European Lakes Research Articles

External Phosphorus Loading in New Lakes

The water quality of lakes is highly dependent on external phosphorus (P) loading. The vast external loadings from sewage and other wastewater discharge that European lakes have historically received have been dramatically reduced today by improved wastewater treatment. Gaining knowledge of the catchment characteristics that influence external P-loading should enable predictions of the achievable water quality of lakes. In this study, we tested this proposition. Data from 90 new Danish lakes show no apparent relationship between the mean summer P-concentration and the size or land use of the catchments. The external P-loading and resulting annual P-concentration were further investigated on a representative subset of 12 of the new lakes, using six methods. Three of the methods used empirical estimates of P-transport from catchments, based on the national average P-transport, runoff-dependent P-transport, and crop-dependent P-transport, and the other three methods used different empirical models tested on the lakes. External P-loading was reliably predicted by several of the methods. The predictions of the annual P-concentration were highly dependent on the inclusion of annual runoff. However, the predicted P-concentrations were generally overestimated, most pronounced for the nutrient-poor and most recently established lakes. In these lakes, internal P-loading was found to be the most important factor in predicting achievable water quality.

Trends of lake temperature, mixing depth and ice cover thickness of European lakes during the last four decades

Lakes are particularly vulnerable ecosystems to global warming. Surface temperature of most lakes in the world has significantly increased. Here, we analysed time-series of water temperature, mixing-depth, and ice depth of 51 European lakes over the last four decades. We used data of surface temperature, total layer water temperature, mix-layer temperature, mix-layer depth, and ice cover depth obtained from the ERA5-Land reanalysis dataset. Our main objectives were a) to identify significant changes of the examined variables that have occurred from 1981 to 2019 and b) to assess the variability of changes in relation with geographical and lake morphological gradients. To this end, time series analysis was conducted using generalized additive models (GAMs). In addition, we quantified the magnitude of change by estimating the Sen's slopes for each variable and then we examined the variability of these slopes to geographical and lake morphological parameters using GAMs. Our results confirmed that water temperature parameters (surface, total-layer and mix-layer temperature) have significantly increased for all lakes during the last four decades. We also found significant changes of the mixing depth for 14 lakes. In addition, the lake ice depth has significantly decreased in all fifteen lakes of the subarctic climate region. Finally, we showed that the Sen's slopes depend on the geographic coordinates and the elevation of the lakes, whereas lake morphometry (e.g. depth) has a smaller effect on the magnitude of changes. These findings hint that lake ecosystems of Europe have substantially changed over the last forty years and urge the need to take precautionary measures to prevent future implications for the freshwater biota.

Indications of polymorphism in the behaviour and morphology of burbot (Lota lota) in a European lake

In this study, polymorphism in behaviour, morphology, and stable isotope signatures of burbot from Lake Southern Konnevesi, Finland, Europe, was examined. First, local knowledge was collected on exceptional polymorphism of the spawning behaviour and morphology of burbot. These phenomena were then studied based on catch samples. Interviews and catch sample analyses suggested two morphs of burbot: one morph spawning in late February in the littoral zone and other in late March, in deep profundal, depths of about 30 m. Fish caught from the profundal zone had higher average proportional somatic body weights and wider heads than those caught from the littoral spawning sites in February. The length-at-age of the individuals from the littoral catch was longer than that of the profundal catch. Stable isotope analysis revealed differences in the mean carbon isotope ratio between sampling sites, suggesting differences in diet. Variability in several of the aforementioned variables was correlated. This study is the first to imply polymorphism in burbot populations from a lake in Eurasia, where burbot are considered as near-threatened species.

Revealing hidden diversity in the Cryptomonas erosa clade (Cryptophyceae), with the description of two new species from acidic habitats

ABSTRACT In this study, the cryptomonads of the northern territories of Russia were explored. Four strains were isolated from the different acidic habitats in the Middle Urals and the North of the European part of Russia. Cells of these strains are flattened in the dorsoventral plane, have an asymmetrical outline and are similar in size and shape to Cryptomonas erosa. Phylogenetic relationships inferred using maximum likelihood and Bayesian interference from datasets of nuclear-encoded SSU, LSU, ITS2 rDNA and psbA cpDNA show that the strains form one clade, which was divided into three subclades with high statistical support. One subclade was attributed to Cryptomonas erosa. Two other subclades represent species new to science. Comparison of ITS2 rRNA secondary structures with the compensatory base changes (CBC) approach confirmed the separation between C. erosa and the two new species, C. macilenta sp. nov. and C. parmana sp. nov. Comparison of nuclear V9 SSU and ITS1 rDNA sequences of two new species with metabarcoding data from 218 lakes in Europe showed that C. macilenta and C. parmana have not previously been recorded in Europe.

Paleoclimate reconstruction of the last 36 kyr based on branched glycerol dialkyl glycerol tetraethers in the Padul palaeolake record (Sierra Nevada, southern Iberian Peninsula)

Quantitative continental climate reconstructions covering the last glacial cycle from the Iberian Peninsula are scarce. In order to fill this gap, we obtained for the first time a high-resolution mean annual air temperature (MAAT) record based on the distribution of specific bacterial membrane lipids (i.e., branched glycerol dialkyl glycerol tetraethers; brGDGTs) from the last 36.0–4.7 kyr palaeolake record recovered by the Padul-15-05 sedimentary core (Padul, Sierra Nevada, southern Iberia). The fractional abundance of the three major groups of GDGTs present in the Padul sediments, GDGT-0, crenarchaeol and the summed brGDGTs, is comparable with that of other shallow and small (<10 km2) European lakes. Despite variations in the lithology in the studied section, the GDGT composition remains relatively stable, except for the uppermost 116 cm of the record, representing the ephemeral/emerged lake stage, which is characterized by higher crenarchaeol fractional abundances. The identification of a specific brGDGT that has only been detected in anoxic lakes provides evidence for in-situ brGDGT production in the water column and/or sediments in the Padul palaeolake. Its presence/absence probably denotes a succession of periods with a variable oxygen content in the bottom waters of the palaeolake. MAAT was reconstructed based on the distribution of brGDGTs using an African lake calibration and ranged between 12 and 20 °C. A new Bayesian calibration to mean temperature of Months Above Freezing (MAF) depicts similar temperature variations with a mean absolute difference of 0.7 °C. The MAAT reconstruction in the Padul palaeolake for the 36.0–4.7 kyr period reveals similarities with climate variability described at high-latitudes and in the westernmost Mediterranean area during this interval, showing cold conditions during the last three Heinrich Stadials and the Younger Dryas and warm conditions during the Dansgaard–Oeschger interstadials (7–1) and the Bölling-Alleröd period. Despite the more stable and warm general climate conditions during the Early and Mid-Holocene, rapid centennial-scale temperature changes are registered in the Padul palaeolake in good agreement with variations observed in the Mediterranean forest record.

Morphological defences and defence–cost trade‐offs in Daphnia in response to two co‐occurring invertebrate predators

Abstract Inducible morphological defences are crucial for understanding predator–prey interactions. Such defences have been mostly studied in a single‐predator context, ignoring the fact that prey organisms are often exposed to multiple predators. In deep peri‐Alpine European lakes, the keystone grazer Daphnia coexists with two cladoceran predators, Bythotrephes longimanus and Leptodora kindtii. Up to now, life history and morphological responses of Daphnia to these two predators have not been analysed systematically. We studied the responses of two life history (age at first reproduction, and offspring production) and five morphological traits (body size, body width, head size, spina size, and eye diameter) of eight Daphnia galeata clones to the presence of Bythotrephes and Leptodora in a common garden experiment. We compared each response trait between treatments using linear mixed models, and investigated the covariation between defence traits and demographic costs (neonate production) for the two predators. Our results show that the responses of Daphnia are predator‐ and trait‐specific. Daphnia developed a typical helmet and a larger eye only in the presence of Bythotrephes, not in the presence of Leptodora. In contrast, both predators induced larger body sizes and longer spines. Age at first reproduction was latest and demographic costs were highest in the Bythotrephes treatment, suggesting that the development of a helmet exceeds the costs of spina elongation. The responses of Daphnia clones revealed a defence‐cost trade‐off for helmet formation in the Bythotrephes, and for spina elongation in the Leptodora treatment. Hence, despite Bythotrephes and Leptodora being closely related co‐occurring predators, Daphnia responds with a unique combination of trait changes and defence‐cost trade‐offs to the two predators. The presence of predator‐specific clonal defence‐cost trade‐offs suggests that the presence of these invertebrate predators can drive different evolutionary processes in natural zooplankton communities. Disentangling the evolutionary ecology of phenotypic responses of prey species to co‐occurring predators will require multi‐trait, multi‐clone studies of induced antipredator defences.

The Integrated Use of Dendrochronological Data and Paleoecological Records From Northwest European Peatlands and Lakes for Understanding Long-Term Ecological and Climatic Changes—A Review

Our overall understanding of long-term climate dynamics is largely based on proxy data generated from archives such as ice cores, ocean sediments, tree rings, speleothems, and corals, whereas reconstructions of long-term changes in vegetation and associated climate during the Holocene are largely based on paleoecological records from peat and lake sequences, primarily pollen and plant macrofossil data. However, since no proxy can provide a complete picture of the past, it is important to integrate different types of data, and to use methods that can support the paleoecological and paleoclimatic interpretations. Here we review how tree-ring data and dendrochronological approaches can be integrated with stratigraphic records to provide complementary paleoecological and paleoclimatic information. The review includes multiproxy studies in which dendrochronological data have been either compared or integrated with stratigraphic records, mainly pollen records, with the aim to contribute to a better understanding of long-term ecosystem and climate dynamics. We mainly focus on studies from northwest Europe in which tree-ring data and at least one type of paleoecological proxy record from the same site or area has been either compared or integrated. We find that integration of dendrochronological data and paleoecological records from peat and lake sequences is a powerful but underutilized approach to reconstruct long-term ecological and climatic changes. One likely reason for its limited use is the contrasting character of the two categories of data, including their different time resolution and occurrence, making them difficult to integrate. For example, subfossil wood providing annual dendrochronological data usually only occurs sporadically in peat and lake sediments, and the presence/absence of the trees are normally expected to be recorded in the pollen data with multi-decadal or coarser resolution. Therefore, we also discuss methods to compare and integrate dendrochronological and stratigraphic records, as well as the relevant paleoecological and paleoclimatic information provided by dendrochronology, pollen, and peat stratigraphy, with the aim to facilitate new multi-proxy initiatives that will contribute to a better understanding of long-term ecosystem and climate dynamics and thereby a firmer basis for future nature conservation initiatives.

Assessment of PCBs in Surface Waters at Ultratrace Levels: Traditional Approaches and Biomonitoring (Lake Baikal, Russia)

This article presents the results of the assessment of PCB concentrations in surface waters at ultratrace level of concentrations. The assessment of PCB concentrations is based on data from monitoring PCBs in Baikal water within the conventional approach as well as from biomonitoring of PCBs using Baikal omul, Coregonus migratorius, Georgi, 1775 (C. migratorius), as a bioindicator. The time cycle of the monitoring covered the period from 2014 to 2021. The concentrations of PCBs in the water were estimated from the concentrations of seven indicator congeners: 28, 52, 101, 118, 138, 153, and 180, and from congeners of dioxin-like (dl) PCBs in the tissues of C. migratorius. The average value and the statistically significant range of the detected total concentrations (Ʃ7PCBs) in Baikal water were 0.30 and 0.26–0.34 ng/L, respectively. In the tissues of C. migratorius, the average value and the range of Ʃ7PCB concentrations were 5.6 and 4.9–6.3 ng/g (ww), respectively, and for dl-PCBs, 1.5 and 1.3–1.7 ng/g (ww), respectively. The total toxicity equivalent of the detected dl-PCBs was in the WHO-TEQ (2005) range from 0.03 to 0.06 pg/g (ww). The concentrations of Ʃ7PCBs in Baikal water and dl-PCBs in the tissues of C. migratorius corresponded to the concentration levels in the European alpine lakes and the tissues of S. trutta fish inhabiting these lakes.

Species distribution models as a tool for early detection of the invasive Raphidiopsis raciborskii in European lakes

In freshwater habitats, invasive species and the increase of cyanobacterial blooms have been identified as a major cause of biodiversity loss. The invasive cyanobacteria Raphidiopsis raciborskii a toxin-producing and bloom-forming species affecting local biodiversity and ecosystem services is currently expanding its range across Europe. We used species distribution models (SDMs) and regional bioclimatic environmental variables, such as temperature and precipitation, to identify suitable areas for the colonization and survival of R. raciborskii, with special focus on the geographic extent of potential habitats in Northern Europe. SDMs predictions uncovered areas of high occurrence probability of R. raciborskii in locations where it has not been recorded yet, e.g. some areas in Central and Northern Europe. In the southeastern part of Sweden, areas of suitable climate for R. raciborskii corresponded with lakes of high concentrations of total phosphorus, increasing the risk of the species to thrive. To our knowledge, this is the first attempt to predict areas at high risk of R. raciborskii colonization in Europe. The results from this study suggest several areas across Europe that would need monitoring programs to determine if the species is present or not, to be able to prevent its potential colonization and population growth. Regarding an undesirable microorganism like R. raciborskii, authorities may need to start information campaigns to avoid or minimize the spread.

The relationship between land cover and microbial community composition in European lakes

Microbes are essential for element cycling and ecosystem functioning. However, many questions central to understanding the role of microbes in ecology are still open. Here, we analyze the relationship between lake microbiomes and the lakes' land cover. By applying machine learning methods, we quantify the covariance between land cover categories and the microbial community composition recorded in the largest amplicon sequencing dataset of European lakes available to date. Our results show that the aggregation of environmental features or microbial taxa before analysis can obscure ecologically relevant patterns. We observe a comparatively high covariation of the lakes' microbial community with herbaceous and open spaces surrounding the lake; nevertheless, the microbial covariation with land cover categories is generally lower than the covariation with physico-chemical parameters. Combining land cover and physico-chemical bioindicators identified from the same amplicon sequencing dataset, we develop analytical data structures that facilitate insights into the ecology of the lake microbiome. Among these, a list of the environmental parameters sorted by the number of microbial bioindicators we have identified for them points towards apparent environmental drivers of the lake microbial community composition, such as the altitude, conductivity, and area covered herbaceous vegetation surrounding the lake. Furthermore, the response map, a similarity matrix calculated from the Jaccard similarity of the environmental parameters' lists of bioindicators, allows us to study the ecosystem's structure from the standpoint of the microbiome. More specifically, we identify multiple clusters of highly similar and possibly functionally linked ecological parameters, including one that highlights the importance of the calcium-bicarbonate equilibrium for lake ecology. Taken together, we demonstrate the use of machine learning approaches in studying the interplay between microbial diversity and environmental factors and introduce novel approaches to integrate environmental molecular diversity into monitoring and water quality assessments.

Environmental stressors alter multiple determinants of individual reproductive output in the acid‐tolerant mayfly Leptophlebia vespertina

Abstract1. Environmental stressors such as acidification modify community composition in freshwater habitats through their direct and indirect effects on individuals. However, the effect of acidification on various aspects of individual fitness is poorly known in aquatic insects, a key group in many freshwater habitats.2. Here, the influence of acidification (acidity and Al toxicity), food quality and habitat properties on the reproduction of an acid‐tolerant mayfly Leptophlebia vespertina (Linnaeus, 1758) in a group of Central European lakes is explored. The focus is on last‐instar larvae as the short‐lived, semelparous adults cannot mitigate stress experienced by the larvae.3. It is shown that the environment affects multiple determinants of individual reproductive output both directly by affecting body size and fecundity in last‐instar larvae, and indirectly by releasing the larvae from density dependence. Populations tended to be denser in more acidic sites and individuals in denser populations were substantially smaller and had lower size‐dependent fecundity and reproductive effort. All else being equal, larvae from colder sites were larger, suggesting an important role of the temperature‐size rule in this species. Size‐dependent fecundity and reproductive effort increased with better food conditions as expected, but neither reproductive measure was affected by acidity or temperature. Finally, a weak egg size‐number trade‐off with slightly smaller eggs in more fecund females was detected.4. These results imply that indirect ecological feedbacks and food quality, rather than the direct effects of stressful environment, may dominate the effects of environmental stressors on the reproductive output of acid‐tolerant species such as L. vespertina.

Empirical evidence on the effects of climate on the viability of common carp (Cyprinus carpio) populations in European lakes

Empirical evidence on the effects of climate on the viability of common carp (Cyprinus carpio) populations in European lakes

Limnogenesis of large l akes in the North-West of the Russian Plain

Abstract. The issues of the formation of the largest lakes in Europe - Ladoga and Onega are considered in the article. The main aim was to identify features of the basins development from their origin to modern condition. The newest geological and geophysical data obtained in 2014-2021 was used to achieve the goal. Both depressions, in which modern lake basins are located, were formed in the Late Proterozoic. In the Late Quaternary, the glacier significantly modeled the pre-Quaternary relief. Glacial tongues significantly expanded the negative forms of the pre-glacial relief. At the same time, the glacier also formed positive landforms, such as moraines and esker ridges. Such ridges intersect the Lake Ladoga center and mark the position of the Neva stage. Structural features of the supraglacial section are considered in detail. It is shown that in both lakes the structure of the upglacial section is approximately the same and is associated with the gradual retreat of the glacier from the lake basins. Thus, it is shown that, despite the similarity of the main stages of paleogeographic development, each lake basin was characterized by its own features and their development itself occurred asynchronously.

ОСОБЛИВОСТІ ГІДРОГРАФІЇ ЄВРОПИ: РІЧКИ, ОЗЕРА, ВОДОСХОВИЩА

Europe has a dense hydrographic network, mainly related to the Atlantic Ocean basin. A certain part of the rivers of Eastern Europe belongs to the basin of the endorheic Caspian sea-lake. Only a few rivers carry their waters to the seas of the Arctic Ocean. Thus, 43 large rivers with a catchment area of more than 50 thousand km2, among which 8 are connected with the territory of Ukraine, are distributed as follows: a) the basin of the Caspian Sea-lake – 9 rivers (Volga, Ural, Kama, Oka, Belaya, Vyatka, Ufa, Sura, Moksha); b) the basin of the Arctic Ocean – 3 rivers (Pechora, Northern Dvina, Mezen); c) North Atlantic basin – 9 rivers (Rhine, Elbe, Vistula, Western Dvina, Neman, Oder, Warta, Seine, Narew); d) the basin of the South Atlantic – 6 rivers (Tagus, Loire, Douro, Guadiana, Guadalquivir, Garonne); e) the Mediterranean Sea basin (together with the Black and Azov Seas) – 16 rivers (Ebro, Rhone, Danube, Dnieper, Don, Dniester, Desna, Siverskyi Donets, Khoper, Tisza, Sava, Kuban, Southern Bug, Pripyat, Po, Maritsa ). With significant water content, the rivers of Northern, Western and Southern Europe are characterized by a small length and basin area. This is due to the relatively small area of the territory of Europe, its strong horizontal dissection and the frequent alternation of mountains and plains. On the expanses of the East European Plain, rivers get the opportunity to develop a catchment area and a channel network. Therefore, among the largest rivers in Europe, whose basin area exceeds 50 thousand km2, the rivers of Eastern Europe account for more than 60%. An important feature of European rivers is the transboundary nature of their basins. Among the huge rivers, with a catchment area of more than 50 thousand km2, transboundary rivers account for 51%. In Europe, there are about 16 thousand lakes with a surface area exceeding 1.0 km2. Three quarters of the continent’s lakes are located in Norway, Sweden, Finland and the Karelian-Kola part of Russia, and are of glacial-tectonic origin. The largest in Europe Ladoga (area 17700 km2) and Onega (9720 km2) lakes are located in Eastern Europe (north-western part of Russia) and significantly exceed other European lakes in size. The deepest lake in Europe is Lake Hornindalsvatnet (Norway) – 514 m. In Europe, about 7,000 large reservoirs have been created with a total area of more than 100 thousand km2, of which 50% is the area of reservoirs in the European part of Russia. Among the 13 European reservoirs with an area of more than 1000 km2, a dozen are located in Russia, two (Kremenchug Reservoir and Kakhovka Reservoir) are in Ukraine, and one (IJsselmeer) is in the Netherlands. The states with the largest number of reservoirs are Spain (about 1200) and Ukraine (about 1050). Other countries with a large number of reservoirs are Turkey (610), Great Britain (570), Italy (570), France (550), Norway (360), Russia (250) and Sweden (190)

Faecal biomarkers as tools to reconstruct land‐use history in maar sediments in the Westeifel Volcanic Field, Germany

The analysis of faecal biomarkers in lake sediments has been used to reconstruct human population densities and animal husbandry practices in an increasing number of studies in recent years. However, terrigenous biomarkers can decompose in soils, can be stored and redeposited in colluvium and on flood‐plains prior to their ultimate deposition in lakes. These and other effects can blur and distort biomarker signals. Therefore, we analysed sediments from two maars in Westeifel to evaluate whether signals of the faecal biomarkers (5β‐stanols, bile acids) demonstrate statistically significant differences between contrasting periods in land‐use intensity. In Holzmaar, palaeoenvironmental data showed evidence for agriculture including cereal cultivation and grassland during the pre‐Roman Iron Age and Middle Ages compared with those from periods that were less influenced by land use and showed a higher abundance of broadleaf forest. However, the specific domesticated taxa of livestock in the locale from these periods remain speculative. We found statistically significantly different faecal biomarker signals, which we interpret to be related to an enhanced deposition of faeces of horses, pigs and ruminants in the core sections that represented periods of amplified land use. The analyses of grass‐ and broadleaf‐tree characteristic n‐alkanes supported the applicability of biomarkers for land‐use reconstruction. Stanol data from a core section dating to the Mesolithic showed no clear results. Analyses of two core sections from Ulmener Maar, which covered periods before and after the decline of elm in the Neolithic, indicated input of pig faeces in the younger section. This study provides important evidence that faecal biomarkers can be used for land‐use reconstruction in central European lakes with small catchment areas for time periods from the Neolithic onwards. The results underscore the importance of bile acid analyses in addition to stanol analyses for an identification of faeces inputs from different animals.

Current chemistry of Lake Onego and its spatial and temporal changes for the last three decades with special reference to nutrient concentrations

Lake Onego is the second largest freshwater lake in Europe experiencing a multifactorial impact. The environmental pressures on the lake ecosystem has changed over the last decade because of the intensive development of aquaculture, reduction of wastewater discharges, internal load, and population redistribution. The purpose of this study was to assess whether these changes have affected the water quality of Lake Onego and to assess their extent. Data collected in 2019–2021 were used to indicate distribution and spatial heterogeneity in the chemical composition of lake water. The following parameters were considered: pH, conductivity, total suspended solids (TSS), Na+, Cl-, nutrients (P-PO4, TP, N-NH4, N-NO3, TN), organic matter (OM) (TOC, lignosulfonates, BOD5, CODMn, CODCr, color), Fe, Mn, and heavy metals (Cu, Ni, Zn, Cd, Pb). Data collected earlier (1992–2018) were used to indicate temporary changes in nutrients and OM concentrations. The largest tributaries deliver nutrients, TSS, and OM associated with Fe, Mn, and Cu to the lake water. Water contamination was observed in the Petrozavodsk and Kondopoga Bays experiencing anthropogenic load from domestic and Pulp and Paper Mill wastewaters accordingly, which is mainly evidenced by increased concentrations of OM and nutrients. The water quality in the Petrozavodsk Bay is significantly deteriorated in winter and spring due to the Shuya River discharge, which caused an increase in TP and OM concentration in the bay in the last three decades. Gradual increase in TP and OM content since 1992 also been observed in the central part of the Kondopoga Bay, which was mainly caused by the trout farm impact. At the same time, oligotrophication was observed in the Povenets Bay. The main waterbody of the lake still preserves its high water quality; however, the tendency for its eutrophication is evident by the decrease of the rate of mineral nitrogen to total phosphorus.

Identifying factors that affect mountain lake sensitivity to atmospheric nitrogen deposition across multiple scales

Increased nitrogen (N) deposition rates over the past century have affected both North American and European mountain lake ecosystems. Ecological sensitivity of mountain lakes to N deposition varies, however, because chemical and biological responses are modulated by local watershed and lake properties. We evaluated predictors of mountain lake sensitivity to atmospheric N deposition across North American and European mountain ranges and included as response variables dissolved inorganic N (DIN = NNH4+ + NNO3–) concentrations and phytoplankton biomass. Predictors of these responses were evaluated at three different spatial scales (hemispheric, regional, subregional) using regression tree, random forest, and generalized additive model (GAM) analysis. Analyses agreed that Northern Hemisphere mountain lake DIN was related to N deposition rates and smaller scale spatial variability (e.g., regional variability between North American and European lakes, and subregional variability between mountain ranges). Analyses suggested that DIN, N deposition, and subregional variability were important for Northern Hemisphere mountain lake phytoplankton biomass. Together, these findings highlight the need for finer-scale, subregional analyses (by mountain range) of lake sensitivity to N deposition. Subregional analyses revealed differences in predictor variables of lake sensitivity. In addition to N deposition rates, lake and watershed features such as land cover, bedrock geology, maximum lake depth (Zmax), and elevation were common modulators of lake DIN. Subregional phytoplankton biomass was consistently positively related with total phosphorus (TP) in Europe, while North American locations showed variable relationships with N or P. This study reveals scale-dependent watershed and lake characteristics modulate mountain lake ecological responses to atmospheric N deposition and provides important context to inform empirically based management strategies.

THE “ONE HEALTH” APPROACH AS A POSSIBLE MODE OF ECOLOGICAL RISK ASSESSMENT (EXAMPLE OF CYANOTOXINS)

Cyanobacteria are a big group of photosynthetic prokaryotic organisms inhabiting fresh and sea waters and damp soils. Cyanobacteria produce secondary metabolites – cyanotoxins, which are potentially dangerous for humans and animals if present in drinking water, and pose real danger for waterfowl, fish, and zooplankton. Therefore, cyanobacteria are often considered as pathogenic organisms albeit they are unable to develop in animals’ organisms. As reported by the UNESCO international hydrological program CYANONET, cyanobacteria and cyanotoxins were found in surface waters in 65 countries. To study the occurrence of cyanobacteria and cyanotoxins in European lakes, two international cooperation programs were implemented, namely CYANOCOST in 2012–2016 and EMLS (European Multi Lake Survey) in 2015. Cyanotoxins are divided into groups according to their action on human organisms (hepatotoxins, neurotoxins, dermatoxins, and cytotoxins). Lately, the health impacts of harmful cyanobacteria have been more frequently detected and reported. However, reports of human and animal illnesses or death associated with harmful cyanobacteria tend to be investigated separately. One Health is an approach that recognizes that the health of people is closely connected to the health of animals and our shared environment. This review illustrates how the investigation of cyanotoxin-associated animal illnesses and death can be used to reduce the risks of human exposure to harmful cyanobacteria. The One Health approach is an environmental risk management method that requires the integration of efforts of different specialists.

High‐Resolution Mapping of Ice Cover Changes in Over 33,000 Lakes Across the North Temperate Zone

AbstractMore than 50% of global lakes periodically freeze, and their lake ice phenology is sensitive to climate change. However, spatially detailed quantification of the changes in lake ice at the global scale is not available. Here, we map ice cover in &gt;33,000 lakes throughout the North Temperate Zone (23.5°–66.5°N) using 0.55 million Landsat images from 1985 to 2020. Over this period, we found a remarkable reduction in median ice cover occurrence (ICO) (61% to 43%), which was strongly related to warming terrestrial mean surface temperatures (R2 = 0.94, p &lt; 0.05). Lakes in Europe showed the most pronounced ice loss (median ICO decreased from 50% to 24%), and extensive lake ice losses were also detected in the northern US, and central and eastern Asia. An overall increase in ice cover was identified from P2 (1999–2006) to P3 (2007–2014) due to regional decreased temperatures associated with the “global warming hiatus.” Thehigh‐resolution mapping of lake ice here provides essentialbaseline information whichcan be used to elucidate ice loss‐induced environmental and societal impacts.

Patterns of Cryptic Diversity and Phylogeography in Four Freshwater Copepod Crustaceans in European Lakes

Comparative phylogeography has become a powerful approach in exploring hidden or cryptic diversity within widespread species and understanding how historical and biogeographical factors shape the modern patterns of their distribution. Most comparative phylogeographic studies so far focus on terrestrial and vertebrate taxa, while aquatic invertebrates (and especially freshwater invertebrates) remain unstudied. In this article, we explore and compare the patterns of molecular diversity and phylogeographic structure of four widespread freshwater copepod crustaceans in European water bodies: the harpacticoids Attheyella crassa, Canthocamptus staphylinus and Nitokra hibernica, and the cyclopoid Eucyclops serrulatus, using sequence data from mtDNA COI and nuclear ITS/18S rRNA genes. The three taxa A. crassa, C. staphylinus and E. serrulatus each consist of deeply diverged clusters and are deemed to represent complexes of species with largely (but not completely) non-overlapping distributions, while in N. hibernica only little differentiation was found, which may however reflect the geographically more restricted sampling. However, the geographical patterns of subdivision differ. The divisions in A. crassa and E. serrulatus follow an east–west pattern in Northern Europe whereas that in C. staphylinus has more of a north–south pattern, with a distinct Fennoscandian clade. The deep mitochondrial splits among populations of A. crassa, C. staphylinus and E. serrulatus (model-corrected distances 26–36%) suggest that divergence of the lineages predate the Pleistocene glaciations. This study provides an insight into cryptic diversity and biogeographic distribution of freshwater copepods.