Pampa plain (Argentina) wetland history through a lake case study: Kakel Huincul Environmental History during the last 600 years

Pampa plain (Argentina) wetland history through a lake case study: Kakel Huincul Environmental History during the last 600 years | 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 Pampa plain (Argentina) wetland history through a lake case study: Kakel Huincul Environmental History during the last 600 years Guillermina Sánchez Vuichard, Marcela Sandra TONELLO, Silvina Stutz, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1712174/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Jan, 2023 Read the published version in Wetlands → Version 1 posted 5 You are reading this latest preprint version Abstract Wetlands are considered key ecosystems because of the greatest number of ecosystem services they provide, but despite their important role these ecosystems are decreasing in size and losing quality. Kakel Huincul lake is located in one of the main wetlands of Argentina. A multi-indicator analysis, including pollen, non-pollen palynomorphs and plant macrofossil remains was performed to reconstruct Kakel Huincul lake environmental history in order to understand Pampean wetlands responses to environmental changes and human impacts during the last 600 years. Results showed that changes in the lake communities before 1880 AD were a result of climatic perturbations (increase/decrease rainfall), and after 1880 AD they were a combination of climatic (increases and decreases of precipitation values) and anthropic forcings (cattle, intensive agriculture and urbanization). Baseline conditions were established at ca . 1870 AD and it was concluded that southeastern Pampa plain has been subjected to human activities (cattle farming and incorporation of agriculture) since then. Eutrophication of the lake occurred during the last 25 years, but this study made it possible to establish that the Pampa wetland has been modified for more than five decades ago. human activities climatic impacts eutrophication SE of South America Late Late Holocene Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Nowadays, wetlands are internationally recognized as the most productive ecosystems that provide the greatest number of ecosystem services to society, also playing a fundamental role in the development of many cultures on the planet (Benzaquen et al. 2017). At the same time, they have an exceptional biodiversity, which makes them areas of great value for protection and conservation, supported by international agreements such as the Ramsar Convention and the International Convention of Biological Diversity (Bobbink et al. 2006). This has led to the consideration of wetlands as key ecosystems, particularly for their role in the storage and purification of water and in their intervention in hydrological cycles. However, on a global scale, these ecosystems are decreasing in size and losing quality. Since the industrial era, human impacts have become dramatically negative and wetlands have suffered alterations ranging from drainage, water retention for reservoirs, use as discharge areas for toxic substances, landfill for urbanization developments and other actions that have gone unnoticed (Benzaquen et al. 2017). As a result, the services they provide also disappear or are restricted. The latest evaluations show that in the 20 th century the global extent of wetlands decreased between 64 and 71% (Kandus et al. 2018), bringing out that most surviving wetland systems require active management and/or restoration work to bring them back to a sustainable state of ecosystem health. One of the many fascinating aspects of wetlands is their ability to preserve an archive of their own history in the accumulating body of sediments beneath the surface. The sedimentary record can be thought of as an archive of monitoring data collected over centuries and millennia (Bunting and Whitehouse 2008), which may be analyzed to reconstruct changes in hydrology and in biological community composition and dynamics through time. This information is valuable to those who are interested in studying the ecological dynamics of the past and to those who have more applied goals, such as wetland creation, enhancement, and restoration (Williams 2011). Effective conservation requires both, a detailed knowledge of the ecology of the concerned biota including the development of habitats and ecosystems through time, and how species have responded to environmental and anthropogenic changes. For the restoration design of some ecosystems, it is also desirable to have adequate knowledge of the pre-disturbance conditions as a starting point (Williams 2011). These conditions are those present in the absence of anthropogenic influence, also termed as baseline or reference conditions (Davies and Bunting 2010). Paleoecological studies of wetland sedimentary deposits offer the possibility of obtaining accurate reconstructions of baseline conditions and ecosystem´s dynamics in the past (e.g. Bennion et al. 2011, 2018; Davidson et al. 2011; Kowalewski et al. 2016). Argentina (southern South America) has a huge variety and quantities of wetlands, which are located in a wide strip, from 33º to 54ºS, and from 2300 m asl in the Andes to the coastal plain of the Atlantic Ocean; and take up the 21.5% (600,000 km 2 ) of the country (Neiff 2001, Kandus et al. 2008). These ecosystems are home to outstanding biodiversity, while providing valuable services for the well-being of society, and were relatively free of the impacts derived from human activities and therefore preserved their original extent, structure and functions until a few decades ago. These conditions began to change due to the intensification of some productive activities and the incorporation of new types of land use and water management, which implied a substantial alteration of the hydrological regime (Benzaquen et al. 2017). The national inventories of wetlands are currently recognized as essential tools for designing policies and other aspects leading to their conservation and rational use (Benzaquen et al. 2017). Resource inventories have traditionally been aimed at answering questions concerning, for example, their type, location and abundance. However, the increasing need for more effective management has expanded the scope to include wetlands functioning and the assessment of consequences resulting from environmental changes and human impacts (Kandus et al- 2018). In the current context of global warming, rapid changes in land use and the current state of transformation and degradation of our country`s wetlands, makes it necessary to advance in the understanding of their functioning and their management, for their conservation and wise use. The Pampa plain, southeastern Argentina, contains one of the main wetlands of the country (Quirós 2005, Kandus et al. 2008) characterized by countless shallow lakes (Geraldi et al. 2011). Past environmental changes of these ecosystems were studied by López-Blanco et al (2021) for the last 700 years, Laprida et al. (2009) and Laprida and Valero Garcés (2009) for the last 500 years, and by Córdoba et al. (2014), Guerra et al. (2015) and Plastani et al. (2019) at high resolution during the last 200 years. In particular, the last 600 years is a key time frame due to pampean shallow lakes established their current configuration regarding trophic level and biological communities, in a landscape characterized by a greater stability associated to a generalized humid climatic conditions similar to modern ones (Stutz et al. 2014; Messineo et al. 2019; De Francesco et al. 2021). This broader temporal frame would allow disentangling climatic from anthropic drivers. The modern landscape has been influenced by human activities since the European settlement in the 1600s, but cattle and agriculture became intensive at 1850-1900 AD. The environments have deteriorated and lost biodiversity, largely due to the land mismanagement associated with extending the surface for agricultural and livestock production, and the misuse of agrochemicals in intensive agriculture (Monti et al. 2017; Bermann et al. 2022). In particular, agrochemical dumps produces increases in algae population in lakes and rivers, affects biodiversity and lake functioning and leads to a degradation of the wetland due to the eutrophication processes (Sequeira et al. 2015; Auer et al. 2019). There are several studies that evaluated the current functioning and account for these changes (e.g. Allende et al. 2009; O’Farrell et al. 2011; Mancini et al. 2013; Sánchez et al. 2015, 2017; Cano et al. 2016; Schiaffino et al. 2019; Quiroga et al. 2021). However, monitoring programs of past lake evolution defining their status prior to anthropic impact are still scarce. The baseline conditions were identified for the first time at central Pampa plain (Cabeza de Buey lake) at ca. 1850 AD, while the onset of intense eutrophication was established ca. 1990 AD based on pollen, non pollen palynomorphs analysis and plant macrofossil remains (Sánchez Vuichard et al. 2021). These baseline conditions were defined as those before intensive cattle and agriculture in the area, whereas the eutrophication was associated to agriculture intensification implemented in the landscape, as well as to the establishment of towns in the surroundings. In southeastern Pampa plain there are several eutrophic shallow lakes subjected to climate dynamics and anthropic impact during the last 600 years. Thus, the objective of this study is to reconstruct the Kakel Huincul lake´s biological community structure and dynamics in the last 600 years, and to establish baseline conditions, documenting subsequent changes until present. The study is based on the analysis of pollen, Non Pollen Palynomorphs (NPPs) and plant macrofossil remains and associated fauna from a sedimentary record. The provided information will contribute to the national wetland inventories in order to understand Pampean wetlands responses to environmental changes and human impacts, for future management and conservation plans. Study site Kakel Huincul (36° 48'S, 57° 47'W) is an elongated shallow lake (20 km 2 , up to 4 m deep) located in the southeastern Pampa plain in Argentina (South America). The region is characterized by the presence of several lakes of variable size, placed on a stabilized aeolian landscape of parabolic and blowout dunes (Fig. 1A, B). Most of these lakes have an aeolian origin with a prevailing west-southwest wind direction during the late Pleistocene. During the Holocene, with the establishment of more humid conditions, the basins became lakes and were filled with sediments (Zárate and Tripaldi 2012; Tripaldi and Zárate 2016). Kakel Huincul lake is considered permanent, but water level can be diminished during periods of drought. The landscape where the lake is located is dominated by livestock (cows) and croplands (e.g. soybean, flax), with small patches of native vegetation , dominated by grasses of the genus Stipa , Piptochaetium and Aristida , with several accompanying herbs such as Phyla sp., Carex sp., Adesmia sp., Alternanthera sp., Pamphalea sp., Vicia sp. and Eryngium sp. (Leon 1991, Tonello 2006). According to Sanchez (2012), the lake is profusely colonized by submerged macrophytes, mainly Myriophyllum aquaticum (Vell.) Verdc. and Ceratophyllum demersum L, and by emergent macrophytes such as Schoenoplectus californicus (C.A. Mey.) Soja´k, Alternanthera philoxeroides (Mart.) Griseb . , Solanum glaucophyllum Desf. and Hydrocotyle ranunculoides L. f. At the study site, several Gleditsia triacanthos L., Eucalyptus spp., Salix spp., Fraxinus sp., Pinus spp. and Cupressus sp. trees grow on the dune next to the lake and in the estancia Kakel (Figs. 1B, C). According to Aliaga et al. (2017) climatic subregions classification, Kakel Huincul lake is located in an area considered as extremely humid. The climate is temperate with annual mean temperature of 15.5°C that presents an annual pattern with a maximum of 29°C in January and a minimum of 4°C in July. Annual precipitation is 995 mm, and rainfall occurs mainly from spring (September) to autumn (March), with a maximum of 109 mm in January and a minimum of 59 mm in August (Estación Meteorológica Aeródromo de Dolores, 36°19´S, 57°43´W, Servicio Meteorológico Nacional). Land transformation Since the first European settlements the native vegetation of Pampa plain was modified. Around 1540 AD, large herbivores such as cows and horses were introduced. Initially, cattle breeding was restricted to Buenos Aires city but expanded into the Pampa plain by the end of the 1800s, increasing the introduction and dispersal of native and exotic weed seeds (Garavaglia 1999). Since 1810, the extensive livestock farming advanced on lands still occupied by indigenous communities. This expansion was not homogeneous neither in space nor time due to geographical and ecological differences as well as to the difficulties related to the conquest of indigenous territories (Sánchez 2017; Banzato et al. 2011; Sánchez Vuichard 2019). After 1880 AD, increasing population caused new transformations in the landscape. A significant transformation was the planting of trees from vegetation units adjacent to grasslands (e.g. Celtis tala (Klotzsch) Liebm. and Senegalia bonariensis (Gillies ex Hook. & Arn.) Seigler & Ebinger) or exotic trees as peridomestic forests (e.g. Populus spp. and Eucalyptus spp) and fruit trees (e.g. Prunus spp. and Malus spp.). During the 1900s, a period of major agricultural development arose with cereal crops, accompanied by a succession of technological improvements. Thus, the Pampa plain presented large areas with crops and cultivated pastures that replaced the native vegetation and promoted the invasion of exotic weeds. During the mid-1970s, the soybean crop generated structural and functional changes like the decrease in livestock activity, the increase in the use of agrochemicals and the intensity of soil tillage, together with different methods to handle crop residues (Ghersa and Martinez Ghersa 1991). As a result, an increase in the diversity of weeds associated with crop species was observed. At 1996, new soybean transgenic varieties were implemented, resulting in soil degradation due to the decrease in the organic matter content and the loss of nutrients (Viglizzo et al. 2001; Pengue 2009). Particularly, the first farmer settlements in Kakel Huincul lake area date back to 1812 and for several years it was a territory shared with indigenous population. The livestock activity started in 1855 AD in the present day estancia Kakel (Guzmán, 1999) and became the main activity because the extremely flat landscape, edaphic features and periodic flooding limited the agriculture. After 1960 some crops (e.g. flax, sunflower and corn) were planted in the area, in small patches. By the end of 1980s 60% of the grassland of the southeastern Pampa plain remained uncultivated (Viglizzo et al. 2001). Demographic growth occurred after 1880 with the arrival of the railroad and the Maipú town foundation 17 km westward from the lake. Currently Kakel Huincul is a eutrophic shallow lake used for recreation and hosts fishing and water sports (Sánchez 2012). Methods And Materials Two sediment cores, KH2 (122 cm) and KH3 (31 cm), were recovered with a vibracorer and a Gravity corer, both equipped with a 5 cm inner diameter tube and operated from a platform in November 2015 and April 2017, respectively (Fig. 1B). The stratigraphy was characterized by granulometry and color based on visual descriptions on KH2. In addition, the organic matter content was analyzed on KH2 and KH3 in order to correlate both cores, and carbonates content was analyzed on KH3. This correlation allowed unifying date information in a single temporal profile, and to get a reliable age-depth model. Samples were treated according to loss-on-ignition (LOI) procedure (Heiri et al. 2001). Results are expressed as percentage of weight loss of the sediment related to the dry weight of the samples at 105°C before combustion. The age-depth model was based on two radiocarbon dates (Table 1) and sixteen 210 Pb dates on KH2, and a chronomarker and the coring date (2017) on KH3. The timing of environmental changes was constrained by 210 Pb/ 137 Cs and 14 C AMS dating. Excess 210 Pb and 137 Cs were measured on 20 samples between 0 and 20 cm depth and analyses were performed at Laboratoire de Radiochronologie-Centre d’ études nordiques, Université Laval (Quebec, Canadá). Ages were calculated using the CRS model which assumes that excess 210 Pb has been supplied to the sediment at a constant rate. Radiocarbon dating was measured on bulk sediment by means of an AMS spectrometer at DirectAMS (Radiocarbon Dating Service) and at Accelerator Mass Spectrometry Laboratory (Seattle, Washington, USA). Radiocarbon ages were calibrated with the Southern Hemisphere calibration curve (SHCal20, Hogg et al. 2020) and smooth spline regressions with smoothing level of 0.4 were applied. In addition, age associated with the introduction of Eucalyptu s spp. (chronomarker) (Sánchez Vuichard et al. 2021), and the age assigned to the top core, were incorporated to the chronology. Finally, the age-depth model was performed by using CLAM 2.2 (Blaauw 2010), a code written in R language (R CoreTeam 2020). The KH3 core was subsampled and pollen and NPPs (non-pollen palynomorphs) analysis was performed at 1 cm intervals, and plant macrofossil remains and associated fauna analysis was performed at 2 cm intervals from 0 to 12 cm depth, and at 1 cm intervals from 13 to 28 cm depth. Samples for pollen and NPPs analysis were prepared following standard techniques, using warm KOH10%, HCl10%, heavy-liquid separation with ZnCl 2 , HF and acetolysis (Bennett and Willis 2001). Two Lycopodium clavatum L. tablets were added before treatment. Pollen sums varied between 500 and 1000 pollen grains. Abundance of each pollen type was calculated as a percentage of the total pollen sum (excluding Eucalyptus , Pinus/Cedrus, Other exotic and long distance trees pollen). NPPs, pollen of Eucalyptus , Pinus/Cedrus and Other exotic trees as well as long distance trees pollen were calculated as a percentage of the pollen sum plus the sum of each group of taxa. Percentages of Azolla filiculoides Lam. , Ricciocarpos natans (L.)Cordaand and Bryophyta spores were calculated as a percentage of the pollen sum plus spores sum. Other exotic trees include Casuarina, Betula , Cupressus , Corylus and Juglans ; Long distance trees include Schinus , Alnus , Podocarpus and Nothofagus dombeyi (Mirb.) Oerst.-type . Other herbs include Chrysanthemum , Rubiaceae, Lamiaceae, Papilionoideae, Solanaceae, Verbenaceae, Rutaceae, Euphorbiaceae, Caryophyllaceae, Ephedra , Rosaceae, Erodium , Onagraceae, Malvaceae, Geraniaceae, Scrophullariaceae and Monocotyledoneae. The identification of pollen grains, spores and NPPs were made with reference to atlases, published keys and the reference collection of the Laboratory of Paleoecology and Palynology, IIMyC CONICET-UNMdP. Samples for plant macrofossil remains and associated fauna were treated with KOH10% for 4 h and sieved through 200 and 100 μm meshes. The volume of each sample was calculated by water displacement, and varied between 5 and 10 cm 3 , and the residue was examined under a stereo-microscope at 50x magnification. Recognizable plant and animal fossils were isolated, identified and counted and the results were expressed in number of remains per 10 cm 3 of sediment. Animal remains (cladocerans ephippia, briozoos statoblasts, gastropods carbonatic shells, chironomid head capsules and ostracods valves) were grouped as associated fauna, but were not taxonomically classified in genus and/or species. The animal fossils were recovered because of their size retained in the mesh; their inclusion does not intend to represent the entire assemblage of each group, just merely give an approximation of them and reinforce the interpretations based on the other indicators, since each type of organism-indicator requires a specific methodology. In particular, zooplankton ephippia remains can be used to infer changes in fish population density and shifts in habitat structure as well as changes in macrophyte density with nutrient enrichment (Bennion et al. 2018 and cites there in). Given their intermediate and important position in the food-web, zooplankton data complement the plant macrofossil records and hence are reported briefly here. Stratigraphic diagrams were plotted with Tilia 2.0.41 (Grimm 2015). The samples were classified by a restricted clustering analysis using the distance of Edwards and Cavalli-Sforza as a measure of dissimilarity. Cluster analysis was performed with CONISS software included in the Tilia-Graph package (Grimm 2015). Pollen, NPPs and plant macrofossils remains were considered for the zonation and CONISS cluster dendrograms are displayed on the right side of the diagrams (Figs. 4, 5) Vascular plant nomenclature follows the database Flora del Conosur, Catálogo de las Plantas Vasculares published online by the Instituto de Botánica Darwinion (http://www.darwin.edu.ar/Proyectos/FloraArgentina/fa.htm). Results Lithology, organic matter and carbonates content Three sedimentary units were defined on KH2 based on variations in sediment lithology (Fig. 2A). The basal Unit A, up to 22 cm, presents massive, black clayed-silty sediments with gastropod presence. Unit B, between 22-19 cm, contains massive, grayish-silty sediments with gastropod presence. The contact between these two units is net and planar. Unit C, between 19-0 cm, comprises massive, brownish-silty, bioturbated sediments. This unit is characterized by a high presence of plant roots. The contact between this unit and the underlying unit is net and planar. The organic matter content values were similar in both cores (KH2 and KH3) and presented the same trends (Fig. 2B). From the base to 20 cm, the values fluctuated between 8% and 19.5%. In the interval between 20 and 7 cm, the organic matter content increased and reached maximum values of up to 55%. A decrease was observed from 6 cm in KH3 with values around 49%, and from 4 cm in KH2 reaching values of 39%. The carbonates content showed a contrary trend between (30-24) cm and (6-0) cm and a similar trend between (24-6) cm to the organic matter content. The values fluctuated between 8.5% and 3.5% from the base to 23 cm, then slightly increased up to 6.5% at 4 cm, and decreased up to 4% to the top (Fig. 2B). The correlation of cores was based on the organic matter content (Fig. 2B). Four apparent features in both cores were used as specific tie points: first, the low values of organic matter at the base of both cores (≥ 12%); second, the decrease of organic matter values (from 20 to 14%); third, the points at 20 cm before the increase in matter organic content, and fourth, when the maximum values start to decline. Chronology An important issue in the chronology of lacustrine sequences in Pampa plain, is the incorporation of the pollen of Eucalyptus spp. as chronomarker in the age-depth model, since that corresponds to exotic trees introduced in the region at 1858 AD. According to the criteria established by Sánchez Vuichard et al. (2021), the first appearance of Eucalyptus spp. pollen at 16 cm depth on KH3 core was assigned to an age of 1880 AD. The activity of 137Cs was used to validate the ages obtained from the 210 Pb chronology, considering the activity peak of 137 Cs at 9 cm as the one corresponding to 1963 AD. According to the age-depth model, the uppermost 30 cm of KH3 core spanned the time between ca .1360 and 2017 years AD (last 600 years)(Fig. 3C). Pollen, NPPs and plant macrofossil remains and associated fauna According to the cluster analysis, four pollen and NPPs assemblage zones (PKH 1-4) (Fig. 4) and three plant macrofossil assemblage zones (MKH 1-3) (Fig. 5) were established. PKH 1 (1360 to 1550 AD; 580 to 390 cal years BP).This zone was characterized by the maximum values of Poaceae and Chenopodioideae (≤53% and ≤47%, respectively), accompanied by Ambrosia and Cyperaceae (≤37% and ≤26%, respectively). Chenopodioideae had the highest values at the base and decreased towards the top of the zone. Rumex presented the highest values (≤2%). Diverse emergent macrophytes, such as Alternanthera , Polygonum and Typha were present with values of up to 10%. Among the NPPs, Pediastrum dominated the zone (≤30%). PKH 2 (1550 to 1670 AD; 390 to 280 cal years BP). This zone was characterized by Poaceae, Ambrosia , Cyperaceae and Chenopodioideae (≤30%, ≤27%, ≤28% and ≤16%, respectively). Carduss , Plantago and Brassicaceae were also present. The other emergent macrophytes were present with similar values that those of the previous zone, although Polygonum was not longer present and Phyla nodiflora appeared in low values. Towards the top of the zone, Myriophyllum began to increase its values. Among the NPPs, Pediastrum dominated the zone with its maximum values (≤62%), accompanied by Scenedesmus, Botryococcus braunii and Tetraedron (≤10%). PKH3 (1670 to 1870 AD; 280 to 80 cal years BP). This zone was dominated by Myriophyllum , which presented the maximum values (≤54%) of the spectra, followed by Cyperaceae and Ambrosia (35% and 20%, respectively). Ceratophyllum demersum increased towards the top of the zone. The other emergent macrophytes maintained the same values as in the previous zone, with the reappearance of Polygonum towards the end of the zone. Among the NPPs, a trend towards a more abundant and diverse community was recognized. Gloeotrichia dominated the zone (≤31%), accompanied by Pediastrum (≤20%), and to a lesser extent by Desmidiaceae, Botryococcus braunni , Tetraedron and Scenedesmus . PKH 4 (1870 to 2017 AD; 80 to -67 cal years BP). This zone was characterized by Myriophyllum (≤38%) and Cyperaceae (≤31%) accompanied by Ambrosia and Ceratophyllum demersum (≤24% and ≤20%, respectively). The presence of exotic tree taxa ( Eucalyptus , Pinus / Cedrus and Other exotic trees) was observed. Other pollen types that included exotic species such as Carduus , Asteraceae subf. Cichorioideae, Rumex , Plantago and Brassicaceae were also recorded. The phytoplankton community was represented by Gloeotrichia (≤22%), Botryococcus braunii (≤17%), Pediastrum (≤13%), Desmidiaceae (≤13%) and Zygnema (≤10%). MKH 1 (1430 to 1590 AD; 520 to 360 cal years BP). Nitella sp. oospores were found in this section with the highest concentration values (104 units/10 cm 3 ). The associated fauna was represented by Ceriodaphnia sp. (52 units/10 cm 3 ), Daphnia sp.1 (20 units/10 cm 3 ), Daphnia sp. 2 and Moina sp. ephippia (12 units/10 cm 3 ), Plumatella sp. statoblasts (18 units/10cm 3 ) and chironomid head capsules (24 units/10cm 3 ). Ostracod valves were present in high concentrations (278 units/10 cm 3 ). MKH 2 (1590 to 1920 AD; 360 to 30 cal years BP). This zone was characterized by high values of Ceratophyllum demersum epidermis remains (814 units/10cm 3 ) and high values of plant-associated fauna, mainly represented by gastropod shells (49 units/10cm 3 ). A marked decrease of the open water fauna ephippia and the ostracod valves was observed. MKH 3 (1920 to 2017 AD, 30 to -67 cal years BP). This zone was characterized by submerged macrophytes remains, oospores of Nitella sp. (70 units/10 cm 3 ) and Tolypella sp. (23 units/10 cm3), Ceratophyllum demersum epidermis (344 units/10cm 3 ) and Zanichellia palustris L. seeds (24 units/10cm 3 ). Gastropods shells and Plumatella sp. statoblasts (62 units/10 cm 3 and 22 units/10 cm 3 , respectively) represented the plant-associated fauna. The sediment-associated fauna was represented by chidorids ephippia that showed their highest values (22 units/10 cm 3 ). Also, ostracod valves exhibited the highest values (382 units/10 cm 3 ). The three oldest pollen and NPP assemblage zones, PKH 1-3, and the first ca . 47 years of PKH4, corresponded to the to plant macrofossil zones MKH 1-2, and the last ca . 95 years of the pollen and NPP assemblage zone, PKH 4, corresponded to the plant macrofossil assemblage zone MKH 3. Discussion Lake evolution The analyzed sedimentary record of Kakel Huincul lake indicated the presence of a water body since 1360 AD to the present. The lake evolved from a charophyte-dominated community towards a much more diverse ecosystem conformed by angiosperms, charophytes and algae through time. According to these characteristics, four moments with different lake structure and functioning were identified. 1360-1550 AD A clear, small, alkaline and oligotrophic lake with low nutrient content was inferred for this period. The aquatic community was dominated by the charophyte Nitella sp. accompanied by Ceratophyllum and Myriophyllum . Charophytes are fast colonizers and competitively superior to phytoplankton in conditions of low nutrient concentration and high light intensity, and can accumulate substantial amounts of nutrients, which consequently causes a reduction of the water nutrient content and a lower availability of these nutrients for phytoplankton (van der Berg et al. 1998; Blindow et al. 2014).The high biomass and dense mats of Nitella sp. provided a suitable habitat, reducing predation pressure and supplying epiphytic algae as a food resource for the existing zooplankton: Daphnia spp., Ceriodaphnia sp., Moina sp., chironomids and Plumatella sp (Wetzel 2001; Blindow et al. 2014). Furthermore, the low organic matter content indicated a less productive lake. According to Blindow et al. (2014) immobilization of nutrients by macrophytes is suggested to be one of the most important mechanisms stabilizing clear water conditions. The emergent macrophyte community around the lake, represented by Cyperaceae, Alternanthera , Polygonum and Typha, was underrepresented because of the greater expression of the regional plant community characterized by grasses and herbs (Poaceae and Ambrosia ) and by the local halophyte community that would have surrounded the lake in previous time. The emergent macrophyte community appeared less diverse and less abundant than the modern one. At the beginning of this period, the highest abundance of Chenopodioideae suggested a lake of reduced size, compared to today, that was recovering and increasing water level to 1550 AD. Pampean shallow lakes decreased in size during dry periods, and halophytic plants quickly colonized the extensive surrounding area that became free of water and consequently characterized by brackish conditions. Tonello and Prieto (2008) proposed Chenopodioideae as a good indicator of low precipitation values, based on a modern pollen-climate analysis at Pampa plain. On the other hand, the high values of Ambrosia sp. and increased values of Rumex sp ca . 1400 AD allowed inferring prolonged floods since these conditions promoted theseedling production and the colonization of areas without competition in grazed grasslands (Insausti et al. 1995; Insausti and Grimoldi 2006). In addition, at the beginning of this period the low organic matter content values, the highest values of carbonate content and the massive deposits (lithological unit A) indicated a small aquatic system subjected to evaporation/desiccation periods. These characteristics allowed inferring climatic conditions drier than present, with some humid pulses. Similar conditions were suggested by Cordoba et al. (2014) for del Monte lake (southwestern Pampa plain) and by Guerra et al. (2015) for Melincué lake (northern Pampa plain). Drought conditions with low water level were inferred for del Monte lake between 1200-1530 AD, while a very shallow and ephemeral saline lake was mentioned for Melincué lake between 1024-1492 AD. The similarity of Kakel Huincul litology with both sedimentary records supported inferring low rainfall at this time with episodic intense precipitation for the Kakel Huincul area. Dry conditions were also reported for other southeastern Pampean lakes (Hinojales-San Leoncio, Tobares, Lonkoy, Nahuel Rucá and Hinojales; Stutz et al. 2014) and for Cabeza de Buey lake, in central Pampa plain (Sánchez Vuichard et al. 2021) for this time . 1550-1670 AD A mesotrophic lake with higher nutrient content and higher water level than the previous one was inferred. A diverse and abundant phytoplanktonic community dominated by Pediastrum , Scenedesmus and Tetraedron, characteristic taxa of turbid pampean shallow lakes (Allende et al. 2009; Sánchez et al. 2013), accompanied by the submerged Myriophyllum and Ceratophyllum , replaced Nitella community. Charophytes decline could be due to poor/low light availability because of a shading effect by phytoplankton and by the angiosperms Myriophyllum and Ceratophyllum , which in this way outcompeted charophytes. According to Blindow (1992), charophytes disappear with the increase in nutrient levels and with the deterioration of the light environment. Besides the shading effect, the increase in lake´s depth could have contributed to the decrease in Nitella , since this algae develops better in low water bodies or shallow areas (Blindow 1992). On the other hand, several studies suggested Pediastrum and Scenedesmus dominance as indicators of higher nutrient content and wet periods (Borel et al. 2003, Medeanic 2006, Sánchez Vuichard et al. 2021). Cladocerans are sensitive to both bottom-up changes in resources (phytoplankton) and top-down shifts in predation (zooplanktivorous fish) (Davidson et al. 2011). A decrease in the open water fauna, more evident in large size taxa such as Daphnia spp., could be related with a high predation pressure by zooplanktivorous fish, since the high nutrients (phytoplankton) available would not be a limiting resource. Zooplankton densities were suggested to be higher at intermediate biomass of submerged vegetation and lower at both, low and high macrophyte biomass (Blindow et al. 2014), and in Kakel Huincul lake higher macrophyte abundance started to develop ca . 1600 AD. As mentioned, the decrease of the refuge function of dense vegetation may be caused by high predation pressure within this vegetation (Jeppesen et al. 1998; Hargeby et al. 2005). Consequently, the lack of zooplankton would have contributed to the development of phytoplankton and turbid conditions during this period. Furthermore, the massive accumulation of the fine sediments and low content of carbonates indicated an enlarging environment in accordance with the entrance of water to the lake. Similar sedimentological characteristics for del Monte and Melincué lakes indicated wetter conditions with higher water levels (Córdoba 2012; Guerra et al. 2015). In addition, the emergent community diminished in diversity, but Cyperaceae started to increase in abundance. This could be interpreted as a change to an enlarging lake, probably associated to an increase in rainfall since Cyperaceae is a good indicator of humid conditions (Tonello and Prieto, 2008). The Pampean lakes morphometry showed a direct correlation with rainfall (Bohn et al. 2016), and during wet periods the lakes increased in size and macrophytes, such as species of the Cyperaceae family, dominated the littoral area (Tonello et al. 2014). Then, higher rainfall was inferred during this period for the area of Kakel Huincul lake. In concordance, Cordoba (2012) suggested wet conditions for del Monte lake (southwestern Pampa plain) during 1530-1750 AD and Fontana (2005) mentioned higher lake levels between 1290-1680 AD at Laguna del Sauce (south Pampa plain). According to historical chronicles 1559, 1567-1568 and 1574 were particular rainy years for Buenos Aires province, and a cold and humid climate was reported during the first half of the 1600s in central Argentina (Gascón and Caviedes 2012; Scarpati and Capriolo 2013). 1670-1870 AD A smaller, clear, meso/eutrophic lake, with medium-high nutrient content and alkaline pH was inferred for this moment. The high abundance of the submerged macrophytes Myriophyllum and Ceratophyllum , the decrease of turbid conditions indicators, Pediastrum , Scenedesmus and Tetraedron , and the carbonate content increase suggested a smaller and shallow water body than previous. Low water levels promoted colonization and growth of macrophytes, since light reached the sediment and germinated seeds (Smith and Barko 1990, Egertson et al. 2004). On the other hand, the requirement of high levels of inorganic nitrogen by Ceratophyllum (Goulder and Boatman 1971) makes this element less available for the development of phytoplankton. The exception is Gloeotrichia, which increase is due to their ability of fixing nitrogen when this element is a limiting resource (van Geel 2001). The high abundance of the plant-associated fauna (especially gastropods) was related to the abundant submerged macrophyte community, where invertebrates find shelter and food supply. Nevertheless, the open water fauna (cladocerans) almost disappeared probably associated to a lower food supply by the decrease in phytoplankton (Davidson et al. 2011). After the intense drought of 2008-2009 years, some southeastern pampean lakes presented clear conditions under shallowness with an important development of submerged macrophytes (author’s personal observations). Thus, Kakel Huincul lake could be indicating a period of low rainfall for 1670-1870 AD. In Cabeza de Buey lake (central Pampa plain), the predominance of submerged macrophytes after a phytoplankton-dominated period indicated a decrease of lake level associated with less precipitation values (Sánchez Vuichard et al. 2021). In agreement, Córdoba et al. (2014) inferred a general drought trend during 1750-1870 AD based on the increase of carbonate content and evaporites in some southwestern shallow lakes. The authors mentioned that extended periods of water deficit or droughts were very frequent during the last quarter of the 1700´s and the beginning of the 1800´s. Between 1827 and 1832 AD, an episode of extreme aridity was documented by Darwin (1860) on his trip through central Argentina, called “The Great Drought”. 1870-2017 AD During this period, a clear-eutrophic, perennial, higher-level lake with high nutrient content and alkaline pH was recognized, suggested by the dominance of the submerged macrophytes (angiosperms and charophytes) Myriophyllum , Ceratophyllum , Nitella and Tolypella along with the increase in the Zygnemataceae, the decrease of the other green algae, Pediastrum , Scenedesmus and Tetraedron . The submerged vegetation wasdominated by Myriophyllum and Ceratophyllum , and at ca . 1965 AD Nitella , Tollypella and Zanichellia palustris were incorporated to the community. The dominance of macrophytes limited the nutrients availability to phytoplankton and resulted in higher water clarity and a predominance of benthic primary production (Bennion et al. 2018. The record indicated that aquatic vegetation composition changed over the last 100 years towards species associated with eutrophic conditions. Besides the dominance of macrophytes, the process of eutrophication was also indicated by the prevalence of Gloeotrichia and Desmidiaceae in the algal community (Scheffer 1998; Borel et al. 2003) as well as by the highest values of organic matter content. Sayer et al. (2010) and Bennion et al. (2018) indicated eutrophic conditions based on the presence of a mixed community dominated by Potamogeton crispus , Zanichellia pallustris and Ceratophyllum demersum accompanied by some charophytes. C. demersum and Z. pallustris performed well on eutrophic, highly organic sediments (Mäemets & Freiberg, 2005). Charophytes still occur in eutrophic waters but are typically out-competed by more nutrient-tolerant species as lakes become enriched and light availability is reduced, often becoming restricted to areas of shallow water (Bennion et al. 2018 and cites there in). Current studies in Kakel Huincul lake showed that the main nutrient concentration corresponds to a lake categorized as eutrophic with low nitrogen values and alkaline pH values (Allende et al. 2009; Sánchez 2012; Sánchez et al. 2013, 2017). According to the cited authors, the low levels of nitrogen observed are probably related to a high consumption by macrophytes, which were denoted dominating the record during this last period. Pampean lakes became more eutrophic because of increased nutrient loading connected mainly with the intensification of agriculture and the increase in the precipitation values during the last 50 years (Quirós et al. 2006; Stutz et al. 2012; Plastani et al. 2019; Sánchez Vuichard et al. 2021). Particularly, Kakel Huincul lake is located in an area subjected to grazing since ~1855 AD and to agriculture since ~1960 AD (Juan Uriguereca personal communication). According to Quirós et al. (2002) pampean lakes presented a pristine clear state prior to human impact. However, this study showed that Kakel Huincul lake experienced a clear pristine state dominated by submerged macrophytes, previous to evidence of human activity. Therefore, based on the observed modified vegetation close to the lake (see Regional vegetation) baseline conditions for this lake were infered ~ 1870 AD.a. Throughout the first half of the 20 th century, numerous pampean lakes and reservoirs experienced water level decreases or complete desiccation due to the phenomenon known as the Pampas Dust Bowl (Herzer 2003; Tripaldi et al. 2013). This was defined for the western Pampa plain with the main drought episode ca . 1930, based on eolic records, but could be considered to have an effect on the eastern Pampa plain. Plastani et al. (2019) suggested that La Barrancosa lake (southeastern Pampa plain) was among the lakes that underwent desiccation caused by the droughts of the 1930s. For Chasicó lake, southwestern Pampa plain, a very dry period and extremely low lake levels between 1930 and 1970 AD were inferred (Frazer et al. 2020). Córdoba et al. (2014) mentioned several short-lived episodes of extremely low lake levels were recorded between 1890-1913 AD and 1928-1939 AD and the predominance of low to intermediate lake levels for the southwestern pampean lakes associated with negative precipitation anomalies for the first half of the 20 th century. According to Maipú city instrumental precipitation record (Instituto Nacional de Tecnología Agropecuaria, INTA) Kakel Huincul area was characterized by low rainfall and dry periods only from 1935 to 1941. Nevertheless, this dry trend was not suggested by the analyzed indicatorsin Kakel Huincul record, probably due to the lake proximity to the ocean and its influence. The differences between Kakel Huincul lake and the aforementioned lakes could be due to the climatic heterogeneity of the Pampan plain (Aliaga et al. 2017).Furthermore, differences could be due to the type of indicator involved (each with strengths and weaknesses), as to the temporal resolution of each reconstruction that does not present the same level of detail. The emergent macrophyte community developed as an abundant littoral ring around the lakeat ca . 1900 AD was similar to that observed today, in agreement with the development of a larger lake. The massive organic fine grain rich muds, along with the increased organic matter and salinity drop (as noted by low carbonate amounts), suggested the development of a lake of intermediate to high water level and a high primary productivity. This was in agreement with the changes in the rainfall spatial distribution due to an increase in the precipitation values detected at 1970, known as Salto Climático (Agosta and Compagnucci 2008), promoted a significant increase in the levels and extension of the lakes and littoral areas, which reached the maximum values reconstructed since the Little Ice Age (Córdoba et al. 2014; Guerra et al. 2015; Plastani et al. 2019). According to Bohn et al. (2016), the variations in morphometry of pampean lakes show a direct correlation with precipitation. During wet years, lakes become larger and macrophytes, like Cyperaceae, dominate the littoral area, as is seen nowadays in Kakel Huincul lake. Then, higher rainfall than previous was inferred during this period for the southeastern Pampa plain. Scarpati and Capriolo (2013) indicated periods of flooding for 1980, 1985, 2001 and 2005. In particular, they highlighted the floods of 1980 as one of the most important that occurred during the 20 th century and that implied great losses for national agricultural-livestock production. Regional vegetation The regional vegetation of Pampa plain has been a grassland and did not show great changes since the Pleistocene-Holocene transition (Prieto 1996, 2000; Tonello and Prieto 2009). In this context, during the last 600 years the regional vegetation in Kakel Huincul area was represented by grasses (Poaceae) accompanied by herbs such as Plantago , Ambrosia, Rumex and taxa belonging to Asteraceae and Brassicaceae families, in agreement with that reported by Stutz et al. (2014) for southeastern pampean lakes. As aforementioned, the modern landscape of the Pampa plain has been influenced by human activities since the European settlement in the 1600s, but cattle became intensive at 1810and agriculture started ca. a-1900 AD. Particularly, Kakel Huincul area was dedicated to cattle raising since 1855 AD with the establishment of Chacabuco estancia (farm) next to the lake(Guzmán 1999), whereas , agriculture implementation started ca . 1960 AD (Juan Uriaguereca (personal communications). Cattle were always the main activity because of the extremely flat landscape, edaphic features and periodic flooding that occurred in the region (Viglizzo et al. 2001). The analyzed indicators in Kakel Huincul lake showed some changes related to the anthropic impacts. The increase of Carduus after 1600 AD suggested cattle impact. Similar abundance of thistles ( Carduus -type) was reported for the northeast Pampa plain after 1790 AD (Prieto et al. 2004). The historical chronologies highlighted that introduction of large domestic herbivores at 1700s caused the replacement of the grassland by extensive thistles ( Cynara cardunculus , Silybum marianum , Carduus acanthoides and C . tenuiflorus ) (Ghersa y León, 2001). Plantago , Rumex, and Brassicaceae were present since ca. 1360 AD, they and Asteraceae subf. Cichorioideae, notoriously increased since 1880 AD. These four pollen types represent exotic and native species. Therefore, their presence in the record between ca. 1360 and ca. 1880 AD could be interpreted as representative f native vegetation, while their increase after 1880 AD could be associated with both native and exotic species. For example, Plantago lanceolata L., Rumex crispus L. and Brassica nigra (L.) W.D.J. Koch, are introduced weeds associated with crops (Vervoorst 1967). The increase of Asteraceae subf. Cichorioideae was related to agriculture since it is regarded as an indicator of soils that have been tiled over several years (Prieto et al. 2004). Besides, the presence of Ambrosia in the record could be related to cattle impact until 1960 AD and later associated to agriculture´s implementation in the area, since it quickly colonizes overgrazed grasslands and is an important crop weed (Vervoorst 1967; Poggio et al. 2015). Similar fluctuations of Ambrosia were detected also in Cabeza de Buey lake, and were associated to different human impacts in the landscape transformation (Sánchez Vuichard et al. 2021). On the other hand, Eucalyptus , Pinus and other exotic trees pollen values appear after ca. 1890 AD and were associated with the use these trees were given in farmlands (see Land Transformation) and with the foundation of Maipú town in 1875 AD, which had a commercial and demographic development after 1900 AD (Sánchez Vuichard et al. 2021). Wetland deterioration and baseline conditions As aforementioned natural grasslands of Pampa plain were initially altered by cattle and later by agriculture (see Land Transformation). However, our results showed that southeastern wetlands were mainly affected because of the intensive agriculture that impacted these ecosystems during the last 50 years. Farmland in Argentina expanded quickly after 1950 at the expense of natural land and without consideration of the related ecological costs. The agricultural expansion over two million ha of native grassland, mostly in the Pampa plain, was significant for the local biodiversity and functioning of the ecosystem (Wiedemeier 2018). Kakel Huincul lake constitutes a good example of how Argentina´s wetlands have been impacted for more than five decades. Through the long-term monitoring analysis performed in this study, it was possible to assess the ecosystem responses to disturbances since 1360 AD, as well as to define the baseline conditions and the effect of the anthropic impact. In Kakel Huincul lake, the anthropic impact was identified through cattle farming from 1870 AD and agriculture implementation after ca . 1960 AD, and the previous clear conditions of the lake were considered as the baseline conditions. Similarly, Sánchez Vuichard et al. (2021) reported baseline conditions at ca. 1850 AD and eutrophication initial process at ca . 1880 AD in Cabeza de Buey lake (central Pampa plain). Differences between both lakes could be due to differences in the resolution of the sedimentary record. Kakel Huincul record could present a better resolution, since Cabeza de Buey lake age-depth model was not build with 210 Pb ages. These clear conditions are those present in the absence of anthropic impact and are currently unknown for most pampean shallow lakes. In addition, given the relatively low intensity of human activity during the early period of the lake history (prior to 1880 AD) the changes in phytoplankton and macrophyte communities were expected to have been mainly controlled by climate. After 1880 AD, the lake changes probably were a result of a combination of climate (increases and decreases of precipitation values) and human impacts (urbanization and agriculture implementation), that generated an accelerated eutrophication. Furthermore, agriculture intensification in southeastern Pampa plain during the last 50 years was detected based on proxies’ analysis. As aforementioned, the agriculture was implemented at 1960 in the Kakel Huincul area and the intensification started by ending 1980´s as denoted by the increase in diagnostic pollen taxa. Moreover, the acceleration in the eutrophication process related to the adoption of soy crops was observed by ca . 1995, represented by the increase in algae and by the presence of submerged macrophytes. In accordance, Wiedemeier (2018) mentioned that the Argentinean Pampas have been a global hotspot of agricultural land use change since the beginning of the 21 st century. Between 2000 and 2010, driven by high prices of soybean, the soybean cultivated area increased by 210% in Latin America, also replacing large parts of the cattle production. Conclusions Through the analysis of Kakel Huincul lake history it was possible to track the environmental change and infer past conditions, which allowed to distinguish the climatic from the anthropic factors, as well as to define their impacts on these ecosystems. The changes observed in the lake communities before 1880 AD were a result of climatic perturbations (increase/decrease rainfall), and after 1880 AD they were a combination of climatic (increases and decreases of precipitation values) and anthropic forcings (cattle, intensive agriculture and urbanization). Moreover, baseline conditions were established at ca . 1870 AD. These conditions were related to a clear, pristine lake with a developed macrophyte community. Currently it is important to establish shallow lakes baseline conditions in terms of restoration and management objectives. In addition, it was concluded that southeastern Pampa plain has been subjected to human activities since 1870 AD, with cattle farming being the main activity and agriculture incorporation at ca . 1960 AD in the area. According to the results, the process of eutrophication in the lake associated with the intensification of agriculture took place during the last 25 years. The Pampa wetland has been modified for more than five decades ago. Although intensive agriculture occurred in the last 25 years, the modifications of the landscape are the result of 170 years of human impacts. Statements & Declarations Funding This work was supported by PIP CONICET 582 (2015-2017) and EXA 1015/20 (UNMdP). Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Guillermina Sánchez Vuichard, Silvina Stutz, Marcela Tonello, Diego Navarro and Caolina Vásquez. The first draft of the manuscript was written by Guillermina Sánchez Vuichard and all authors commented on previous versions of the manuscript. 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The Holocene 29:244–261 Mjelde M, Faafeng B (1997) Ceratophyllum demersum hampers phytoplankton development in some small Norwegian lakes over a wide range of phosphorus concentrations and geographical latitude. Freshw Biol 37:355–365 Monti M, Pozzi R, Correa Luna M, Barbich C, Rosell F, Lozeco C, Montico M (2016) Variabilidad Climática y Anegamientos en la Pampa Húmeda Argentina. https://www.researchgate.net/publication/319967835_ Neiff JJ (2001) Humedales de la Argentina: sinopsis, problemas y perspectivas futuras. El Agua en Iberoamerica, Funciones de los humedales, calidad de vida y agua segura (AF Cirelli). CYTED, Argentina, pp 83–112 O’Farrell I, Izaguirre I, Chaparro G, Unrein F, Sinistro R, Pizarro H, Rodrı´guez P, Tezanos Pinto P, Lombardo R, Tell G (2011) Water level as the main driver of the alternation between a free-floating plant and a phytoplankton dominated state: a long-term study in a floodplain lake. Aquat Sci 73:275–287 Pengue WA (2009) Cuestiones económico-ambientales de las transformaciones agrícolas en las Pampas. Probl Desarro 40:137–161 Plastani MS, Laprida C, Montes de Oca F, Massaferro J, Panarello HO, Ramón Mercau J, Lami A (2019) Recent environmental changes inferred from sediments in a shallow lake of the Argentinean pampas. J Paleolimnol 61:37–52 Poggio SL, Perelman SB, Mollard FPO, Leon RJC (2015) Guests and gatecrashers in a New World’s banquet: Old World plant species introduced from the Mediterranean Basin enriched the flora of grasslands and croplands in the Pampas of Argentina. Flora Mediterránea 25:39–54 Prieto AR (1996) Late quaternary vegetational and climatic changes in the Pampa grassland of Argentina. Quat Res 45:73–88 Prieto AR (2000) Vegetational history of the Late glacial Holocene transition in the grassland of eastern Argentina. Palaeogeogr Palaeoclimatol Palaeoecol 157:167–188 Prieto AR, Blasi AM, De Francesco CG, Fernández C (2004) Environmental history since 11,000 14C yr B.P. of the northeastern Pampas, Argentina, from alluvial sequences of the Luján River. Quat Res 62:146–161 Quiroga MV, Huber P, Ospina-Serna J, Diovisalvi N, Odriozola M, Cueto GR, Lagomarsino L, Fermani P, Bustingorry J, Escaray R, Zagarese J, Unrein F (2021) The dynamics of picocyanobacteria from a hypereutrophic shallow lake is affected by light-climate and small-bodied zooplankton: a 10-year cytometric time-series analysis. FEMS Microbiol. Ecol. FEMS Microbiology Ecology. https://doi.org/10.1093/femsec/fiab055 Quirós R (2005) La ecología de las lagunas de las Pampas. Investigación y Ciencia 1:1–13 Quirós R, Rennella AM, Boveri MB, Rosso JJ, Sosnovsky A (2002) Factores que afectan la estructura y el funcionamiento de las lagunas pampeanas. Ecol A ustral 12:175–185 Quirós R, Boveri MB, Renella AM, Rosso J, Sosnovsky A, von Bernard HT (2006) Los efectos de la agriculturización del humedal pampeano sobre la eutrofización de sus lagunas. Causas, conseqüências e tecnologias de gerenciamentoe controle. Eutrofização na América do Sul: 1–16 Reynolds CS (2006) Ecology of phytoplankton. Cambridge University Press, Cambridge, UK, p 535 Team RC (2020) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria: Available at: https://www. R-project. org/ Sánchez PN (2017) De oratorio familiar a Parroquia: párrocos rurales y feligreses en el pago de San Vicente entre 1730 y 1827. PhD Thesis, National University of the Center of the Province of Buenos AiresArgentina, 177pp. (inédito) Sánchez ML (2012) Estructura de la comunidad perifítica y sus interacciones con la comunidad fitoplanctónica en lagunas turbias y claras de la llanura Pampeana (Provincia de Buenos Aires, Argentina). PhD Thesis. Buenos Aires University, Argentina, 210 pp. (inédito) Sánchez ML, Pérez GL, Izaguirre I, Pizarro HN (2013) Influence of underwater light climate on periphyton and phytoplankton communities in shallow lakes from the Pampa plain (Argentina) with contrasting steady states. J Limnol 72:62–78 Sánchez ML, Lagomarsino L, Allende L, Izaguirre I (2015) Changes in the phytoplankton structure in a Pampean shallow lake in the transition from a clear to a turbid regime. Hydrobiologia 752:65–76 Sánchez ML, Rodríguez P, Torremorell AM, Izaguirre I, Pizarro H (2017) Phytoplankton and periphyton primary production in clear and turbid shallow lakes: influence of the light environment on the interactions between these communities. Wetlands 37:67–77 Sánchez Vuichard G (2019) Historia reciente (últimos 500 años) de los lagos someros de la llanura Pampeana a partir del análisis de múltiples indicadores. PhD Thesis. National University of Mar del Plata, Argentina Sánchez Vuichard G, Stutz S, Tonello MS, Navarro D, Schmelz M, Fontana SL (2021) Structure and dynamics of a Pampa plain, (Argentina) shallow lake over the last 600 years. J Paleolimnol 66:141–155 Sayer CD, Burgess A, Kari K, Davidson TA, Peglar S, Yang H, Rose N (2010) Long-term dynamics of submerged macrophytes and algae in a small and shallow, eutrophic lake: implications for the stability of the macrophyte dominance. Freshw Biol 55:565–583 Scarpati OE, Capriolo AD (2013) Sequías e inundaciones en la provincia de Buenos Aires (Argentina) y su distribución espacio-temporal. Investigaciones Geográficas, Boletín del Instituto de Geografía, 82: 38–51 Scheffer M (1998) Ecology of shallow lakes. Ed. Chapman & Hall. Londres, p 357 Schiaffino MR, Diovisalvi N, Molina DM, Fermani P, Puma CL, Lagomarsino L, Quiroga MV, Pérez GL (2019) Microbial food-web components in two hypertrophic human-impacted Pampean shallow lakes: interactive effects of environmental, hydrological, and temporal drivers. Hydrobiologia 830:255–276 Sequeira N, Vazquez P, Zulaica L (2015) Consecuencias ambientales de la expansión agrícola en el partido de Benito Juárez (Buenos Aires, Argentina), en el período 2003–2011, 5 edn. Revista Geoaraguaia Smith CS, Barko JW (1990) Ecology of Eurasian watermilfoil. J Aquat Plant Manag 28:55–64 Stutz S, Borel CM, Fontana SL, Tonello MS (2012) Holocene evolution of three shallow lakes in the SE Pampa plain (Argentina) as evidenced by analyses of pollen, non-pollen palynomorphs and plant macrofossils. The Holocene 22:1215–1222 Stutz S, Tonello MS, González Sagrario MS, Navarro D, Fontana SL (2014) Historia ambiental de los lagos someros de la llanura Pampeana (Argentina) desde el Holoceno medio: inferencias paleoclimáticas. Lat Am J Sedimentol Basin Anal 21:119–138 Tonello MS (2006) Reconstrucciones paleoclimaticas cuantitativas para el cuaternario tardío de los pastizales pampeanos basadas en la calibración de las relaciones polen-clima. PhD Thesis, National de Mar del Plata University, 167 pp. (inédito) Tonello MS, Prieto AR (2008) Modern vegetation-pollen-climate relationship for the Pampa grasslands of Argentina. J Biogeogr 35:926–938 Tonello MS, Prieto AR (2009) Pastizales pampeanos: unidades de vegetación natural potencial y su relación con el espectro polínico actual. Quaternário do Rio Grande do Sul: Integrando conhecimentos. Monografias da Sociedade Brasileira de Paleontologia, pp 95–105 Tonello MS, Stutz S, y Navarro D (2014) Variabilidad climática durante los últimos 1500 años a partir del análisis de múltiples indicadores en el Sudeste de la llanura Pampeana. En Actas XIX Congreso Geológico Argentino Tripaldi A, Zárate MA, Forman SL, Badger T, Doyle ME, Ciccioli P (2013) Geological evidence for a drought episode in the western Pampas (Argentina, South America) during the early–mid 20th century. The Holocene 23:1731–1746 Tripaldi A, Zárate MA (2016) A review of Late Quaternary inland dune systems of South America east of the Andes. Quat Int 410:96–110 van den Berg MS, Coops H, Meijer ML, Scheffer M, Simons J (1998) Clear water associated with a dense Chara vegetation in the shallow and turbid Lake Veluwemeer, The Netherlands. In: Jeppesen E, Sondergaard M, Sondergaard M, Christoffersen K (eds) The structuring role of submerged macrophytes in lakes. Springer-Verlag, New York, pp 339–352 Van Geel B (2001) Non-pollen palynomorphs. In: Smol JP, Birks HJB, Last WM (eds) Tracking Environmental Change using Lake Sediments: Terrestrial, Algal and Siliceous Indicators, 3 edn. Kluwer, Dordrecht, pp 99–119 Vervoorst F (1967) La vegetación de la República Argentina. VII Las comunidades vegetales de la depresión del Salado (Provincia de Buenos Aires). INTA Serie Fitogeográfica 7 Buenos Aires, 262 pp Viglizzo EF, Lértora F, Pordomingo AJ, Bernardos JN, Roberto ZE, Del Valle H (2001) Ecological lessons and applications from one century of low external-input farming in the pampas of Argentina. Agricul. Ecosys. Environ., 83: 65–81 Wetzel RG (2001) Limnology: Lake and river ecosystems. Academic Press (ed.), En, p 985 Wiedemeier J (2018) The Role of Wetlands in Ecosystem Services Trade-Offs in La Picasa Basin, Argentina. Tesis de Master en Natural Resources Management and Development, University of Applied Sciences, Cologne, 139 pp. (inédito) Williams CJ (2011) A paleoecological perspective on wetland restoration. Wetlands, pp 67–91 Zárate MA, Tripaldi A (2012) The aeolian system of central Argentina. Aeolian Res 3:401–417 Table Table 1 Lab number Depth (cm) 14C yr BP Median probability Upper 2 σ intercept D-AMS 024148 20-21 281±29 299 275-327 D-AMS 020646 29-30 618± 29 583 528-570 Cite Share Download PDF Status: Published Journal Publication published 23 Jan, 2023 Read the published version in Wetlands → Version 1 posted Reviewers agreed at journal 11 Jul, 2022 Reviewers invited by journal 11 Jul, 2022 Editor invited by journal 09 Jun, 2022 Editor assigned by journal 07 Jun, 2022 First submitted to journal 31 May, 2022 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. 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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-1712174","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":120215145,"identity":"78d320e5-571e-4967-930a-4834219bae5b","order_by":0,"name":"Guillermina Sánchez Vuichard","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFklEQVRIiWNgGAWjYLACxgYIyQwi+xkYDIA0MwlaZjYQrwWijHHDAQJa5P0PP3vwc4eNvcGN5MbPBTX3ZDdfO7ztAUOFdWID+9kH2LQY3kgzN+w9k8ZscCOxWXrGsWLjbbfTyg0YzqQnNvCkG2DVMoPBTJqx7TCb5IzENmYetoTEbbdzzCSAIokNDGlYHWbYf/wbUMt/HoiWfwmJm2eDtPwDauF/ht0vDDkgWw5I8EsAtfC2JSRukAZpaQBqkcBui4FETplkb1uyAT/Pw2Zp3r4E4xkgvyQcSzduk8BhS//xbRI/2+zs2djTH37m+ZYg2z87eduDDzXWsv38OGw5gEWQjSEBTGIH8g1YtYyCUTAKRsEoQAIACVZfYqXUql0AAAAASUVORK5CYII=","orcid":"","institution":"IIMYC: Instituto de Investigaciones Marinas y Costeras","correspondingAuthor":true,"prefix":"","firstName":"Guillermina","middleName":"Sánchez","lastName":"Vuichard","suffix":""},{"id":120215146,"identity":"367da317-9bb6-4e7f-ba2e-5d33f254a45f","order_by":1,"name":"Marcela Sandra TONELLO","email":"","orcid":"","institution":"IIMYC: Instituto de Investigaciones Marinas y Costeras","correspondingAuthor":false,"prefix":"","firstName":"Marcela","middleName":"Sandra","lastName":"TONELLO","suffix":""},{"id":120215147,"identity":"91da7333-b7b4-4439-9969-15504dc25e53","order_by":2,"name":"Silvina Stutz","email":"","orcid":"","institution":"IIMYC: Instituto de Investigaciones Marinas y Costeras","correspondingAuthor":false,"prefix":"","firstName":"Silvina","middleName":"","lastName":"Stutz","suffix":""},{"id":120215148,"identity":"f9796d80-1ff5-401e-94e8-07db0dd555e6","order_by":3,"name":"Diego Navarro","email":"","orcid":"","institution":"IIMYC: Instituto de Investigaciones Marinas y Costeras","correspondingAuthor":false,"prefix":"","firstName":"Diego","middleName":"","lastName":"Navarro","suffix":""},{"id":120215149,"identity":"9618866d-2197-4ae8-9e64-d96622787396","order_by":4,"name":"Carolina Vásquez","email":"","orcid":"","institution":"IIMYC: Instituto de Investigaciones Marinas y Costeras","correspondingAuthor":false,"prefix":"","firstName":"Carolina","middleName":"","lastName":"Vásquez","suffix":""}],"badges":[],"createdAt":"2022-05-31 13:58:54","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1712174/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1712174/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s13157-023-01660-z","type":"published","date":"2023-01-23T18:29:45+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":23834603,"identity":"5710d0ca-a798-43ee-b146-ee2c1d10b048","added_by":"auto","created_at":"2022-07-13 19:57:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":400902,"visible":true,"origin":"","legend":"\u003cp\u003ea. Map of study area in Pampa plain showing the location of Kakel Huincul lake and other sites mentioned in the text. b. Location of KH2 and KH3 cores on a Google Map image. c. Image of Kakel Huincul lake during core extraction (2015)\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-1712174/v1/9ad4c03170f13e8bc9e81f84.png"},{"id":23834605,"identity":"63125111-baf7-40c9-af84-9bd74e662011","added_by":"auto","created_at":"2022-07-13 19:57:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":193392,"visible":true,"origin":"","legend":"\u003cp\u003ea. Sedimentological units and description for KH2. b. Organic matter (O.M) profiles for KH2 and KH3 and carbonate (CaCO3) profile for KH3. Red circles represent tie points for cores correlation\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-1712174/v1/003f6259a50b9249cbb619c6.png"},{"id":23835051,"identity":"f3b8b700-95fe-445f-b24f-9f4d8b4e64df","added_by":"auto","created_at":"2022-07-13 20:02:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":68902,"visible":true,"origin":"","legend":"\u003cp\u003ea. Radioisotope activity of \u003csup\u003e210\u003c/sup\u003ePb (total, unsupported, and supported) and associated errors (Bq Kg-1) for KH3 core. b. Age-depth model based on the unsupported radioisotope \u003csup\u003e210\u003c/sup\u003ePb for the upper 16 cm of KH3core. The white triangles represent the ages obtained for each cm, with their respective standard errors. c. Age-depth model for Kakel Huincul lake, based on radiocarbon and radioisotopic \u003csup\u003e210\u003c/sup\u003ePb dating. The blue dots are the radiocarbon dates and the green dots represent \u003csup\u003e210\u003c/sup\u003ePb and additional information dates used in the construction of the model\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-1712174/v1/9a644108a007c6006deaf5ca.png"},{"id":23835052,"identity":"28b575eb-49cd-4cdf-b386-d0840682d909","added_by":"auto","created_at":"2022-07-13 20:02:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":119107,"visible":true,"origin":"","legend":"\u003cp\u003ePollen and NPPs diagram for KH3 showing also the organic matter (O.M) content. Bold horizontal lines correspond to the pollen zone divisions\u0026nbsp;defined using CONISS (right side)\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-1712174/v1/83f24d19b20ac62e3cc46b2e.png"},{"id":23834607,"identity":"870bb91d-b2a8-4d66-8901-1690784e2515","added_by":"auto","created_at":"2022-07-13 19:57:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":95485,"visible":true,"origin":"","legend":"\u003cp\u003ePlant macrofossil remains and associated fauna diagram showing also the\u0026nbsp;organic matter (O.M) content. Bold horizontal lines correspond to the plant macrofossil zone divisions defined using CONISS (right side)\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-1712174/v1/2238c8fc821786b6ae0a8e52.png"},{"id":44717648,"identity":"fa686bcb-6484-4b34-893e-5fc0ce64abe9","added_by":"auto","created_at":"2023-10-16 18:38:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1148221,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1712174/v1/91487e97-09de-4ed8-85fd-7a551e3ce91f.pdf"}],"financialInterests":"","formattedTitle":"Pampa plain (Argentina) wetland history through a lake case study: Kakel Huincul Environmental History during the last 600 years","fulltext":[{"header":"Introduction","content":"\u003cp\u003eNowadays, wetlands are internationally recognized as the most productive ecosystems that provide the greatest number of ecosystem services to society, also playing a fundamental role in the development of many cultures on the planet (Benzaquen et al. 2017). At the same time, they have an exceptional biodiversity, which makes them areas of great value for protection and conservation, supported by international agreements such as the Ramsar Convention and the International Convention of Biological Diversity (Bobbink et al.\u0026nbsp;2006). This has led to the consideration of wetlands as key ecosystems, particularly for their role in the storage and purification of water and in their intervention in hydrological cycles. However, on a global scale, these ecosystems are decreasing in size and losing quality. Since the industrial era, human impacts have become dramatically negative and wetlands have suffered alterations ranging from drainage, water retention for reservoirs, use as discharge areas for toxic substances, landfill for urbanization developments and other actions that have gone unnoticed (Benzaquen et al. 2017). As a result, the services they provide also disappear or are restricted. The latest evaluations show that in the 20\u003csup\u003eth\u003c/sup\u003e century the global extent of wetlands decreased between 64 and 71% (Kandus et al. 2018), bringing out that most surviving wetland systems require active management and/or restoration work to bring them back to a sustainable state of ecosystem health.\u003c/p\u003e\n\u003cp\u003eOne of the many fascinating aspects of wetlands is their ability to preserve an archive of their own history in the accumulating body of sediments beneath the surface. The sedimentary record can be thought of as an archive of monitoring data collected over centuries and millennia (Bunting and Whitehouse 2008), which may be analyzed to reconstruct changes in hydrology and in biological community composition and dynamics through time. This information is valuable to those who are interested in studying the ecological dynamics of the past and to those who have more applied goals, such as wetland creation, enhancement, and restoration (Williams 2011). Effective conservation requires both, a detailed knowledge of the ecology of the concerned biota including the development of habitats and ecosystems through time, and how species have responded to environmental and anthropogenic changes. For the restoration design of some ecosystems, it is also desirable to have adequate knowledge of the pre-disturbance conditions as a starting point (Williams 2011). These conditions are those present in the absence of anthropogenic influence, also termed as baseline or reference conditions (Davies and Bunting 2010). Paleoecological studies of wetland sedimentary deposits offer the possibility of obtaining accurate reconstructions of baseline conditions and ecosystem\u0026acute;s dynamics in the past (e.g. Bennion et al. 2011, 2018; Davidson et al. 2011; Kowalewski et al. 2016).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eArgentina (southern South America) has a huge variety and quantities of wetlands,\u0026nbsp;which are\u0026nbsp;located in a wide strip, from 33\u0026ordm; to 54\u0026ordm;S, and from 2300 m asl in the Andes to the coastal plain of the Atlantic Ocean; and take up the 21.5% (600,000 km\u003csup\u003e2\u003c/sup\u003e) of the country (Neiff 2001, Kandus et al. 2008). These ecosystems are home to outstanding biodiversity, while providing valuable services for the well-being of society, and were relatively free of the impacts derived from human activities and therefore preserved their original extent, structure and functions until a few decades ago. These conditions began to change due to the intensification of some productive activities and the incorporation of new types of land use and water management, which implied a substantial alteration of the hydrological regime (Benzaquen et al. 2017). The national inventories of wetlands are currently recognized as essential tools for designing policies and other aspects leading to their conservation and rational use (Benzaquen et al. 2017). Resource inventories have traditionally been aimed at answering questions concerning, for example, their type, location and abundance. However, the increasing need for more effective management has expanded the scope to include wetlands functioning and the assessment of consequences resulting from environmental changes and human impacts (Kandus et al- 2018).\u0026nbsp;In the current context of global warming, rapid changes in land use and the current state of transformation and degradation of our country`s wetlands, makes it necessary to advance in the understanding of their functioning and their management, for their conservation and wise use.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe Pampa plain, southeastern Argentina, contains one of the main wetlands of the country (Quir\u0026oacute;s 2005, Kandus et al. 2008) characterized by countless shallow lakes (Geraldi et al. 2011). Past environmental changes of these ecosystems were studied by L\u0026oacute;pez-Blanco et al (2021) for the last 700 years, Laprida et al. (2009) and Laprida and Valero Garc\u0026eacute;s (2009) for the last 500 years, and by C\u0026oacute;rdoba et al. (2014), Guerra et al. (2015) and Plastani et al. (2019) at high resolution during the last 200 years. In particular, the last 600 years is a key time frame due to pampean shallow lakes established their current configuration regarding trophic level and biological communities, in a landscape characterized by a greater stability associated to a generalized humid climatic conditions similar to modern ones (Stutz et al. 2014; Messineo et al. 2019; De Francesco et al. 2021). This broader temporal frame would allow disentangling climatic from anthropic drivers. The modern landscape has been influenced by human activities since the European settlement in the 1600s, but cattle and agriculture became intensive at 1850-1900 AD. The environments\u0026nbsp;have deteriorated\u0026nbsp;and lost biodiversity, largely due to the land mismanagement associated\u0026nbsp;with extending\u0026nbsp;the surface for agricultural and livestock production, and the misuse of agrochemicals in intensive agriculture (Monti et al. 2017;\u0026nbsp;Bermann et al. 2022). In particular, agrochemical dumps produces increases in algae population in lakes and rivers, affects biodiversity and lake functioning and leads to a degradation of the wetland due to the eutrophication processes (Sequeira et al. 2015; Auer et al. 2019). There are several studies that evaluated the current functioning and account for these changes (e.g. Allende et al. 2009; O\u0026rsquo;Farrell et al. 2011; Mancini et al. 2013; S\u0026aacute;nchez et al. 2015, 2017; Cano et al. 2016; Schiaffino et al. 2019; Quiroga et al. 2021). However, monitoring programs of past lake evolution defining their status prior to anthropic impact are still scarce. The baseline conditions were identified\u0026nbsp;for the first\u0026nbsp;time at central Pampa plain (Cabeza de Buey lake) at ca. 1850 AD, while the onset of intense eutrophication was established ca. 1990 AD\u0026nbsp;based on pollen, non pollen palynomorphs analysis and plant macrofossil remains\u0026nbsp;(S\u0026aacute;nchez Vuichard et al. 2021). These baseline conditions were defined as those before intensive cattle and agriculture in the area, whereas the eutrophication was associated to agriculture intensification implemented in the landscape, as well as to the establishment of towns in the surroundings.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn southeastern Pampa plain there are several eutrophic shallow lakes subjected to climate dynamics and anthropic impact during the last 600 years. Thus, the objective of this study is to reconstruct the Kakel Huincul lake\u0026acute;s biological community structure and dynamics in the last 600 years, and to establish baseline conditions, documenting subsequent changes until present. The study is based on the analysis of pollen, Non Pollen Palynomorphs (NPPs) and plant macrofossil remains and associated fauna from a sedimentary record.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe provided information will contribute to the national wetland inventories in order to understand Pampean wetlands responses to environmental changes and human impacts, for future management and conservation plans.\u003c/p\u003e\n\u003cp\u003eStudy site\u003c/p\u003e\n\u003cp\u003eKakel Huincul (36\u0026deg; 48\u0026apos;S, 57\u0026deg; 47\u0026apos;W) is an elongated shallow lake (20 km\u003csup\u003e2\u003c/sup\u003e, up to 4 m deep) located in the southeastern Pampa plain in Argentina (South America). The region is characterized by the presence of several lakes of variable size, placed on a stabilized aeolian landscape of parabolic and blowout dunes (Fig. 1A, B). Most of these lakes have an aeolian origin with a prevailing west-southwest wind direction during the late Pleistocene. During the Holocene, with the establishment of more humid conditions, the basins \u0026nbsp; \u0026nbsp; \u0026nbsp;became lakes and were filled with sediments (Z\u0026aacute;rate and Tripaldi 2012; Tripaldi and Z\u0026aacute;rate 2016). Kakel Huincul lake is considered permanent, but water level can be diminished during periods of drought.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe landscape where the lake is located is dominated by livestock (cows) and croplands (e.g. soybean, flax), with small patches of native vegetation \u0026nbsp; \u0026nbsp; , \u0026nbsp; \u0026nbsp; \u0026nbsp;dominated by grasses of the genus \u003cem\u003eStipa\u003c/em\u003e, \u003cem\u003ePiptochaetium\u003c/em\u003e and \u003cem\u003eAristida\u003c/em\u003e, with several accompanying herbs such as \u003cem\u003ePhyla\u003c/em\u003e sp., \u003cem\u003eCarex\u003c/em\u003e sp., \u003cem\u003eAdesmia\u003c/em\u003e sp., \u003cem\u003eAlternanthera\u003c/em\u003e sp., \u003cem\u003ePamphalea\u003c/em\u003e sp., \u003cem\u003eVicia\u003c/em\u003e sp. and \u003cem\u003eEryngium\u003c/em\u003e sp. (Leon 1991, Tonello 2006). According to Sanchez (2012), the lake is profusely colonized by submerged macrophytes, mainly \u003cem\u003eMyriophyllum aquaticum\u003c/em\u003e (Vell.) Verdc. and \u003cem\u003eCeratophyllum demersum\u0026nbsp;\u003c/em\u003eL, and by emergent macrophytes such as \u003cem\u003eSchoenoplectus californicus\u0026nbsp;\u003c/em\u003e(C.A. Mey.) Soja\u0026acute;k, \u003cem\u003eAlternanthera philoxeroides\u0026nbsp;\u003c/em\u003e(Mart.) Griseb\u003cem\u003e.\u003c/em\u003e, \u003cem\u003eSolanum glaucophyllum\u003c/em\u003e Desf. and \u003cem\u003eHydrocotyle\u003c/em\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003cem\u003e\u0026nbsp;ranunculoides\u0026nbsp;\u003c/em\u003eL. f. At the study site, several \u003cem\u003eGleditsia triacanthos\u0026nbsp;\u003c/em\u003eL., \u003cem\u003eEucalyptus\u003c/em\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;spp., \u003cem\u003eSalix\u003c/em\u003e spp., \u003cem\u003eFraxinus\u003c/em\u003e sp., \u003cem\u003ePinus\u003c/em\u003e spp. and \u003cem\u003eCupressus\u003c/em\u003e sp. trees grow on the dune next to the lake and in the \u003cem\u003eestancia Kakel\u003c/em\u003e (Figs. 1B, C).\u003c/p\u003e\n\u003cp\u003eAccording to Aliaga et al. (2017) climatic subregions classification, Kakel Huincul lake is located in an area considered as extremely humid. The climate is temperate with annual mean temperature of 15.5\u0026deg;C that presents an annual pattern with a maximum of 29\u0026deg;C in January and a minimum of 4\u0026deg;C in July. Annual precipitation is 995 mm, and rainfall occurs mainly from spring (September) to autumn (March), with a maximum of 109 mm in January and a minimum of 59 mm in August (Estaci\u0026oacute;n Meteorol\u0026oacute;gica Aer\u0026oacute;dromo de Dolores, 36\u0026deg;19\u0026acute;S, 57\u0026deg;43\u0026acute;W, Servicio Meteorol\u0026oacute;gico Nacional).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLand transformation\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSince the first European settlements the native vegetation of Pampa plain was modified. Around 1540 AD, large herbivores such as cows and horses were introduced. Initially, cattle breeding\u0026nbsp;was\u0026nbsp;restricted to Buenos Aires city but expanded into the Pampa plain by the end of the 1800s, increasing the introduction and dispersal of native and exotic weed seeds (Garavaglia 1999). Since 1810, the extensive livestock farming advanced on lands still occupied by indigenous communities. This expansion was not homogeneous neither in space nor time due to geographical and ecological differences as well as to the difficulties related to the conquest of indigenous territories (S\u0026aacute;nchez 2017;\u0026nbsp;Banzato et al. 2011; S\u0026aacute;nchez Vuichard 2019). After 1880 AD, increasing population caused new transformations in the landscape. A significant transformation was the planting of trees from vegetation units adjacent to grasslands (e.g. \u003cem\u003eCeltis tala\u003c/em\u003e (Klotzsch) Liebm. and \u003cem\u003eSenegalia bonariensis\u003c/em\u003e (Gillies ex Hook. \u0026amp; Arn.) Seigler \u0026amp; Ebinger)\u0026nbsp;or\u0026nbsp;exotic trees as peridomestic forests\u0026nbsp;(e.g.\u003cem\u003e\u0026nbsp;Populus\u0026nbsp;\u003c/em\u003espp. and \u003cem\u003eEucalyptus\u003c/em\u003e spp) and\u0026nbsp;fruit trees\u0026nbsp;(e.g.\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ePrunus\u003c/em\u003e spp. and \u003cem\u003eMalus\u003c/em\u003e spp.). During the 1900s, a period of major agricultural development arose with cereal crops, accompanied by a succession of technological improvements. Thus, the Pampa plain presented large areas with crops and cultivated pastures that replaced the native vegetation and promoted the invasion of exotic weeds. During the mid-1970s, the soybean crop generated structural and functional changes like the decrease in livestock activity, the increase in the use of agrochemicals and the intensity of soil tillage, together with different methods to handle crop residues (Ghersa and Martinez Ghersa 1991). As a result, an increase in the diversity of weeds associated\u0026nbsp;with crop\u0026nbsp;species was observed. At 1996, new soybean transgenic varieties were implemented, resulting in soil degradation due to the decrease in the organic matter content and the loss of nutrients (Viglizzo et al. 2001; Pengue 2009). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eParticularly, the first farmer settlements in Kakel Huincul lake area date back to 1812 and for several years it was a territory shared with indigenous population. The livestock activity started\u0026nbsp;in 1855\u0026nbsp;AD in the present day \u003cem\u003eestancia\u003c/em\u003e Kakel (Guzm\u0026aacute;n, 1999) and became the main activity because the extremely flat landscape, edaphic features and periodic flooding limited the agriculture. After 1960 some crops (e.g. flax, sunflower and corn) were planted in the area, in small patches. By the end of 1980s 60% of the grassland of the southeastern Pampa plain remained uncultivated (Viglizzo et al. 2001). Demographic growth occurred after 1880 with the arrival of the railroad and the Maip\u0026uacute; town foundation 17 km westward from the lake. Currently Kakel Huincul is a eutrophic shallow lake used for recreation and hosts fishing and water sports (S\u0026aacute;nchez 2012).\u003c/p\u003e"},{"header":"Methods And Materials","content":"\u003cp\u003eTwo sediment cores, KH2 (122 cm) and KH3 (31 cm), were recovered with a vibracorer and a \u003cem\u003eGravity\u003c/em\u003e corer, both\u0026nbsp;equipped with a 5 cm inner diameter tube\u0026nbsp;and\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp;operated from a platform in November 2015 and April 2017, respectively (Fig. 1B). The stratigraphy was characterized by granulometry and color based on visual descriptions on KH2. In addition, the organic matter content was analyzed on KH2 and KH3 in order to correlate both cores, and carbonates content was analyzed on KH3. This correlation allowed unifying date information in a single temporal profile, and to get a reliable age-depth model. Samples were treated according to loss-on-ignition (LOI) procedure (Heiri et al. 2001). Results are expressed as percentage of weight loss of the sediment related to the dry weight of the samples at 105\u0026deg;C before combustion.\u003c/p\u003e\n\u003cp\u003eThe age-depth model was based on two radiocarbon dates (Table 1) and sixteen \u003csup\u003e210\u003c/sup\u003ePb dates on KH2, and a chronomarker and the coring date (2017) on KH3. The timing of environmental changes was constrained by \u003csup\u003e210\u003c/sup\u003ePb/\u003csup\u003e137\u003c/sup\u003eCs and \u003csup\u003e14\u003c/sup\u003eC AMS dating. Excess \u003csup\u003e210\u003c/sup\u003ePb and \u003csup\u003e137\u003c/sup\u003eCs were measured on 20 samples between 0 and 20 cm depth and analyses were performed at \u003cem\u003eLaboratoire de Radiochronologie-Centre d\u0026rsquo; \u0026eacute;tudes nordiques, Universit\u0026eacute; Laval\u0026nbsp;\u003c/em\u003e(Quebec, Canad\u0026aacute;). Ages were calculated using the CRS model which assumes that excess \u003csup\u003e210\u003c/sup\u003ePb has been supplied to the sediment at a constant rate. Radiocarbon dating was measured on bulk sediment by means of an AMS spectrometer at DirectAMS (Radiocarbon Dating Service) and at Accelerator Mass Spectrometry Laboratory (Seattle, Washington, USA). Radiocarbon ages were calibrated with the Southern Hemisphere calibration curve (SHCal20,\u0026nbsp;Hogg et al. 2020) and smooth spline regressions with smoothing level of 0.4 were applied. In addition, age associated\u0026nbsp;with\u0026nbsp;the introduction of\u0026nbsp;\u003cem\u003eEucalyptu\u003c/em\u003es spp. (chronomarker)\u0026nbsp;\u0026nbsp;(S\u0026aacute;nchez Vuichard et al. 2021), and the age assigned to the top core, were incorporated to the chronology. Finally, the age-depth model was performed by using CLAM 2.2 (Blaauw 2010), a code written in R language (R CoreTeam 2020).\u003c/p\u003e\n\u003cp\u003eThe KH3 core was subsampled and pollen and NPPs (non-pollen palynomorphs) analysis was performed at 1 cm intervals, and plant macrofossil remains and associated fauna\u0026nbsp;analysis was performed at 2 cm intervals from 0 to 12 cm depth, and at 1 cm intervals from 13 to 28 cm depth. Samples for pollen and NPPs analysis were prepared following standard techniques, using warm KOH10%, HCl10%, heavy-liquid separation with ZnCl\u003csub\u003e2\u003c/sub\u003e, HF and acetolysis (Bennett and Willis 2001). Two \u003cem\u003eLycopodium clavatum\u0026nbsp;\u003c/em\u003eL. tablets were added before treatment. Pollen sums varied between 500 and 1000 pollen grains. Abundance of each pollen type was calculated as a percentage of the total pollen sum (excluding\u0026nbsp;\u003cem\u003eEucalyptus\u003c/em\u003e, \u003cem\u003ePinus/Cedrus,\u003c/em\u003e Other exotic \u0026nbsp;and long distance trees pollen). NPPs, pollen of\u0026nbsp;\u003cem\u003eEucalyptus\u003c/em\u003e, \u003cem\u003ePinus/Cedrus\u003c/em\u003e and Other exotic trees as well as long distance trees pollen were calculated as a percentage of the pollen sum plus the sum of each group of taxa. Percentages of \u003cem\u003eAzolla filiculoides\u0026nbsp;\u003c/em\u003eLam.\u003cem\u003e, Ricciocarpos natans\u003c/em\u003e (L.)Cordaand and Bryophyta spores were calculated as a percentage of the pollen sum plus spores sum. Other exotic trees include \u003cem\u003eCasuarina, Betula\u003c/em\u003e, \u003cem\u003eCupressus\u003c/em\u003e, \u003cem\u003eCorylus\u0026nbsp;\u003c/em\u003eand \u003cem\u003eJuglans\u003c/em\u003e; Long distance trees include \u003cem\u003eSchinus\u003c/em\u003e, \u003cem\u003eAlnus\u003c/em\u003e, \u003cem\u003ePodocarpus\u003c/em\u003e and \u003cem\u003eNothofagus dombeyi\u003c/em\u003e (Mirb.) Oerst.-type\u003cem\u003e.\u0026nbsp;\u003c/em\u003eOther herbs include \u003cem\u003eChrysanthemum\u003c/em\u003e, Rubiaceae, Lamiaceae, Papilionoideae, Solanaceae, Verbenaceae, Rutaceae, Euphorbiaceae, Caryophyllaceae, \u003cem\u003eEphedra\u003c/em\u003e, Rosaceae, \u003cem\u003eErodium\u003c/em\u003e, Onagraceae, Malvaceae, Geraniaceae, Scrophullariaceae and Monocotyledoneae. The identification of pollen grains, spores and NPPs were made with reference to atlases, published keys and the reference collection of the Laboratory of Paleoecology and Palynology, IIMyC CONICET-UNMdP.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSamples for plant macrofossil remains and associated fauna were treated with KOH10% for 4 h and sieved through 200 and 100\u0026nbsp;\u0026mu;m meshes. The volume of each sample was calculated by water displacement, and varied between 5 and 10 cm\u003csup\u003e3\u003c/sup\u003e, and the residue was examined under a stereo-microscope at 50x magnification. Recognizable plant and animal fossils were isolated, identified and counted and the results were expressed in number of remains per 10 cm\u003csup\u003e3\u0026nbsp;\u003c/sup\u003eof sediment. Animal remains (cladocerans ephippia, briozoos statoblasts, gastropods carbonatic shells, chironomid head capsules and ostracods valves) were grouped as associated fauna, but were not\u0026nbsp;taxonomically\u0026nbsp;classified in\u0026nbsp;genus\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;and/or species. The animal fossils were recovered because of their size retained in the mesh; their inclusion does not intend to represent the entire assemblage of each group, just merely give an approximation of them and reinforce the interpretations based on the other indicators, since each type of organism-indicator requires a specific methodology. In particular, zooplankton ephippia remains can be\u0026nbsp;used to infer changes in fish population density and shifts in habitat structure as well as changes in macrophyte density with nutrient enrichment (Bennion et al. 2018 and cites there in). Given their intermediate and important position in the food-web, zooplankton data complement the plant macrofossil records and hence are reported briefly here. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStratigraphic diagrams were plotted with Tilia 2.0.41 (Grimm 2015). The samples were classified\u0026nbsp;by\u0026nbsp;a restricted clustering analysis using the distance of Edwards and Cavalli-Sforza as a measure of dissimilarity. Cluster analysis was performed with CONISS software included in the Tilia-Graph package (Grimm 2015). Pollen, NPPs and plant macrofossils remains were considered for the zonation and CONISS cluster dendrograms are displayed on the right side of the diagrams (Figs. 4, 5)\u003c/p\u003e\n\u003cp\u003eVascular plant nomenclature follows the database Flora del Conosur, Cat\u0026aacute;logo de las Plantas Vasculares published online by the Instituto de Bot\u0026aacute;nica Darwinion (http://www.darwin.edu.ar/Proyectos/FloraArgentina/fa.htm).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eLithology, organic matter and carbonates content\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree sedimentary units were defined on KH2 based on variations in sediment lithology (Fig. 2A). The basal Unit A, up to 22 cm, presents massive, black clayed-silty sediments with gastropod presence. Unit B, between 22-19 cm, contains massive, grayish-silty sediments with gastropod presence. The contact between these two units is net and planar. Unit C, between 19-0 cm, comprises massive, brownish-silty, bioturbated sediments. This unit is characterized\u0026nbsp;by a high\u0026nbsp;presence of plant roots. The contact between this unit and the underlying unit is net and planar.\u003c/p\u003e\n\u003cp\u003eThe organic matter content values were similar in both cores (KH2 and KH3) and presented the same trends (Fig. 2B). From the base to 20 cm, the values fluctuated between 8% and 19.5%. In the interval between 20 and 7 cm, the organic matter content increased and reached maximum values of up to 55%. A decrease was observed from 6 cm in KH3 with values around 49%, and from 4 cm in KH2 reaching values of 39%. The carbonates content showed a contrary trend between (30-24) cm and (6-0) cm and a similar trend between (24-6) cm to the organic matter content. The values fluctuated between 8.5% and 3.5% from the base to 23 cm, then slightly increased up to 6.5% at 4 cm, and decreased up to 4% to the top (Fig. 2B).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe correlation of cores was based on the organic matter content (Fig. 2B). Four apparent features in both cores were used as specific tie points: first, the low values of organic matter at the base of both cores (\u0026ge;\u0026nbsp;12%); second, the decrease of organic matter values (from 20 to 14%); third, the points at 20 cm before the increase in matter organic content, and fourth, when the maximum values start to decline.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eChronology\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn important issue in the chronology of lacustrine sequences in Pampa plain, is the incorporation of the pollen of \u003cem\u003eEucalyptus\u003c/em\u003e spp. as chronomarker in the age-depth model, since that corresponds to exotic trees introduced in the region at 1858 AD. According to the criteria established by S\u0026aacute;nchez Vuichard et al. (2021), the first appearance of Eucalyptus spp. pollen at 16 cm depth on KH3 core was assigned to an age of 1880 AD.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe activity of 137Cs was used to validate the ages obtained from the \u003csup\u003e210\u003c/sup\u003ePb chronology, considering the activity peak of \u003csup\u003e137\u003c/sup\u003eCs at 9 cm as the one corresponding to 1963 AD.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to the age-depth model, the uppermost 30 cm of KH3 core spanned the time between \u003cem\u003eca\u003c/em\u003e.1360 and 2017 years AD (last 600 years)(Fig. 3C).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePollen, NPPs and plant macrofossil remains and associated fauna\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the cluster\u0026nbsp;analysis, four\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;pollen and NPPs assemblage zones (PKH 1-4) (Fig. 4) and three plant macrofossil assemblage zones (MKH 1-3) (Fig. 5) were established.\u003c/p\u003e\n\u003cp\u003ePKH 1 (1360 to 1550 AD; 580 to 390 cal years BP).This zone was characterized by the maximum values of Poaceae and Chenopodioideae (\u0026le;53% and\u0026nbsp;\u0026le;47%, respectively), accompanied by Ambrosia and Cyperaceae (\u0026le;37% and\u0026nbsp;\u0026le;26%, respectively). Chenopodioideae had the highest values at the base and decreased towards the top of the zone.\u0026nbsp;\u003cem\u003eRumex\u003c/em\u003e presented the highest values (\u0026le;2%). Diverse emergent macrophytes, such as\u0026nbsp;\u003cem\u003eAlternanthera\u003c/em\u003e, \u003cem\u003ePolygonum\u003c/em\u003e and \u003cem\u003eTypha\u003c/em\u003e were present with values of up to 10%. Among the NPPs,\u0026nbsp;\u003cem\u003ePediastrum\u0026nbsp;\u003c/em\u003edominated the zone (\u0026le;30%).\u003c/p\u003e\n\u003cp\u003ePKH 2 (1550 to 1670 AD; 390 to 280 cal years BP). This zone was characterized by Poaceae, \u003cem\u003eAmbrosia\u003c/em\u003e, Cyperaceae and Chenopodioideae (\u0026le;30%,\u0026nbsp;\u0026le;27%,\u0026nbsp;\u0026le;28% and\u0026nbsp;\u0026le;16%, respectively).\u0026nbsp;\u003cem\u003eCarduss\u003c/em\u003e, \u003cem\u003ePlantago\u0026nbsp;\u003c/em\u003eand Brassicaceae were also present. The other emergent macrophytes were present with similar values that those of the previous zone, although \u003cem\u003ePolygonum\u003c/em\u003e was not longer present and \u003cem\u003ePhyla nodiflora\u003c/em\u003e appeared in low values. Towards the top of the zone,\u0026nbsp;\u003cem\u003eMyriophyllum\u0026nbsp;\u003c/em\u003ebegan to increase its values. Among the NPPs,\u0026nbsp;\u003cem\u003ePediastrum\u003c/em\u003e dominated the zone with its maximum values (\u0026le;62%), accompanied by\u0026nbsp;\u003cem\u003eScenedesmus, Botryococcus braunii\u003c/em\u003e and \u003cem\u003eTetraedron\u0026nbsp;\u003c/em\u003e(\u0026le;10%).\u003c/p\u003e\n\u003cp\u003ePKH3 (1670 to 1870 AD; 280 to 80 cal years BP). This zone was dominated by \u003cem\u003eMyriophyllum\u003c/em\u003e, which presented the maximum values (\u0026le;54%) of the spectra, followed by Cyperaceae and\u0026nbsp;\u003cem\u003eAmbrosia\u003c/em\u003e (35% and 20%, respectively). \u003cem\u003eCeratophyllum demersum\u003c/em\u003e increased towards the top of the zone. The other emergent macrophytes maintained the same values as in the previous zone, with the reappearance of \u003cem\u003ePolygonum\u003c/em\u003e towards the end of the zone. Among the NPPs, a trend towards a more abundant and diverse community was recognized. \u003cem\u003eGloeotrichia\u0026nbsp;\u003c/em\u003edominated the zone (\u0026le;31%), accompanied by\u0026nbsp;\u003cem\u003ePediastrum\u003c/em\u003e (\u0026le;20%), and to a lesser extent by Desmidiaceae,\u003cem\u003e\u0026nbsp;Botryococcus braunni\u003c/em\u003e, \u003cem\u003eTetraedron\u0026nbsp;\u003c/em\u003eand\u003cem\u003e\u0026nbsp;Scenedesmus\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003ePKH 4 (1870 to 2017 AD; 80 to -67 cal years BP). This zone was characterized by \u003cem\u003eMyriophyllum\u0026nbsp;\u003c/em\u003e(\u0026le;38%) and Cyperaceae (\u0026le;31%) accompanied by\u0026nbsp;\u003cem\u003eAmbrosia\u0026nbsp;\u003c/em\u003eand \u003cem\u003eCeratophyllum demersum\u0026nbsp;\u003c/em\u003e(\u0026le;24% and\u0026nbsp;\u0026le;20%, respectively). The presence of exotic tree taxa (\u003cem\u003eEucalyptus\u003c/em\u003e, \u003cem\u003ePinus\u003c/em\u003e/\u003cem\u003eCedrus\u003c/em\u003e and Other exotic trees) was observed. Other pollen types that included exotic species such as \u003cem\u003eCarduus\u003c/em\u003e, Asteraceae subf. Cichorioideae, \u003cem\u003eRumex\u003c/em\u003e,\u003cem\u003e\u0026nbsp;Plantago\u003c/em\u003e and Brassicaceae were also recorded. The phytoplankton community was represented by \u003cem\u003eGloeotrichia\u003c/em\u003e (\u0026le;22%),\u0026nbsp;\u003cem\u003eBotryococcus\u003c/em\u003e \u003cem\u003ebraunii\u003c/em\u003e (\u0026le;17%),\u0026nbsp;\u003cem\u003ePediastrum\u003c/em\u003e (\u0026le;13%), Desmidiaceae (\u0026le;13%) and\u0026nbsp;\u003cem\u003eZygnema\u003c/em\u003e (\u0026le;10%).\u003c/p\u003e\n\u003cp\u003eMKH 1 (1430 to 1590 AD;\u003cem\u003e\u0026nbsp;\u003c/em\u003e520 to 360 cal years BP). \u003cem\u003eNitella\u0026nbsp;\u003c/em\u003esp. oospores were found in this section with the highest concentration values (104 units/10 cm\u003csup\u003e3\u003c/sup\u003e). The associated fauna was represented by \u003cem\u003eCeriodaphnia\u0026nbsp;\u003c/em\u003esp. (52 units/10 cm\u003csup\u003e3\u003c/sup\u003e), \u003cem\u003eDaphnia\u0026nbsp;\u003c/em\u003esp.1 (20 units/10 cm\u003csup\u003e3\u003c/sup\u003e), \u003cem\u003eDaphnia\u0026nbsp;\u003c/em\u003esp. 2 and \u003cem\u003eMoina\u0026nbsp;\u003c/em\u003esp. ephippia (12 units/10 cm\u003csup\u003e3\u003c/sup\u003e),\u0026nbsp;\u003cem\u003ePlumatella\u0026nbsp;\u003c/em\u003esp. statoblasts (18 units/10cm\u003csup\u003e3\u003c/sup\u003e) and chironomid head capsules (24 units/10cm\u003csup\u003e3\u003c/sup\u003e).\u0026nbsp;Ostracod\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;valves were present in high concentrations (278 units/10 cm\u003csup\u003e3\u003c/sup\u003e).\u003c/p\u003e\n\u003cp\u003eMKH 2 (1590 to 1920 AD; 360 to 30 cal years BP). This zone was characterized by high values of \u003cem\u003eCeratophyllum demersum\u003c/em\u003e epidermis remains (814 units/10cm\u003csup\u003e3\u003c/sup\u003e) and high values of plant-associated fauna, mainly represented by\u0026nbsp;gastropod\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;shells (49 units/10cm\u003csup\u003e3\u003c/sup\u003e). A marked decrease of the open water fauna ephippia and the\u0026nbsp;ostracod\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;valves was observed.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMKH 3 (1920 to 2017 AD, 30 to -67 cal years BP). This zone was characterized by submerged macrophytes remains, oospores of \u003cem\u003eNitella\u003c/em\u003e sp. (70 units/10 cm\u003csup\u003e3\u003c/sup\u003e) and \u003cem\u003eTolypella\u0026nbsp;\u003c/em\u003esp. (23 units/10 cm3), \u003cem\u003eCeratophyllum demersum\u003c/em\u003e epidermis (344 units/10cm\u003csup\u003e3\u003c/sup\u003e) and \u003cem\u003eZanichellia\u003c/em\u003e \u003cem\u003epalustris\u003c/em\u003e L. seeds (24 units/10cm\u003csup\u003e3\u003c/sup\u003e). Gastropods shells and \u003cem\u003ePlumatella\u003c/em\u003e sp. statoblasts (62 units/10 cm\u003csup\u003e3\u003c/sup\u003e and 22 units/10 cm\u003csup\u003e3\u003c/sup\u003e, respectively) represented the plant-associated fauna. The sediment-associated fauna was represented by chidorids ephippia that showed their highest values (22 units/10 cm\u003csup\u003e3\u003c/sup\u003e). Also,\u0026nbsp;ostracod\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;valves exhibited the highest values (382 units/10 cm\u003csup\u003e3\u003c/sup\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe three oldest pollen and NPP assemblage zones, PKH 1-3, and the first \u003cem\u003eca\u003c/em\u003e. 47 years of PKH4, corresponded to the to plant macrofossil zones MKH 1-2, and the last \u003cem\u003eca\u003c/em\u003e. 95 years of the pollen and NPP assemblage zone, PKH 4, corresponded to the plant macrofossil assemblage zone MKH 3.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cstrong\u003eLake evolution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe analyzed sedimentary record of Kakel Huincul lake indicated the presence of a water body since 1360 AD to the present. The lake evolved from a charophyte-dominated community towards a much\u0026nbsp;more\u0026nbsp;diverse ecosystem conformed by angiosperms, charophytes and algae through time. According to these characteristics, four moments with different lake structure and functioning were identified.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1360-1550 AD\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA clear, small, alkaline and oligotrophic lake with low nutrient content was inferred for this period. The aquatic community was dominated by the charophyte \u003cem\u003eNitella\u003c/em\u003e sp. accompanied by \u003cem\u003eCeratophyllum\u0026nbsp;\u003c/em\u003eand\u003cem\u003e\u0026nbsp;Myriophyllum\u003c/em\u003e. Charophytes are fast colonizers and competitively superior to phytoplankton in conditions of low nutrient concentration and high light intensity, and \u0026nbsp; can accumulate substantial amounts of nutrients, which consequently causes a reduction of the water nutrient content and a lower availability of these nutrients for phytoplankton (van der Berg et al. 1998; Blindow et al. 2014).The high biomass and dense mats of \u003cem\u003eNitella\u003c/em\u003e sp. provided a suitable habitat, reducing predation pressure and supplying epiphytic algae as a food resource for the existing zooplankton: \u003cem\u003eDaphnia\u0026nbsp;\u003c/em\u003espp., \u003cem\u003eCeriodaphnia\u003c/em\u003e sp., \u003cem\u003eMoina\u003c/em\u003e sp.,\u0026nbsp;chironomids\u0026nbsp;and \u003cem\u003ePlumatella\u003c/em\u003e sp (Wetzel 2001; Blindow et al. 2014). Furthermore, the low organic matter content indicated a less productive lake. According to Blindow et al. (2014) immobilization of nutrients by macrophytes is suggested to be one of the most important mechanisms stabilizing clear water conditions.\u003c/p\u003e\n\u003cp\u003eThe emergent macrophyte community around the lake, represented by Cyperaceae, \u003cem\u003eAlternanthera\u003c/em\u003e, \u003cem\u003ePolygonum\u003c/em\u003e and \u003cem\u003eTypha,\u003c/em\u003e was underrepresented because of the greater expression of the regional plant community characterized by grasses and herbs (Poaceae and \u003cem\u003eAmbrosia\u003c/em\u003e)\u0026nbsp;and by the local halophyte community that would have surrounded the lake in previous time. The emergent macrophyte\u0026nbsp;\u0026nbsp;community appeared less diverse and less abundant than the modern one.\u003c/p\u003e\n\u003cp\u003eAt the beginning of this period, the highest abundance of Chenopodioideae suggested a lake of reduced size, compared to today, that was recovering and increasing water level to 1550 AD. Pampean shallow lakes decreased in size during dry periods, and halophytic plants quickly colonized the extensive surrounding area that became free of water and consequently characterized by brackish conditions. Tonello and Prieto (2008) proposed Chenopodioideae as a good indicator of low precipitation values, based on a modern pollen-climate analysis at Pampa plain. On the other hand, the high values of \u003cem\u003eAmbrosia\u003c/em\u003e\u003cem\u003e\u0026nbsp;sp.\u003c/em\u003e and increased values of \u003cem\u003eRumex\u003c/em\u003e sp\u003cem\u003e\u0026nbsp;ca\u003c/em\u003e. 1400 AD allowed inferring prolonged floods since these conditions promoted theseedling production and the colonization of\u0026nbsp;areas without competition in grazed grasslands (Insausti et al. 1995; Insausti and Grimoldi 2006). In addition, at the beginning of this period the low organic matter content values, the highest values of carbonate content and the massive deposits (lithological unit A) indicated a small aquatic system subjected to evaporation/desiccation periods. These characteristics allowed inferring climatic conditions drier than present, with some humid pulses. Similar conditions were suggested by Cordoba et al. (2014)\u0026nbsp;for del Monte lake (southwestern Pampa plain) and by Guerra et al. (2015) for Melincu\u0026eacute; lake (northern Pampa plain). Drought conditions with low water level were inferred for del Monte lake between 1200-1530 AD, while\u0026nbsp;a\u0026nbsp;very shallow and ephemeral saline lake was\u0026nbsp;mentioned for Melincu\u0026eacute; lake between 1024-1492 AD. The similarity of Kakel Huincul litology with both sedimentary records supported inferring low rainfall at this time with episodic intense precipitation for the Kakel Huincul area. Dry conditions\u0026nbsp;were\u0026nbsp;also reported for other southeastern Pampean lakes (Hinojales-San Leoncio, Tobares, Lonkoy, Nahuel Ruc\u0026aacute; and Hinojales; Stutz et al. 2014) and\u0026nbsp;for\u0026nbsp;Cabeza de Buey lake,\u0026nbsp;in central Pampa plain (S\u0026aacute;nchez Vuichard et al. 2021) for this time\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp;.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1550-1670 AD\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA mesotrophic lake with higher nutrient content and higher water level than the previous one was inferred. A diverse and abundant phytoplanktonic community dominated by \u003cem\u003ePediastrum\u003c/em\u003e, \u003cem\u003eScenedesmus\u003c/em\u003e and \u003cem\u003eTetraedron,\u003c/em\u003e characteristic taxa of turbid pampean shallow lakes (Allende et al. 2009; S\u0026aacute;nchez et al. 2013), accompanied by the submerged \u003cem\u003eMyriophyllum\u003c/em\u003e and \u003cem\u003eCeratophyllum\u003c/em\u003e\u003cem\u003e,\u003c/em\u003ereplaced \u003cem\u003eNitella\u003c/em\u003e community.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCharophytes decline could be due to poor/low light availability because of a shading effect by phytoplankton and by the angiosperms \u003cem\u003eMyriophyllum\u003c/em\u003e and \u003cem\u003eCeratophyllum\u003c/em\u003e, which in this way outcompeted charophytes. According to Blindow (1992), charophytes disappear with the increase in nutrient levels and with the deterioration of the light environment. Besides the shading effect, the increase in lake\u0026acute;s depth could have contributed to the decrease in \u003cem\u003eNitella\u003c/em\u003e, since this algae develops better in low water bodies or shallow areas (Blindow 1992). On the\u0026nbsp;other hand,\u0026nbsp;several studies suggested\u0026nbsp;\u003cem\u003ePediastrum\u003c/em\u003e and \u003cem\u003eScenedesmus\u003c/em\u003e dominance as indicators\u0026nbsp;of higher nutrient content and wet periods (Borel et al. 2003, Medeanic 2006, S\u0026aacute;nchez Vuichard et al. 2021).\u003c/p\u003e\n\u003cp\u003eCladocerans are sensitive to both bottom-up changes in resources (phytoplankton) and top-down shifts in predation (zooplanktivorous fish) (Davidson et al. 2011). A decrease in the open water fauna, more evident in large size taxa such as \u003cem\u003eDaphnia\u003c/em\u003e spp., could be related with a high predation pressure by zooplanktivorous fish, since the high\u0026nbsp;nutrients (phytoplankton) available would not be a limiting resource. Zooplankton densities were suggested to be higher at intermediate biomass of submerged vegetation and lower at both, low and high macrophyte biomass (Blindow et al. 2014), and in Kakel Huincul lake higher macrophyte abundance started to develop \u003cem\u003eca\u003c/em\u003e. 1600 AD. As mentioned, the decrease of the refuge function of dense vegetation may be caused by high predation pressure within this vegetation (Jeppesen et al. 1998; Hargeby et al. 2005). Consequently, the lack of zooplankton would have contributed to the development of phytoplankton and turbid conditions during this period.\u003c/p\u003e\n\u003cp\u003eFurthermore, the massive accumulation of the fine sediments and low content of carbonates indicated an enlarging environment in accordance with the entrance of water to the lake. Similar sedimentological characteristics for del Monte and Melincu\u0026eacute; lakes indicated wetter conditions with higher water levels (C\u0026oacute;rdoba 2012; Guerra et al. 2015). In addition, the emergent community diminished in diversity, but Cyperaceae started to increase in abundance.\u0026nbsp;This\u0026nbsp;could be interpreted as a change to an enlarging lake, probably associated to an increase in rainfall since Cyperaceae is a good indicator of humid conditions (Tonello and Prieto, 2008).\u0026nbsp;The Pampean lakes morphometry showed a direct correlation with rainfall (Bohn et al. 2016), and during wet periods the lakes increased in size and macrophytes, such as species of the Cyperaceae family, dominated the littoral area (Tonello et al. 2014).\u0026nbsp;Then,\u0026nbsp;higher rainfall was inferred\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;during this period for the area of Kakel Huincul lake. In concordance, Cordoba (2012) suggested wet conditions for del Monte lake (southwestern Pampa plain) during 1530-1750 AD and\u0026nbsp;Fontana (2005) mentioned higher lake levels between 1290-1680 AD at Laguna del Sauce (south Pampa plain). According to historical chronicles 1559, 1567-1568 and 1574 were particular rainy years for Buenos Aires province, and a cold and humid climate was reported during the first half of the 1600s in central Argentina (Gasc\u0026oacute;n and Caviedes 2012; Scarpati and Capriolo 2013).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1670-1870 AD\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA\u0026nbsp;smaller, clear, meso/eutrophic lake, with medium-high nutrient content and\u0026nbsp;alkaline pH was inferred for this moment. The high abundance of the submerged macrophytes \u003cem\u003eMyriophyllum\u003c/em\u003e and \u003cem\u003eCeratophyllum\u003c/em\u003e, the decrease of turbid conditions indicators, \u003cem\u003ePediastrum\u003c/em\u003e, \u003cem\u003eScenedesmus\u003c/em\u003e and \u003cem\u003eTetraedron\u003c/em\u003e, and the carbonate content increase suggested a\u0026nbsp;smaller\u0026nbsp;and shallow water body than previous. Low water levels promoted colonization and growth of macrophytes, since light reached the\u0026nbsp;sediment and germinated seeds (Smith and Barko 1990, Egertson et al. 2004). On the other hand, the requirement of high levels of inorganic nitrogen by Ceratophyllum (Goulder and Boatman 1971) makes this element less available for the development of phytoplankton. The exception is Gloeotrichia, which increase is due to their ability of fixing nitrogen when this element is a limiting resource (van Geel 2001). The high abundance of the plant-associated fauna (especially gastropods) was related to the abundant submerged macrophyte community, where invertebrates find shelter and food supply. Nevertheless, the open water fauna (cladocerans) almost disappeared probably associated to a lower food supply by the decrease in phytoplankton (Davidson et al. 2011).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAfter the intense drought of 2008-2009\u0026nbsp;years, some southeastern pampean lakes presented clear conditions under shallowness with an important development of submerged macrophytes (author\u0026rsquo;s personal observations). Thus, Kakel Huincul lake could be indicating a period of low rainfall for 1670-1870 AD.\u0026nbsp;In Cabeza de Buey lake (central Pampa plain), the predominance of submerged macrophytes after a phytoplankton-dominated period indicated a decrease of lake level\u0026nbsp;associated with less precipitation values (S\u0026aacute;nchez Vuichard et al. 2021). \u0026nbsp;In agreement, C\u0026oacute;rdoba et al. (2014) inferred a general drought trend during 1750-1870 AD based on the increase of carbonate content and evaporites in some southwestern shallow lakes. The authors mentioned that extended periods of water deficit or droughts were very frequent during the last quarter of the 1700\u0026acute;s and the beginning of the 1800\u0026acute;s. Between 1827 and 1832 AD, an episode of extreme aridity was documented by Darwin (1860) on his trip through central Argentina, called \u0026ldquo;The Great Drought\u0026rdquo;.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1870-2017 AD\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring this period, a clear-eutrophic, perennial, higher-level lake with high nutrient content and alkaline pH was recognized, suggested by the dominance of the submerged macrophytes (angiosperms and charophytes) \u003cem\u003eMyriophyllum\u003c/em\u003e, \u003cem\u003eCeratophyllum\u003c/em\u003e, \u003cem\u003eNitella\u003c/em\u003e and \u003cem\u003eTolypella\u003c/em\u003e along with the increase in the Zygnemataceae,\u0026nbsp;the decrease of the other green algae, \u003cem\u003ePediastrum\u003c/em\u003e, \u003cem\u003eScenedesmus\u003c/em\u003e and \u003cem\u003eTetraedron\u003c/em\u003e. The submerged vegetation wasdominated by\u003cem\u003e\u0026nbsp;Myriophyllum\u003c/em\u003e and \u003cem\u003eCeratophyllum\u003c/em\u003e, and at \u003cem\u003eca\u003c/em\u003e. 1965 AD \u003cem\u003eNitella\u003c/em\u003e, \u003cem\u003eTollypella\u003c/em\u003e and \u003cem\u003eZanichellia palustris\u003c/em\u003e were incorporated to the community. The dominance of macrophytes limited the nutrients\u0026nbsp;availability\u0026nbsp;to phytoplankton and resulted in higher water clarity and a predominance of benthic primary production (Bennion\u0026nbsp;et al. 2018.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe record indicated\u0026nbsp;that aquatic vegetation composition changed over the last 100 years towards species associated with eutrophic conditions. Besides the dominance of macrophytes, the process of eutrophication was also indicated by the prevalence of \u003cem\u003eGloeotrichia\u003c/em\u003e and Desmidiaceae in the algal community (Scheffer 1998; Borel et al. 2003) as well as by the highest values of organic matter content. Sayer et al. (2010) and Bennion et al. (2018) indicated eutrophic conditions based on the presence of a mixed community dominated by \u003cem\u003ePotamogeton crispus\u003c/em\u003e, \u003cem\u003eZanichellia pallustris\u003c/em\u003e and \u003cem\u003eCeratophyllum demersum\u003c/em\u003e accompanied by some charophytes. \u003cem\u003eC. demersum\u003c/em\u003e and \u003cem\u003eZ. pallustris\u003c/em\u003e performed well on eutrophic, highly organic sediments (M\u0026auml;emets \u0026amp; Freiberg, 2005). Charophytes still occur in eutrophic waters but are typically out-competed by more nutrient-tolerant species as lakes become enriched and light availability is reduced, often becoming restricted to areas of shallow water (Bennion et al. 2018 and cites there in). Current studies in Kakel Huincul lake showed that the main nutrient concentration corresponds to a lake categorized as eutrophic with low nitrogen values and alkaline pH values (Allende et al. 2009; S\u0026aacute;nchez 2012; S\u0026aacute;nchez et al. 2013, 2017). According to the cited authors, the low levels of nitrogen observed are probably related to a high consumption by macrophytes, which were denoted dominating the record during this last period. Pampean lakes became more eutrophic because of increased nutrient loading connected mainly with the intensification of agriculture\u0026nbsp;and the increase in the precipitation values\u0026nbsp;during the last 50 years (Quir\u0026oacute;s et al. 2006; Stutz et al. 2012; Plastani et al. 2019; S\u0026aacute;nchez Vuichard et al. 2021).\u0026nbsp;Particularly,\u0026nbsp;Kakel Huincul lake is located in an area subjected to grazing\u0026nbsp;since ~1855 AD and to agriculture since ~1960 AD (Juan Uriguereca personal communication). According to Quir\u0026oacute;s et al. (2002) pampean lakes presented a pristine clear state prior to human impact. However, this study showed that Kakel Huincul lake experienced a clear pristine state dominated by submerged macrophytes, previous to evidence of human activity. Therefore, based on the observed modified vegetation close to the lake (see Regional vegetation) baseline conditions for this lake were infered ~ 1870 AD.a.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThroughout the first half of the 20\u003csup\u003eth\u003c/sup\u003e century, numerous pampean lakes and reservoirs experienced water level decreases or complete desiccation due to the phenomenon known as the \u003cem\u003ePampas Dust Bowl\u0026nbsp;\u003c/em\u003e(Herzer 2003; Tripaldi et al. 2013). This was defined for the western Pampa plain with the main drought episode \u003cem\u003eca\u003c/em\u003e. 1930, based on eolic records, but could be considered to have an effect on the eastern Pampa plain. Plastani et al. (2019) suggested that La Barrancosa lake (southeastern Pampa plain) was among the lakes that underwent desiccation caused by the droughts of the 1930s. For Chasic\u0026oacute; lake, southwestern Pampa plain, a very dry period and extremely low lake\u0026nbsp;levels\u0026nbsp;between 1930 and 1970 AD were inferred (Frazer et al. 2020). C\u0026oacute;rdoba et al. (2014) mentioned several short-lived episodes of extremely low lake levels were recorded between 1890-1913 AD and 1928-1939 AD and the predominance of low to intermediate lake levels for the southwestern pampean lakes associated with negative precipitation anomalies for the first half of the 20\u003csup\u003eth\u003c/sup\u003e century. According to Maip\u0026uacute;\u0026nbsp;city\u0026nbsp;instrumental precipitation record (Instituto Nacional de Tecnolog\u0026iacute;a Agropecuaria, INTA) Kakel Huincul area was characterized by low rainfall and dry periods only from 1935 to 1941. Nevertheless, this dry trend was not suggested by the analyzed\u0026nbsp;indicatorsin Kakel Huincul record, probably due to the lake proximity to the ocean and its influence. The differences between Kakel Huincul lake and the aforementioned lakes could be due to the climatic heterogeneity of the Pampan plain (Aliaga et al. 2017).Furthermore, differences could be due to the type of\u0026nbsp;indicator involved (each with strengths and weaknesses), as to the temporal resolution of each reconstruction that\u0026nbsp;does not\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;present the same level of detail.\u003c/p\u003e\n\u003cp\u003eThe emergent macrophyte community developed as an abundant littoral ring around the lakeat\u003cem\u003e\u0026nbsp;ca\u003c/em\u003e. 1900 AD was similar\u0026nbsp;to that\u0026nbsp;observed today, in agreement with the development of a larger lake. The massive organic fine grain rich muds, along with the increased organic matter and salinity\u0026nbsp;drop (as noted by low carbonate amounts), suggested the development of a lake\u0026nbsp;of intermediate to high water level and a high primary productivity. This was in agreement with the changes in the rainfall spatial distribution due to an increase in the precipitation values detected at 1970, known as \u003cem\u003eSalto Clim\u0026aacute;tico\u003c/em\u003e (Agosta and Compagnucci 2008), promoted a significant increase in the levels and extension of the lakes and littoral areas, which reached the maximum values reconstructed since the Little Ice Age (C\u0026oacute;rdoba et al. 2014; Guerra et al. 2015; Plastani et al. 2019). According to Bohn et al. (2016), the variations in morphometry of pampean lakes show a direct correlation with precipitation. During wet years, lakes become larger and macrophytes, like Cyperaceae, dominate the littoral area, as is seen nowadays in Kakel Huincul lake. Then,\u0026nbsp;higher rainfall than previous was inferred\u0026nbsp;during this period for the southeastern Pampa plain. Scarpati and Capriolo (2013) indicated periods of flooding for 1980, 1985, 2001 and 2005. In particular, they highlighted the floods of 1980 as one of the most important that occurred during the 20\u003csup\u003eth\u003c/sup\u003e century and that implied great losses for national agricultural-livestock production.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRegional vegetation\u003c/p\u003e\n\u003cp\u003eThe regional vegetation of Pampa plain\u0026nbsp;has been a grassland and\u0026nbsp;did\u0026nbsp;not show great changes since the Pleistocene-Holocene transition (Prieto 1996, 2000; Tonello and Prieto 2009). In this context,\u0026nbsp;during the last 600 years\u0026nbsp;the regional vegetation\u0026nbsp;in Kakel Huincul area\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;was represented by grasses (Poaceae) accompanied by herbs such as \u003cem\u003ePlantago\u003c/em\u003e,\u003cem\u003eAmbrosia,\u003c/em\u003e \u003cem\u003eRumex\u003c/em\u003e and taxa belonging to Asteraceae and Brassicaceae families, in agreement with that reported by Stutz et al. (2014) for southeastern pampean lakes.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs aforementioned, the modern landscape of the Pampa plain has been influenced by human activities since the European settlement in the 1600s, but cattle became intensive at 1810and agriculture started \u003cem\u003eca.\u003c/em\u003e a-1900 AD.\u0026nbsp;Particularly,\u0026nbsp;\u0026nbsp;Kakel Huincul area\u0026nbsp;\u0026nbsp;was dedicated to cattle raising\u0026nbsp;since\u0026nbsp;1855 AD\u0026nbsp;with the establishment of\u0026nbsp;\u003cem\u003eChacabuco\u003c/em\u003e \u003cem\u003eestancia\u003c/em\u003e\u003cem\u003e\u0026nbsp;(farm)\u003c/em\u003e next to the lake(Guzm\u0026aacute;n 1999), whereas\u0026nbsp;, agriculture implementation started\u003cem\u003e\u0026nbsp;ca\u003c/em\u003e. 1960 AD (Juan Uriaguereca (personal communications). Cattle were always the main activity because of\u0026nbsp;the\u0026nbsp;extremely flat landscape, edaphic features and periodic flooding that occurred in the region (Viglizzo et al. 2001). The analyzed indicators in Kakel Huincul lake showed some changes related to the anthropic impacts. The increase of \u003cem\u003eCarduus\u0026nbsp;\u003c/em\u003eafter 1600 AD suggested cattle impact. Similar abundance of thistles (\u003cem\u003eCarduus\u003c/em\u003e-type) was reported for the northeast Pampa plain after 1790 AD (Prieto et al. 2004). The historical chronologies highlighted that introduction of large domestic herbivores at 1700s caused the replacement of the grassland by extensive thistles (\u003cem\u003eCynara cardunculus\u003c/em\u003e, \u003cem\u003eSilybum marianum\u003c/em\u003e, \u003cem\u003eCarduus acanthoides\u003c/em\u003e and \u003cem\u003eC\u003c/em\u003e. \u003cem\u003etenuiflorus\u003c/em\u003e) (Ghersa y Le\u0026oacute;n, 2001). \u003cem\u003ePlantago\u003c/em\u003e, \u003cem\u003eRumex,\u003c/em\u003e and Brassicaceae were present since ca. 1360 AD, they and Asteraceae subf. Cichorioideae, notoriously increased since 1880 AD. These four pollen types represent exotic and native species. Therefore, their presence in the record between ca. 1360 and ca. 1880 AD could be interpreted as representative f native vegetation, while their increase after 1880 AD could be associated with both native and exotic species. For example, \u003cem\u003ePlantago lanceolata\u003c/em\u003e L., \u003cem\u003eRumex crispus\u003c/em\u003e L. and \u003cem\u003eBrassica nigra\u003c/em\u003e (L.) W.D.J. Koch, are introduced weeds associated with crops (Vervoorst 1967). The increase of Asteraceae subf. Cichorioideae was related to agriculture since it is regarded as an indicator of soils that have been tiled over several years (Prieto et al. 2004). Besides, the presence of Ambrosia in the record could be related to cattle impact until 1960 AD and later associated to agriculture\u0026acute;s implementation in the area, since it quickly colonizes overgrazed grasslands and is an important crop weed (Vervoorst 1967; Poggio et al. 2015). Similar fluctuations of \u003cem\u003eAmbrosia\u0026nbsp;\u003c/em\u003ewere detected also in Cabeza de Buey lake, and were associated to different human impacts in the landscape transformation (S\u0026aacute;nchez Vuichard et al. 2021). On the other hand, \u003cem\u003eEucalyptus\u003c/em\u003e, \u003cem\u003ePinus\u003c/em\u003e and other exotic trees pollen values appear after ca. 1890 AD and were associated with the use these trees were given in farmlands (see Land Transformation) and with the foundation of Maip\u0026uacute; town in 1875 AD, which had a commercial and demographic development after 1900 AD (S\u0026aacute;nchez Vuichard et al. 2021).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWetland deterioration and baseline conditions\u003c/p\u003e\n\u003cp\u003eAs aforementioned natural grasslands of Pampa plain were initially altered by cattle and later by agriculture (see Land Transformation). However, our results showed that southeastern wetlands were mainly affected because of the\u0026nbsp;intensive agriculture that impacted these ecosystems during the last 50 years.\u0026nbsp;Farmland in Argentina expanded quickly after 1950 at the expense of natural land and without consideration of the related ecological costs. The agricultural expansion\u0026nbsp;over\u0026nbsp;two million ha of native grassland, mostly in the Pampa plain,\u0026nbsp;was\u0026nbsp;significant for the local biodiversity and functioning of the ecosystem (Wiedemeier 2018). Kakel Huincul lake constitutes a good example of how Argentina\u0026acute;s wetlands have been impacted for more than five decades. Through the long-term monitoring analysis performed in this study,\u0026nbsp;it was\u0026nbsp;possible to assess the ecosystem responses to disturbances since 1360 AD, as well as to define the baseline conditions and the effect of the anthropic impact.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn Kakel Huincul lake, the\u0026nbsp;anthropic\u0026nbsp;impact was identified through cattle farming from 1870 AD and agriculture implementation after \u003cem\u003eca\u003c/em\u003e. 1960 AD, and the previous clear conditions of the lake were considered as the baseline conditions. Similarly, S\u0026aacute;nchez Vuichard et al. (2021) reported baseline conditions at \u003cem\u003eca.\u003c/em\u003e 1850 AD and eutrophication initial process at \u003cem\u003eca\u003c/em\u003e. 1880 AD in Cabeza de Buey lake (central Pampa plain). Differences between both lakes could be due to differences in the resolution of the sedimentary record. Kakel Huincul record could present a better resolution, since Cabeza de Buey lake age-depth model was not build with 210 Pb ages. These clear conditions are those present in the absence of anthropic impact and are\u0026nbsp;currently\u0026nbsp;unknown for most pampean shallow lakes. In addition, given the relatively low intensity of human activity during the early period of the lake history (prior to 1880 AD) the changes in phytoplankton and macrophyte communities were expected to have been mainly controlled by climate. After 1880 AD, the lake changes probably were a result of a combination of climate (increases and decreases of precipitation values) and human impacts (urbanization and agriculture implementation),\u0026nbsp;that\u0026nbsp;generated an accelerated eutrophication.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFurthermore, agriculture intensification in southeastern Pampa plain during the last 50 years was detected based on proxies\u0026rsquo; analysis. As aforementioned, the agriculture was implemented at 1960 in the Kakel Huincul area and\u0026nbsp;the intensification started by ending 1980\u0026acute;s as denoted by the increase in diagnostic pollen taxa. Moreover, the acceleration in the eutrophication process related to the adoption of soy crops was observed by \u003cem\u003eca\u003c/em\u003e. 1995, represented by the increase in algae and by the presence of submerged macrophytes. In accordance, Wiedemeier (2018) mentioned that the Argentinean Pampas have been a global hotspot of agricultural land use change since the beginning of the 21\u003csup\u003est\u003c/sup\u003e century. Between 2000 and 2010, driven by high prices of soybean, the soybean cultivated area increased by 210% in Latin America, also replacing large parts of the cattle production.\u0026nbsp;\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThrough the analysis of Kakel Huincul lake history\u0026nbsp;it\u0026nbsp;was possible to track the environmental change and infer past conditions,\u0026nbsp;which\u0026nbsp;allowed to distinguish the climatic from the anthropic\u0026nbsp;factors, as well as to define their impacts on these ecosystems. The changes observed in the lake communities before 1880 AD were a result of climatic perturbations (increase/decrease rainfall), and after 1880 AD\u0026nbsp;they\u0026nbsp;were a combination of climatic (increases and decreases of precipitation values)\u0026nbsp;and anthropic forcings (cattle, intensive agriculture and urbanization). Moreover, baseline conditions were established at \u003cem\u003eca\u003c/em\u003e. 1870 AD. These conditions were related to a clear, pristine lake with a developed macrophyte community.\u0026nbsp;Currently it is important\u0026nbsp;to establish shallow lakes baseline conditions in terms of restoration and management objectives. In addition, it was concluded that southeastern Pampa plain has been subjected to human activities since 1870 AD, with cattle farming being the main activity and agriculture incorporation at \u003cem\u003eca\u003c/em\u003e. 1960 AD in the area. According to the results, the process of eutrophication in the lake associated with the intensification of agriculture took place during the last 25 years. The Pampa wetland has been modified for more than five decades ago. Although intensive agriculture occurred in the last 25 years, the modifications of the landscape are the result of 170 years of human impacts. \u003c/p\u003e\n"},{"header":"Statements \u0026 Declarations","content":"\u003cp\u003eFunding\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was supported by PIP CONICET 582 (2015-2017) and EXA 1015/20 (UNMdP).\u003c/p\u003e\n\u003cp\u003eCompeting Interests\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Guillermina S\u0026aacute;nchez Vuichard, Silvina Stutz, Marcela Tonello, \u0026nbsp;Diego Navarro and Caolina V\u0026aacute;squez. The first draft of the manuscript was written by Guillermina S\u0026aacute;nchez Vuichard and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript\u003c/p\u003e\n\u003cp\u003eData Availability\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cspan\u003eAgosta EA, Compagnucci RH (2008) The 1976/77 austral summer climate transition effects on the atmospheric circulation and climate in southern South America. J Clim 21:4365\u0026ndash;4383\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eAliaga VS, Ferrelli F, Alberdi-Algara\u0026ntilde;az ED, Bohn VY, Piccolo MC (2016) Distribution and variability of precipitation in the Pampas, Argentina. 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INTA Serie Fitogeogr\u0026aacute;fica 7 Buenos Aires, 262 pp\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eViglizzo EF, L\u0026eacute;rtora F, Pordomingo AJ, Bernardos JN, Roberto ZE, Del Valle H (2001) Ecological lessons and applications from one century of low external-input farming in the pampas of Argentina. Agricul. Ecosys. Environ., 83: 65\u0026ndash;81\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eWetzel RG (2001) Limnology: Lake and river ecosystems. Academic Press (ed.), En, p 985\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eWiedemeier J (2018) The Role of Wetlands in Ecosystem Services Trade-Offs in La Picasa Basin, Argentina. Tesis de Master en Natural Resources Management and Development, University of Applied Sciences, Cologne, 139 pp. (in\u0026eacute;dito)\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eWilliams CJ (2011) A paleoecological perspective on wetland restoration. 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Aeolian Res 3:401\u0026ndash;417\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"16.27906976744186%\"\u003e\n \u003cp\u003eLab number\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.891472868217054%\"\u003e\n \u003cp\u003eDepth (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.116279069767442%\"\u003e\n \u003cp\u003e14C yr BP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"26.356589147286822%\"\u003e\n \u003cp\u003eMedian probability\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"26.356589147286822%\"\u003e\n \u003cp\u003eUpper 2\u0026nbsp;\u0026sigma;\u0026nbsp;intercept\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"16.27906976744186%\"\u003e\n \u003cp\u003eD-AMS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;024148\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.891472868217054%\"\u003e\n \u003cp\u003e20-21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.116279069767442%\"\u003e\n \u003cp\u003e281\u0026plusmn;29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"26.356589147286822%\"\u003e\n \u003cp\u003e299\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"26.356589147286822%\"\u003e\n \u003cp\u003e275-327\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"16.27906976744186%\"\u003e\n \u003cp\u003eD-AMS 020646\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.891472868217054%\"\u003e\n \u003cp\u003e29-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.116279069767442%\"\u003e\n \u003cp\u003e618\u0026plusmn; 29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"26.356589147286822%\"\u003e\n \u003cp\u003e583\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"26.356589147286822%\"\u003e\n \u003cp\u003e528-570\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"wetlands","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wela","sideBox":"Learn more about [Wetlands](https://www.springer.com/journal/13157)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/wela/default.aspx","title":"Wetlands","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"human activities, climatic impacts, eutrophication, SE of South America, Late Late Holocene","lastPublishedDoi":"10.21203/rs.3.rs-1712174/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1712174/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWetlands are considered key ecosystems because of the greatest number of ecosystem services they provide, but despite their important role these ecosystems are decreasing in size and losing quality. Kakel Huincul lake is located in one of the main wetlands of Argentina. A multi-indicator analysis, including pollen, non-pollen palynomorphs and plant macrofossil remains was performed to reconstruct Kakel Huincul lake environmental history in order to understand Pampean wetlands responses to environmental changes and human impacts during the last 600 years. Results showed that changes in the lake communities before 1880 AD were a result of climatic perturbations (increase/decrease rainfall), and after 1880 AD they were a combination of climatic (increases and decreases of precipitation values) and anthropic forcings (cattle, intensive agriculture and urbanization). Baseline conditions were established at \u003cem\u003eca\u003c/em\u003e. 1870 AD and it was concluded that southeastern Pampa plain has been subjected to human activities (cattle farming and incorporation of agriculture) since then.\u0026nbsp;Eutrophication of the lake occurred during the last 25 years, but this study made it possible to establish that the Pampa wetland has been modified for more than five decades ago.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"Pampa plain (Argentina) wetland history through a lake case study: Kakel Huincul Environmental History during the last 600 years","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-07-13 19:57:04","doi":"10.21203/rs.3.rs-1712174/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2022-07-11T16:38:05+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-07-11T14:35:36+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Wetlands","date":"2022-06-09T19:50:07+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-06-08T03:56:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Wetlands","date":"2022-05-31T09:55:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"wetlands","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wela","sideBox":"Learn more about [Wetlands](https://www.springer.com/journal/13157)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/wela/default.aspx","title":"Wetlands","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"6d7f65f2-c237-463e-947f-0fd5d999a9a2","owner":[],"postedDate":"July 13th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2023-10-16T18:35:08+00:00","versionOfRecord":{"articleIdentity":"rs-1712174","link":"https://doi.org/10.1007/s13157-023-01660-z","journal":{"identity":"wetlands","isVorOnly":false,"title":"Wetlands"},"publishedOn":"2023-01-23 18:29:45","publishedOnDateReadable":"January 23rd, 2023"},"versionCreatedAt":"2022-07-13 19:57:04","video":"","vorDoi":"10.1007/s13157-023-01660-z","vorDoiUrl":"https://doi.org/10.1007/s13157-023-01660-z","workflowStages":[]},"version":"v1","identity":"rs-1712174","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1712174","identity":"rs-1712174","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}