remains challenging.\u003c/p\u003e \u003cp\u003eFinally, we report empowerment of the community of fishers by the co-design process. Perhaps most importantly however is the longer-term effect of a community of scientifically engaged fishers, contributing to the conservation of the lake. We further advocate for citizen science projects to measure and report societal outcomes of projects alongside the scientific results.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eall procedures were approved by the University of Geneva Ethical Board (CUREG-2021-08-82). Participants signed informed consent forms \u0026nbsp;and their identities were anonymised.\u0026nbsp; Interviews were transcribed with the aid of the online software Happyscribe (Happy Scribe Ltd.) and transcripts were deleted from the cloud after use.\u003c/p\u003e\n\u003cp\u003eEthical approval is not required to sample water from the lake and we do not conduct or report on experiments on human participants.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003ethis manuscript does not contain personal data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe dataset TP and P-PO4 dataset is currently being reviewed in Dryad \u0026nbsp;https://doi.org/10.5061/dryad.73n5tb379.\u003c/p\u003e\n\u003cp\u003eAnonymised interview transcripts are available on request from the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors state no competing interests.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e CoFish was an SNSF funded COST project - \u003cem\u003eIZCOZ0_198179\u0026nbsp;\u003c/em\u003eawarded to B.J.S and B.W.I.. The kick-off workshop was co-funded by a grant awarded to T.J. by the Mercator Foundation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eT.J., B.J.S. and B.I. conceived the idea behind CoFish. T.J. and E.R. designed the co-creation methodology; D.C., L.F., A.F., Y.D.,\u0026nbsp;M.D., N.R., L.L., B.I., T.J., E.R., M.A.,O.A. co-designed the research question and the sampling methodology. O.A. gave input on the historical sampling of SHL2. D.C., L.F., A.F., Y.D., M.D., N.R., P.A., M.A., M.G., collected the data; R.F., M.A. ,Y.M.,P.A. conducted the lab analysis. M.K.T. provided input on data analysis. T.J., B.W.I. and O.A. wrote the manuscript. All authors contributed critically to the drafts and gave final approval for publication.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSeveral people supported this work at various stages of the project with discussions,: \u0026nbsp;Adrian Aeschlimann, Marc Babut, Isabel Blasco Costa, Tom Boersen, Jakob Broedersen, Till Bruckermann, Egle Butkeviciene, Jonas Bylemans, Franck Cattaneo, Joelyn de Lima, Nicole Gallina, Rudolf Gerber, Christian Gillet, Chlo\u0026eacute; Goulon, Jean Guillard, Fr\u0026eacute;d\u0026eacute;ric Hofmann, Dimitri Jaquet, Kostas Kampourakis, Sylvain Kramer, , Alexandre Lemopoulos, Jean-Daniel Morel, Ilan Page, Theres Paulsen, Alexandra Sa Pinto, Baptiste Paquereau, Peter Ehrensperger, Guy-Charles Monney, Pierre Marle, Maxime Prevedello, Livio Riboli Sasco, Alexandre Richard, Tiina St\u0026auml;mpfli, Jean-Jacques Steiner, Hugues W\u0026uuml;rsten, Daniel W\u0026uuml;thrich, Candice Yvon, Bernard Carridroit, Henri-Daniel Champier, Ren\u0026eacute; Luthi. td-net (Sibylle Studer, Theres Paulsen) is acknowleged for its consultancy on co-design and transdisciplinary research principles.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe are grateful to the following for data collection Laurent Charenton, Jean Jacquier, Jean-Claude Doriot, Morgane Lef\u0026eacute;v\u0026egrave;re, Natalino Lucchetta, Michel Picotin, Yannick Rosset, Jet Osmankaq, Patrice Valentin, la Brigade du Lac, \u0026nbsp;S\u0026eacute;bastian Leblanche, Cedric Henry.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePhosphorus concentrations at SHL2\u0026nbsp;\u003c/strong\u003e are contributed by the Observatory of alpine Lakes (OLA), \u0026copy; SOERE OLA-IS, AnaEE-France, INRAE at Thonon-les-Bains and CIPEL\u003c/p\u003e\n\u003cp\u003eWe thank the Mus\u0026eacute;e du L\u0026eacute;man and Anne-Sophie Deville for hosting several of our workshops.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAuthor information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis article is the outcome of a joint collaboration between fishers L.F., A.F., D.C., Y.D., M.D., N.R., L.L. and researchers at academic instiutions T.J., O.A., P.A. ,M.A., R.F., M.G., Y.M., M.K.T, B.J.S., E.R., B.W.I.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRapin F, Blanc P, Pelletier JP, Balvay G, Gerdeaux D. Impacts humains sur les syst\u0026egrave;mes lacustres: exemple du L\u0026eacute;man. 1995; \u003c/li\u003e\n\u003cli\u003eSoares L, Desgu\u0026eacute;‐itier O, Barouillet C, Casenave C, Domaizon I, Frossard V, et al. Unraveling Lake Geneva\u0026rsquo;s hypoxia crisis in the Anthropocene [Internet]. Limnology and Oceanography Letters. Wiley; 2024. Available from: https://hal.inrae.fr/hal-04727996\u003c/li\u003e\n\u003cli\u003eHuisman J, Codd GA, Paerl HW, Ibelings BW, Verspagen JM, Visser PM. Cyanobacterial blooms. Nat Rev Microbiol. 2018;16(8):471\u0026ndash;83. \u003c/li\u003e\n\u003cli\u003eAnneville O, Domaizon I, Kerimoglu O, Rimet F, Jacquet S. Blue-Green Algae in a \u0026ldquo;Greenhouse Century\u0026rdquo;? New Insights from Field Data on Climate Change Impacts on Cyanobacteria Abundance. Ecosystems [Internet]. 2015 Apr 1;18(3):441\u0026ndash;58. Available from: https://doi.org/10.1007/s10021-014-9837-6\u003c/li\u003e\n\u003cli\u003eReinl KL, Harris TD, North RL, Almela P, Berger SA, Bizic M, et al. Blooms also like it cold. Limnol Oceanogr Lett [Internet]. 2023 Aug 1 [cited 2025 Feb 11];8(4):546\u0026ndash;64. Available from: https://doi.org/10.1002/lol2.10316\u003c/li\u003e\n\u003cli\u003eKraemer BM, Boudet S, Burlakova LE, Haltiner L, Ibelings BW, Karatayev AY, et al. An abundant future for quagga mussels in deep European lakes. Environ Res Lett [Internet]. 2023 Nov 7;18(12):124008. Available from: https://dx.doi.org/10.1088/1748-9326/ad059f\u003c/li\u003e\n\u003cli\u003eKaratayev AY, Burlakova LE. What we know and don\u0026rsquo;t know about the invasive zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels. Hydrobiologia [Internet]. 2022 Oct 13; Available from: https://doi.org/10.1007/s10750-022-04950-5\u003c/li\u003e\n\u003cli\u003eBninska M. Commercial fisheries versus water quality in lakes with special reference to coregonid management. Fish Manag Ecol [Internet]. 2000 Feb 1 [cited 2024 Dec 3];7(1\u0026ndash;2):105\u0026ndash;14. Available from: https://doi.org/10.1046/j.1365-2400.2000.00199.x\u003c/li\u003e\n\u003cli\u003eIbelings BW, Fastner J, Bormans M, Visser PM. Cyanobacterial blooms. Ecology, prevention, mitigation and control: Editorial to a CYANOCOST Special Issue. Aquat Ecol [Internet]. 2016 Sep 1;50(3):327\u0026ndash;31. Available from: https://doi.org/10.1007/s10452-016-9595-y\u003c/li\u003e\n\u003cli\u003eLepori F, Capelli C. Effects of phosphorus control on primary productivity and deep-water oxygenation: insights from Lake Lugano (Switzerland and Italy). Hydrobiologia [Internet]. 2021 Feb 1;848(3):613\u0026ndash;29. Available from: https://doi.org/10.1007/s10750-020-04467-9\u003c/li\u003e\n\u003cli\u003eEckmann R, Gerdeaux D, Muller R, R\u0026ouml;sch R. Re-oligotrophication and whitefish fisheries management - a workshop summary. In: 9 International Symposium on the Biology and Management of Coregonid Fishes [Internet]. Olsztyn, Poland; 2005. Available from: https://hal.inrae.fr/hal-02832476\u003c/li\u003e\n\u003cli\u003eGerdeaux D, Anneville O, Hefti D. Fishery changes during re-oligotrophication in 11 peri-alpine Swiss and French lakes over the past 30 years. Acta Oecologica. 2006;30(2):161\u0026ndash;7. \u003c/li\u003e\n\u003cli\u003eAlexander T, Seehausen O. Diversity, distribution and community composition of fish in perialpine lakes. Proj Lac\u0026raquo; Synth Rep. 2021;282. \u003c/li\u003e\n\u003cli\u003eSinclair JS, Fraker ME, Hood JM, Reavie ED, Ludsin SA. Eutrophication, water quality, and fisheries: a wicked management problem with insights from a century of change in Lake Erie. Ecol Soc [Internet]. 2023;28(3). Available from: https://www.ecologyandsociety.org/vol28/iss3/art10/\u003c/li\u003e\n\u003cli\u003eLesht BM, Scofield AE, Bockwoldt KA. Lake-wide measurements of primary productivity in Lake Erie. Aquat Ecosyst Health Manag [Internet]. 2024 Jan 1 [cited 2024 Nov 25];27(1):30\u0026ndash;45. Available from: https://doi.org/10.14321/aehm.027.01.30\u003c/li\u003e\n\u003cli\u003eGao Y, Gao J, Chen J. Spatial variation of surface soil available phosphorous and its relation with environmental factors in the Chaohu Lake watershed. Int J Environ Res Public Health. 2011;8(8):3299\u0026ndash;317. \u003c/li\u003e\n\u003cli\u003eWu T, Qin B, Brookes JD, Yan W, Ji X, Feng J. Spatial distribution of sediment nitrogen and phosphorus in Lake Taihu from a hydrodynamics-induced transport perspective. Sci Total Environ [Internet]. 2019 Feb 10;650:1554\u0026ndash;65. Available from: https://www.sciencedirect.com/science/article/pii/S0048969718335897\u003c/li\u003e\n\u003cli\u003eJohnson MG, Nicholls KH. Temporal and Spatial Variability in Sediment and Phosphorus Loads to Lake Simcoe, Ontario. J Gt Lakes Res [Internet]. 1989 Jan 1;15(2):265\u0026ndash;82. Available from: https://www.sciencedirect.com/science/article/pii/S0380133089714817\u003c/li\u003e\n\u003cli\u003eZong Y, Chen SS, Kattel GR, Guo Z. Spatial distribution of non-point source pollution from total nitrogen and total phosphorous in the African city of Mwanza (Tanzania). Front Environ Sci [Internet]. 2023;11. Available from: https://www.frontiersin.org/articles/10.3389/fenvs.2023.1084031\u003c/li\u003e\n\u003cli\u003eOstrovsky I, Yacobi YZ. Temporal evolution and spatial heterogeneity of ecosystem parameters in a subtropical lake. In 2009. \u003c/li\u003e\n\u003cli\u003eGao Y, Gao J, Yin H, Liu C, Xia T, Wang J, et al. Remote sensing estimation of the total phosphorus concentration in a large lake using band combinations and regional multivariate statistical modeling techniques. J Environ Manage [Internet]. 2015 Mar 15;151:33\u0026ndash;43. Available from: https://www.sciencedirect.com/science/article/pii/S0301479714005775\u003c/li\u003e\n\u003cli\u003eSoulignac F, Danis PA, Bouffard D, Chanudet V, Dambrine E, Gu\u0026eacute;nand Y, et al. Using 3D modeling and remote sensing capabilities for a better understanding of spatio-temporal heterogeneities of phytoplankton abundance in large lakes. J Gt Lakes Res [Internet]. 2018 Aug 1;44(4):756\u0026ndash;64. Available from: https://www.sciencedirect.com/science/article/pii/S0380133018300807\u003c/li\u003e\n\u003cli\u003eDabrowski T, Berry A. Use of numerical models for determination of best sampling locations for monitoring of large lakes. Sci Total Environ [Internet]. 2009 Jul 1;407(14):4207\u0026ndash;19. Available from: https://www.sciencedirect.com/science/article/pii/S0048969709002502\u003c/li\u003e\n\u003cli\u003eKarabork H. Selection of appropriate sampling stations in a lake through mapping. Environ Monit Assess [Internet]. 2010 Apr 1;163(1):27\u0026ndash;40. Available from: https://doi.org/10.1007/s10661-009-0813-0\u003c/li\u003e\n\u003cli\u003eLi J, Tian L, Wang Y, Jin S, Li T, Hou X. Optimal sampling strategy of water quality monitoring at high dynamic lakes: A remote sensing and spatial simulated annealing integrated approach. Sci Total Environ [Internet]. 2021 Jul 10;777:146113. Available from: https://www.sciencedirect.com/science/article/pii/S0048969721011803\u003c/li\u003e\n\u003cli\u003eStrasser BJ, Baudry J, Mahr D, Sanchez G, Tancoigne E. \u0026ldquo;Citizen Science\u0026rdquo;? Rethinking Science and Public Participation. Sci Technol Stud. 2019;52\u0026ndash;76. \u003c/li\u003e\n\u003cli\u003eFraisl D, Hager G, Bedessem B, Gold M, Hsing PY, Danielsen F, et al. Citizen science in environmental and ecological sciences. Nat Rev Methods Primer. 2022;2(1):64. \u003c/li\u003e\n\u003cli\u003eTauginienė L, Hummer P, Albert A, Cigarini A, Vohland K. Ethical challenges and dynamic informed consent. Sci Citiz Sci. 2021;397. \u003c/li\u003e\n\u003cli\u003eMirowski P. The future(s) of open science. Soc Stud Sci [Internet]. 2018 Apr 1 [cited 2024 Apr 9];48(2):171\u0026ndash;203. Available from: https://doi.org/10.1177/0306312718772086\u003c/li\u003e\n\u003cli\u003eHaklay M. Citizen science and volunteered geographic information: Overview and typology of participation. In: Crowdsourcing geographic knowledge. Springer; 2013. p. 105\u0026ndash;22. \u003c/li\u003e\n\u003cli\u003eNorstr\u0026ouml;m AV, Cvitanovic C, L\u0026ouml;f MF, West S, Wyborn C, Balvanera P, et al. Principles for knowledge co-production in sustainability research. Nat Sustain [Internet]. 2020 Mar 1;3(3):182\u0026ndash;90. Available from: https://doi.org/10.1038/s41893-019-0448-2\u003c/li\u003e\n\u003cli\u003evan Noordwijk T, Bishop I, Staunton-Lamb S, Oldfield A, Loiselle S, Geoghegan H, et al. Creating positive environmental impact through citizen science. Sci Citiz Sci. 2021;373\u0026ndash;95. \u003c/li\u003e\n\u003cli\u003eConallin JC, Dickens C, Hearne D, Allan C. Chapter 7 - Stakeholder Engagement in Environmental Water Management. In: Horne AC, Webb JA, Stewardson MJ, Richter B, Acreman M, editors. Water for the Environment [Internet]. Academic Press; 2017. p. 129\u0026ndash;50. Available from: https://www.sciencedirect.com/science/article/pii/B9780128039076000073\u003c/li\u003e\n\u003cli\u003eCollins JP. Gene drives in our future: challenges of and opportunities for using a self-sustaining technology in pest and vector management. BMC Proc [Internet]. 2018;12(Suppl 8):9. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6069294/\u003c/li\u003e\n\u003cli\u003eFujitani M, McFall A, Randler C, Arlinghaus R. Participatory adaptive management leads to environmental learning outcomes extending beyond the sphere of science. Sci Adv. 2017;3(6):e1602516. \u003c/li\u003e\n\u003cli\u003eGranek EF, Madin EM, Brown MA, Figureueira W, Cameron DS, Hogan Z, et al. Engaging recreational fishers in management and conservation: global case studies. Conserv Biol. 2008;22(5):1125\u0026ndash;34. \u003c/li\u003e\n\u003cli\u003ePearson E, Hunter E, Steer A, Arscott K, Hart PJ. Fishermen and scientists in the same boat. A story of collaboration in the UK South Devon crab fishery. Collab Res Fish Co-Creat Knowl Fish Gov Eur. 2020;27\u0026ndash;41. \u003c/li\u003e\n\u003cli\u003eHolm P, Hadjimichael M, Mackinson S, Linke S. Bridging Gaps, Reforming Fisheries. In: Collaborative Research in Fisheries. Springer; 2020. p. 279\u0026ndash;303. \u003c/li\u003e\n\u003cli\u003eWehn U, Gharesifard M, Ceccaroni L, Joyce H, Ajates R, Woods S, et al. Impact assessment of citizen science: state of the art and guiding principles for a consolidated approach. Sustain Sci [Internet]. 2021 Sep 1;16(5):1683\u0026ndash;99. Available from: https://doi.org/10.1007/s11625-021-00959-2\u003c/li\u003e\n\u003cli\u003eKieslinger B, Sch\u0026auml;fer T, Heigl F, D\u0026ouml;rler D, Richter A, Bonn A. Evaluating citizen science. Citiz Sci Innov Open Sci Soc Policy Bonn Hecker Haklay M Bowser Makuch Z Vogel J Eds. 2017;81\u0026ndash;96. \u003c/li\u003e\n\u003cli\u003ePassani A, Janssen A, H\u0026ouml;lscher K, Di Lisio G. A participatory, multidimensional and modular impact assessment methodology for citizen science projects. Fteval J Res Technol Policy Eval. 2022;(54):33\u0026ndash;42. \u003c/li\u003e\n\u003cli\u003eBaulaz Y. Chroniques de la p\u0026ecirc;che fran\u0026ccedil;aise au L\u0026eacute;man. 2019 Jan 18; \u003c/li\u003e\n\u003cli\u003eCIPEL. Tableau de Bord [Internet]. Nyon: CIPEL: Commission internationale pour la protection des eaux du L\u0026eacute;man; 2023. Available from: https://www.cipel.org/wp-content/uploads/2024/01/tb-cipel-2023.pdf\u003c/li\u003e\n\u003cli\u003eCohen L, Manion L, Morrison K. Research methods in education. routledge; 2017. \u003c/li\u003e\n\u003cli\u003ePohl C, Wuelser G. Methods for Coproduction of Knowledge Among Diverse Disciplines and Stakeholders. In: Hall KL, Vogel AL, Croyle RT, editors. Strategies for Team Science Success: Handbook of Evidence-Based Principles for Cross-Disciplinary Science and Practical Lessons Learned from Health Researchers [Internet]. Cham: Springer International Publishing; 2019. p. 115\u0026ndash;21. Available from: https://doi.org/10.1007/978-3-030-20992-6_8\u003c/li\u003e\n\u003cli\u003eMantzouki E, Campbell J, Van Loon E, Visser P, Konstantinou I, Antoniou M, et al. A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins. Sci Data. 2018;5(1):1\u0026ndash;13. \u003c/li\u003e\n\u003cli\u003eMonod, R. Le L\u0026eacute;man: synth\u0026egrave;se des travaux de la Commission internationale pour la protection des eaux du L\u0026eacute;man contre la pollution. Lausanne: CIPEL: Commission internationale pour la protection des eaux du L\u0026eacute;man; 1984 p. 67. \u003c/li\u003e\n\u003cli\u003eSommer U, Adrian R, De Senerpont Domis L, Elser JJ, Gaedke U, Ibelings B, et al. Beyond the Plankton Ecology Group(PEG) Model: Mechanisms Driving Plankton Succession. Annu Rev Ecol Evol Syst. 2012;43(429):2012. \u003c/li\u003e\n\u003cli\u003eVogler P. Beitr\u0026auml;ge zur Phosphatanalytik in der Limnologie. Die Bestimmung des gel\u0026ouml;sten Orthophosphates. Fortschr Wasserchem Grenzgeb 109-119. 1965;2:109\u0026ndash;19. \u003c/li\u003e\n\u003cli\u003ePhillips TB, Ballard HL, Lewenstein BV, Bonney R. Engagement in science through citizen science: Moving beyond data collection. Sci Educ [Internet]. 2019 May 1 [cited 2020 Mar 30];103(3):665\u0026ndash;90. Available from: https://doi.org/10.1002/sce.21501\u003c/li\u003e\n\u003cli\u003eLederman NG, Abd‐El‐Khalick F, Bell RL, Schwartz RS. Views of nature of science questionnaire: Toward valid and meaningful assessment of learners\u0026rsquo; conceptions of nature of science. J Res Sci Teach. 2002;39(6):497\u0026ndash;521. \u003c/li\u003e\n\u003cli\u003eLederman JS, Lederman NG, Bartos SA, Bartels SL, Meyer AA, Schwartz RS. Meaningful assessment of learners\u0026rsquo; understandings about scientific inquiry\u0026mdash;The views about scientific inquiry (VASI) questionnaire. J Res Sci Teach. 2014;51(1):65\u0026ndash;83. \u003c/li\u003e\n\u003cli\u003eM\u0026uuml;ller B, Steinsberger T, St\u0026ouml;ckli A, W\u0026uuml;est A. Increasing Carbon-to-Phosphorus Ratio (C:P) from Seston as a Prime Indicator for the Initiation of Lake Reoligotrophication. Environ Sci Technol [Internet]. 2021 May 4;55(9):6459\u0026ndash;66. Available from: https://doi.org/10.1021/acs.est.0c08526\u003c/li\u003e\n\u003cli\u003eSas H. Lake restoration by reduction of nutrient loading: Expectations, experiences, extrapolations. SIL Proc 1922-2010 [Internet]. 1990 Dec 1;24(1):247\u0026ndash;51. Available from: https://doi.org/10.1080/03680770.1989.11898731\u003c/li\u003e\n\u003cli\u003eSuttle CA, Harrison PJ. Ammonium and phosphate uptake rates, N: P supply ratios, and evidence for N and P limitation in some oligotrophic lakes 1. Limnol Oceanogr. 1988;33(2):186\u0026ndash;202. \u003c/li\u003e\n\u003cli\u003eRasconi S., Rimet F., Perney, P. Rapports sur les \u0026eacute;tudes et recherches entreprises dans le bassin L\u0026eacute;manique, campagne 2023. [Internet]. Nyon: CIPEL: Commission internationale pour la protection des eaux du L\u0026eacute;man; 2024. Available from: htttp//www.cipel.org\u003c/li\u003e\n\u003cli\u003eBeletsky D, Hawley N, Rao YR. Modeling summer circulation and thermal structure of Lake Erie. J Geophys Res Oceans [Internet]. 2013 Nov 1 [cited 2024 Nov 25];118(11):6238\u0026ndash;52. Available from: https://doi.org/10.1002/2013JC008854\u003c/li\u003e\n\u003cli\u003eSalmaso N, Anneville O, Straile D, Viaroli P. European large perialpine lakes under anthropogenic pressures and climate change: present status, research gaps and future challenges. Hydrobiologia [Internet]. 2018 Nov 1;824(1):1\u0026ndash;32. Available from: https://doi.org/10.1007/s10750-018-3758-x\u003c/li\u003e\n\u003cli\u003eIrani Rahaghi A, Odermatt D, Anneville O, Sep\u0026uacute;lveda Steiner O, Reiss RS, Amadori M, et al. Combined Earth observations reveal the sequence of conditions leading to a large algal bloom in Lake Geneva. Commun Earth Environ [Internet]. 2024 May 1;5(1):229. Available from: https://doi.org/10.1038/s43247-024-01351-5\u003c/li\u003e\n\u003cli\u003eAnneville O, Beniston M, Gallina N, Gillet C, Jacquet S, Lazzarotto J, et al. L\u0026rsquo;empreinte du changement climatique sur le L\u0026eacute;man. Arch Sci. 2013;66:157\u0026ndash;72. \u003c/li\u003e\n\u003cli\u003eChorus I, Fastner J, Welker M. Cyanobacteria and cyanotoxins in a changing environment: Concepts, controversies, challenges. Water. 2021;13(18):2463. \u003c/li\u003e\n\u003cli\u003eSuarez EL, De Ventura L, St\u0026ouml;ckli A, Ord\u0026oacute;\u0026ntilde;ez C, Thomas MK, Ibelings BW, et al. The emergence and dominance of Planktothrix rubescens as an hypolimnetic cyanobacterium in response to re‐oligotrophication of a deep peri‐alpine lake. Limnol Oceanogr. 2023;68(6):1346\u0026ndash;59. \u003c/li\u003e\n\u003cli\u003eFournier C, Riehle E, Dietrich DR, Schleheck D. Is Toxin-Producing Planktothrix sp. an Emerging Species in Lake Constance? Toxins. 2021;13(9). \u003c/li\u003e\n\u003cli\u003eJacquet S, Kerimoglu O, Rimet F, Paolini G, Anneville O. Cyanobacterial bloom termination: the disappearance of Planktothrix rubescens from Lake Bourget (France) after restoration. Freshw Biol [Internet]. 2014 Dec 1 [cited 2024 Nov 25];59(12):2472\u0026ndash;87. Available from: https://doi.org/10.1111/fwb.12444\u003c/li\u003e\n\u003cli\u003eKnapp D, Fern\u0026aacute;ndez Castro B, Marty D, Loher E, K\u0026ouml;ster O, W\u0026uuml;est A, et al. The Red Harmful Plague in Times of Climate Change: Blooms of the Cyanobacterium Planktothrix rubescens Triggered by Stratification Dynamics and Irradiance. Front Microbiol [Internet]. 2021;12. Available from: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.705914\u003c/li\u003e\n\u003cli\u003eJenkins T, Jenkins T, participants C. Guide de bonnes pratiques des sciences participatives avec les p\u0026ecirc;cheurs et p\u0026ecirc;cheuses du L\u0026eacute;man. University of Geneva. 2024. \u003c/li\u003e\n\u003cli\u003eRutten M, Minkman E, van der Sanden M. How to get and keep citizens involved in mobile crowd sensing for water management? A review of key success factors and motivational aspects. WIREs Water [Internet]. 2017 Jul 1 [cited 2024 Oct 9];4(4):e1218. Available from: https://doi.org/10.1002/wat2.1218\u003c/li\u003e\n\u003cli\u003eNiveen Ismail and Paul Seguin and Lola Pricam and Elisabeth Janssen and Tamar Kohn and Bas Ibelings and Anna Carratala. Seasonality of cyanobacteria and eukaryotes in Lake Geneva and the impacts of cyanotoxins on growth of the model ciliate Tetrahymena pyriformis. 2025 Jan 25;279. Available from: https://infoscience.epfl.ch/handle/20.500.14299/246362\u003c/li\u003e\n\u003cli\u003eVanni MJ. Invasive mussels regulate nutrient cycling in the largest freshwater ecosystem on Earth. Proc Natl Acad Sci [Internet]. 2021 Feb 23 [cited 2025 Feb 27];118(8):e2100275118. Available from: https://doi.org/10.1073/pnas.2100275118\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 3","content":"\u003cp\u003eTable 3 is available in the Supplementary Files section.\u003c/p\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-ecology-and-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"evob","sideBox":"Learn more about [BMC Ecology and Evolution](http://bmcevolbiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/evob/default.aspx","title":"BMC Ecology and Evolution","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"phosphorus, fisheries, citizen science, co-design, lake, spatial variation","lastPublishedDoi":"10.21203/rs.3.rs-6170350/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6170350/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEutrophication, followed by re-oligotrophication during lake restoration, in many peri-alpine lakes has caused important changes to the functioning and biodiversity of freshwater ecosystems. In Lake Geneva, total phosphorus (TP) concentration has been reduced since the eutrophic years, and is now close to the upper value of the target range of 10-15 µg/L. For over 60 years the lake has been monitored at SHL2, the central and deepest point in the Eastern basin, complemented by data from GE3 in the Western basin. Selection of these reference points was based on a lake-wide analysis of TP in the 1950s. Fishers have for some time expressed concerns that further reductions in TP could damage the sustainability of their livelihoods. They have called for a re-evaluation of the historical sampling points to determine whether SHL2 and GE3 can still be considered representative in terms of nutrient concentration of the lake.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHere, we present the scientific and societal impacts of CoFish, a co-designed research project between scientists and fishers of Lake Geneva. To reassess the spatial variability of TP we applied a low-cost method to collect integrated water samples across the lake, using stoppered hosepipes as a collection instrument. In this article, we present four key messages:\u003c/p\u003e\n\u003cp\u003ei) There is spatial variation in phosphorous levels, and in most cases the two points fall withinan acceptable range of variability;\u003c/p\u003e\n\u003cp\u003eii) The concentrations of phosphorus are generally low across the lake in ranges that could have an impact for plankton development.\u003c/p\u003e\n\u003cp\u003eiii) Citizen science can complement long-term monitoring, allowing for instance for better spatial coverage of environmental data;\u003c/p\u003e\n\u003cp\u003eiv) The co-design process resulted in community empowerment, a willingness to further collaborate.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe management implications of this work are that using a single reference station as being representative for the lake as a whole is not straightforward. In the discussion we advocate for a re-evaluation of the TP targets, given radical changes in the lake`s physical structure and food web. We further highlight the important role of engaging fishers in citizen science, which resulted in bridging existing gaps between lake management, science and fisheries, providing a broader basis for lake conservation.\u003c/p\u003e","manuscriptTitle":"CoFish: co-designing citizen science between fishers and scientists to monitor the phosphorus distribution across two Lake Geneva basins","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 06:33:28","doi":"10.21203/rs.3.rs-6170350/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-09T07:03:46+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-03T13:24:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"76274018173669142808240917850771761792","date":"2025-04-28T13:03:17+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-25T12:42:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"147899799817670898716921097517575435080","date":"2025-04-01T12:41:15+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-18T08:14:13+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-17T20:52:14+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-17T08:41:18+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Ecology and Evolution","date":"2025-03-17T08:40:09+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-ecology-and-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"evob","sideBox":"Learn more about [BMC Ecology and Evolution](http://bmcevolbiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/evob/default.aspx","title":"BMC Ecology and Evolution","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ae0e612c-fd4a-4a6a-8066-d9754f2a92c1","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-11-03T23:23:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-07 06:33:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6170350","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6170350","identity":"rs-6170350","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}