Reconstructing the effects of anthropogenic activities and climate change in three lakes of the Fildes Peninsula, Maritime Antarctic

Reconstructing the effects of anthropogenic activities and climate change in three lakes of the Fildes Peninsula, Maritime Antarctic | 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 Reconstructing the effects of anthropogenic activities and climate change in three lakes of the Fildes Peninsula, Maritime Antarctic Florencia Bertoglio, Samuel Yergeau, Claudia Piccini, Santiago Giralt, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8138817/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract The Fildes Peninsula (maritime Antarctica) is greatly affected by global warming and local human impacts since it is in one of the Antarctic regions with the highest intensity of human activity. To establish the effect of human activities on Fildes Peninsula lakes, we compared trends in diatom assemblages, bacterial communities and metal concentrations in sediment cores from two lakes close to human infrastructure with those in a more remote lake. In the two lakes close to stations and the airport, we found heavy metal enrichments and diatom teratologies, as well as notable changes in diatom assemblages in one of these lakes, roughly coincident with the time when the first two stations were built (~ 1970). Due to the known association between diatom teratologies and metal enrichment, metal stress is a convincing explanation for these changes. Certain bacterial taxa determined to be indicators of pollution were also found to be more abundant in the impacted lakes in recent sediments (i.e., Hungateiclostridiacea e , OPB41, Anaerovorax and Leptolinea ). Metal, diatom and bacteria changes observed in the lake more distant to infrastructure were more subtle and are likely related to climate change alone. Given the proximity of the affected lakes to the airport and roads, our data suggests that transportation infrastructure and activity on Fildes Peninsula is likely a key cause of contamination in the region’s ecosystems. This study provides important insights into how human activities and climate change have affected Fildes Peninsula aquatic ecosystems and how they may respond to future stressors. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The geography of the Antarctic Peninsula (AP) distinguishes it from the rest of the continent in aspects such as climate and human activities. The AP has experienced accelerated climate warming during the past 50 years and is amongst the most rapidly warming regions in the Southern Hemisphere (Turner et al., 2020 ). Maritime Antarctic temperatures show strong interannual variability and are highly dependent on seawater temperature and annual changes in sea ice extent (Meredith and King, 2005 ; Kejna et al., 2013 ). Superimposed on this interannual variability, Bellingshausen Station temperatures showed a significant (p < 0.05) increasing trend of 0.23°C per decade between 1969 and 2024 (READER, 2025). Scientific pursuits became an important component of anthropogenic Antarctic activities with the establishment of stations that permitted year-round human presence (Schiffer, 2013 ). For example, since Bellingshausen Station (Russia) was built in 1968, King George Island (situated in the AP) has seen a surge in the construction and expansion of research and other infrastructure, with twelve stations present on the island (COMNAP, 2025). These developments have placed increasing strain on sensitive polar ecosystems and led to a growing concern about the threats, including contamination of terrestrial and aquatic environments, modification of animal behavior and the introduction of non-indigenous species, that the increased human traffic may pose to the continent’s natural systems (Holmes et al., 2006 , Tin et al., 2009 , Martins et al., 2010 , Cowan et al., 2011 , Choi et al., 2022 ). However, monitoring programs in general have only been undertaken since the agreement of the Protocol on Environmental Protection to the Antarctic Treaty, which came into effect in 1998. Paleolimnological techniques, by which lake sediments are used to reconstruct changes over time at local and regional scales, can be applied retrospectively to understand impacts caused by human activities (Smol, 2008 ). In Antarctic lakes, such approaches permit comparisons of present conditions with those of the past several decades and enable the determination of pristine baseline conditions by reaching samples prior to the onset of local human activities (Hodgson et al., 2004 ). We studied the Fildes Peninsula, which in addition to being the largest ice-free area of King George Island and the site of numerous lakes is also amongst the areas of Antarctica most impacted by humans (Peter et al., 2013 ). Since the construction of Bellingshausen Station in 1968 the population of the peninsula has gradually increased, with six permanent stations built between 1968 and 1994, belonging to Chile, China, Russia and Uruguay, that accommodate up to 375 people at peak occupation in the austral summer (COMNAP, 2025). An airfield constructed in 1980 and a harbor master station also serve as logistics hubs for entry by scientists and tourists to the South Shetland Islands (Braun et al., 2020 ). The strong human presence resulting from tourism and the high density of bases implies an accrued risk of environmental contamination, including from fuel spills, poor waste management, habitat destruction and damage to vegetation by vehicles, and indeed the ground around many stations has been suggested to show traces of contamination (Bargagli, 2008 ; Braun et al., 2012 ., Peter et al., 2013 ). Several studies have focused on long-term regional climate and landscape evolution in the Fildes Peninsula (Tatur et al., 1991 , García-Rodríguez et al., 2021 ; Oliva et al., 2023 ; Piccini et al., 2024 ), while one assessed changes on shorter time scales caused by human activities (Bertoglio et al., 2025 ). This study demonstrated that DNA was well preserved in sediments, allowing the detection of changes in bacterial communities over time, and identified indicator bacteria of human presence related to lakes impacted by metals, enabling their use as sedimentary proxies to reconstruct anthropogenic impacts. The only available assessment of recent changes in pre- and post-impact conditions used a top-bottom approach (Bertoglio et al., 2025 ); here we evaluated detailed profiles in three lakes of metal concentrations, bacterial DNA and diatom assemblages and teratologies in the sedimentary record to develop a comprehensive picture of the effects of human activities for the last ca. 150 years. We compared trends over the past century in microbial community composition in two lakes close to stations (Las Estrellas and Hotel lakes) to those in one more remote lake (Mondsee Lake) to assess the hypothesis that perturbations related to the stations have altered microbial diversity in lakes close to human activities. Methods 3.1 Study area Fildes Peninsula (62°11′ S, 58°58′ W) is located at the southwestern tip of King George Island in the South Shetland Islands of the maritime Antarctic region (Fig. 1 ). The 38 km 2 peninsula is surrounded by the waters of the Drake Passage, Fildes Strait and Maxwell Bay. It is free of ice except for its northeast end which is covered by the Collins Glacier (Fig. 1 b). Numerous lakes that formed following glacial recession during the Late Holocene are present on the peninsula (Simonov, 1977 ), some of which are used as water sources for various stations. Our study included three Fildes Peninsula lakes (Fig. 1 b): two are situated adjacent to stations, while one is more distant from human infrastructure. The lakes included Hotel Lake, which is adjacent to the Teniente Marsh Aerodrome and was formerly its water supply, and which has ceased to be used for drinking water due to elevated levels of heavy metals (Peter et al., 2013 ); Las Estrellas Lake, which previously supplied water to Escudero Station (Chile), and is ~ 200 m from the nearest roads and infrastructure; and Mondsee Lake, situated 3.5 km from Frei Station (Chile) and 2.6 km from Artigas Station (Uruguay). 3.2 Sampling Sediment cores were taken in November-December 2016 (Las Estrellas and Mondsee lakes) and in December 2013 (Hotel Lake), at the deepest known point of each lake. Holes were drilled in the lake ice with a manual ice auger, and cores were recovered using a universal corer (Aquatic Research Instruments) with tenite butyrate core tubes of either 67 or 95 mm internal diameter. Based on sedimentation rates obtained from earlier studies, a general target length of 30 cm was established for the sediment cores, which was long enough to far exceed the period of human presence on Fildes Peninsula. The sediment-water interfaces were stabilized with sodium polyacrylate (Tomkins et al., 2008 ), and cores were then sealed and transported whole, cold and in the dark to Université Laval (Canada). The cores were then split lengthwise and sectioned at fine intervals for the analysis of diatoms, DNA, metals and radioisotopes. Subsamples followed visible layers in the stratigraphy of each sedimentary record and ranged from 0.1 to 0.5 cm thickness. Samples were studied to sufficient depths to reach at least the mid-20th century, in order to encompass the entire period of human influence on Fildes Peninsula and reach baseline conditions prior to local anthropogenic impacts. More details about the number of samples analyzed for each proxy as well as the sediment range included are available in Table S.1. All subsampling was carried out under sterile protocols to preclude contamination, and separate subsamples were taken for analysis of diatoms, DNA and radioisotopic dating, placed in sterile Whirl-Pak bags, and kept frozen at -80°C until analysis. 3.3 Chronologies Sediment chronologies were generated from 210 Pb activities measured by alpha spectroscopy at Chronos Scientific Inc. in Ottawa, Canada. Freeze-dried samples sectioned at fine intervals (~ 4 mm) were ground and spiked with 209 Po, after which HNO 3 (nitric acid) and HCl (hydrochloric acid) were added, and the samples were heated at 80°C for 16 hours. The solutions were then centrifuged and evaporated to dryness three times, with HCl added after each cycle. Finally, the Po isotopes were electroplated on silver disks and measured using alpha spectroscopy. Age-depth models were generated with the R package serac using the constant rate of supply (CRS) model, with interpolated ages generated to cover the specific depths of the subsamples for all lakes and indicators (Appleby, 2001 ; Bruel and Sabatier, 2020 ). 3.4 Metals Metal concentrations (i.e., Cd, Ni, Cr, Pb, Co, Zn, Cu, Fe, Mn, As, Se, Ti) were measured on ~ 1 g (dry weight) sediment subsamples using inductively coupled plasma-mass spectrometry (ICP-MS) in the Laboratory for the Analysis of Natural and Synthetic Environmental Toxins (LANSET) at the University of Ottawa, Canada. Duplicates, blanks and standard reference materials were used for quality assurance/quality control. Values are expressed in milligrams per kilogram of dry sediment (mg kg − 1 ). Metal enrichment factors (EF) were calculated in each lake using the following equation: where x refers to the metal measured by ICP-MS; Ti is titanium, a reliable indicator of changes in allochthonous sedimentation (Davies et al., 2015 ) used to normalize metal concentrations; and reference represents pre-human background values, calculated using the last sample in each core that age models indicated to be from the 19th century (i.e., 1890, 1895, and 1876 CE in Mondsee, Hotel and Las Estrellas lakes, respectively). EF values around 1 show no sign of enrichment, while values over 3 and 10 show moderate and severe enrichment, respectively (Chen et al., 2007 ). EFs for Ti were calculated as concentrations relative to those of the reference sample. 3.5 Diatom analysis 0.1 g of dried sediment was prepared for diatom analysis by oxidizing organic matter with 30% H 2 O 2 . Following digestion, samples were allowed to settle for 24 h, the supernatants aspirated, and slurries were rinsed several times with distilled water to return them to neutral pH. Slurries were then placed on cover slips to dry on in a dust-free environment and fixed on microscope slides using Naphrax mounting medium. A minimum of 300 valves were counted in each sample using a Zeiss Axioscop 2 microscope equipped with differential interference contrast (DIC) optics at 1000x magnification under immersion oil. Primary taxonomic references for the identification of the diatom flora included Zidarova et al. ( 2016 ), Van de Vijver and Kopalová ( 2014 ), Sterken et al., ( 2015 ) and Wetzel et al., ( 2015 ). The identification of some species was verified using a scanning electron microscope (SEM) at Centres Cientifics i Tecnològics of the Universitat de Barcelona (CCiTUB), Spain. In addition to taxonomic identifications, teratologies were enumerated in separate scans of 500 valves to determine the proportion of diatom deformities in each lake. Scans to determine the proportion of diatom deformities in each lake began with the surface sample and continued downcore until 3 consecutive samples showed an absence of teratologies after 200 valves were counted. The teratology percentage was based only on specimens found in valve view, as teratologies are generally not visible in girdle view (Lavoie et al., 2017 ). 3.6 DNA extraction, sequencing and taxonomic assignment To detect changes in bacterial community composition, bacterial diversity was analyzed by 16S rRNA amplicon sequencing. All material employed for manipulation of DNA sediment subsamples, as well as the vertical laminar flow cabinet (ESCO Class II, Type A2) where the DNA was extracted, was previously sterilized by irradiation with UV light. 0.5 g of wet sediment were aseptically transferred to sterile microtubes containing ceramic beads and an extraction buffer composed of 1% CTAB (Hexadecyltrimethylammonium bromide) and EDTA (Ethylenediaminetetraacetic acid) and homogenized with a FastPrep homogenizer (MP). After centrifugation at 12000 g the supernatants were subjected 3 times to chloroform:isoamyl alcohol (24:1) extractions and the pellets were precipitated with 0.6 volumes of cold isopropanol at room temperature during 24 h. These precipitates were then subjected to centrifugation for 40 min at 12000 g at room temperature, and the DNA obtained in the pellets was washed with cold ethanol, dried and suspended in ultrapure water overnight at 4°C. The concentration and purity of DNA was determined spectrophotometrically at 260 and 280 nm, and its quality was checked by the amplification of a variable region (V4) of the ribosomal 16S gene. PCR (polymerase chain reaction) products were verified by gel electrophoresis on 1% agarose gel in 0.5X TBE buffer. DNA samples were sent to Novogene for Illumina MiSeq paired-end sequencing of the V4 region, using the 515F and 806R primers (Caporaso et al., 2011 ). To correct for sequencing errors and create Amplicon Sequence Variants (ASVs), reads were processed in R using the DADA2 pipeline following a modified version of the DADA2 Bioconductor workflow (Callahan et al., 2017 ). Briefly, reads were filtered and trimmed by the filterAndTrim function based on the quality score which estimates the error probability of the DNA sequence. Reads with a maximum expected error (maxEE) greater than 2 were removed and based on quality profiles, reads were truncated at 200 and 190 bp for forward and reverse reads, respectively. Sequence variations were inferred with the learnerrors and dada functions. Chimeric sequences were eliminated, and taxonomy assignments from kingdom to genus were performed with assignTaxonomy based on the SILVA database (v138) (Quast et al., 2012 ). ASV sequences assigned as Archaea, Chloroplasts and Mitochondria were removed. Sequences obtained were submitted to the nucleotide archive GenBank with the BioProject ID PRJNA1365190. 3.7 Data analysis Multivariate analyses were used to explore patterns in the variation over time of metals, diatoms and bacteria. Principal component analysis (PCA) was performed separately for each proxy (metals, diatoms and bacteria); the ICP-MS metals data were log transformed prior to PCA while the diatom and bacteria datasets were Hellinger-transformed. Results and discussion 4.1 Chronology Log 210 Pb activities were low and showed roughly linear decreasing trends over time in each lake, with activities in surface sediments of 95.4, 61.2, and 189.7 Bq kg − 1 , and reaching background at 55, 54 and 31 mm depth in Mondsee, Las Estrellas and Hotel lakes, respectively (Fig. S.1). CRS models indicated that the year 1968 CE, when Bellingshausen base was established, corresponded to ~ 21, ~23, and ~ 5.7 mm depth in Mondsee, Las Estrellas and Hotel lakes, respectively (Fig. S.1). 4.2 Metal concentrations and enrichment factors The metals with the greatest variation throughout the three sediment cores were Pb, Zn, As, Cu, and Cr (Fig. S.2). Mondsee Lake showed little change, with concentrations that ranged between 6.7 and 7.5 mg kg − 1 for Pb, 51.4 and 59.9 mg kg − 1 for Zn, As between 3.3 and 8.2 mg kg − 1 , Cu between 84.4 and 111.5 mg kg − 1 and Cr between 7.9 and 10.2 mg kg − 1 (Fig. S.2). There was greater variation in metals in Las Estrellas Lake, with concentrations ranging between 5.2–10.6 mg kg − 1 for Pb, 39.8-148.8 mg kg − 1 for Zn, 2.6–9.7 mg kg − 1 for As, 44-107.2 mg kg − 1 for Cu and 10.6–18.3 mg kg − 1 for Cr (Fig. S.2). Hotel Lake showed by far the highest metal concentrations as well as the greatest variation, varying between 5.4-683.9 mg kg − 1 for Pb, 47.3-350.7 mg kg − 1 for Zn, 1.8–5.4 mg kg − 1 for As, 62-189.4 mg kg − 1 for Cu and 9.9–30.5 mg kg − 1 for Cr (Fig. S.2). The first two axes of the PCA of metal concentrations explained 80.0% of the variance in the dataset, with PC1 explaining 62.1% and PC2 explaining 17.9%. First axis scores for Mondsee Lake did not change through the core, while Las Estrellas Lake PC1 values undulated slightly between 1950 and the present, and Hotel Lake PC1 values changed markedly beginning between 1940 and 1998 (Fig. 2 ). Enrichment factors for Ti were close to 1 and showed little variation throughout all three sediment cores, indicating relatively constant supplies of allochthonous sediment over time (Fig. 3 ). The highest EFs were observed for Pb, Zn, As, Cu, Cr and Cd (Fig. 3 , Table S.2), apart from Mondsee Lake where EFs throughout the core were close to 1 (i.e., no enrichment) except for As, which increased moderately between 2012 and 2017 reaching a maximum EF of 3.0 in 2015 (Fig. 3 ). EFs for Pb, Cu Cr and Cd in Las Estrellas Lake were close to 1 and varied little in the core, except in 2017 for Pb which was moderately enriched (EF: 2.9) and Cr that increased somewhat but at 1.9 remained below threshold for moderate enrichment (i.e., 3; Chen et al., 2007 ) (Fig. 3 ). The metal showing the greatest enrichment in Las Estrellas Lake was Zn, which increased upwards from 1974 to the surface, with moderately enriched values in 1982 and a maximum at the surface of the core (2017) of 5.7 (Fig. 3 ). As was moderately enriched from 1962 to the most recent sample (2017), with the maximum values in 1974 and 1978 (EFs: 4.9 and 5.6 respectively; Fig. 3 ). EFs of many metals in Hotel Lake showed pronounced enrichment and had similar trends, increasing slightly in the early 20th century, and greatly after ~ 1976 to a maximum in 1998, and then decreasing somewhat in the surface sediment (Fig. 3 ). Pb, Zn and Cd showed severe enrichment in 1998 (maximum EFs of 146.2, 14.9 and 10.6) while As, Cu and Cr showed moderate enrichment at this point (maximum EFs: 6.1, 5.5 and 6.2) (Fig. 3 ). 4.3 Diatom composition Ninety-one diatom taxa belonging to 30 genera were identified in the three study lakes (Table S.3, Fig. S.3). In general, assemblages were dominated by small benthic diatoms (< 20 µm), mainly from the genera Achnanthidium , Psammothidium , Planothidium , Sellaphora and Staurosirella . A total of 78 species from 25 different genera was identified in Mondsee Lake (Fig. 4 ). Some species showed pronounced stratigraphic changes. There was a step-change in Achnanthidium indistinctum , which averaged 4.2% relative abundance prior to ~ 1991 and 26.5% thereafter. This was coincident with an increase of Planothidium frequentissimum and decreases in Staurosirella antarctica and other, less abundant species including Chamaepinnularia australomediocris and Psammothidium confusoneglectum . Seventy-four diatom species from 28 genera were identified in the Las Estrellas Lake core (Fig. 4 ). There were three horizons of pronounced assemblage change in the core: at ~ 1955, ~1968 and ~ 1976. After ~ 1955, assemblages that had shown relative stability were marked by increases in Achnanthidium indistinctum , Staurosirella antarctica and Psammothidium incognitum , and the period had low abundances of Planothidium renei . Between ~ 1968 and ~ 1976, there was an abrupt decrease of Achnanthidium indistinctum from 22% relative abundance to values ~ 1%, an abrupt increase of Staurosirella antarctica , and gradual increases of Planothidium renei , Stauroneis sofia and Psammothidium abundans . Around 1975, there were sharp decreases of Staurosirella antarctica and Planothidium renei coincident with sharp increases in Sellaphora nigri and Cavinula pseudoscutiformis (Fig. 4 ). A total of 50 species from 18 genera was identified in the Hotel Lake core, with no taxa having an average abundance exceeding 20%, representing the lowest diversity among the three lakes (Fig. 4 ). The species that showed the most evident trend was Psammothidium papilio , which was abundant in the lower part of the core (average 10.3%, 1867–1907) and then decreased dramatically above this horizon (average 0.8%), as well as Psammothidium abundans which also peaked ~ 1907 but had a higher abundance in the upper section of the core (between 10 and 18%). Sellaphora nigri was present at generally low relative abundances during most of the 20th century until the most recent sample (2014) when it increased to a relative abundance of 14% (Fig. 4 ), and Achnanthidium maritimo-antarcticum increased after 1976, but with lower relative abundances (between 0.3 and 5%) (Fig. 4 ). The first axis of the diatom PCA explained 33.8% of the variation in the diatom data while the second axis explained 16.6%. Based on first axis scores, the most pronounced change in diatom composition occurred in Las Estrellas Lake from 1967 to 1979, while compositional changes in Mondsee and Hotel lakes were less notable (Fig. 2 ). 4.4 Bacterial composition We detected a total of 14,567 ASVs across the three cores. Rarefaction curves based on the observed ASVs reached plateaus, indicating that sequencing depth was adequate to capture the overall diversity of all lakes (Fig. S.4). As was observed in our previous study (Bertoglio et al., 2025 ), bacterial communities from each lake were composed of a few very abundant ASVs while most taxa had low abundances. In Mondsee Lake the taxa that showed the most evident trends over time were Sulfurifustis and Phycisphaerae, which decreased after ~ 1956 (Fig. 5 ). Additionally, certain species dominated in the most recent sample in Mondsee Lake (2017) while others decreased dramatically. For example, Janthinobacterium , Rokubacteriales, Delftia , Clostridium sensu stricto 13, and Desulfosporosinus were more abundant in this sample, whereas Desulfatirhabdium and P9X2b3D02 (phylum Nitrospinota) decreased (Fig. 5 ). The abundances of several bacteria in Las Estrellas and Hotel lakes changed notably after ∼1970 (Fig. 5 ). For example, Holophagaceae and Desulfatirhabdium increased while Phycisphaerae and CCM11a decreased in both lakes (Fig. 5 ). Other groups also showed considerable shifts but with different patterns in each lake, such as Pseudomonas and Zixibacteria that increased after ∼1970 in Las Estrellas Lake while Phycisphaerae decreased, and MBNT15, Latescibacterota, Rokubacteriales and Zixibacteria decreased in Hotel Lake after ~ 1976. The first axis of the bacteria PCA explained 28.9% of the variation in bacterial composition data while the second axis explained 18.0%. In addition, based on first axis scores, the most pronounced change was observed in the most recent sample of Mondsee Lake (2017), whereas changes in Las Estrellas and Hotel lakes were more muted (Fig. 2 ). 4.5 Diatom teratologies and bacterial indicators of contamination Diatom teratologies are deformations of cell morphology that have been observed to increase in contaminated water bodies, particularly those with high concentrations of heavy metals and pesticides (Falasco et al., 2021 ). In Mondsee Lake they had a maximum occurrence of 1.2% (Fig. 2 ). Teratologies were most notable in Las Estrellas Lake, where they increased between 1975–1982 to ~ 2% of the enumerated valves, and sharply thereafter with frequencies of 6.6 and 10.0% (in 1997 and 2017, respectively), including 30% of the valves of P. abundans (Fig. 2 ). The surface sample of Hotel Lake also had more prevalent teratologies, increasing from 1998 to a maximum of 2.9% deformed valves in the surface sample (Fig. 2 ). We tested correlations between different metal EFs and the abundances of certain bacteria that were identified as indicators of contamination (i.e., Anaerovorax , Hungateiclostridiaceae, OPB41, Pseudorhodoplanes , and Leptolinea ; Bertoglio et al., 2025 ). Of the five taxa evaluated, all except Pseudorhodoplanes were positively correlated with enrichments of multiple metals (Table 1 ). Pb, Zn, Cu, Cr and Cd had positive, significant and high correlation coefficients (i.e., R 2 = 0.40–0.70) with between two and four taxa each (Table 1 ). 4.6 Separating the effects of environmental change and anthropogenic activities Fildes Peninsula lakes are subject to multiple stressors, including rapidly rising temperatures and strong UV exposure due to ozone depletion, in addition to any direct anthropogenic impacts. We hypothesized that, due to its remoteness from infrastructure, Mondsee Lake could be used as a control site to determine changes in diatom and bacterial communities due primarily to natural environmental change, including ongoing warming. This hypothesis was supported by the differing trends in metal enrichment between Mondsee Lake and the other two sites (Fig. 3 ). The limnological consequences of recent warming in maritime Antarctica include changing lake ice cover duration and thickness and thermal stratification regimes (Izaguirre et al., 2021 ). Decreases in ice cover duration influence diatom communities, as has been observed in many lakes in the Northern Hemisphere (Lotter and Bigler, 2000 ; Sorvari et al., 2002 ; Smol et al., 2005 ; Rühland et al., 2015 ). Although somewhat muted, recent diatom shifts in Mondsee Lake likely reflect changes to ice cover duration and extent, including declines of Staurosirella antarctica , which is associated with colder conditions and prolonged ice cover (Lotter and Bigler 2000 ; Keatley et al., 2008 ), and increases after ~ 1991 of Achnanthidium indistinctum , a taxon that thrives in nearshore lake environments where external disturbances such as wind are common (McCabe and Cyr 2006 ; Cyr, 2016 ). A coincident decline in Staurosirella antarctica in Las Estrellas Lake (after the mid-1970s) also likely reflects the broader effects of climate warming on ice cover duration and thickness, although the species was absent in the 20th century in Hotel Lake. In fact, diatom assemblages in Hotel Lake showed no systematic changes, either in overall assemblage composition or in the abundances of most taxa. Hotel Lake had much thicker ice cover than the other two lakes during spring 2017 and autumn 2018 (1.60 and 0.55 m vs. 0.98 and 0.13 m on average for both seasons, respectively; Bertoglio et al., 2023 ). Although the precise reasons are uncertain, Hotel Lake is located in the upper section of the Grande Valley, which appears to channel cold winds between the Drake Passage to the west and Maxwell Bay to the east (pers. obs.). Its thick ice may therefore reflect a colder microclimate and imply the delayed onset of the effects of warming in this lake. Certain bacteria found with higher abundances in the most recent sample of Mondsee Lake may potentially be associated with the consequences of warming. For example, Janthinobacterium produce the pigment violacein which confers resistance to UV radiation (Alem et al., 2020 ), which is expected to increase as ice cover thins. Moreover, Rokubacteriales and Desulfosporosinus are common soil taxa that were also found in peatlands (Pester et al., 2010 ; Ivanova et al., 2021 ), and their increases could be related to increasing runoff and aeolian deposition in longer melting seasons. The increase of Janthinobacterium after ~ 1995 in Las Estrellas Lake may also be a consequence of climate warming; it also increased in Hotel Lake but much more subtly. This reaffirms the muted nature of climate change effects in Hotel Lake as suggested by diatom trends. The lack of increases in other bacteria taxa reflecting climate change in Hotel and Las Estrellas lakes may be because the influence of climate change in shaping communities in these lakes is overshadowed by the pronounced impact of anthropogenic activities. Indeed, in the presence of multiple stressors related to climate change and human activities, lakes may differ in responses compared with those that only experience single stressors (Jackson et al., 2016 ). The increase in metal EFs in Las Estrellas and Hotel lakes since the establishment of bases on the peninsula is consistent with our hypothesis that the sites nearest human activities would show increases in contaminants over time, and the contrast with the lack of changes in Mondsee Lake suggests that these increases cannot be ascribed to natural environmental changes. The changes we observed in Las Estrellas and Hotel Lakes therefore represent the cumulative effects of climate change and human impacts. There is growing evidence for human impacts in terrestrial and marine ecosystems in maritime Antarctica. For example, elevated Cu, Zn, Cd and Pb have been found in marine sediments, soil, lichens and mosses from Fildes Peninsula close to stations and contaminated sites (Aronson et al., 2011 ; Lu et al., 2012 ; Padeiro et al., 2016 ; Pereira et al., 2017 ; Fabri-Jr et al., 2018 ). These results are comparable to our findings, since heavy metal contamination may be related to intense human activity such as transportation, fossil fuel combustion, accidental oil spills, waste incineration and sewage disposal (Chu et al., 2019 ). Our results give temporal context to these findings, showing that the affected sites not only had high metal concentrations but that they increased over time, while those in our remote site showed little to no change over the same period. Biological proxies also showed greater changes in the proximal vs. remote lake and provided evidence of the ecological effects of anthropogenic impact. While shifts in overall community composition of diatoms and bacteria did not differ markedly between the three lakes, we found trends in taxa that were indicators of pollution and may thus have adaptive advantages in metal-impacted environments. The diatom Sellaphora nigri is an indicator species that is found in greater abundances in environments where eutrophication, organic contaminants or pollution by pesticides and heavy metals are observed (Morin et al., 2012 , 2014 ; Wetzel et al., 2015 ). Given its tolerance to pollution, the increase in S. nigri relative abundances in Las Estrellas Lake around 1975, coincident with increasing human activities as well as with the construction of numerous stations in the subsequent years (Braun et al., 2012 ; Peter et al. 2013 ) may therefore reflect contamination due to human activity. The increase of this species in the surface sediments of Hotel Lake, while less than that observed in Las Estrellas Lake, may also reflect such impacts. By comparison, S. nigri always had abundances < 1% in Mondsee Lake, which reinforces the hypothesis of the pristine nature of the lake relative to our other sites. Diatom teratologies represent an individual-level response to environmental stress (Falasco et al., 2021 ). Deformed frustules associated with heavy metal stress have been reported in various studies (Falasco et al., 2009 ; Cantonati et al., 2014 ; Pandey and Bergey, 2018 ). While the exact mechanism of the deformations has not been demonstrated, it has been suggested that contaminants alter cell membrane polarity and cause cytoplasmic acidification, leading to disruption of cytoplasmic homeostasis (Pinto et al., 2003 ). While some authors have attributed diatom teratologies to high UV exposure (summarized in Falasco et al., 2021 ), such as that due to thinning of the stratospheric ozone layer in the Antarctic, this mechanism cannot explain the differing trends between Mondsee Lake and the other two sites. The increase in teratologies in Las Estrellas and Hotel lakes, and their absence in Mondsee Lake, however, is consistent with the observed changes in metal enrichment and thus demonstrates the ecological effects of pollution. Within bacterial communities, particular taxa with higher tolerances to contaminants became more abundant over time in Hotel and Las Estrellas lakes, such as Sulfurifustis and Desulfatirhabdium . These sulfur bacteria may be related to the presence of pollutants as they can employ a variety of electron donors or inorganic sulfur compounds as electron acceptors (Balk et al., 2008 , Kojima and Fukui 2015), such as those found in contaminants originating from the burning of fossil fuels. However, we do not exclude that the presence of these bacteria may be related to changes in sediment habitats, for example due to anoxia, influencing active bacteria rather than reflecting historical changes. Desulfatirhabdium increased in both Las Estrellas and Hotel lakes after ~ 1982, while Sulfurifustis also increased in Las Estrellas Lake over the same period. Neither increased in abundance in Mondsee Lake where their abundances in fact decreased there after ∼1956 and 1991, respectively. Several groups of sulfur bacteria (e.g. Geobacteraceae, Desulfurivibrionaceae and Rhodobacteraceae) were also previously observed in the bacterial community in water samples from Hotel Lake (Bertoglio et al., 2023 ). Moreover, the significant relationships between bacterial indicators of pollution and metal EFs (i.e., Hungateiclostridiaceae, OPB41, Anaerovorax and Leptolinea ; Bertoglio et al., 2025 ), provide further evidence that human impacts are modifying aquatic communities in Fildes Peninsula’s lakes. Conclusions Lakes in maritime Antarctica are subject to stress from rapidly warming climates, and, in some cases, from anthropogenic activities in their catchments. We analyzed sedimentary proxies (metals, diatoms and bacterial DNA) in three lakes and showed notable changes in metal enrichment, diatom teratologies and bacteria indicators of pollution in two (Las Estrellas and Hotel lakes) that were located near to logistics infrastructure. The changes of the same indicators in Mondsee Lake, more distant from human activities, were muted by comparison. We conclude that Mondsee Lake represents the baseline of recent changes due to climate change, and that the more pronounced shifts in the other two lakes can therefore not be attributed to warming alone. Although based on our study we cannot draw direct causal links between changes in lake sediments and anthropogenic activities, the trends we observed provide strong evidence for significant human effects on aquatic ecosystems. Further studies are needed to better quantify the effects and prevent further deterioration of these sensitive Antarctic environments. Declarations Funding This work was supported by the Instituto Antártico Chileno (Project ANID/FONDAP/2014), the Fonds de recherche du Québec - Nature et technologies (FRQNT), the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Agencia Nacional de Investigación e Innovación (ANII). We also thank the Instituto Antártico Uruguayo for logistical support. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions Roberto Urrutia, Santiago Giralt and Dermot Antoniades contributed to the study conception and design and conducted fieldwork. Florencia Bertoglio and Samuel Yergeau processed and analyzed the samples. Florencia Bertoglio, Claudia Piccini and Dermot Antoniades interpreted the data. The first draft of the manuscript was written by Florencia Bertoglio and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Data Availability The datasets analysed during the current study are available on the Open Science (OSF) repository (https://osf.io/ma3tg/overview?view_only=1773bc9b695649f4817426efef5b17df) References Alem, D., Marizcurrena, J.J., Saravia, V., Davyt, D., Martinez-Lopez, W., Castro-Sowinski, S., 2020. Production and antiproliferative effect of violacein, a purple pigment produced by an Antarctic bacterial isolate. World Journal of Microbiology and Biotechnology 36, 120. https://doi.org/10.1007/s11274-020-02893-4 Appleby, P.G., 2001. Chronostratigraphic Techniques in Recent Sediments, in: Last, W.M., Smol, J.P. (Eds.), Tracking Environmental Change Using Lake Sediments: Basin Analysis, Coring, and Chronological Techniques. Springer Netherlands, Dordrecht, pp. 171–203. https://doi.org/10.1007/0-306-47669-X_9 Aronson, R.B., Thatje, S., McClintock, J.B., Hughes, K.A., 2011. Anthropogenic impacts on marine ecosystems in Antarctica. Annals of the New York Academy of Sciences 1223, 82–107. https://doi.org/10.1111/j.1749-6632.2010.05926.x Balk, M., Altınbas, M., Rijpstra, W. I. C., Sinninghe Damste, J. S., & Stams, A. J. (2008). Desulfatirhabdium butyrativorans gen. nov., sp. nov., a butyrate-oxidizing, sulfate-reducing bacterium isolated from an anaerobic bioreactor. International Journal of Systematic and Evolutionary Microbiology, 58(1), 110-115. https://doi.org/10.1099/ijs.0.65396-0 Bargagli, R., 2008. Environmental contamination in Antarctic ecosystems. Science of The Total Environment 400, 212–226. https://doi.org/10.1016/j.scitotenv.2008.06.062 Bertoglio, F., Piccini, C., Urrutia, R., Antoniades, D., 2023. Seasonal shifts in microbial diversity in the lakes of Fildes Peninsula, King George Island, Maritime Antarctica. Antarctic Science 35(2), 89–102. https://doi.org/10.1017/S0954102023000068 Bertoglio, F., Piccini, C., Giralt, S., Urrutia, R., Antoniades, D., 2025. Sedimentary indicators of anthropogenic impact in Fildes Peninsula lakes (King George Island, Maritime Antarctica). Anthropocene 49, 100465. https://doi.org/10.1016/j.ancene.2025.100465 Braun, C., Mustafa, O., Nordt, A., Pfeiffer, S., Peter, H.-U., 2012. Environmental monitoring and management proposals for the Fildes Region, King George Island, Antarctica. Polar Research 31, 18206. https://doi.org/10.3402/polar.v31i0.18206 Braun, C., Ritter, R., Hans-Ulrich Peter, 2020. Substantial increase of ship and air traffic on Fildes Peninsula, King George Island, the main logistic hub for the Antarctic Peninsula. Conference SCAR 2020 Online. https://doi.org/10.13140/RG.2.2.12504.72960 Bruel, R., & Sabatier, P. (2020). serac: An R package for ShortlivEd RAdionuclide chronology of recent sediment cores. Journal of Environmental Radioactivity, 225, 106449. https://doi.org/10.1016/j.jenvrad.2020.106449 Callahan, B.J., McMurdie, P.J., Holmes, S.P., 2017. Exact sequence variants should replace operational taxonomic units in marker-gene data analysis. The ISME journal 11, 2639–2643. https://doi.org/10.1038/ismej.2017.119 Cantonati, M., Angeli, N., Virtanen, L., Wojtal, A.Z., Gabrieli, J., Falasco, E., Lavoie, I., Morin, S., Marchetto, A., Fortin, C., Smirnova, S., 2014. Achnanthidium minutissimum (Bacillariophyta) valve deformities as indicators of metal enrichment in diverse widely-distributed freshwater habitats. Science of The Total Environment 475, 201–215. https://doi.org/10.1016/j.scitotenv.2013.10.018 Caporaso, J. G., Lauber, C. L., Walters, W. A., Berg-Lyons, D., Lozupone, C. A., Turnbaugh, P. J., Fierer, N. & Knight, R. (2011). Global patterns of 16S rRNA diversity at a depth of millions of sequences per sample. Proceedings of the national academy of sciences, 108(supplement_1), 4516-4522. https://doi.org/10.1073/pnas.100008010 Chen, C.W., Kao, C.M., Chen, C.F., Dong, C.D., 2007. Distribution and accumulation of heavy metals in the sediments of Kaohsiung Harbor, Taiwan. Chemosphere 66(8), 1431–1440. https://doi.org/10.1016/j.chemosphere.2006.09.030 Choi, H.-B., Lim, H.S., Yoon, Y.-J., Kim, J.-H., Kim, O.-S., Yoon, H.I., Ryu, J.-S., 2022. Impact of anthropogenic inputs on Pb content of moss Sanionia uncinata (Hedw.) Loeske in King George Island, West Antarctica revealed by Pb isotopes. Geosciences Journa l 26(2), 225–234. https://doi.org/10.1007/s12303-021-0032-4 Chu, Z., Yang, Z., Wang, Y., Sun, L., Yang, W., Yang, L., Gao, Y., 2019. Assessment of heavy metal contamination from penguins and anthropogenic activities on Fildes Peninsula and Ardley Island, Antarctic. Science of The Total Environment 646, 951–957. https://doi.org/10.1016/j.scitotenv.2018.07.152 COMNAP. 2025. Council of Managers of National Antarctic Programs. Antarctic Facilities Information. https://www.comnap.aq/antarctic-facilities-information. Accessed March 24, 2025. Cowan, D.A., Chown, S.L., Convey, P., Tuffin, M., Hughes, K., Pointing, S., Vincent, W.F., 2011. Non-indigenous microorganisms in the Antarctic: assessing the risks. Trends in Microbiology 19, 540–548. https://doi.org/10.1016/j.tim.2011.07.008 Cyr, H. (2016). Wind‐driven thermocline movements affect the colonisation and growth of Achnanthidium minutissimum, a ubiquitous benthic diatom in lakes. Freshwater Biology, 61(10), 1655-1670. https://doi.org/10.1111/fwb.12806 Davies, S., Lamb, H., Roberts, S. (2015). Micro-XRF Core Scanning in Palaeolimnology: Recent Developments. In: Croudace, I., Rothwell, R. (Eds), Micro-XRF Studies of Sediment Cores. Developments in Paleoenvironmental Research, vol 17. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-9849-5_7 Fabri-Jr, R., Krause, M., Dalfior, B.M., Salles, R.C., De Freitas, A.C., Da Silva, H.E., Licinio, M.V.V.J., Brandão, G.P., Carneiro, M.T.W.D., 2018. Trace elements in soil, lichens, and mosses from Fildes Peninsula, Antarctica: spatial distribution and possible origins. Environment Earth Sciences 77, 124. https://doi.org/10.1007/s12665-018-7298-5 Falasco, E., Bona, F., Badino, G., Hoffmann, L., Ector, L., 2009. Diatom teratological forms and environmental alterations: a review. Hydrobiologia 623, 1–35. https://doi.org/10.1007/s10750-008-9687-3 Falasco, E., Ector, L., Wetzel, C. E., Badino, G., & Bona, F. (2021). Looking back, looking forward: A review of the new literature on diatom teratological forms (2010–2020). Hydrobiologia, 848, 1675–1753. https://doi.org/10.1007/s10750-021-04540-x García-Rodríguez, F., Piccini, C., Carrizo, D., Sánchez-García, L., Pérez, L., Crisci, C., Oaquim, A.B.J., Evangelista, H., Soutullo, A., Azcune, G., Lüning, S., 2021. Centennial glacier retreat increases sedimentation and eutrophication in Subantarctic periglacial lakes: A study case of Lake Uruguay. Science of The Total Environment 754, 142066. https://doi.org/10.1016/j.scitotenv.2020.142066 Hodgson, D. A., Doran, P. T., Roberts, D., & McMinn, A. (2004). Paleolimnological studies from the Antarctic and subantarctic islands. In Long-term environmental change in Arctic and Antarctic lakes, Pienitz, R., Douglas, M. S. V., & Smol, J. P. (Eds.), pp. 419-474, Dordrecht: Springer Netherlands. 10.1007/978-1-4020-2126-8_14 Holmes, N.D., Giese, M., Achurch, H., Robinson, S., Kriwoken, L.K., 2006. Behaviour and breeding success of gentoo penguins Pygoscelis papua in areas of low and high human activity. Polar Biology 29(5), 399–412. https://doi.org/10.1007/s00300-005-0070-9 Ivanova, A. A., Oshkin, I. Y., Danilova, O. V., Philippov, D. A., Ravin, N. V., & Dedysh, S. N. (2021). Rokubacteria in northern peatlands: habitat preferences and diversity patterns. Microorganisms, 10(1), 11. https://doi.org/10.3390/microorganisms10010011 Izaguirre, I., Allende, L., Romina Schiaffino, M., 2021. Phytoplankton in Antarctic lakes: biodiversity and main ecological features. Hydrobiologia 848, 177–207. https://doi.org/10.1007/s10750-020-04306-x Jackson, M. C., Loewen, C. J., Vinebrooke, R. D., & Chimimba, C. T. (2016). Net effects of multiple stressors in freshwater ecosystems: A meta‐analysis. Global change biology, 22(1), 180-189. https://doi.org/10.1111/gcb.13028 Keatley, B. E., Douglas, M. S. V., & Smol, J. P. (2008). Prolonged Ice Cover Dampens Diatom Community Responses to Recent Climatic Change in High Arctic Lakes. Arctic, Antarctic, and Alpine Research, 40(2), 364–372. https://doi.org/10.1657/1523-0430(06-068)[KEATLEY]2.0.CO;2 Kejna, M., Araźny, A., & Sobota, I. (2013). Climatic change on King George Island in the years 1948–2011. Polish Polar Research, 34(2), 213–235. https://doi.org/10.2478/popore−2013−0004 Kojima, H., Shinohara, A., & Fukui, M. (2015). Sulfurifustis variabilis gen. nov., sp. nov., a sulfur oxidizer isolated from a lake, and proposal of Acidiferrobacteraceae fam. nov. and Acidiferrobacterales ord. nov. International journal of systematic and evolutionary microbiology, 65(Pt_10), 3709-3713. https://doi.org/10.1099/ijsem.0.000479 Lavoie, I., Hamilton, P.B., Morin, S., Tiam, S.K., Kahlert, M., Gonçalves, S., Falasco, E., Fortin, C., Gontero, B., Heudre, D., 2017. Diatom teratologies as biomarkers of contamination: Are all deformities ecologically meaningful? Ecological Indicators 82, 539–550. 10.1016/j.ecolind.2017.06.048. Lotter, A., Bigler, C. Do diatoms in the Swiss Alps reflect the length of ice-cover? Aquatic sciences 62, 125–141 (2000). https://doi.org/10.1007/s000270050002 Lu, Z., Cai, M., Wang, J., Yang, H., He, J., 2012. Baseline values for metals in soils on Fildes Peninsula, King George Island, Antarctica: the extent of anthropogenic pollution. Environmental Monitoring Assessment 184, 7013–7021. https://doi.org/10.1007/s10661-011-2476-x Martins, C.C., Bícego, M.C., Rose, N.L., Taniguchi, S., Lourenço, R.A., Figueira, R.C.L., Mahiques, M.M., Montone, R.C., 2010. Historical record of polycyclic aromatic hydrocarbons (PAHs) and spheroidal carbonaceous particles (SCPs) in marine sediment cores from Admiralty Bay, King George Island, Antarctica. Environmental Pollution 158, 192–200. https://doi.org/10.1016/j.envpol.2009.07.025 McCabe, K., & Cyr, H. (2006). Environmental variability influences the structure of benthic algal communities in an oligotrophic lake. Oikos, 115(2), 197–206. https://doi.org/10.1111/j.2006.0030-1299.14939.x Meredith, M.P., King, J.C., 2005. Rapid climate change in the ocean west of the Antarctic Peninsula during the second half of the 20th century. Geophysical Research Letters 32(19). https://doi.org/10.1029/2005gl024042 Morin, S., Corcoll, N., Bonet, B., Tlili, A., Guasch, H., 2014. Diatom responses to zinc contamination along a Mediterranean river. Plecevo 147, 325–332. https://doi.org/10.5091/plecevo.2014.986 Morin, S., Cordonier, A., Lavoie, I., Arini, A., Blanco, S., Duong, T.T., Tornés, E., Bonet, B., Corcoll, N., Faggiano, L., Laviale, M., Pérès, F., Becares, E., Coste, M., Feurtet-Mazel, A., Fortin, C., Guasch, H., Sabater, S., 2012. Consistency in Diatom Response to Metal-Contaminated Environments, in: Guasch, H., Ginebreda, A., Geiszinger, A. (Eds.), Emerging and Priority Pollutants in Rivers, The Handbook of Environmental Chemistry. Springer Berlin Heidelberg, Berlin, Heidelberg, pp. 117–146. https://doi.org/10.1007/978-3-642-25722-3_5 Oliva, M., Palacios, D., Fernández‐Fernández, J.M., Fernandes, M., Schimmelpfennig, I., Vieira, G., Antoniades, D., Pérez‐Alberti, A., García‐Oteyza, J., ASTER TEAM, 2023. Holocene deglaciation of the northern Fildes Peninsula, King George Island, Antarctica. Land Degradation and Development 34(13), 3973–3990. https://doi.org/10.1002/ldr.4730 Padeiro, A., Amaro, E., Dos Santos, M.M.C., Araújo, M.F., Gomes, S.S., Leppe, M., Verkulich, S., Hughes, K.A., Peter, H.-U., Canário, J., 2016. Trace element contamination and availability in the Fildes Peninsula, King George Island, Antarctica. Environmental Science: Processes & Impacts, 18, 648–657. https://doi.org/10.1039/C6EM00052E Pandey, L.K., Bergey, E.A., 2018. Metal toxicity and recovery response of riverine periphytic algae. Science of The Total Environment 642, 1020–1031. https://doi.org/10.1016/j.scitotenv.2018.06.069 Pereira, J.L., Pereira, P., Padeiro, A., Gonçalves, F., Amaro, E., Leppe, M., Verkulich, S., Hughes, K.A., Peter, H.-U., Canário, J., 2017. Environmental hazard assessment of contaminated soils in Antarctica: Using a structured tier 1 approach to inform decision-making. Science of The Total Environment 574, 443–454. https://doi.org/10.1016/j.scitotenv.2016.09.091 Pester, M., Bittner, N., Deevong, P., Wagner, M., & Loy, A. (2010). A ‘rare biosphere’ microorganism contributes to sulfate reduction in a peatland. The ISME Journal, 4(12), 1591–1602. https://doi.org/10.1038/ismej.2010.75 Peter H-U., Braun C, Janowski S, Nordt A, Nordt A & Stelter M. (2013). The current environmental situation and proposals for the management of the Fildes Peninsula region. Federal Environment Agency (Germany), 195 pp. Piccini, C., Bertoglio, F., Sommaruga, R., Martínez De La Escalera, G., Pérez, L., Bugoni, L., Bergamino, L., Evangelista, H., García-Rodriguez, F., 2024. Prokaryotic richness and diversity increased during Holocene glacier retreat and onset of an Antarctic Lake. Communication Earth & Environment 5(1), 94. https://doi.org/10.1038/s43247-024-01245-6 Pinto, E., Sigaud‐kutner, T.C.S., Leitão, M.A.S., Okamoto, O.K., Morse, D., Colepicolo, P., 2003. Heavy metal-induced oxidative stress in algae. Journal of Phycology 39, 1008–1018. https://doi.org/10.1111/j.0022-3646.2003.02-193.x Quast, C., Pruesse, E., Yilmaz, P., Gerken, J., Schweer, T., Yarza, P., Peplies, J., Glöckner, F.O., 2012. The SILVA ribosomal RNA gene database project: improved data processing and web-based tools. Nucleic Acids Research 41, D590–D596. https://doi.org/10.1093/nar/gks1219 READER (Reference Antarctic Data for Environmental Research). 2025. Data - Reference Antarctic Data for Environmental Research Project. Scientific Committee on Antarctic Research (SCAR). https://legacy.bas.ac.uk/met/READER/surface/Bellingshausen.00.temperature.html Accessed March 24, 2025. Rühland, K. M., Paterson, A. M., & Smol, J. P. (2015). Lake diatom responses to warming: Reviewing the evidence. Journal of Paleolimnology, 54, 1–35. https://doi.org/10.1007/s10933-015-9837-3 Schiffer, M.B. 2013. Scientific Expeditions to Antarctica. In Manuals in Archaeological Method, Theory and Technique. Volume 9: The archaeology of science. Springer. pp. 137-144.10.1007/978-3-319-00077-0_10. Simonov, I. M. (1977). Physical‐geographic description of the Fildes Peninsula (South Shetland Islands). Polar Geography, 1(3), 223–242. https://doi.org/10.1080/10889377709388627 Smol, J. P., Wolfe, A. P., Birks, H. J. B., Douglas, M. S. V., Jones, V. J., Korhola, A., Pienitz, R., Rühland, K., Sorvari, S., Antoniades, D., Brooks, S. J., Fallu, M.-A., Hughes, M., Keatley, B. E., Laing, T. E., Michelutti, N., Nazarova, L., Nyman, M., Paterson, A. M., Perren, B., Quinlan, R., Rautio, M., Saulnier-Talbot, É., Siitonen, S., Solovieva, N., & Weckström, J. (2005). Climate-driven regime shifts in the biological communities of arctic lakes. Proceedings of the National Academy of Sciences of the United States of America, 102(12), 4397–4402. https://doi.org/10.1073/pnas.0500245102 Smol, J.P. 2008. Pollution of lakes and rivers. A paleoenvironmental perspective. Blackwell Publishing. 383 pp. Sorvari, S., Korhola, A., & Thompson, R. (2002). Lake diatom response to recent Arctic warming in Finnish Lapland. Global Change Biology, 8(2), 171–181. https://doi.org/10.1046/j.1365-2486.2002.00463.x Sterken, M., Verleyen, E., Jones, V., Hodgson, D., Vyverman, W., Sabbe, K., Van de Vijver, B., 2015. An illustrated and annotated checklist of freshwater diatoms (Bacillariophyta) from Livingston, Signy and Beak Island (Maritime Antarctic Region). Plant Ecology and Evolution 148, 431–455. https://doi.org/10.5091/plecevo.2015.1103 Tatur, A., Del Valle, R., Pazdur, M., 1991. Lake sediments in maritime Antarctic zone: A record of landscape and biota evolution: preliminary report. Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen 24, 3022–3024. https://doi.org/10.1080/03680770.1989.11899222 Tin, T., Fleming, Z.L., Hughes, K.A., Ainley, D.G., Convey, P., Moreno, C.A., Pfeiffer, S., Scott, J., Snape, I., 2009. Impacts of local human activities on the Antarctic environment. Antartic Science 21(1), 3–33. https://doi.org/10.1017/S0954102009001722 Tomkins, J.D., Antoniades, D., Lamoureux, S.F., Vincent, W.F., 2008. A simple and effective method for preserving the sediment–water interface of sediment cores during transport. Journal of Paleolimnology 40(1), 577–582. https://doi.org/10.1007/s10933-007-9175-1 Turner, J., Marshall, G.J., Clem, K., Colwell, S., Phillips, T., Lu, H., 2020. Antarctic temperature variability and change from station data. International Journal of Climatology 40, 2986–3007. https://doi.org/10.1002/joc.6378 Van de Vijver, B., Kopalová, K., 2014. Four Achnanthidium species (Bacillariophyta) formerly identified as Achnanthidium minutissimum from the Antarctic Region. European Journal of Taxonomy (79). https://doi.org/10.5852/ejt.2014.79 Wetzel, Carlos E., Ector, L., Van De Vijver, B., Compère, P., Mann, D.G., 2015. Morphology, typification and critical analysis of some ecologically important small naviculoid species (Bacillariophyta). Fottea/Czech Phycological Society.-Praha, Czech Republic, 2007, currens, 15(2), 203-234https://doi.org/10.5507/fot.2015.020 Zidarova, R., Kopalová, K., Van De Vijver, B., Spaulding, S.A., Lange-Bertalot, H., Potapova, M., 2016. Diatoms from the Antarctic Region: Maritime Antarctica, Iconographia Diatomologica 24, 504 p. Koeltz Botanical Books. Table Table 1 Spearman correlations between indicator bacteria and metal EFs. R 2 values are shown in the table, and significant correlations (p < 0.05) are indicated by bold values Indicator bacteria Ti Pb Zn As Cu Cr Cd Anaerovorax 0 0.53 0.53 0 0.54 0.57 0.70 Hungateiclostridiaceae 0 0 0 0 0.59 0.40 0.61 OBP41 0 0 0 0 0.48 0.45 0.66 Pseudorhodoplanes 0 0 0 0 0 0 0 Leptolinea -0.52 0.51 0.58 0 0.54 0.60 0.69 Supplementary Files SupplementaryInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 11 Dec, 2025 Reviewers invited by journal 11 Dec, 2025 Editor assigned by journal 19 Nov, 2025 First submitted to journal 17 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Concepcion","correspondingAuthor":false,"prefix":"","firstName":"Roberto","middleName":"","lastName":"Urrutia","suffix":""},{"id":547619363,"identity":"7f1c3de4-6947-4043-9a9b-e85978e2ee24","order_by":5,"name":"Dermot Antoniades","email":"","orcid":"","institution":"Université Laval Faculté de Foresterie de Géographie et de Géomatique: Universite Laval Faculte de foresterie de geographie et de geomatique","correspondingAuthor":false,"prefix":"","firstName":"Dermot","middleName":"","lastName":"Antoniades","suffix":""}],"badges":[],"createdAt":"2025-11-17 20:18:30","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8138817/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8138817/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":97135989,"identity":"14ecc4a8-b30d-4732-9b0f-bee24886dd96","added_by":"auto","created_at":"2025-12-01 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15:38:10","extension":"xml","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":164072,"visible":true,"origin":"","legend":"","description":"","filename":"AECTD25007580structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/2a35276091ff687611e9c0f6.xml"},{"id":96932043,"identity":"9788d4f9-b671-479f-b28a-4fa071814548","added_by":"auto","created_at":"2025-11-27 15:38:10","extension":"html","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":171057,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/50de42d8415d58452de1ac2c.html"},{"id":96932023,"identity":"422fdd96-2cbf-49b4-9048-c9f0fbf4c1f6","added_by":"auto","created_at":"2025-11-27 15:38:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":381641,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of the study region. a. King George Island and the Fildes Peninsula. b. Map of Fildes Peninsula indicating the study lakes: 1) Mondsee, 2) Hotel and 3) Las Estrellas. Maps were created with geospatial data from the SCAR Antarctic Digital database, accessed 2021\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/4c5ef8026c45b296168a3d3b.png"},{"id":96932021,"identity":"67b6a5c8-0c10-4f6e-90f9-d6566119785a","added_by":"auto","created_at":"2025-11-27 15:38:09","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":244011,"visible":true,"origin":"","legend":"\u003cp\u003ePCA axis 1 scores (PC1) for metals, diatoms and bacteria, and the frequency of diatom teratologies in the three study lakes. Blue lines: Mondsee Lake; orange lines: Las Estrellas Lake; Pink lines: Hotel lake\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/d8b656a74ee90319b7f3a2ee.png"},{"id":97135543,"identity":"1bcefd85-1e64-4164-96ff-bdfcd1db4d17","added_by":"auto","created_at":"2025-12-01 09:50:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":255940,"visible":true,"origin":"","legend":"\u003cp\u003eEnrichment factors (EFs) for metals: Ti, Pb, Zn, As, Cu, Cr and Cd in the three study lakes. Note the different x-axis for Pb in Hotel Lake (top)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/8bbeaca55080077d3d655eca.png"},{"id":96932028,"identity":"74ccf27c-832f-4348-b19b-302f0b674b96","added_by":"auto","created_at":"2025-11-27 15:38:09","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":502401,"visible":true,"origin":"","legend":"\u003cp\u003eRelative abundances of the most abundant diatoms and those that changed the most over time. Top: Mondsee Lake; middle: Las Estrellas Lake; bottom: Hotel Lake\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/0bc689e7ae6c696c1fce25e6.jpeg"},{"id":96932026,"identity":"19c49c77-585a-4f5f-a004-d1b436228e31","added_by":"auto","created_at":"2025-11-27 15:38:09","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":500389,"visible":true,"origin":"","legend":"\u003cp\u003eRead abundances of the most abundant bacteria and those that changed the most over time. Top: Mondsee Lake; middle: Las Estrellas Lake; bottom: Hotel Lake\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/a34e75bc2db8e8934f9aee6c.jpeg"},{"id":97144535,"identity":"47071f3c-983e-48b1-a40f-64e8b51beef5","added_by":"auto","created_at":"2025-12-01 10:11:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2582244,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/fc29839c-3346-43bb-b93f-222e6d864e52.pdf"},{"id":96932040,"identity":"6763a3ca-de58-40f2-a894-de260f4fcd62","added_by":"auto","created_at":"2025-11-27 15:38:10","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":29050850,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8138817/v1/150d823d5295fb167a651d04.docx"}],"financialInterests":"","formattedTitle":"Reconstructing the effects of anthropogenic activities and climate change in three lakes of the Fildes Peninsula, Maritime Antarctic","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe geography of the Antarctic Peninsula (AP) distinguishes it from the rest of the continent in aspects such as climate and human activities. The AP has experienced accelerated climate warming during the past 50 years and is amongst the most rapidly warming regions in the Southern Hemisphere (Turner et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Maritime Antarctic temperatures show strong interannual variability and are highly dependent on seawater temperature and annual changes in sea ice extent (Meredith and King, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Kejna et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Superimposed on this interannual variability, Bellingshausen Station temperatures showed a significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) increasing trend of 0.23\u0026deg;C per decade between 1969 and 2024 (READER, 2025).\u003c/p\u003e\u003cp\u003eScientific pursuits became an important component of anthropogenic Antarctic activities with the establishment of stations that permitted year-round human presence (Schiffer, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). For example, since Bellingshausen Station (Russia) was built in 1968, King George Island (situated in the AP) has seen a surge in the construction and expansion of research and other infrastructure, with twelve stations present on the island (COMNAP, 2025). These developments have placed increasing strain on sensitive polar ecosystems and led to a growing concern about the threats, including contamination of terrestrial and aquatic environments, modification of animal behavior and the introduction of non-indigenous species, that the increased human traffic may pose to the continent\u0026rsquo;s natural systems (Holmes et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, Tin et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2009\u003c/span\u003e, Martins et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, Cowan et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2011\u003c/span\u003e, Choi et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, monitoring programs in general have only been undertaken since the agreement of the Protocol on Environmental Protection to the Antarctic Treaty, which came into effect in 1998. Paleolimnological techniques, by which lake sediments are used to reconstruct changes over time at local and regional scales, can be applied retrospectively to understand impacts caused by human activities (Smol, \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). In Antarctic lakes, such approaches permit comparisons of present conditions with those of the past several decades and enable the determination of pristine baseline conditions by reaching samples prior to the onset of local human activities (Hodgson et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWe studied the Fildes Peninsula, which in addition to being the largest ice-free area of King George Island and the site of numerous lakes is also amongst the areas of Antarctica most impacted by humans (Peter et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Since the construction of Bellingshausen Station in 1968 the population of the peninsula has gradually increased, with six permanent stations built between 1968 and 1994, belonging to Chile, China, Russia and Uruguay, that accommodate up to 375 people at peak occupation in the austral summer (COMNAP, 2025). An airfield constructed in 1980 and a harbor master station also serve as logistics hubs for entry by scientists and tourists to the South Shetland Islands (Braun et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The strong human presence resulting from tourism and the high density of bases implies an accrued risk of environmental contamination, including from fuel spills, poor waste management, habitat destruction and damage to vegetation by vehicles, and indeed the ground around many stations has been suggested to show traces of contamination (Bargagli, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Braun et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2012\u003c/span\u003e., Peter et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSeveral studies have focused on long-term regional climate and landscape evolution in the Fildes Peninsula (Tatur et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e1991\u003c/span\u003e, Garc\u0026iacute;a-Rodr\u0026iacute;guez et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Oliva et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Piccini et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), while one assessed changes on shorter time scales caused by human activities (Bertoglio et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). This study demonstrated that DNA was well preserved in sediments, allowing the detection of changes in bacterial communities over time, and identified indicator bacteria of human presence related to lakes impacted by metals, enabling their use as sedimentary proxies to reconstruct anthropogenic impacts. The only available assessment of recent changes in pre- and post-impact conditions used a top-bottom approach (Bertoglio et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e); here we evaluated detailed profiles in three lakes of metal concentrations, bacterial DNA and diatom assemblages and teratologies in the sedimentary record to develop a comprehensive picture of the effects of human activities for the last ca. 150 years. We compared trends over the past century in microbial community composition in two lakes close to stations (Las Estrellas and Hotel lakes) to those in one more remote lake (Mondsee Lake) to assess the hypothesis that perturbations related to the stations have altered microbial diversity in lakes close to human activities.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Study area\u003c/h2\u003e\n \u003cp\u003eFildes Peninsula (62\u0026deg;11\u0026prime; S, 58\u0026deg;58\u0026prime; W) is located at the southwestern tip of King George Island in the South Shetland Islands of the maritime Antarctic region (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The 38 km\u003csup\u003e2\u003c/sup\u003e peninsula is surrounded by the waters of the Drake Passage, Fildes Strait and Maxwell Bay. It is free of ice except for its northeast end which is covered by the Collins Glacier (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb). Numerous lakes that formed following glacial recession during the Late Holocene are present on the peninsula (Simonov, \u003cspan class=\"CitationRef\"\u003e1977\u003c/span\u003e), some of which are used as water sources for various stations. Our study included three Fildes Peninsula lakes (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb): two are situated adjacent to stations, while one is more distant from human infrastructure. The lakes included Hotel Lake, which is adjacent to the Teniente Marsh Aerodrome and was formerly its water supply, and which has ceased to be used for drinking water due to elevated levels of heavy metals (Peter et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e); Las Estrellas Lake, which previously supplied water to Escudero Station (Chile), and is ~\u0026thinsp;200 m from the nearest roads and infrastructure; and Mondsee Lake, situated 3.5 km from Frei Station (Chile) and 2.6 km from Artigas Station (Uruguay).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Sampling\u003c/h2\u003e\n \u003cp\u003eSediment cores were taken in November-December 2016 (Las Estrellas and Mondsee lakes) and in December 2013 (Hotel Lake), at the deepest known point of each lake. Holes were drilled in the lake ice with a manual ice auger, and cores were recovered using a universal corer (Aquatic Research Instruments) with tenite butyrate core tubes of either 67 or 95 mm internal diameter. Based on sedimentation rates obtained from earlier studies, a general target length of 30 cm was established for the sediment cores, which was long enough to far exceed the period of human presence on Fildes Peninsula. The sediment-water interfaces were stabilized with sodium polyacrylate (Tomkins et al., \u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e), and cores were then sealed and transported whole, cold and in the dark to Universit\u0026eacute; Laval (Canada). The cores were then split lengthwise and sectioned at fine intervals for the analysis of diatoms, DNA, metals and radioisotopes. Subsamples followed visible layers in the stratigraphy of each sedimentary record and ranged from 0.1 to 0.5 cm thickness. Samples were studied to sufficient depths to reach at least the mid-20th century, in order to encompass the entire period of human influence on Fildes Peninsula and reach baseline conditions prior to local anthropogenic impacts. More details about the number of samples analyzed for each proxy as well as the sediment range included are available in Table S.1. All subsampling was carried out under sterile protocols to preclude contamination, and separate subsamples were taken for analysis of diatoms, DNA and radioisotopic dating, placed in sterile Whirl-Pak bags, and kept frozen at -80\u0026deg;C until analysis.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Chronologies\u003c/h2\u003e\n \u003cp\u003eSediment chronologies were generated from \u003csup\u003e210\u003c/sup\u003ePb activities measured by alpha spectroscopy at Chronos Scientific Inc. in Ottawa, Canada. Freeze-dried samples sectioned at fine intervals (~\u0026thinsp;4 mm) were ground and spiked with \u003csup\u003e209\u003c/sup\u003ePo, after which HNO\u003csub\u003e3\u003c/sub\u003e (nitric acid) and HCl (hydrochloric acid) were added, and the samples were heated at 80\u0026deg;C for 16 hours. The solutions were then centrifuged and evaporated to dryness three times, with HCl added after each cycle. Finally, the Po isotopes were electroplated on silver disks and measured using alpha spectroscopy. Age-depth models were generated with the R package serac using the constant rate of supply (CRS) model, with interpolated ages generated to cover the specific depths of the subsamples for all lakes and indicators (Appleby, \u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e; Bruel and Sabatier, \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Metals\u003c/h2\u003e\n \u003cp\u003eMetal concentrations (i.e., Cd, Ni, Cr, Pb, Co, Zn, Cu, Fe, Mn, As, Se, Ti) were measured on ~\u0026thinsp;1 g (dry weight) sediment subsamples using inductively coupled plasma-mass spectrometry (ICP-MS) in the Laboratory for the Analysis of Natural and Synthetic Environmental Toxins (LANSET) at the University of Ottawa, Canada. Duplicates, blanks and standard reference materials were used for quality assurance/quality control. Values are expressed in milligrams per kilogram of dry sediment (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e).\u003c/p\u003e\n \u003cp\u003eMetal enrichment factors (EF) were calculated in each lake using the following equation:\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/58895_8739fc6c57c1c19a/58895_custom_files/img1764257477.png\" width=\"244\" height=\"166\"\u003e\u003c/p\u003e\n \u003cp\u003ewhere x refers to the metal measured by ICP-MS; Ti is titanium, a reliable indicator of changes in allochthonous sedimentation (Davies et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) used to normalize metal concentrations; and reference represents pre-human background values, calculated using the last sample in each core that age models indicated to be from the 19th century (i.e., 1890, 1895, and 1876 CE in Mondsee, Hotel and Las Estrellas lakes, respectively). EF values around 1 show no sign of enrichment, while values over 3 and 10 show moderate and severe enrichment, respectively (Chen et al., \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e). EFs for Ti were calculated as concentrations relative to those of the reference sample.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Diatom analysis\u003c/h2\u003e\n \u003cp\u003e0.1 g of dried sediment was prepared for diatom analysis by oxidizing organic matter with 30% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Following digestion, samples were allowed to settle for 24 h, the supernatants aspirated, and slurries were rinsed several times with distilled water to return them to neutral pH. Slurries were then placed on cover slips to dry on in a dust-free environment and fixed on microscope slides using Naphrax mounting medium. A minimum of 300 valves were counted in each sample using a Zeiss Axioscop 2 microscope equipped with differential interference contrast (DIC) optics at 1000x magnification under immersion oil. Primary taxonomic references for the identification of the diatom flora included Zidarova et al. (\u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e), Van de Vijver and Kopalov\u0026aacute; (\u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e), Sterken et al., (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) and Wetzel et al., (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). The identification of some species was verified using a scanning electron microscope (SEM) at Centres Cientifics i Tecnol\u0026ograve;gics of the Universitat de Barcelona (CCiTUB), Spain. In addition to taxonomic identifications, teratologies were enumerated in separate scans of 500 valves to determine the proportion of diatom deformities in each lake. Scans to determine the proportion of diatom deformities in each lake began with the surface sample and continued downcore until 3 consecutive samples showed an absence of teratologies after 200 valves were counted. The teratology percentage was based only on specimens found in valve view, as teratologies are generally not visible in girdle view (Lavoie et al., \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 DNA extraction, sequencing and taxonomic assignment\u003c/h2\u003e\n \u003cp\u003eTo detect changes in bacterial community composition, bacterial diversity was analyzed by 16S rRNA amplicon sequencing. All material employed for manipulation of DNA sediment subsamples, as well as the vertical laminar flow cabinet (ESCO Class II, Type A2) where the DNA was extracted, was previously sterilized by irradiation with UV light. 0.5 g of wet sediment were aseptically transferred to sterile microtubes containing ceramic beads and an extraction buffer composed of 1% CTAB (Hexadecyltrimethylammonium bromide) and EDTA (Ethylenediaminetetraacetic acid) and homogenized with a FastPrep homogenizer (MP). After centrifugation at 12000 g the supernatants were subjected 3 times to chloroform:isoamyl alcohol (24:1) extractions and the pellets were precipitated with 0.6 volumes of cold isopropanol at room temperature during 24 h. These precipitates were then subjected to centrifugation for 40 min at 12000 g at room temperature, and the DNA obtained in the pellets was washed with cold ethanol, dried and suspended in ultrapure water overnight at 4\u0026deg;C. The concentration and purity of DNA was determined spectrophotometrically at 260 and 280 nm, and its quality was checked by the amplification of a variable region (V4) of the ribosomal 16S gene. PCR (polymerase chain reaction) products were verified by gel electrophoresis on 1% agarose gel in 0.5X TBE buffer. DNA samples were sent to Novogene for Illumina MiSeq paired-end sequencing of the V4 region, using the 515F and 806R primers (Caporaso et al., \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eTo correct for sequencing errors and create Amplicon Sequence Variants (ASVs), reads were processed in R using the DADA2 pipeline following a modified version of the DADA2 Bioconductor workflow (Callahan et al., \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). Briefly, reads were filtered and trimmed by the \u003cem\u003efilterAndTrim\u003c/em\u003e function based on the quality score which estimates the error probability of the DNA sequence. Reads with a maximum expected error (maxEE) greater than 2 were removed and based on quality profiles, reads were truncated at 200 and 190 bp for forward and reverse reads, respectively. Sequence variations were inferred with the \u003cem\u003elearnerrors\u003c/em\u003e and \u003cem\u003edada\u003c/em\u003e functions. Chimeric sequences were eliminated, and taxonomy assignments from kingdom to genus were performed with \u003cem\u003eassignTaxonomy\u003c/em\u003e based on the SILVA database (v138) (Quast et al., \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). ASV sequences assigned as Archaea, Chloroplasts and Mitochondria were removed. Sequences obtained were submitted to the nucleotide archive GenBank with the BioProject ID PRJNA1365190.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 Data analysis\u003c/h2\u003e\n \u003cp\u003eMultivariate analyses were used to explore patterns in the variation over time of metals, diatoms and bacteria. Principal component analysis (PCA) was performed separately for each proxy (metals, diatoms and bacteria); the ICP-MS metals data were \u003cem\u003elog\u003c/em\u003e transformed prior to PCA while the diatom and bacteria datasets were Hellinger-transformed.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Chronology\u003c/h2\u003e\u003cp\u003eLog\u003csup\u003e210\u003c/sup\u003ePb activities were low and showed roughly linear decreasing trends over time in each lake, with activities in surface sediments of 95.4, 61.2, and 189.7 Bq kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and reaching background at 55, 54 and 31 mm depth in Mondsee, Las Estrellas and Hotel lakes, respectively (Fig. S.1). CRS models indicated that the year 1968 CE, when Bellingshausen base was established, corresponded to ~\u0026thinsp;21, ~23, and ~\u0026thinsp;5.7 mm depth in Mondsee, Las Estrellas and Hotel lakes, respectively (Fig. S.1).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Metal concentrations and enrichment factors\u003c/h2\u003e\u003cp\u003eThe metals with the greatest variation throughout the three sediment cores were Pb, Zn, As, Cu, and Cr (Fig. S.2). Mondsee Lake showed little change, with concentrations that ranged between 6.7 and 7.5 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Pb, 51.4 and 59.9 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Zn, As between 3.3 and 8.2 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Cu between 84.4 and 111.5 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Cr between 7.9 and 10.2 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. S.2). There was greater variation in metals in Las Estrellas Lake, with concentrations ranging between 5.2\u0026ndash;10.6 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Pb, 39.8-148.8 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Zn, 2.6\u0026ndash;9.7 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for As, 44-107.2 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Cu and 10.6\u0026ndash;18.3 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Cr (Fig. S.2). Hotel Lake showed by far the highest metal concentrations as well as the greatest variation, varying between 5.4-683.9 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Pb, 47.3-350.7 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Zn, 1.8\u0026ndash;5.4 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for As, 62-189.4 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Cu and 9.9\u0026ndash;30.5 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for Cr (Fig. S.2).\u003c/p\u003e\u003cp\u003eThe first two axes of the PCA of metal concentrations explained 80.0% of the variance in the dataset, with PC1 explaining 62.1% and PC2 explaining 17.9%. First axis scores for Mondsee Lake did not change through the core, while Las Estrellas Lake PC1 values undulated slightly between 1950 and the present, and Hotel Lake PC1 values changed markedly beginning between 1940 and 1998 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eEnrichment factors for Ti were close to 1 and showed little variation throughout all three sediment cores, indicating relatively constant supplies of allochthonous sediment over time (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The highest EFs were observed for Pb, Zn, As, Cu, Cr and Cd (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Table S.2), apart from Mondsee Lake where EFs throughout the core were close to 1 (i.e., no enrichment) except for As, which increased moderately between 2012 and 2017 reaching a maximum EF of 3.0 in 2015 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). EFs for Pb, Cu Cr and Cd in Las Estrellas Lake were close to 1 and varied little in the core, except in 2017 for Pb which was moderately enriched (EF: 2.9) and Cr that increased somewhat but at 1.9 remained below threshold for moderate enrichment (i.e., 3; Chen et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The metal showing the greatest enrichment in Las Estrellas Lake was Zn, which increased upwards from 1974 to the surface, with moderately enriched values in 1982 and a maximum at the surface of the core (2017) of 5.7 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). As was moderately enriched from 1962 to the most recent sample (2017), with the maximum values in 1974 and 1978 (EFs: 4.9 and 5.6 respectively; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). EFs of many metals in Hotel Lake showed pronounced enrichment and had similar trends, increasing slightly in the early 20th century, and greatly after ~\u0026thinsp;1976 to a maximum in 1998, and then decreasing somewhat in the surface sediment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Pb, Zn and Cd showed severe enrichment in 1998 (maximum EFs of 146.2, 14.9 and 10.6) while As, Cu and Cr showed moderate enrichment at this point (maximum EFs: 6.1, 5.5 and 6.2) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Diatom composition\u003c/h2\u003e\u003cp\u003eNinety-one diatom taxa belonging to 30 genera were identified in the three study lakes (Table S.3, Fig. S.3). In general, assemblages were dominated by small benthic diatoms (\u0026lt;\u0026thinsp;20 \u0026micro;m), mainly from the genera \u003cem\u003eAchnanthidium\u003c/em\u003e, \u003cem\u003ePsammothidium\u003c/em\u003e, \u003cem\u003ePlanothidium\u003c/em\u003e, \u003cem\u003eSellaphora\u003c/em\u003e and \u003cem\u003eStaurosirella\u003c/em\u003e. A total of 78 species from 25 different genera was identified in Mondsee Lake (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Some species showed pronounced stratigraphic changes. There was a step-change in \u003cem\u003eAchnanthidium indistinctum\u003c/em\u003e, which averaged 4.2% relative abundance prior to ~\u0026thinsp;1991 and 26.5% thereafter. This was coincident with an increase of \u003cem\u003ePlanothidium frequentissimum\u003c/em\u003e and decreases in \u003cem\u003eStaurosirella antarctica\u003c/em\u003e and other, less abundant species including \u003cem\u003eChamaepinnularia australomediocris\u003c/em\u003e and \u003cem\u003ePsammothidium confusoneglectum\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eSeventy-four diatom species from 28 genera were identified in the Las Estrellas Lake core (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). There were three horizons of pronounced assemblage change in the core: at ~\u0026thinsp;1955, ~1968 and ~\u0026thinsp;1976. After ~\u0026thinsp;1955, assemblages that had shown relative stability were marked by increases in \u003cem\u003eAchnanthidium indistinctum\u003c/em\u003e, \u003cem\u003eStaurosirella antarctica\u003c/em\u003e and \u003cem\u003ePsammothidium incognitum\u003c/em\u003e, and the period had low abundances of \u003cem\u003ePlanothidium renei\u003c/em\u003e. Between ~\u0026thinsp;1968 and ~\u0026thinsp;1976, there was an abrupt decrease of \u003cem\u003eAchnanthidium indistinctum\u003c/em\u003e from 22% relative abundance to values\u0026thinsp;~\u0026thinsp;1%, an abrupt increase of \u003cem\u003eStaurosirella antarctica\u003c/em\u003e, and gradual increases of \u003cem\u003ePlanothidium renei\u003c/em\u003e, \u003cem\u003eStauroneis sofia\u003c/em\u003e and \u003cem\u003ePsammothidium abundans\u003c/em\u003e. Around 1975, there were sharp decreases of \u003cem\u003eStaurosirella antarctica\u003c/em\u003e and \u003cem\u003ePlanothidium renei\u003c/em\u003e coincident with sharp increases in \u003cem\u003eSellaphora nigri\u003c/em\u003e and \u003cem\u003eCavinula pseudoscutiformis\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eA total of 50 species from 18 genera was identified in the Hotel Lake core, with no taxa having an average abundance exceeding 20%, representing the lowest diversity among the three lakes (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The species that showed the most evident trend was \u003cem\u003ePsammothidium papilio\u003c/em\u003e, which was abundant in the lower part of the core (average 10.3%, 1867\u0026ndash;1907) and then decreased dramatically above this horizon (average 0.8%), as well as \u003cem\u003ePsammothidium abundans\u003c/em\u003e which also peaked\u0026thinsp;~\u0026thinsp;1907 but had a higher abundance in the upper section of the core (between 10 and 18%). \u003cem\u003eSellaphora nigri\u003c/em\u003e was present at generally low relative abundances during most of the 20th century until the most recent sample (2014) when it increased to a relative abundance of 14% (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), and \u003cem\u003eAchnanthidium maritimo-antarcticum\u003c/em\u003e increased after 1976, but with lower relative abundances (between 0.3 and 5%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe first axis of the diatom PCA explained 33.8% of the variation in the diatom data while the second axis explained 16.6%. Based on first axis scores, the most pronounced change in diatom composition occurred in Las Estrellas Lake from 1967 to 1979, while compositional changes in Mondsee and Hotel lakes were less notable (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Bacterial composition\u003c/h2\u003e\u003cp\u003eWe detected a total of 14,567 ASVs across the three cores. Rarefaction curves based on the observed ASVs reached plateaus, indicating that sequencing depth was adequate to capture the overall diversity of all lakes (Fig. S.4). As was observed in our previous study (Bertoglio et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), bacterial communities from each lake were composed of a few very abundant ASVs while most taxa had low abundances. In Mondsee Lake the taxa that showed the most evident trends over time were \u003cem\u003eSulfurifustis\u003c/em\u003e and Phycisphaerae, which decreased after ~\u0026thinsp;1956 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Additionally, certain species dominated in the most recent sample in Mondsee Lake (2017) while others decreased dramatically. For example, \u003cem\u003eJanthinobacterium\u003c/em\u003e, Rokubacteriales, \u003cem\u003eDelftia\u003c/em\u003e, \u003cem\u003eClostridium\u003c/em\u003e sensu stricto 13, and \u003cem\u003eDesulfosporosinus\u003c/em\u003e were more abundant in this sample, whereas \u003cem\u003eDesulfatirhabdium\u003c/em\u003e and P9X2b3D02 (phylum Nitrospinota) decreased (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe abundances of several bacteria in Las Estrellas and Hotel lakes changed notably after \u0026sim;1970 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). For example, Holophagaceae and \u003cem\u003eDesulfatirhabdium\u003c/em\u003e increased while Phycisphaerae and CCM11a decreased in both lakes (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Other groups also showed considerable shifts but with different patterns in each lake, such as \u003cem\u003ePseudomonas\u003c/em\u003e and Zixibacteria that increased after \u0026sim;1970 in Las Estrellas Lake while Phycisphaerae decreased, and MBNT15, Latescibacterota, Rokubacteriales and Zixibacteria decreased in Hotel Lake after ~\u0026thinsp;1976.\u003c/p\u003e\u003cp\u003eThe first axis of the bacteria PCA explained 28.9% of the variation in bacterial composition data while the second axis explained 18.0%. In addition, based on first axis scores, the most pronounced change was observed in the most recent sample of Mondsee Lake (2017), whereas changes in Las Estrellas and Hotel lakes were more muted (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e4.5 Diatom teratologies and bacterial indicators of contamination\u003c/h2\u003e\u003cp\u003eDiatom teratologies are deformations of cell morphology that have been observed to increase in contaminated water bodies, particularly those with high concentrations of heavy metals and pesticides (Falasco et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In Mondsee Lake they had a maximum occurrence of 1.2% (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Teratologies were most notable in Las Estrellas Lake, where they increased between 1975\u0026ndash;1982 to ~\u0026thinsp;2% of the enumerated valves, and sharply thereafter with frequencies of 6.6 and 10.0% (in 1997 and 2017, respectively), including 30% of the valves \u003cem\u003eof P. abundans\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The surface sample of Hotel Lake also had more prevalent teratologies, increasing from 1998 to a maximum of 2.9% deformed valves in the surface sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWe tested correlations between different metal EFs and the abundances of certain bacteria that were identified as indicators of contamination (i.e., \u003cem\u003eAnaerovorax\u003c/em\u003e, Hungateiclostridiaceae, OPB41, \u003cem\u003ePseudorhodoplanes\u003c/em\u003e, and \u003cem\u003eLeptolinea\u003c/em\u003e; Bertoglio et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Of the five taxa evaluated, all except \u003cem\u003ePseudorhodoplanes\u003c/em\u003e were positively correlated with enrichments of multiple metals (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Pb, Zn, Cu, Cr and Cd had positive, significant and high correlation coefficients (i.e., R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.40\u0026ndash;0.70) with between two and four taxa each (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e4.6 Separating the effects of environmental change and anthropogenic activities\u003c/h2\u003e\u003cp\u003eFildes Peninsula lakes are subject to multiple stressors, including rapidly rising temperatures and strong UV exposure due to ozone depletion, in addition to any direct anthropogenic impacts. We hypothesized that, due to its remoteness from infrastructure, Mondsee Lake could be used as a control site to determine changes in diatom and bacterial communities due primarily to natural environmental change, including ongoing warming. This hypothesis was supported by the differing trends in metal enrichment between Mondsee Lake and the other two sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe limnological consequences of recent warming in maritime Antarctica include changing lake ice cover duration and thickness and thermal stratification regimes (Izaguirre et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Decreases in ice cover duration influence diatom communities, as has been observed in many lakes in the Northern Hemisphere (Lotter and Bigler, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Sorvari et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Smol et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; R\u0026uuml;hland et al., \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Although somewhat muted, recent diatom shifts in Mondsee Lake likely reflect changes to ice cover duration and extent, including declines of \u003cem\u003eStaurosirella antarctica\u003c/em\u003e, which is associated with colder conditions and prolonged ice cover (Lotter and Bigler \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Keatley et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), and increases after ~\u0026thinsp;1991 of \u003cem\u003eAchnanthidium indistinctum\u003c/em\u003e, a taxon that thrives in nearshore lake environments where external disturbances such as wind are common (McCabe and Cyr \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Cyr, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). A coincident decline in \u003cem\u003eStaurosirella antarctica\u003c/em\u003e in Las Estrellas Lake (after the mid-1970s) also likely reflects the broader effects of climate warming on ice cover duration and thickness, although the species was absent in the 20th century in Hotel Lake. In fact, diatom assemblages in Hotel Lake showed no systematic changes, either in overall assemblage composition or in the abundances of most taxa. Hotel Lake had much thicker ice cover than the other two lakes during spring 2017 and autumn 2018 (1.60 and 0.55 m vs. 0.98 and 0.13 m on average for both seasons, respectively; Bertoglio et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Although the precise reasons are uncertain, Hotel Lake is located in the upper section of the Grande Valley, which appears to channel cold winds between the Drake Passage to the west and Maxwell Bay to the east (pers. obs.). Its thick ice may therefore reflect a colder microclimate and imply the delayed onset of the effects of warming in this lake.\u003c/p\u003e\u003cp\u003eCertain bacteria found with higher abundances in the most recent sample of Mondsee Lake may potentially be associated with the consequences of warming. For example, \u003cem\u003eJanthinobacterium\u003c/em\u003e produce the pigment violacein which confers resistance to UV radiation (Alem et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), which is expected to increase as ice cover thins. Moreover, Rokubacteriales and Desulfosporosinus are common soil taxa that were also found in peatlands (Pester et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Ivanova et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), and their increases could be related to increasing runoff and aeolian deposition in longer melting seasons. The increase of \u003cem\u003eJanthinobacterium\u003c/em\u003e after ~\u0026thinsp;1995 in Las Estrellas Lake may also be a consequence of climate warming; it also increased in Hotel Lake but much more subtly. This reaffirms the muted nature of climate change effects in Hotel Lake as suggested by diatom trends. The lack of increases in other bacteria taxa reflecting climate change in Hotel and Las Estrellas lakes may be because the influence of climate change in shaping communities in these lakes is overshadowed by the pronounced impact of anthropogenic activities. Indeed, in the presence of multiple stressors related to climate change and human activities, lakes may differ in responses compared with those that only experience single stressors (Jackson et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe increase in metal EFs in Las Estrellas and Hotel lakes since the establishment of bases on the peninsula is consistent with our hypothesis that the sites nearest human activities would show increases in contaminants over time, and the contrast with the lack of changes in Mondsee Lake suggests that these increases cannot be ascribed to natural environmental changes. The changes we observed in Las Estrellas and Hotel Lakes therefore represent the cumulative effects of climate change and human impacts. There is growing evidence for human impacts in terrestrial and marine ecosystems in maritime Antarctica. For example, elevated Cu, Zn, Cd and Pb have been found in marine sediments, soil, lichens and mosses from Fildes Peninsula close to stations and contaminated sites (Aronson et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Lu et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Padeiro et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Pereira et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Fabri-Jr et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). These results are comparable to our findings, since heavy metal contamination may be related to intense human activity such as transportation, fossil fuel combustion, accidental oil spills, waste incineration and sewage disposal (Chu et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Our results give temporal context to these findings, showing that the affected sites not only had high metal concentrations but that they increased over time, while those in our remote site showed little to no change over the same period.\u003c/p\u003e\u003cp\u003eBiological proxies also showed greater changes in the proximal vs. remote lake and provided evidence of the ecological effects of anthropogenic impact. While shifts in overall community composition of diatoms and bacteria did not differ markedly between the three lakes, we found trends in taxa that were indicators of pollution and may thus have adaptive advantages in metal-impacted environments. The diatom \u003cem\u003eSellaphora nigri\u003c/em\u003e is an indicator species that is found in greater abundances in environments where eutrophication, organic contaminants or pollution by pesticides and heavy metals are observed (Morin et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Wetzel et al., \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Given its tolerance to pollution, the increase in \u003cem\u003eS. nigri\u003c/em\u003e relative abundances in Las Estrellas Lake around 1975, coincident with increasing human activities as well as with the construction of numerous stations in the subsequent years (Braun et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Peter et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) may therefore reflect contamination due to human activity. The increase of this species in the surface sediments of Hotel Lake, while less than that observed in Las Estrellas Lake, may also reflect such impacts. By comparison, \u003cem\u003eS. nigri\u003c/em\u003e always had abundances\u0026thinsp;\u0026lt;\u0026thinsp;1% in Mondsee Lake, which reinforces the hypothesis of the pristine nature of the lake relative to our other sites.\u003c/p\u003e\u003cp\u003eDiatom teratologies represent an individual-level response to environmental stress (Falasco et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Deformed frustules associated with heavy metal stress have been reported in various studies (Falasco et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Cantonati et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Pandey and Bergey, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). While the exact mechanism of the deformations has not been demonstrated, it has been suggested that contaminants alter cell membrane polarity and cause cytoplasmic acidification, leading to disruption of cytoplasmic homeostasis (Pinto et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). While some authors have attributed diatom teratologies to high UV exposure (summarized in Falasco et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), such as that due to thinning of the stratospheric ozone layer in the Antarctic, this mechanism cannot explain the differing trends between Mondsee Lake and the other two sites. The increase in teratologies in Las Estrellas and Hotel lakes, and their absence in Mondsee Lake, however, is consistent with the observed changes in metal enrichment and thus demonstrates the ecological effects of pollution.\u003c/p\u003e\u003cp\u003eWithin bacterial communities, particular taxa with higher tolerances to contaminants became more abundant over time in Hotel and Las Estrellas lakes, such as \u003cem\u003eSulfurifustis\u003c/em\u003e and \u003cem\u003eDesulfatirhabdium\u003c/em\u003e. These sulfur bacteria may be related to the presence of pollutants as they can employ a variety of electron donors or inorganic sulfur compounds as electron acceptors (Balk et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, Kojima and Fukui 2015), such as those found in contaminants originating from the burning of fossil fuels. However, we do not exclude that the presence of these bacteria may be related to changes in sediment habitats, for example due to anoxia, influencing active bacteria rather than reflecting historical changes. \u003cem\u003eDesulfatirhabdium\u003c/em\u003e increased in both Las Estrellas and Hotel lakes after ~\u0026thinsp;1982, while \u003cem\u003eSulfurifustis\u003c/em\u003e also increased in Las Estrellas Lake over the same period. Neither increased in abundance in Mondsee Lake where their abundances in fact decreased there after \u0026sim;1956 and 1991, respectively. Several groups of sulfur bacteria (e.g. Geobacteraceae, Desulfurivibrionaceae and Rhodobacteraceae) were also previously observed in the bacterial community in water samples from Hotel Lake (Bertoglio et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Moreover, the significant relationships between bacterial indicators of pollution and metal EFs (i.e., Hungateiclostridiaceae, OPB41, \u003cem\u003eAnaerovorax\u003c/em\u003e and \u003cem\u003eLeptolinea\u003c/em\u003e; Bertoglio et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), provide further evidence that human impacts are modifying aquatic communities in Fildes Peninsula\u0026rsquo;s lakes.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eLakes in maritime Antarctica are subject to stress from rapidly warming climates, and, in some cases, from anthropogenic activities in their catchments. We analyzed sedimentary proxies (metals, diatoms and bacterial DNA) in three lakes and showed notable changes in metal enrichment, diatom teratologies and bacteria indicators of pollution in two (Las Estrellas and Hotel lakes) that were located near to logistics infrastructure. The changes of the same indicators in Mondsee Lake, more distant from human activities, were muted by comparison. We conclude that Mondsee Lake represents the baseline of recent changes due to climate change, and that the more pronounced shifts in the other two lakes can therefore not be attributed to warming alone. Although based on our study we cannot draw direct causal links between changes in lake sediments and anthropogenic activities, the trends we observed provide strong evidence for significant human effects on aquatic ecosystems. Further studies are needed to better quantify the effects and prevent further deterioration of these sensitive Antarctic environments.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Instituto Ant\u0026aacute;rtico Chileno (Project ANID/FONDAP/2014), the Fonds de recherche du Qu\u0026eacute;bec - Nature et technologies (FRQNT), the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Agencia Nacional de Investigaci\u0026oacute;n e Innovaci\u0026oacute;n (ANII). We also thank the Instituto Ant\u0026aacute;rtico Uruguayo for logistical support.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRoberto Urrutia, Santiago Giralt and Dermot Antoniades contributed to the study conception and design and conducted fieldwork. Florencia Bertoglio and Samuel Yergeau processed and analyzed the samples. Florencia Bertoglio, Claudia Piccini and Dermot Antoniades interpreted the data. The first draft of the manuscript was written by Florencia Bertoglio and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets analysed during the current study are available on the Open Science (OSF) repository (https://osf.io/ma3tg/overview?view_only=1773bc9b695649f4817426efef5b17df)\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlem, D., Marizcurrena, J.J., Saravia, V., Davyt, D., Martinez-Lopez, W., Castro-Sowinski, S., 2020. Production and antiproliferative effect of violacein, a purple pigment produced by an Antarctic bacterial isolate. World Journal of Microbiology and Biotechnology 36, 120. https://doi.org/10.1007/s11274-020-02893-4\u003c/li\u003e\n\u003cli\u003eAppleby, P.G., 2001. Chronostratigraphic Techniques in Recent Sediments, in: Last, W.M., Smol, J.P. (Eds.), Tracking Environmental Change Using Lake Sediments: Basin Analysis, Coring, and Chronological Techniques. Springer Netherlands, Dordrecht, pp. 171\u0026ndash;203. https://doi.org/10.1007/0-306-47669-X_9 \u003c/li\u003e\n\u003cli\u003eAronson, R.B., Thatje, S., McClintock, J.B., Hughes, K.A., 2011. Anthropogenic impacts on marine ecosystems in Antarctica. Annals of the New York Academy of Sciences 1223, 82\u0026ndash;107. https://doi.org/10.1111/j.1749-6632.2010.05926.x\u003c/li\u003e\n\u003cli\u003eBalk, M., Altınbas, M., Rijpstra, W. I. C., Sinninghe Damste, J. S., \u0026amp; Stams, A. J. (2008). Desulfatirhabdium butyrativorans gen. nov., sp. nov., a butyrate-oxidizing, sulfate-reducing bacterium isolated from an anaerobic bioreactor. International Journal of Systematic and Evolutionary Microbiology, 58(1), 110-115. https://doi.org/10.1099/ijs.0.65396-0\u003c/li\u003e\n\u003cli\u003eBargagli, R., 2008. Environmental contamination in Antarctic ecosystems. Science of The Total Environment 400, 212\u0026ndash;226. https://doi.org/10.1016/j.scitotenv.2008.06.062\u003c/li\u003e\n\u003cli\u003eBertoglio, F., Piccini, C., Urrutia, R., Antoniades, D., 2023. Seasonal shifts in microbial diversity in the lakes of Fildes Peninsula, King George Island, Maritime Antarctica. Antarctic Science 35(2), 89\u0026ndash;102. https://doi.org/10.1017/S0954102023000068\u003c/li\u003e\n\u003cli\u003eBertoglio, F., Piccini, C., Giralt, S., Urrutia, R., Antoniades, D., 2025. Sedimentary indicators of anthropogenic impact in Fildes Peninsula lakes (King George Island, Maritime Antarctica). Anthropocene 49, 100465. https://doi.org/10.1016/j.ancene.2025.100465\u003c/li\u003e\n\u003cli\u003eBraun, C., Mustafa, O., Nordt, A., Pfeiffer, S., Peter, H.-U., 2012. Environmental monitoring and management proposals for the Fildes Region, King George Island, Antarctica. Polar Research 31, 18206. https://doi.org/10.3402/polar.v31i0.18206\u003c/li\u003e\n\u003cli\u003eBraun, C., Ritter, R., Hans-Ulrich Peter, 2020. Substantial increase of ship and air traffic on Fildes Peninsula, King George Island, the main logistic hub for the Antarctic Peninsula. Conference SCAR 2020 Online. https://doi.org/10.13140/RG.2.2.12504.72960\u003c/li\u003e\n\u003cli\u003eBruel, R., \u0026amp; Sabatier, P. (2020). serac: An R package for ShortlivEd RAdionuclide chronology of recent sediment cores. Journal of Environmental Radioactivity, 225, 106449. https://doi.org/10.1016/j.jenvrad.2020.106449\u003c/li\u003e\n\u003cli\u003eCallahan, B.J., McMurdie, P.J., Holmes, S.P., 2017. Exact sequence variants should replace operational taxonomic units in marker-gene data analysis. The ISME journal 11, 2639\u0026ndash;2643. https://doi.org/10.1038/ismej.2017.119\u003c/li\u003e\n\u003cli\u003eCantonati, M., Angeli, N., Virtanen, L., Wojtal, A.Z., Gabrieli, J., Falasco, E., Lavoie, I., Morin, S., Marchetto, A., Fortin, C., Smirnova, S., 2014. Achnanthidium minutissimum (Bacillariophyta) valve deformities as indicators of metal enrichment in diverse widely-distributed freshwater habitats. Science of The Total Environment 475, 201\u0026ndash;215. https://doi.org/10.1016/j.scitotenv.2013.10.018\u003c/li\u003e\n\u003cli\u003eCaporaso, J. G., Lauber, C. L., Walters, W. A., Berg-Lyons, D., Lozupone, C. A., Turnbaugh, P. J., Fierer, N. \u0026amp; Knight, R. (2011). Global patterns of 16S rRNA diversity at a depth of millions of sequences per sample. Proceedings of the national academy of sciences, 108(supplement_1), 4516-4522. https://doi.org/10.1073/pnas.100008010\u003c/li\u003e\n\u003cli\u003eChen, C.W., Kao, C.M., Chen, C.F., Dong, C.D., 2007. Distribution and accumulation of heavy metals in the sediments of Kaohsiung Harbor, Taiwan. Chemosphere 66(8), 1431\u0026ndash;1440. https://doi.org/10.1016/j.chemosphere.2006.09.030\u003c/li\u003e\n\u003cli\u003eChoi, H.-B., Lim, H.S., Yoon, Y.-J., Kim, J.-H., Kim, O.-S., Yoon, H.I., Ryu, J.-S., 2022. Impact of anthropogenic inputs on Pb content of moss Sanionia uncinata (Hedw.) Loeske in King George Island, West Antarctica revealed by Pb isotopes. Geosciences Journa\u003cem\u003el\u003c/em\u003e26(2), 225\u0026ndash;234. https://doi.org/10.1007/s12303-021-0032-4\u003c/li\u003e\n\u003cli\u003eChu, Z., Yang, Z., Wang, Y., Sun, L., Yang, W., Yang, L., Gao, Y., 2019. Assessment of heavy metal contamination from penguins and anthropogenic activities on Fildes Peninsula and Ardley Island, Antarctic. Science of The Total Environment 646, 951\u0026ndash;957. https://doi.org/10.1016/j.scitotenv.2018.07.152\u003c/li\u003e\n\u003cli\u003eCOMNAP. 2025. Council of Managers of National Antarctic Programs. Antarctic Facilities Information. https://www.comnap.aq/antarctic-facilities-information. Accessed March 24, 2025.\u003c/li\u003e\n\u003cli\u003eCowan, D.A., Chown, S.L., Convey, P., Tuffin, M., Hughes, K., Pointing, S., Vincent, W.F., 2011. Non-indigenous microorganisms in the Antarctic: assessing the risks. Trends in Microbiology 19, 540\u0026ndash;548. https://doi.org/10.1016/j.tim.2011.07.008\u003c/li\u003e\n\u003cli\u003eCyr, H. (2016). Wind‐driven thermocline movements affect the colonisation and growth of Achnanthidium minutissimum, a ubiquitous benthic diatom in lakes. Freshwater Biology, 61(10), 1655-1670. https://doi.org/10.1111/fwb.12806\u003c/li\u003e\n\u003cli\u003eDavies, S., Lamb, H., Roberts, S. (2015). Micro-XRF Core Scanning in Palaeolimnology: Recent Developments. In: Croudace, I., Rothwell, R. (Eds), Micro-XRF Studies of Sediment Cores. Developments in Paleoenvironmental Research, vol 17. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-9849-5_7 \u003c/li\u003e\n\u003cli\u003eFabri-Jr, R., Krause, M., Dalfior, B.M., Salles, R.C., De Freitas, A.C., Da Silva, H.E., Licinio, M.V.V.J., Brand\u0026atilde;o, G.P., Carneiro, M.T.W.D., 2018. Trace elements in soil, lichens, and mosses from Fildes Peninsula, Antarctica: spatial distribution and possible origins. Environment Earth Sciences 77, 124. https://doi.org/10.1007/s12665-018-7298-5\u003c/li\u003e\n\u003cli\u003eFalasco, E., Bona, F., Badino, G., Hoffmann, L., Ector, L., 2009. Diatom teratological forms and environmental alterations: a review. Hydrobiologia 623, 1\u0026ndash;35. https://doi.org/10.1007/s10750-008-9687-3\u003c/li\u003e\n\u003cli\u003eFalasco, E., Ector, L., Wetzel, C. E., Badino, G., \u0026amp; Bona, F. (2021). Looking back, looking forward: A review of the new literature on diatom teratological forms (2010\u0026ndash;2020). Hydrobiologia, 848, 1675\u0026ndash;1753. https://doi.org/10.1007/s10750-021-04540-x\u003c/li\u003e\n\u003cli\u003eGarc\u0026iacute;a-Rodr\u0026iacute;guez, F., Piccini, C., Carrizo, D., S\u0026aacute;nchez-Garc\u0026iacute;a, L., P\u0026eacute;rez, L., Crisci, C., Oaquim, A.B.J., Evangelista, H., Soutullo, A., Azcune, G., L\u0026uuml;ning, S., 2021. Centennial glacier retreat increases sedimentation and eutrophication in Subantarctic periglacial lakes: A study case of Lake Uruguay. Science of The Total Environment 754, 142066. https://doi.org/10.1016/j.scitotenv.2020.142066\u003c/li\u003e\n\u003cli\u003eHodgson, D. A., Doran, P. T., Roberts, D., \u0026amp; McMinn, A. (2004). Paleolimnological studies from the Antarctic and subantarctic islands. In Long-term environmental change in Arctic and Antarctic lakes, Pienitz, R., Douglas, M. S. V., \u0026amp; Smol, J. P. (Eds.), pp. 419-474, Dordrecht: Springer Netherlands. 10.1007/978-1-4020-2126-8_14\u003c/li\u003e\n\u003cli\u003eHolmes, N.D., Giese, M., Achurch, H., Robinson, S., Kriwoken, L.K., 2006. Behaviour and breeding success of gentoo penguins Pygoscelis papua in areas of low and high human activity. Polar Biology 29(5), 399\u0026ndash;412. https://doi.org/10.1007/s00300-005-0070-9\u003c/li\u003e\n\u003cli\u003eIvanova, A. A., Oshkin, I. Y., Danilova, O. V., Philippov, D. A., Ravin, N. V., \u0026amp; Dedysh, S. N. (2021). Rokubacteria in northern peatlands: habitat preferences and diversity patterns. Microorganisms, 10(1), 11. https://doi.org/10.3390/microorganisms10010011\u003c/li\u003e\n\u003cli\u003eIzaguirre, I., Allende, L., Romina Schiaffino, M., 2021. Phytoplankton in Antarctic lakes: biodiversity and main ecological features. Hydrobiologia 848, 177\u0026ndash;207. https://doi.org/10.1007/s10750-020-04306-x\u003c/li\u003e\n\u003cli\u003eJackson, M. C., Loewen, C. J., Vinebrooke, R. D., \u0026amp; Chimimba, C. T. (2016). Net effects of multiple stressors in freshwater ecosystems: A meta‐analysis. Global change biology, 22(1), 180-189. https://doi.org/10.1111/gcb.13028\u003c/li\u003e\n\u003cli\u003eKeatley, B. E., Douglas, M. S. V., \u0026amp; Smol, J. P. (2008). Prolonged Ice Cover Dampens Diatom Community Responses to Recent Climatic Change in High Arctic Lakes. Arctic, Antarctic, and Alpine Research, 40(2), 364\u0026ndash;372. https://doi.org/10.1657/1523-0430(06-068)[KEATLEY]2.0.CO;2\u003c/li\u003e\n\u003cli\u003eKejna, M., Araźny, A., \u0026amp; Sobota, I. (2013). Climatic change on King George Island in the years 1948\u0026ndash;2011. Polish Polar Research, 34(2), 213\u0026ndash;235. https://doi.org/10.2478/popore\u0026minus;2013\u0026minus;0004\u003c/li\u003e\n\u003cli\u003eKojima, H., Shinohara, A., \u0026amp; Fukui, M. (2015). \u003cem\u003eSulfurifustis variabilis\u003c/em\u003e gen. nov., sp. nov., a sulfur oxidizer isolated from a lake, and proposal of Acidiferrobacteraceae fam. nov. and Acidiferrobacterales ord. nov. International journal of systematic and evolutionary microbiology, 65(Pt_10), 3709-3713. https://doi.org/10.1099/ijsem.0.000479\u003c/li\u003e\n\u003cli\u003eLavoie, I., Hamilton, P.B., Morin, S., Tiam, S.K., Kahlert, M., Gon\u0026ccedil;alves, S., Falasco, E., Fortin, C., Gontero, B., Heudre, D., 2017. Diatom teratologies as biomarkers of contamination: Are all deformities ecologically meaningful? Ecological Indicators 82, 539\u0026ndash;550. 10.1016/j.ecolind.2017.06.048.\u003c/li\u003e\n\u003cli\u003eLotter, A., Bigler, C. Do diatoms in the Swiss Alps reflect the length of ice-cover? Aquatic sciences 62, 125\u0026ndash;141 (2000). https://doi.org/10.1007/s000270050002\u003c/li\u003e\n\u003cli\u003eLu, Z., Cai, M., Wang, J., Yang, H., He, J., 2012. Baseline values for metals in soils on Fildes Peninsula, King George Island, Antarctica: the extent of anthropogenic pollution. Environmental Monitoring Assessment 184, 7013\u0026ndash;7021. https://doi.org/10.1007/s10661-011-2476-x\u003c/li\u003e\n\u003cli\u003eMartins, C.C., B\u0026iacute;cego, M.C., Rose, N.L., Taniguchi, S., Louren\u0026ccedil;o, R.A., Figueira, R.C.L., Mahiques, M.M., Montone, R.C., 2010. Historical record of polycyclic aromatic hydrocarbons (PAHs) and spheroidal carbonaceous particles (SCPs) in marine sediment cores from Admiralty Bay, King George Island, Antarctica. Environmental Pollution 158, 192\u0026ndash;200. https://doi.org/10.1016/j.envpol.2009.07.025\u003c/li\u003e\n\u003cli\u003eMcCabe, K., \u0026amp; Cyr, H. (2006). Environmental variability influences the structure of benthic algal communities in an oligotrophic lake. Oikos, 115(2), 197\u0026ndash;206. https://doi.org/10.1111/j.2006.0030-1299.14939.x\u003c/li\u003e\n\u003cli\u003eMeredith, M.P., King, J.C., 2005. Rapid climate change in the ocean west of the Antarctic Peninsula during the second half of the 20th century. Geophysical Research Letters 32(19). https://doi.org/10.1029/2005gl024042\u003c/li\u003e\n\u003cli\u003eMorin, S., Corcoll, N., Bonet, B., Tlili, A., Guasch, H., 2014. Diatom responses to zinc contamination along a Mediterranean river. Plecevo 147, 325\u0026ndash;332. https://doi.org/10.5091/plecevo.2014.986\u003c/li\u003e\n\u003cli\u003eMorin, S., Cordonier, A., Lavoie, I., Arini, A., Blanco, S., Duong, T.T., Torn\u0026eacute;s, E., Bonet, B., Corcoll, N., Faggiano, L., Laviale, M., P\u0026eacute;r\u0026egrave;s, F., Becares, E., Coste, M., Feurtet-Mazel, A., Fortin, C., Guasch, H., Sabater, S., 2012. Consistency in Diatom Response to Metal-Contaminated Environments, in: Guasch, H., Ginebreda, A., Geiszinger, A. (Eds.), Emerging and Priority Pollutants in Rivers, The Handbook of Environmental Chemistry. Springer Berlin Heidelberg, Berlin, Heidelberg, pp. 117\u0026ndash;146. https://doi.org/10.1007/978-3-642-25722-3_5\u003c/li\u003e\n\u003cli\u003eOliva, M., Palacios, D., Fern\u0026aacute;ndez‐Fern\u0026aacute;ndez, J.M., Fernandes, M., Schimmelpfennig, I., Vieira, G., Antoniades, D., P\u0026eacute;rez‐Alberti, A., Garc\u0026iacute;a‐Oteyza, J., ASTER TEAM, 2023. Holocene deglaciation of the northern Fildes Peninsula, King George Island, Antarctica. Land Degradation and Development 34(13), 3973\u0026ndash;3990. https://doi.org/10.1002/ldr.4730\u003c/li\u003e\n\u003cli\u003ePadeiro, A., Amaro, E., Dos Santos, M.M.C., Ara\u0026uacute;jo, M.F., Gomes, S.S., Leppe, M., Verkulich, S., Hughes, K.A., Peter, H.-U., Can\u0026aacute;rio, J., 2016. Trace element contamination and availability in the Fildes Peninsula, King George Island, Antarctica. Environmental Science: Processes \u0026amp; Impacts, 18, 648\u0026ndash;657. https://doi.org/10.1039/C6EM00052E\u003c/li\u003e\n\u003cli\u003ePandey, L.K., Bergey, E.A., 2018. Metal toxicity and recovery response of riverine periphytic algae. Science of The Total Environment 642, 1020\u0026ndash;1031. https://doi.org/10.1016/j.scitotenv.2018.06.069\u003c/li\u003e\n\u003cli\u003ePereira, J.L., Pereira, P., Padeiro, A., Gon\u0026ccedil;alves, F., Amaro, E., Leppe, M., Verkulich, S., Hughes, K.A., Peter, H.-U., Can\u0026aacute;rio, J., 2017. Environmental hazard assessment of contaminated soils in Antarctica: Using a structured tier 1 approach to inform decision-making. Science of The Total Environment 574, 443\u0026ndash;454. https://doi.org/10.1016/j.scitotenv.2016.09.091\u003c/li\u003e\n\u003cli\u003ePester, M., Bittner, N., Deevong, P., Wagner, M., \u0026amp; Loy, A. (2010). A \u0026lsquo;rare biosphere\u0026rsquo; microorganism contributes to sulfate reduction in a peatland. The ISME Journal, 4(12), 1591\u0026ndash;1602. https://doi.org/10.1038/ismej.2010.75\u003c/li\u003e\n\u003cli\u003ePeter H-U., Braun C, Janowski S, Nordt A, Nordt A \u0026amp; Stelter M. (2013). The current environmental situation and proposals for the management of the Fildes Peninsula region. Federal Environment Agency (Germany), 195 pp.\u003c/li\u003e\n\u003cli\u003ePiccini, C., Bertoglio, F., Sommaruga, R., Mart\u0026iacute;nez De La Escalera, G., P\u0026eacute;rez, L., Bugoni, L., Bergamino, L., Evangelista, H., Garc\u0026iacute;a-Rodriguez, F., 2024. Prokaryotic richness and diversity increased during Holocene glacier retreat and onset of an Antarctic Lake. Communication Earth \u0026amp; Environment 5(1), 94. https://doi.org/10.1038/s43247-024-01245-6\u003c/li\u003e\n\u003cli\u003ePinto, E., Sigaud‐kutner, T.C.S., Leit\u0026atilde;o, M.A.S., Okamoto, O.K., Morse, D., Colepicolo, P., 2003. Heavy metal-induced oxidative stress in algae. Journal of Phycology 39, 1008\u0026ndash;1018. https://doi.org/10.1111/j.0022-3646.2003.02-193.x\u003c/li\u003e\n\u003cli\u003eQuast, C., Pruesse, E., Yilmaz, P., Gerken, J., Schweer, T., Yarza, P., Peplies, J., Gl\u0026ouml;ckner, F.O., 2012. The SILVA ribosomal RNA gene database project: improved data processing and web-based tools. Nucleic Acids Research 41, D590\u0026ndash;D596. https://doi.org/10.1093/nar/gks1219\u003c/li\u003e\n\u003cli\u003eREADER (Reference Antarctic Data for Environmental Research). 2025. Data - Reference Antarctic Data for Environmental Research Project. Scientific Committee on Antarctic Research (SCAR). https://legacy.bas.ac.uk/met/READER/surface/Bellingshausen.00.temperature.html Accessed March 24, 2025.\u003c/li\u003e\n\u003cli\u003eR\u0026uuml;hland, K. M., Paterson, A. M., \u0026amp; Smol, J. P. (2015). Lake diatom responses to warming: Reviewing the evidence. Journal of Paleolimnology, 54, 1\u0026ndash;35. https://doi.org/10.1007/s10933-015-9837-3\u003c/li\u003e\n\u003cli\u003eSchiffer, M.B. 2013. Scientific Expeditions to Antarctica. In Manuals in Archaeological Method, Theory and Technique. Volume 9: The archaeology of science. Springer. pp. 137-144.10.1007/978-3-319-00077-0_10.\u003c/li\u003e\n\u003cli\u003eSimonov, I. M. (1977). Physical‐geographic description of the Fildes Peninsula (South Shetland Islands). Polar Geography, 1(3), 223\u0026ndash;242. https://doi.org/10.1080/10889377709388627\u003c/li\u003e\n\u003cli\u003eSmol, J. P., Wolfe, A. P., Birks, H. J. B., Douglas, M. S. V., Jones, V. J., Korhola, A., Pienitz, R., R\u0026uuml;hland, K., Sorvari, S., Antoniades, D., Brooks, S. J., Fallu, M.-A., Hughes, M., Keatley, B. E., Laing, T. E., Michelutti, N., Nazarova, L., Nyman, M., Paterson, A. M., Perren, B., Quinlan, R., Rautio, M., Saulnier-Talbot, \u0026Eacute;., Siitonen, S., Solovieva, N., \u0026amp; Weckstr\u0026ouml;m, J. (2005). Climate-driven regime shifts in the biological communities of arctic lakes. Proceedings of the National Academy of Sciences of the United States of America, 102(12), 4397\u0026ndash;4402. https://doi.org/10.1073/pnas.0500245102\u003c/li\u003e\n\u003cli\u003eSmol, J.P. 2008. Pollution of lakes and rivers. A paleoenvironmental perspective. Blackwell Publishing. 383 pp. \u003c/li\u003e\n\u003cli\u003eSorvari, S., Korhola, A., \u0026amp; Thompson, R. (2002). Lake diatom response to recent Arctic warming in Finnish Lapland. Global Change Biology, 8(2), 171\u0026ndash;181. https://doi.org/10.1046/j.1365-2486.2002.00463.x\u003c/li\u003e\n\u003cli\u003eSterken, M., Verleyen, E., Jones, V., Hodgson, D., Vyverman, W., Sabbe, K., Van de Vijver, B., 2015. An illustrated and annotated checklist of freshwater diatoms (Bacillariophyta) from Livingston, Signy and Beak Island (Maritime Antarctic Region). Plant Ecology and Evolution 148, 431\u0026ndash;455. https://doi.org/10.5091/plecevo.2015.1103\u003c/li\u003e\n\u003cli\u003eTatur, A., Del Valle, R., Pazdur, M., 1991. Lake sediments in maritime Antarctic zone: A record of landscape and biota evolution: preliminary report. Internationale Vereinigung f\u0026uuml;r theoretische und angewandte Limnologie: Verhandlungen 24, 3022\u0026ndash;3024. https://doi.org/10.1080/03680770.1989.11899222\u003c/li\u003e\n\u003cli\u003eTin, T., Fleming, Z.L., Hughes, K.A., Ainley, D.G., Convey, P., Moreno, C.A., Pfeiffer, S., Scott, J., Snape, I., 2009. Impacts of local human activities on the Antarctic environment. Antartic Science 21(1), 3\u0026ndash;33. https://doi.org/10.1017/S0954102009001722\u003c/li\u003e\n\u003cli\u003eTomkins, J.D., Antoniades, D., Lamoureux, S.F., Vincent, W.F., 2008. A simple and effective method for preserving the sediment\u0026ndash;water interface of sediment cores during transport. Journal of Paleolimnology 40(1), 577\u0026ndash;582. https://doi.org/10.1007/s10933-007-9175-1\u003c/li\u003e\n\u003cli\u003eTurner, J., Marshall, G.J., Clem, K., Colwell, S., Phillips, T., Lu, H., 2020. Antarctic temperature variability and change from station data. International Journal of Climatology 40, 2986\u0026ndash;3007. https://doi.org/10.1002/joc.6378\u003c/li\u003e\n\u003cli\u003eVan de Vijver, B., Kopalov\u0026aacute;, K., 2014. Four \u003cem\u003eAchnanthidium\u003c/em\u003e species (Bacillariophyta) formerly identified as \u003cem\u003eAchnanthidium minutissimum\u003c/em\u003e from the Antarctic Region. European Journal of Taxonomy (79). https://doi.org/10.5852/ejt.2014.79\u003c/li\u003e\n\u003cli\u003eWetzel, Carlos E., Ector, L., Van De Vijver, B., Comp\u0026egrave;re, P., Mann, D.G., 2015. Morphology, typification and critical analysis of some ecologically important small naviculoid species (Bacillariophyta). Fottea/Czech Phycological Society.-Praha, Czech Republic, 2007, currens, 15(2), 203-234https://doi.org/10.5507/fot.2015.020\u003c/li\u003e\n\u003cli\u003eZidarova, R., Kopalov\u0026aacute;, K., Van De Vijver, B., Spaulding, S.A., Lange-Bertalot, H., Potapova, M., 2016. Diatoms from the Antarctic Region: Maritime Antarctica, Iconographia Diatomologica 24, 504 p. Koeltz Botanical Books.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e Spearman correlations between indicator bacteria and metal EFs. R\u003csup\u003e2\u003c/sup\u003e values are shown in the table, and significant correlations (p \u0026lt; 0.05) are indicated by bold values\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"548\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 167px;\"\u003e\n \u003cp\u003e\u0026nbsp;Indicator bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 61px;\"\u003e\n \u003cp\u003eTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 51px;\"\u003e\n \u003cp\u003eZn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 65px;\"\u003e\n \u003cp\u003eCu\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 57px;\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 59px;\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 167px;\"\u003e\n \u003cp\u003e\u003cem\u003eAnaerovorax\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 61px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.53\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 51px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.53\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 65px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.54\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 57px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.57\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 59px;\"\u003e\n 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Toxicology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8138817/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8138817/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Fildes Peninsula (maritime Antarctica) is greatly affected by global warming and local human impacts since it is in one of the Antarctic regions with the highest intensity of human activity. To establish the effect of human activities on Fildes Peninsula lakes, we compared trends in diatom assemblages, bacterial communities and metal concentrations in sediment cores from two lakes close to human infrastructure with those in a more remote lake. In the two lakes close to stations and the airport, we found heavy metal enrichments and diatom teratologies, as well as notable changes in diatom assemblages in one of these lakes, roughly coincident with the time when the first two stations were built (~\u0026thinsp;1970). Due to the known association between diatom teratologies and metal enrichment, metal stress is a convincing explanation for these changes. Certain bacterial taxa determined to be indicators of pollution were also found to be more abundant in the impacted lakes in recent sediments (i.e., Hungateiclostridiacea\u003cem\u003ee\u003c/em\u003e, OPB41, \u003cem\u003eAnaerovorax\u003c/em\u003e and \u003cem\u003eLeptolinea\u003c/em\u003e). Metal, diatom and bacteria changes observed in the lake more distant to infrastructure were more subtle and are likely related to climate change alone. Given the proximity of the affected lakes to the airport and roads, our data suggests that transportation infrastructure and activity on Fildes Peninsula is likely a key cause of contamination in the region\u0026rsquo;s ecosystems. This study provides important insights into how human activities and climate change have affected Fildes Peninsula aquatic ecosystems and how they may respond to future stressors.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e","manuscriptTitle":"Reconstructing the effects of anthropogenic activities and climate change in three lakes of the Fildes Peninsula, Maritime Antarctic","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-27 15:38:04","doi":"10.21203/rs.3.rs-8138817/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-12-12T00:47:56+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-11T13:56:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-19T15:01:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"Archives of Environmental Contamination and Toxicology","date":"2025-11-17T15:18:07+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"archives-of-environmental-contamination-and-toxicology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"aect","sideBox":"Learn more about [Archives of Environmental Contamination and Toxicology](https://www.springer.com/journal/244)","snPcode":"244","submissionUrl":"https://submission.nature.com/new-submission/244/3","title":"Archives of Environmental Contamination and Toxicology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"74105c70-de96-40c9-9154-bb4592d4a19f","owner":[],"postedDate":"November 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-28T15:44:39+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-27 15:38:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8138817","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8138817","identity":"rs-8138817","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}