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Zooplankton monitoring is important for understanding their population dynamics and life history, ecosystem health, and environmental changes. Compared with traditional morphological identification, environmental DNA (eDNA) analysis allows for more sensitive and efficient monitoring of zooplankton diversity. Previous eDNA studies have primarily used metabarcoding approaches to reveal their richness and composition, whereas its performance in predicting zooplankton abundance remains understudied. We conducted water and bulk sampling in Lake Biwa, Japan, showing that the number of sequence reads by metabarcoding moderately correlated with eDNA concentrations estimated by quantitative real-time PCR (qPCR). In addition, the eDNA read number was significantly related to cladoceran and copepod abundance estimated by microscopy sorting, although there remained too much uncertainty in the read-abundance relationship. Moreover, there was a significant difference in species composition between eDNA metabarcoding and sorting. Although our results indicated the potential applicability of eDNA metabarcoding for quantifying multiple zooplankton abundance, several methodological validations in eDNA metabarcoding would also be required to optimize its performance in the future. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the environmental factors having the greatest influence on the distribution and abundance of epipelic diatom species in different wetlands in southern Spain. We previously defined four groups of conductivity categories: fresh (< 0.8 mS cm−1), oligosaline (< 8 mS cm−1), mesosaline (8–30 mS cm−1) and eusaline (> 30 mS cm−1). A dbRDA analysis performed on a subset of 36 of the 53 wetlands, using a total of 25 environmental variables, showed that five environmental variables (conductivity, pH, wetland area, silicates, and total suspended solids) were the best explanatory variables for the diatom assemblage, with conductivity being the main explanatory variable. Nonmetric multidimensional scaling (nMDS) analysis performed on the set of 53 wetlands revealed significant differences in diatom composition among the four conductivity groups. The key species in the eusaline group were Tryblionella pararostrata, Halamphora sp.1 and Cocconeis euglypta, whereas in the mesosaline and oligosaline group, these were Navicula veneta, Tryblionella hungarica and Nitzschia inconspicua. Finally, in the fresh group dominated Achnanthidium minutissimum, Navicula veneta and Gomphonema exilissimum. This study on epipelic diatoms can therefore contribute to the knowledge of these organisms in a European region with a high diversity of wetland typologies. [ABSTRACT FROM AUTHOR]

Currently, more and more lakes around the world are experiencing outbreaks of cyanobacterial blooms, and high-precision and rapid monitoring of the spatial distribution of algae in water bodies is an important task. Remote sensing technology is one of the effective means for monitoring algae in water bodies. Studies have shown that the Floating Algae Index (FAI) is superior to methods such as the Standardized Differential Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) in monitoring cyanobacterial blooms. However, compared to the NDVI method, the FAI method has difficulty in determining the threshold, and how to choose the threshold with the highest classification accuracy is challenging. In this study, FAI linear fitting model (FAI-L) is selected to solve the problem that FAI threshold is difficult to determine. Innovatively combine FAI index and NDVI index, and use NDVI index to find the threshold of FAI index. In order to analyze the applicability of FAI-L to extract cyanobacterial blooms, this paper selected multi-temporal Landsat8, HJ-1B, and Sentinel-2 remote sensing images as data sources, and took Chaohu Lake and Taihu Lake in China as research areas to extract cyanobacterial blooms. The results show that (1) the accuracy of extracting cyanobacterial bloom by FAI-L method is generally higher than that by NDVI and FAI. Under different data sources and different research areas, the average accuracy of extracting cyanobacterial blooms by FAI-L method is 95.13%, which is 6.98% and 18.43% higher than that by NDVI and FAI respectively. (2) The average accuracy of FAI-L method for extracting cyanobacterial blooms varies from 84.09 to 99.03%, with a standard deviation of 4.04, which is highly stable and applicable. (3) For simultaneous multi-source image data, the FAI-L method has the highest average accuracy in extracting cyanobacterial blooms, at 95.93%, which is 6.77% and 13.26% higher than NDVI and FAI methods, respectively. In this paper, it is found that FAI-L method shows high accuracy and stability in extracting cyanobacterial blooms, and it can extract the spatial distribution of cyanobacterial blooms well, which can provide a new method for monitoring cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Lake Zminje Jezero (1535 m a.s.l.) in Montenegro was studied for chironomid and other aquatic invertebrate remains in a sediment sequence dating back to 12,000 calibrated 14C years before present (cal yr BP), providing, to our knowledge, the first lake-sediment record studied for chironomids and other associated chitinous aquatic invertebrate remains in the Dinaric Alps. Changes in chironomid and other invertebrate remains along the record make it possible to constrain changes of relevant environmental variables for aquatic invertebrates in the lake including temperature, oxygen availability, trophic status and water depth. The results suggest moderate changes in trophic conditions with chironomid assemblages indicating meso- to eutrophic conditions during the analysed interval. Invertebrate assemblages were typical for lakes with relatively high oxygen availability with a minor trend during the middle to late Holocene to conditions observed in lakes that are more hypoxic. A change in temperature is suggested in the earlier part of the record when the share of chironomid taxa adapted to warmer conditions increased, at the Younger Dryas to Holocene transition, whereas later no particularly pronounced shifts in temperature-sensitive taxa were observed. July air temperatures were estimated based on chironomid assemblages using a transfer function based on calibration data consisting of 117 lakes sampled in the Swiss Alps and northern Switzerland. The results suggest that temperatures rapidly increased by 5 °C at the onset of the Holocene (11,500 cal yr BP) leading to a relatively warm early to mid-Holocene and thereafter slightly decreased during the late Holocene. Reconstructed temperatures are discussed together with a previously published pollen record for our study site and are broadly consistent with other chironomid-based temperature reconstructions from Central, Eastern and Southern Europe. From ca. 3000 cal yr BP sedimentation rates increased and from ca. 500 cal yr BP onwards pollen data suggest that the vegetation and lake catchment were affected by human activities, possibly influencing chironomid and other invertebrate assemblages in the lake and thereby also reconstructed temperatures. Overall, our results show that combining analyses of chironomid and other invertebrate assemblages can provide valuable insights into long-term environmental changes and can provide temperature reconstructions for small mountain lakes in the Balkans, such as Zminje Jezero. [ABSTRACT FROM AUTHOR]

Most information on rotifers living in lake sands comes from the 1930s, when the first reports on this subject by Jerzy Wiszniewski appeared. After some decline in the interest in lake psammon in the following years, research on lake psammon returned in the last decade of the twentieth century. The last comprehensive review of ecology of psammon Rotifera was included in the excellent 1998 publication by Schmid-Araya on Rotifera in interstitial sediments. More than 20 papers have been published since that time. So far, research conducted almost exclusively in the northern hemisphere have dealt with issues related to distribution of rotifers, their species structure and diversity as well as to their relation to abiotic and biotic factors. The aim of the present study was to collect all available information on psammon rotifers, assess the shortcomings in our knowledge and fill these gaps with the results of some of my recent research. The results of the study show that the species richness of this group in geographical terms is still unknown. It means we also do not know the level of endemism among the psammon rotifers. The role of psammon rotifers in benthic food webs is another issue requiring research. [ABSTRACT FROM AUTHOR]

Artificial neural networks offer a viable route in assessing and understanding the presence and concentration of heavy metals that can cause dangerous complications in the wider context of water quality prediction for the sustainability of the ecosystem. In order to estimate the heavy metal concentrations in Iznik Lake, which is an important water source for the surrounding communities, characterization data were taken from five different water sources flowing into the lake between 2015 and 2021. These characterization results were evaluated with IBM SPSS Statistics 23 software, with the addition of the lake water quality system. For this purpose, seven distinct physicochemical parameters were measured and monitored in Karasu, Kırandere, Olukdere and Sölöz water sources flowing into the lake, to serve as input data. Concentration levels of 15 distinct heavy metals in Karsak Stream originating from the lake were as the output. Specifically, Sn for Karasu (0.999), Sb for Kırandere (1.000), Cr for Olukdere (1.000) and Pb and Se for Sölöz (0.995) indicate parameter estimation R2 coefficients close to 1.000. Sn stands out as the common heavy metal parameter with best estimation prospects. Given the importance of the independent variable in estimating heavy metal pollution, conductivity, COD, COD and temperature stood out as the most effective parameters for Karasu, Olukdere, Kırandere and Sölöz, respectively. The ANN model emerges as a good prediction tool that can be used effectively in determining the heavy metal pollution in the lake as part of the efforts to protect the water budget of Lake Iznik and to eliminate the existing pollution. [ABSTRACT FROM AUTHOR]

Anodonta woodiana samples from Xidong Water Works and Mashan in Taihu Lake, Yiyang near Dongting Lake, and Taiping Harbor in Gehu Lake preserved in a “specimen bank” established for the “Freshwater Mussel Watch” monitoring program were used to determine the historical metal backgrounds from different waters in the present study. The elements Co, Ni, Mo, Cd, Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were determined using A. woodiana from four lacustrine sites. The results showed that Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were all detected, whereas Co, Ni, Mo, and Cd were below the detection limits of 0.0165, 0.0106, 0.0189 and 0.0182 µg kg− 1, respectively. In particular, A. woodiana was noted to be an unusual Mn hyperaccumulator (ranged from 5124.09 to 13015.47 µg g− 1). The results of discriminant analysis showed that the four water samples could be accurately separated. This difference has the potential to infer the background difference of heavy metal pollution in different lacustrine habitats. [ABSTRACT FROM AUTHOR]

A sorption–diffusion model of 137Cs absorption by bottom soils has been used to forecast 137Cs concentration in global fallouts and emergency release from the Chernobyl NPP in water of the deep (Hav = 30 m) Lake Onega. The natural conditions and the morphohydrological characteristics of the lake caused a rapid (2–3 years) transformation of 137Cs-polluted water to pseudoequilibrium concentrations. For 56 years (from 1964 to 2020), the concentration of 137Cs in water was determined with acceptable accuracy by a sorption-diffusion model of 137Cs adsorption by bottom soils with coefficients of sorption Kd = 4000 L/kg and diffusion D = 1.0 × 10–7 cm2/s. The effect of water exchange in the lake on 137Cs migration is taken into account in the characteristic of conditional exchange of Lake Onega water W = 16.4 years. The correctness of the forecast of water pollution by 137Cs was verified by comparison with experimental data and the conditions of 137Cs pollution of the waters of deep lakes in the northwestern Russia and Finnish Lapland. [ABSTRACT FROM AUTHOR]

The study of algological material from tundra lakes of the adjacent territories of the Ust-Lena Reserve (Yakutia) using scanning electron microscopy revealed a new species of diatoms for science—Buryatia strelnikovae sp. nov. The new species has morphological similarities with other species of the genus B. oviformis and B. crassa. It differs from the former in the larger number of striae and areoles per 10 µm and from the latter in the smaller length and width of the valve and a larger number of striae and areoles per 10 µm. [ABSTRACT FROM AUTHOR]

In this study, we quantify the differences in gross primary production (GPP), respiration (R), and algal nutrient limitation (nitrogen and phosphorus) in the littoral and pelagic habitats of an oligotrophic Patagonian lake (southern South America). We used submerged high frequency sensors that measure light, temperature, and dissolved oxygen and wind data to calculate GPP and R in both lake habitats. In addition, we carry out nutrient enrichment bioassays with nitrate, ammonium, and phosphate to determine which nutrient(s) limit algal growth in each lake habitat. On average, the productivity rate was 7.2 times higher at the epi-littoral (32.0 to 5.3 mmol O2 m−2 d−1) relative to the epi-pelagic (4.1 to 1.3 mmol O2 m−2 d−1). Algal growth in the littoral habitat was limited by nitrate and ammonium, while the pelagic habitat was co-limited by nitrogen (nitrate or ammonium) and phosphorus. Our work demonstrates that the littoral habitat of a Patagonian oligotrophic lake is more productive than the pelagic habitat and that the nutrients limiting algal growth in both habitats are different. These results underscore habitat variations and their significance in shaping the lake's trophic dynamics for the first time in the southern hemisphere. [ABSTRACT FROM AUTHOR]

Lakes are hotspots for the biogeochemical processing of carbon, including dissolved organic matter (DOM). A less degradable fraction of DOM, preserved for a long time, can be categorized as recalcitrant DOM (RDOM). Lake RDOM is an important but neglected carbon sink, and its characteristics and transformation processes remain largely unknown. Highlights: • Recalcitrant dissolved organic matter (RDOM) is an important but neglected carbon sink in lakes. • The heterogeneity of lake environments determines the diversity and complexity of RDOM. • New techniques allow detailed studies of the mechanisms of RDOM formation and related processes. [ABSTRACT FROM AUTHOR]

The quality and quantity of dissolved organic matter (DOM) in lakes as well as its environmental effects associated with the unintended disinfection by-products (DBPs) have received continuous attention. This work investigated the spatiotemporal dynamics of DOM in Shengzhong Lake in southwest China and the formed DBPs during the chlorine disinfection process. The results showed that lake water in summer had significantly higher dissolved oxygen and dissolved organic carbon than that in winter. In contrast, DOM in winter demonstrated an obviously higher aromaticity and molecular weight than that in summer. Four fluorescence components, i.e., terrestrial humic-like substances (C1), protein-like substances (C2), and microbial humic-like substances (C3 and C4), were identified, and their relative abundance followed in the order of C3 > C4 > C2 > C1 in winter and C4 > C3 > C1 > C2 in summer. The formation potential of trihalomethanes and haloacetic acids in winter was higher and lower than that in summer, which was mainly ascribed to the content of aromatic and hydrophobic substances. Compared to the significant seasonal dynamic, the spatial variation of DOM and the formed DBPs was not obvious. This work sheds light on the spatial-temporal distribution of DOM and the potentially formed DBPs in Shengzhong Lake, and will be helpful for understanding the biogeochemical cycle of carbon and assessing the drinking water safety. [ABSTRACT FROM AUTHOR]

The ecological and geographical differentiation and dynamics of the spring migration of water and semiaquatic birds of the Putorana Plateau are analyzed. In 1988–2007, eight points were surveyed in the northern, southern, western, and eastern parts of the region on an area of 250 000 km2 using the method of route census. The water and semiaquatic avifauna of the Putorana Plateau during the spring migration includes 68 species. The tundra species (53%) from among the Anseriformes and Charadriiformes, accounting for 94%, make a significant contribution to the avifauna formation. Birds fly to the north, east, and west. They make stops at the river deltas that are freed from snow and ice early. The species distributed at stopover sites everywhere (38%), locally (22%), and pointwise (40%) are distinguished. Bird population density at stopovers is from 15 to 227 (on average (n = 8) 94) ind./km of shoreline. The population of birds on lakes is always much smaller than on adjacent river sections. The vast majority of individuals of almost all migratory species are united in monospecific and (rarely) polyspecific flocks. The entire spring migration of water and semiaquatic birds on the Putorana Plateau takes place from May 19 to June 27 and lasts on average (n = 10) 23 days. The main passage runs from May 25 to June 17 and lasts an average of (n = 8) 7 days. Spring migration is most intense in the west of the Putorana Plateau, where at least 20 000–30 000 individuals of aquatic and semiaquatic birds fly through the surveyed points. The passage is much weaker in the center and, especially, in the east of the region. There are 19 species among the dominants of water and semiaquatic habitats, including the common teal, Eurasian wigeon, northern pintail, grey-tailed tattler, and little stint. [ABSTRACT FROM AUTHOR]

Trophic state index (TSI) only considers the influence of phytoplankton excluding that of macrophytes. It is necessary to combine the contribution of macrophytes into trophic classification systems in waters with extensive growths of macrophytes. A novel trophic level index (TLIECa) combined both trophic level index (TLI) and the TSI based on equivalent chlorophyll a (TSIECa) with the Chl a of submerged macrophytes as an addition in Chl a was developed to assess the spatial trophic state of 15 lakes and annual trophic state of four lakes in China. TLIECa obtained different but significantly correlated results as those of the traditional TLI, concerning the influences of both phytoplankton and macrophytes. The result of TLIECa indicated that the trophic state of the 15 lakes varied from mild-eutrophic to moderate-eutrophic. Small particles were the dominant factor for the trophic state of most sampling sites in the 15 lakes. Total phosphorus was the dominant factor for the trophic state for most time of the year in Lake Jinniu. Both small particles and total phosphorus were the dominant factors for the annual trophic state of Lake Taihu, Lake Xuanwu, and Lake Baijia. [ABSTRACT FROM AUTHOR]

The explosive rate of population growth demands a revision of existing protective measures to address water scarcity that urges water body monitoring models to be developed using satellite image-based change detection approaches. And the main objective of this proposed work was to investigate the spectral indices for spatial object extraction in satellite images with respect to water body extraction. The Landsat 8 coastal/aerosol band (0.433–0.453 μm) is still an unexplored band with spectral signatures that favor water extraction, and it has been used in the proposed deep blue normalized difference water index (DBNDWI). The multi-temporal Landsat 8 data products of three lakes with distinct geographical importance from India and Iran are chosen for assessment. Widely used spectral indices for water body extraction such as the normalized difference water index (NDWI), modified normalized difference water index, and automated water extraction index are the benchmark results used for comparative assessment. Along with these conventional water indices, the most recent water indices weighted normalized difference water index (WNDWI) and Wavelet-based normalized difference water index (WAWI) are also compared for extended validation. The use of standard image quality analysis and statistical histogram distance measures justifies the significance of coastal band in extracting water bodies. The experimental results tabulated show that proposed DBNDWI outperforms the most recent WNDWI and WAWI with higher accuracy, even in moderate-resolution images. [ABSTRACT FROM AUTHOR]

Closed-circuit hypolimnetic withdrawal and treatment systems (HWTS) represent a novel lake restoration technique in which nutrient-rich near-bottom water is pumped through a treatment system and returned to the same lake. However, the design of such systems is not yet standardized and routing of effluent waters must be planned carefully to minimize the risk of adverse water quality impacts. Here we assessed the risk of HWTS effluent to elevate epilimnetic nutrient concentrations under a range of withdrawal and effluent discharge scenarios (4.5–45 L/s, sand filtration only and sand filtration combined with wetland) at Lake Kymijärvi, Finland. The filter of the HWTS removed most of the phosphorus (67%), but only a small fraction of nitrogen (14%). For both nutrients, filter effluent concentrations were elevated with respect to the lake epilimnion. However, the results of our calculations suggest only minor increases (0–12%) in epilimnetic phosphorus concentrations in all withdrawal and discharge scenarios. For nitrogen, somewhat higher increases (1–17%) are expected unless the filter effluent is first discharged into a wetland as part of the HWTS circuit. We conclude that the impacts of the filter effluent on the epilimnion do not mask the benefits gained in the treated lake by the closed-circuit HWTS, but use of a buffering system such as a wetland decreases the risks further. [ABSTRACT FROM AUTHOR]

Cobalt distribution and speciation were quantified in space and time in the water column of a small, stratified, eutrophic lake, Linsley Pond, North Branford, CT. While scrupulously employing clean techniques, we used ligand exchange with dimethylglyoxime and cathodic stripping voltammetry to evaluate free and complexed forms of Co. Free aquo Co ion concentrations [Co2+] were found in the range from 0.014 to 0.28 nM from June to October 2018. Despite the orthograde distribution for total dissolved Co (0.42–3.34 nM), free Co2+ was higher in the epilimnion, decreasing with depth. Natural organic ligand concentrations [L] were in the span from 0.7 to 8.1 nM, with conditional stability constants (as logK) in the range from 9.43 to 11.13. Nearly all of the Co was complexed with highly selective ligands, and patterns suggest three controlling processes: (1) Co release from dissolving Mn (and perhaps Fe) oxides, (2) possible limitation by solubility of CoS(s), and (3) stabilization in solution via complexation by strong ligands. No correlation was observed between dissolved organic carbon and [L] in this study, suggesting that the ligands are not a simple subset of total dissolved organic matter, but may be specific compounds, perhaps S based. The hypothesis that the biological activity of plankton in Linsley Pond might be limited by micronutrient Co is only weakly supported. Cobalamin (VB12) measured via enzyme-linked immunosorbent assays ranged from 0.033 to 0.048 nM in this lake and does not follow a simple pattern with either total dissolved Co or Co2+, or with biological activity as indicated by chlorophyll levels. [ABSTRACT FROM AUTHOR]

The northern part of James Ross Island is the largest deglaciated area in the Antarctic Peninsula region with a unique ecosystem created during the Late Glacial. This research aims to evaluate the degree of contamination of the locality with toxic metals (As, Hg, Cd, and Pb) through bioindicators in the aquatic environment—colonies of cyanobacteria and algae. For this purpose, bottom lake sediments of Big Lachman Lake were studied for contents of Fe, As, Hg, Cd, Pb, Cr, Co, Ni, Cu, and Zn, as well as samples of cyanobacterial mat, in which Fe, As, Hg, Cd, and Pb were determined. Metal contents were determined by means of inductively coupled plasma optical emission spectrometry and atomic absorption spectrometry. The contents of metals in sediments did not differ from the usual values in the area of the Antarctic Peninsula. The bioaccumulation of metals in cyanobacterial mat was evaluated by calculating enrichment factors (the calculation to Fe as a reference element). According to this method, moderate pollution of Big Lachman Lake was confirmed for Hg and Cd. [ABSTRACT FROM AUTHOR]

Great Lakes coastlines are mosaics of wetland, stream, and lake habitats, characterized by a high degree of spatial heterogeneity that may facilitate the co-occurrence of seemingly incompatible biogeochemical processes due to variation in environmental factors that favor each process. We measured nutrient limitation and rates of N2 fixation and denitrification along transects in 5 wetland–stream–lake ecotones with different nutrient loading in Lakes Superior and Huron. We hypothesized that rates of both processes would be related to nutrient limitation status, habitat type, and environmental characteristics including temperature, nutrient concentrations, and organic matter quality. We found that median denitrification rates (914 μg N m−2 h−1) were 166 × higher than N2 fixation rates (5.5 μg N m−2 h−1), but the processes co-occurred in 48% of 83 points measured across all 5 transects and habitat types. N2 fixation occurred on sediment and macrophyte substrate, while denitrification occurred mostly in sediment. Nutrient-diffusing substrate experiments indicated that biofilm chlorophyll-a was limited by N and/or P at 55% and biofilm AFDM was limited at 26% of sample points. N2 fixation and denitrification rates did not differ significantly with differing nutrient limitation. Predictive models for N2 fixation and denitrification rates both included variables related to the composition of dissolved organic matter, while the model for N2 fixation also included P concentrations. These results demonstrate the potential for heterogeneity in habitat characteristics, nutrient availability, and organic matter composition to lead to biogeochemical complexity at the local scale, despite overall N removal at broader scales. [ABSTRACT FROM AUTHOR]

The article gives an example of the choice and implementation of a method for water quality assessment for a large high-mountain lake with long-term unstable level regime and variable morphometry (artificial level decrease by 19 m followed by an increase by 4 m and more). The choice of a procedure for water quality assessment for such a water body requires non-standard solutions. This is made with the use of a modern modification of the Delphi expert panel method. This method gives a quantitative estimate of water quality relative to the initial/desirable state that all managers strive for in order to achieve and maintain water quality. The index of Lake Sevan water quality index SWQI is based on seven priority characteristics with the weight of each of them taken into account. The long-term dynamics of this index confirmed the managerial impact of lake level rise on water quality: a poor water quality (a minimal value of SWQI = 20) was recorded in the years of the lowest level (1976–1990), while a good water quality (the maximal value of SWQI = 69), in the years of highest level (2016–2020); (the coefficient of correlation was 0.82). The advantages of the used index SWQI include the relatively low dependence of the index on the availability of a database and the possibility to use the estimate for balancing the environmental and socioeconomic interests. The general approach to SWQI model can be used to evaluate the water quality of such lakes all over the world. [ABSTRACT FROM AUTHOR]

In this study, for the first-time research has been conducted on the macro- (>2 cm) and microplastics (MPs, <5 mm) abundance in the freshwater of Sarab Niloofar Lake, Kermanshah, Iran. The selected MPs were characterized by FTIR, SEM, and EDX. The results revealed that the abundance of MPs was ranged from 4400 to 18,800 particles/m3, and significant differences (p<0.002) in MPs abundance among the sampling stations were also observed. The high frequency of MPs in the term of shapes was related to fibers (68%), film (23%), fragment (9%), respectively, mostly black (52%), and blue (24%). Moreover, the majority of MPs (65%) had a size range between 0.025 and 1 mm (25–1000 μm). The results of polymer composition by the FT-IR analysis confirmed that polypropylene (PP) and polyethylene (PE) were dominant. Moreover, the presence of specific metals (especially Al, Si, and Ca) on the MPs surface, confirming the interactions between the MPs and the aquatic environment. As a result of this study, the mean level (±SD) of macro- and microplastics in the freshwater was determined to be 178.2 ± 77.024 particles/m2 and 10175 ± 4958.019 particles/m3, respectively. All in all, the results of this work showed that this lake is highly polluted by plastic particles, consequently stringent management strategies for the understanding the sources, transport ways, and adverse effects of plastic pollution on the aquatic in this area must be taken. [ABSTRACT FROM AUTHOR]

Antibiotics are commonly detected in natural waters. The organic matter (OM) in suspended particulate matter (SPM) has a critical impact on the adsorption of antibiotics in water. We investigated the contribution of OM content and form to the adsorption of tetracycline (TC) and norfloxacin (NOR) in the SPM of Taihu Lake. To change the content and form of OM in SPM, the samples were subjected to pyrolysis at 505 ˚C and oxidization with H2O2, respectively. Combustion almost completely removed OM, while oxidation removed most of the OM and transformed the remaining OM. Regardless of whether the OM changed or not, the adsorption of NOR and TC by SPM was more in line with the pseudo-second-order kinetic model instead of pseudo-first-order. The fitting of the intraparticle diffusion model showed that the removal of OM had a certain degree of change in the adsorption process. The isothermal adsorption of TC in all samples was more in line with the Temkin model. The isothermal adsorption of NOR in the oxidized sample conformed to the Temkin model, while it conformed to the Langmuir model in the original sample and the sample removed OM via combustion. The adsorption capacity of SPM with almost complete removal of OM significantly decreased, while conversely, the adsorption capacity of SPM after oxidation increased. This indicates that both the content and form of OM affect the adsorption of antibiotics by SPM, and the form of OM has a greater impact. The contribution of OM to NOR adsorption was greater than that of TC. In conclusion, the results verify the importance of OM in adsorbing antibiotics onto SPM, which may provide basic data for antibiotic migration in surface water. [ABSTRACT FROM AUTHOR]

Some biological invasions can result in algae blooms in the nearshore of clear lakes. We studied if an invasive crayfish (Pacifastacus leniusculus) modified the biomass and community composition of benthic macroinvertebrates and therefore led to a trophic cascade resulting in increased periphyton biomass, elevated littoral primary productivity, and benthic algae bloom in a lake with remarkable transparency [Crater Lake, Oregon, USA]. After quantifying the changes in the spatial distribution of invasive crayfish over a 13-year period, we compared biomass and community composition of littoral–benthic macroinvertebrates, periphyton biovolume, community composition, nutrient limitation, and the development of benthic algae bloom in locations with high and low crayfish density. In addition, we determined if the alteration in community structure resulted in directional changes to gross primary production and ecosystem respiration. The extent of crayfish distribution along the shoreline of Crater Lake doubled over a 13-year period, leaving less than 20% of the shoreline free from crayfish. At high crayfish density sites, benthic macroinvertebrate biomass was 99% lower, and taxa richness was 50% lower than at low crayfish areas. High crayfish sites show tenfold greater periphyton biovolume, sixfold higher periphyton biomass (chlorophyll a), twofold higher metabolic productivity, and the presence of large filamentous algae (Cladophora sp.). The invasion of crayfish had negative consequences for a lake protected under the management of the USA National Park Service, with direct impacts on many levels of ecological organization. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks. This paper reviewed the CO2 partial pressure (pCO2) and its diffusion flux (FCO2) in karst surface aquatic ecosystems, mainly rivers, lakes, and reservoirs, and their influencing factors summarized the methods for monitoring CO2 emissions in karst aquatic ecosystems and discussed their adaptation conditions in karst areas. The pCO2 and FCO2 decreased in the order of rivers > reservoirs > lakes, and the values in karst lakes were eventually significantly lower than those in global lakes. The pCO2 and FCO2 of karst aquatic ecosystems had patterns of variation with diurnal, seasonal, water depth and hydrological cycles, and spatial and temporal heterogeneity. The sources of CO2 in karst waters are influenced by both internal and external sources, and the key spatial and temporal factors affecting the CO2 emissions from karst rivers, lakes, and reservoirs were determined in terms of physicochemical indicators, biological factors, and biogenic elements; additionally, the process of human activity interference on CO2 emissions was discussed. Finally, a conceptual model illustrating the impacts of urban development, agriculture, mining, and dam construction on the CO2 emissions at the karst surface aquatic ecosystem is presented. Meanwhile, based on the disadvantages existing in current research, we proposed several important research fields related to CO2 emissions from karst surface aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Although ostracods are important components in aquatic ecosystems, little is known about their microbiomes. Here, we analyzed the microbiomes of the putative ancient asexual ostracod species, Darwinula stevensoni, in three natural populations from different freshwater habitats in the UK, Belgium, and Spain. We applied high-throughput amplicon sequencing approaches to analyze the V3–V4 part of the bacterial 16S rRNA region. We tested for host-specific microbiomes by comparing bacterial assemblages of ostracods with those of sediment and water samples from the same locations. Around 2,200 Amplicon Sequence Variants (ASVs) were identified from ostracod samples with universal primers and 1,700 ASVs with endosymbiotic-specific primers, illustrating a high microbiome diversity in D. stevensoni. Most bacterial taxa were unique to the microbiome of D. stevensoni as compared to other freshwater invertebrates and to non-marine ostracods. Alpha diversity of ostracod microbiomes did not differ significantly between the three populations, but PERMANOVA detected significant differences in bacterial compositions. Microbiomes varied highly among ostracod specimens from the same population. Possible factors shaping ostracod microbiomes could be latitude, food, age, and environmental variables. Preliminary functionality analyses showed that Darwinula-specific microbiomes contribute to lipid, carbohydrate, nucleotide, and amino acid metabolic processes and the synthesis of co-factors and vitamins. [ABSTRACT FROM AUTHOR]

The submerged surface sediment of the artificial lake at Jordan University of Science and Technology in Irbid, Jordan, was investigated to evaluate its contamination with trace metals. Chemical characterization was applied to leachates of sediment samples collected from 11 sampling stations at the study zone. The metal concentration (Pb, Cu, Cr, Cd, Ni, Zn, Fe, and Hg) in the sediment samples was matched to the limits set by the Jordanian standard for water-sludge-uses of treated sludge and sludge disposal. According to the results obtained via thermal decomposition, mercury amalgamation, and inductively coupled plasma—atomic emission spectrometry (ICP-AES), most metals were below the detection limit. Several metals were found to be below the limits fixed by the Jordanian standards except for stations 10 and 11 which connected the wastewater channels to the lake. At these two stations, Pb recorded contents were 439 and 335 mg/kg dry matter, respectively, and thus exceeded the limits set by the Jordanian standard. Thus, the overall results were in favor of the environmental safety of the JUST lake for setting up a fish aquaculture. [ABSTRACT FROM AUTHOR]

A sedimentary record of the 19 organochlorine pesticides (OCPs) pollutants from Dongping Lake, north China, is presented in this study. According to the dating of core sediment and OCP content analysis in samples, from 1904 to 2016, the total concentration of OCPs varied from undetectable levels (n.d.) to 33.1 ng/g. The OCP concentration was first detected in the samples of 1938, and then gradually increased to a peak level in 2000 thereafter decreased until 2016. Among the detected OCPs, hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the predominant and the most frequently detected contaminants in the core sediment, with concentrations ranging from n.d. to 16.9 ng/g and from n.d. to 8.8 ng/g, respectively. The distribution of OCPs in the sediments was affected by organic carbon concentration, showing a significant positive correlation (r = 0.93, p < 0.001), especially for HCHs (r = 0.98, p < 0.001). The source analysis showed that HCH contamination mainly derived from historical use of technical HCHs, while in recent years, it derived from lindane usage. DDT pollution was attributed to historical use of technical DDTs, as well as the microbial degradation of historic DDT residues. Finally, risk analysis was performed for OCPs in sediment cores based on sediment quality guidelines from the Canadian Council of Ministers of the Environment, showing that DDTs presented a high ecological toxicity risk during the period of 1959–2010. [ABSTRACT FROM AUTHOR]

Bacteria and archaea play a fundamental role in the biogeochemical cycles of organic matter, pollutants, and nutrients to maintain the trophic state of aquatic ecosystems. However, very little is known about the composition patterns of microbial communities in vertical distribution (water column) in freshwater lakes and their relationship with the physicochemical properties of water. "La Encantada" lake in the Lagunas de Montebello National Park (LMNP) is a site of interest due to the anthropogenic impact received and the little information about it. In this study, 3 sites were evaluated; samples were collected using 0–15 m deep water columns and analyzed using Illumina MiSeq sequencing technology based on the 16S rRNA gene. The physical parameters of pH, temperature, dissolved oxygen, electrolytic conductivity, and PO−4 were determined. The results revealed clear differences in the microbial composition of the water throughout the column; the most abundant phyla in bacterial communities were Proteobacteria (23.2%), Cyanobacteria (17.3%), and Bacteroidetes (17.2%), and for archaea were Crenarchaeota (35.9%) and Euryarchaeota (33.2%). PICRUSt metabolic inference analysis revealed that the main functional genes were related to cellular processes and biodegradation of xenobiotics, indicating an increasing trend of contaminants and residual discharges that may act as a precursor to alter microbial communities and stability of the lakes. At depths of 10 and 15 m, the microbial diversity was greater; likewise, the correlation between the physicochemical parameters and the microbial communities at the genus level showed that Chlorobaculum, Desulfomonile, and Candidatus Xiphinematobacter were favored by an increase in dissolved phosphates and by the decrease in pH and temperature. These results highlight that the microbial communities exhibit variation in their composition due to the effect of depth and physicochemical parameters, which could play a role as biological factors in the trophic states of a lake. [ABSTRACT FROM AUTHOR]

During the irrigation period, the interactions between the linked lake-groundwater systems are complicated and change. This is because natural and human activities are happening at the same time, which makes it harder to identify the interactions. This study uses data on water level, hydrochemistry, and hydrogen-oxygen stable isotopes to analyze the hydrodynamics, electrical conductivity (EC), isotopic characteristics, and spatial distribution of lake water and groundwater to reveal lake-groundwater interactions. The results indicate that the hydrochemical type of Chagan Lake and groundwater is dominated by the HCO3-Na type. The key hydrochemical indicator EC obtained by principal component analysis (PCA) can be used to reveal the lake–groundwater interaction, and the interaction should be identified by location according to the significant correlation between hierarchical clustering results and regional distribution. The lake body's geographic coefficient of variation for EC and δ18O is small, and irrigation return flow is one factor in the region's surface water's significant spatial variation for EC and δ18O. The three study methods indicate that the groundwater supplies the lake in the vicinity of the Huoling River-Hongzi Pool, while in other sections, the lake water leaks and replenishes the groundwater, exhibiting geographic inconsistency. The isotope method was employed as a support tool to determine that groundwater might recharge the lake at Xinmiao Pool. According to the calculations of the Mix SIAR model, the groundwater recharge contribution rate in the Xinmiao Pool section is approximately 51%, while in the remaining sections, the contribution rate of lake water to groundwater ranges from approximately 25% to 52%. Therefore, the identification of the interaction is crucial for the linked irrigated lake-groundwater system where water sources are scarce and threatened by agricultural pollution. [ABSTRACT FROM AUTHOR]

The pan-Arctic region has the largest number of lakes in the world, which is rather sensitive to changing climate. It is urgently needed to understand how these lakes were changing in the long term. However, there are few lakes with long-term historical monitoring of water level, understanding the hydrologic changes of pan-Arctic lakes over the past century requires the data reconstruction by state-of-art techniques. This study used machine learning algorithms to reconstruct the water level of pan-Arctic lakes on a centennial scale. It further investigated their relationship with long-term hydro-logical and climatic variables. Comparison of the reconstructed results by four different machine learning models shows that the extreme gradient boosting tree (XGBoost) is better than other three models. Overall, the centennial-scale reconstruction using the XGBoost model performs best for most study lakes. Based on the reconstructed results, we can observe that water level changes of several North American lakes are correlated with potential evapotranspiration, followed by precipitation, while the Eurasian lakes are more strongly associated with temperature and wet day frequency. The water level dynamics of pan-Arctic lakes could be largely attributed to Arctic Oscillation and Atlantic Multi-decadal Oscillation. This study is expected to advance our understanding of the pan-Arctic lake water level changes in the past century and to provide a feasible method for reconstructing the regional lake water level in the long term. [ABSTRACT FROM AUTHOR]

A procedure has been proposed to assess the hydrophysical and chemical–biological characteristics of unexplored small and medium lakes (with an area of up to 100 km2) in the Arctic territories of Russia using the methods of remote sensing and mathematical modeling. The procedure is based on the use of a one-dimensional model of hydro-thermodynamic and chemical-biological processes in water bodies. The technique makes it possible to obtain an estimate of heat transport between the atmosphere, ice, water, and bottom sediments and the date of ice cover formation, its thickness, and the duration of existence of freeze-up to calculate the temperature profiles of water and bottom sediments and dissolved oxygen by depth based on information on the geographical coordinates and lake surface area. Contact measurements are not required, which is extremely important for hard-to-reach and poorly explored northern territories of our country. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms in lakes fueled by increasing eutrophication have garnered global attention, and high-precision remote sensing retrieval of chlorophyll-a (Chla) is essential for monitoring eutrophication. Previous studies have focused on the spectral features extracted from remote sensing images and their relationship with chlorophyll-a concentrations in water bodies, ignoring the texture features in remote sensing images which is beneficial to improve interpreting accuracy. This study explores the texture features in remote-sensing images. It proposes a retrieval method for estimating lake Chla concentration by combining spectral and texture features of remote sensing images. Remote sensing images from Landsat 5 TM and 8 OLI were used to extract spectral bands combination. The gray-level co-occurrence matrix (GLCM) of remote sensing images was used to obtain a total of 8 texture features; then, three texture indices were calculated using texture features. Finally, a random forest regression was used to establish a retrieval model of in situ Chla concentration from texture and spectral index. Results showed that texture features are significantly correlated with lake Chla concentration, and they can reflect the temporal and spatial distribution change of Chla. The retrieval model combining spectral and texture indices performs better (MAE = 15.22 μg·L−1, bias = 9.69%, MAPE = 47.09%) than the model without texture features (MAE = 15.76 μg·L−1, bias = 13.58%, MAPE = 49.44%). The proposed model performance varies in different Chla concentration ranges and is excellent in predicting higher concentrations. This study evaluates the potential of incorporating texture features of remote sensing images in lake water quality estimation and provides a novel remote sensing method to better estimate lake Chla concentration. [ABSTRACT FROM AUTHOR]

Periphyton communities in freshwater systems play an essential role in biogeochemical processes, but knowledge of their structure and dynamics lags far behind other environments. We used eDNA metabarcoding of 16S and 18S rRNA markers to investigate the formation and establishment of a periphytic community, in addition to a morphology-based approach for peritrich ciliate determinations, its most abundant group. We sampled two nearby sites within a large Neotropical lake at four time points, aiming to assess whether periphyton establishment can be replicated on this local scale. Producers and denitrifiers were abundant in the community, illustrating the relevant role of biofilms in freshwater nutrient recycling. Among microeukaryotes, peritrich ciliates dominated the community, with genera Epistylis and Vorticella being the most abundant and showing a clear succession at both sites. Other ciliates were morphologically identified and, in some cases, their occurrence was strongly related to bacterial abundance. The structure of both prokaryotic and eukaryotic components of periphyton was not different, while the turnover dynamics differed between the two sites, in spite of their adjacent locations and similar abiotic properties. This indicates that the establishment of these communities can vary even on a local scale within a lake ecosystem. [ABSTRACT FROM AUTHOR]

In the macrobenthos of Lake Pleshcheyevo and the adjacent river sites, 112 lower definable taxa (LDTs) have been noted. Chironomids and oligochaetes continue to form the main part of the fauna. The greatest species richness and diversity are noted in the sublittoral zone, where the biocenoses of Dreissena polymorpha formed, and in the rivers adjacent to the lake. The appearance and mass development of the zebra mussel has had a significant impact on the benthos and ecosystem of the reservoir. According to the indicator organisms of the zoobenthos, there has been a decrease in the saprobity of the lake. [ABSTRACT FROM AUTHOR]

Microsporidia are a large group of obligate intracellular eukaryotic parasites. Recent studies suggest that their diversity can be huge in freshwater lake ecosystems especially in the < 150-µm size fraction. However, little is known about their hosts and therefore their impact on the trophic food web functioning. In this study, single cell analysis and fluorescence microscopy were used to detect new host-parasite association within rotifer communities in lake Aydat (France). Our analysis showed the existence of a potential new species belonging to the Crispospora genus able of infecting the rotifer Kellicottia with a high prevalence (42.5%) suggesting that Microsporidia could have a great impact on the rotifer populations' regulation in lakes. [ABSTRACT FROM AUTHOR]

Mining areas and in particular those containing massive sulfides have left a heavy environmental legacy with soils and hydrographic networks highly contaminated with metals and metalloids as for example in the Iberian Pyrite Belt (Huelva, Spain). Here, we present new data on copper (Cu) isotopic composition of waters and solids collected along a continuum Mine (Tharsis)—River (Meca)—Lake (Sancho) in the Iberian Pyrite Belt. Our results show that the isotopic signature of pit lakes is spatially variable, but remains stable over the seasons; this signature seems to be controlled by water–rock interaction processes. The data obtained on the Meca River imply a number of attenuation processes such as decrease in the metal concentration by precipitation of secondary minerals. This is accompanied by preferential retention of the heavy isotope (65Cu) with a possibility of living organisms (e.g., algae) participation. The terminal Sancho lake demonstrated constant isotopic signature over the entire depth of the water column despite sizable variations in Cu concentrations, which can be tentatively explained by a superposition of counter-interacting biotic and abiotic processes of Cu fractionation. Overall, the understanding of the isotopic variations along the hydrological continuum is useful for a better understanding of metal element transfer within mining environments and surrounding surface waters. [ABSTRACT FROM AUTHOR]

Zooplankton community could be affected by aquatic environment, land use patterns, and climate factors. However, few studies have evaluated the relative importance of these factors to the zooplankton community succession on a long-term scale. In this study, long-term data were used to analyze the succession characteristics and drivers of zooplankton communities in Honghu Lake, a large-scale shallow lake in central China. Results showed that zooplankton community structure changed greatly in 1959–2021. In general, the species number decreased, abundance and biomass increased, and the number and proportion of pollution tolerant species among dominant species increased during the past ~ 60 years. For the driving factors of zooplankton from 1992 to 2021, redundancy analysis showed that nutrients, wind speed, and aquaculture enclosure and pond were the main drivers of Protozoa and Rotifera, while phytoplankton abundance, wind speed, dissolved oxygen, and farmland were the main drivers of Cladocera and Copepoda. Generalized additive model showed that the aquatic environment had the highest direct explanation (mean is 60.2%) to zooplankton variation, followed by land use (mean is 35.6%) and climate factors (mean is 33.1%). Variance partitioning analysis showed that the effects of human activities (32.9–43.1%) associated with land use, water quality, and phytoplankton on the zooplankton succession are stronger than that of climate factors (19.9–29.2%). Additionally, lake eutrophication is an important factor for the decline in the richness index (p = 0.0017, r = − 0.8411) and Shannon index (p = 0.0301, r = − 0.8020) of zooplankton from 2019 to 2021. Our results highlighted that anthropogenic activity has stronger driving effects on zooplankton succession in the long term than climate changes in the lake. These findings can provide insights into zooplankton conservation in response to global climate change and complex anthropogenic actions. [ABSTRACT FROM AUTHOR]

A cascading rainfall–landslide–tsunami event occurred on June 29th, 2022, in Todos los Santos Lake, located in southern Chile, affecting the tourist town of Petrohué. The event took place after several days of heavy rain during an extratropical cyclone. Important data were collected during a field survey, including hillslope 3D scans, lake–river bathymetry, orthomosaic photos, and an assessment of damage to public infrastructure. The analysis showed that the landslide had an estimated length, width, and depth of 175 m, 40 m, and 1.5 m, respectively, which resulted in a total volume of 10,500 m3. The underwater runout distance of the landslide was estimated at 40 m, with a final water depth of 12 m. The initial tsunami wave was observed to be ~1 m, and since the distance from the landslide to the town was ~500 m, an arrival time of ~1 min was observed. Despite the small tsunami amplitudes, the pedestrian bridge of the floating pontoon collapsed due to the flow current and vertical oscillations. The results of the numerical simulation of the tsunami supported the observed data. They showed that the impact of the tsunami was only in the near field and was influenced by the bathymetry, such that refraction and edge waves were observed. The landslide occurred in an area where previous debris flows took place in 2013 and 2015. The main finding of the present research is that the occurrences of this and previous landslides were controlled by the presence of the Liquiñe–Ofqui fault zone, which generates broad areas of structural damage, with mechanical and chemical weathering significantly reducing rock strength. These observations provide a warning regarding the susceptibility of similar regions to other trigger events such as earthquakes and rainfall. This recent landslide highlights the need for a more comprehensive hazard assessment, for which probabilistic analysis could be focused on large active strike-slip fault systems. It also highlights the importance of community awareness, particularly in areas where tourism and real estate speculation have significantly increased urban development. [ABSTRACT FROM AUTHOR]

The world's largest lakes, including the Laurentian Great Lakes, have experienced significant surface warming and loss of ice cover over the last several decades. Although changing surface conditions have received substantial research interest, changes below the surface remain largely unexplored, despite their importance for turbulent mixing, nutrient cycling, and primary production. In this study, we investigate changes in subsurface thermal structure and timing in Lake Michigan-Huron related to ongoing climate warming. This work utilizes atmospheric reanalysis data to drive the Great Lakes Finite Volume Community Ocean Model (GL-FVCOM), providing three-dimensional hydrodynamic and ice simulations between 1979 and 2021. Results are used to analyze trends in ice and temperature dynamics, revealing significant changes in annually averaged ice cover (− 2.1– − 5.2%/decade), ice thickness (− 0.68 – − 2.0 cm/decade), surface temperature (+ 0.47– + 0.51 ∘ C /decade), and bottom temperature (+ 0.26– + 0.29 ∘ C /decade) over the last 40 years, especially in ecologically important bays (e.g., Green Bay, Saginaw Bay). Significant warming was observed at all depth layers (0–270 m), with warming trends in the epilimnion and hypolimnion that agreed well with recent analysis of observational data in Lake Michigan. Shifting stratification dynamics led to dramatic changes in modelled overturning behavior, and earlier spring turnover dates (− 2.2– − 7.5 days/decade) and later fall turnover dates (+ 2.5– + 6.3 days/decade) led to a net lengthening of the stratified period. This study presents one of the most comprehensive analyses of changes in Great Lakes subsurface temperatures to date, providing important context for future climate modelling and coastal management efforts in the region. [ABSTRACT FROM AUTHOR]

We estimated chlorophyll-a (Chl-a) concentration using various combinations of routine sampling, automatic station measurements, and MERIS satellite images. Our study site was the northern part of the large, shallow, mesotrophic Lake Pyhäjärvi located in southwestern Finland. Various combinations of measurements were interpolated spatiotemporally using a data fusion system (DFS) based on an ensemble Kalman filter and smoother algorithms. The estimated concentrations together with corresponding 68% confidence intervals are presented as time series at routine sampling and automated stations, as maps and as mean values over the EU Water Framework Directive monitoring period, to evaluate the efficiency of various monitoring methods. The mean Chl-a calculated with DFS in June–September was 6.5–7.5 µg/l, depending on the observations used as input. At the routine monitoring station where grab samples were used, the average uncertainty (standard deviation, SD) decreased from 2.7 to 1.6 µg/l when EO data were also included in the estimation. At the automatic station, located 0.9 km from the routine monitoring site, the SD was 0.7 µg/l. The SD of spatial mean concentration decreased from 6.7 to 2.9 µg/l when satellite observations were included in June–September, in addition to in situ monitoring data. This demonstrates the high value of the information derived from satellite observations. The conclusion is that the confidence of Chl-a monitoring could be increased by deploying spatially extensive measurements in the form of satellite imaging or transects conducted with flow-through sensors installed on a boat and spatiotemporal interpolation of the multisource data. [ABSTRACT FROM AUTHOR]

As an emerging pollutant, microplastics have attracted widespread concern around the world. Research on microplastics was first conducted in oceans, and in recent years, inland water, especially lakes, has gradually become a hot spot. This paper systematically reviews the sampling, separation, purification, and identification technologies used to assess microplastics in lakes and summarizes the occurrence of lake microplastics worldwide. The results show that microplastics are widespread in lake water and sediment. There are obvious geographical differences in the occurrence of microplastics. The abundance of microplastics in different lakes varies greatly. The forms are mostly fibrous and fragments, and the main polymers are polypropylene (PP) and polyethylene (PE). Previous papers have failed to comment in as much detail on the microplastic sampling techniques employed within lake systems. The sampling and analysis methods are critical to accurately evaluating contamination results. Due to the widespread presence of microplastics and the lack of uniform standards, there are various sampling methods. Trawls and grabs are most widely used in the sampling of lake water bodies and sediment, and sodium chloride and hydrogen peroxide are the most widely used media for flotation and digestion, respectively. In the future, it will be critical to establish unified standards for lake microplastic sampling and analysis technology, further explore the migration mechanism of microplastics in lake systems, and pay attention to the impact of microplastics on lake ecosystems. [ABSTRACT FROM AUTHOR]

The spatial and seasonal distribution of heterotrophic bacterioplankton has been studied in Lake Pleshcheyevo. Over the past 30 years, the abundance of microorganisms has increased threefold. The maximum values have been recorded at littoral stations. The main part of bacterial production is also produced there. Trophic levels have increased, but the ecosystem of the lake withstands the increased load. [ABSTRACT FROM AUTHOR]

Anguillid eels are near globally distributed catadromous fishes with marine spawning areas and inshore and inland growth areas in both lotic (rivers, estuaries) and lentic (lakes, ponds, lagoons) water bodies. As predators, anguillid eels play an important ecological role in both marine and freshwater systems, and several species are harvested commercially for food. However, some of the more widely distributed species have undergone severe declines in recruitment and their population status is now of significant concern. Given the multiple and lengthy migrations undertaken by anguillid eels, understanding of the drivers of movement is fundamental for species conservation and management. Yet, despite the importance of lentic systems to their ecology, most studies on anguillid eel movement have been conducted in lotic systems. Given that key influences on eel migration in lotic water bodies, such as fluctuations in flow and water temperature, may be minimised in lentic environments, the transferability of findings between lotic and lentic systems cannot be assumed. A systematic map was constructed to synthesise current knowledge on the extrinsic and intrinsic drivers of anguillid eel movement in lentic systems. The current state of knowledge of the drivers of eel movement in lentic systems is presented and compared to the relatively well-understood drivers of movement in lotic systems. We also discuss current knowledge gaps and limitations, and identify key future research requirements to inform the management and conservation of anguillid eels in understudied lentic systems. [ABSTRACT FROM AUTHOR]

For decades, diatoms have been recognized as powerful bio-indicators of modern water quality. They have also been utilized in the design of transfer functions, which can be applied to diatom assemblages in lake sediment cores to infer aspects of past lake hydrochemistry and estimate variables that can be incorporated into paleohydrology models. The Ounianga lakes, in the heart of the Chadian Sahara, possess unique and well-preserved sediment records that extend back beyond the middle Holocene. Today, the lakes display a range of hydrochemical conditions, from fresh to hypersaline. Mainly fed by fossil groundwater that originates in the Nubian Sandstone Aquifer System, measured conductivity across these lakes varies from 217 to 352,000 µS cm−1, values that are influenced by factors such as hydrology, local geomorphology (e.g., depth and area), and aquatic vegetation. Although these lakes have been on the UNESCO World Heritage List since 2012, they have never been studied in detail because they are located on the fringes of the Chadian Sahara. The distribution of diatom taxa in the lakes today is closely linked to water-column physical and chemical conditions, especially conductivity. Whereas each lake has particular features that influence its diatom flora, diatoms across a conductivity gradient enabled identification of three distinct waterbody types, freshwater lakes, meso-saline to hyper-saline lakes, and freshwater springs. Relationships between diatom species distributions and environmental variables were examined using multivariate analysis, which revealed that conductivity is the variable that explains most of the variance in the diatom flora. We used modern diatom assemblages from the lakes to develop a predictive model (transfer function) for conductivity, using the weighted averaging method. Our conductivity prediction model is strong, with a coefficient of determination (R2) of 0.89 between estimated and measured values, and a value of 0.78 using jackknife estimates of prediction. This study better constrained conductivity optima and tolerance values for diatom species found in the Ounianga lakes, thereby enabling development of a model that will yield better inferences for past conductivity, using diatoms from lake sediment records in the region. [ABSTRACT FROM AUTHOR]

The rapid development of modern society has resulted in discharge of large, heavy metal quantities into wetlands that have been continuously accumulating, causing severe pollution. Dajiuhu, located in the Shennongjia Forest District of Hubei Province in China, is a wetland of significant value internationally, serving as a model wetland ecosystem with heightened scientific research value. In this study, 27 surface sediment samples from nine sub-lakes in Dajiuhu were collected in August 2020. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the sediments were determined. The heavy metal occurrence and speciation characteristics were analyzed by an improved BCR (European Community Bureau of Reference) extraction method. Four methods were used to evaluate heavy metals' pollution degree and ecological risk. The possible source of heavy metals was inferred using correlation analysis and principal component analysis. The heavy metal content in the lake sediments of Dajiuhu wetland was from the highest to the lowest concentration as follows: Zn > Cr > Ni > Pb > Cu > Cd. The average Cd content exceeded the national nature reserve threshold values, while the other heavy metals measured were below their respective threshold values. However, due to the occurrence of Pb and Cd in different forms, they still pose certain pollution and ecological risk to the lake wetlands. On the other hand, Zn, Cr, Ni, and Cu do not pose an ecological risk in the lakes of the Dajiuhu wetland. The spatial distribution of heavy metal content in the nine sub-lakes did vary significantly. Regarding the heavy metal sources in the lake sediments, Ni, Cr, and Cu originate from natural factors, and Cd and Pb have mainly anthropogenic origins. In contrast, Zn has both natural and anthropogenic origins. This study provides further insights into the study of heavy metal pollution in lake wetlands. It provides a framework and a direction for managing heavy metal pollution in the Dajiuhu wetland. [ABSTRACT FROM AUTHOR]

Lakes can be monitored using benthic diatoms as proposed by Water Framework Directive. In recent years, in addition to the indices developed for rivers, the indices developed for lakes have been also used. The relationship between environmental parameters and diatom assemblages was investigated monthly to understand temporal and spatial changes in diatom community structure, and to specify the ecological status of the three lakes between May 2015 and April 2016. Based on the Redundancy Analysis (RDA) result, main environmental parameters (orthophosphate, total phosphorus, specific conductance, soluble silica, water transparency, nitrate-nitrogen, and pH) strongly affected the temporal and spatial distribution of diatom assemblages. Shannon diversity index, evenness, and species richness were measured, however, they were not effective in explaining the water quality. The ecological status assessment of the lakes was also performed by using Trophic Index Turkey (TIT), Trophic Diatom Index for Lakes (TDIL), and Specific Pollution Sensitivity Index (IPS). Based on the results of three indices, TIT gave more consistent results with environmental parameters and indicator species and is more sensitive to changes in the trophic status of lakes over time. According to TIT, Lake Little Akgöl had a poor ecological condition, while the water qualities of Lake Taşkısığı and Lake Poyrazlar were determined as moderate. Due to the sensitivity of the changes in the diatom community structure with the effect of environmental parameters during one year, TIT is an effective tool to assist in the ecological assessment of three natural lakes within the borders of Sakarya province in the north of Turkey. [ABSTRACT FROM AUTHOR]

Changes to water conditions due to eutrophication and climate change have resulted in the proliferation of algae blooms in freshwater and marine environments globally, including in Canadian lakes. We developed and administered an online survey to evaluate the awareness of these blooms and the perceptions of health risks in a sample of New Brunswick waterfront cottage and homeowners. The survey was distributed to lake and cottage associations in New Brunswick and was completed by 186 eligible respondents (18 years of age or older). Participants were asked about the water quality of their lake, awareness about algae blooms, sociodemographic and cottage characteristics, and to complete a self-rated measure of physical and mental health. While approximately 73% of participants reported that the quality of their lake water was good or very good, 41% indicated a concern about algae blooms. We found no differences in self-reported physical or mental health between those who were aware of algae blooms at their cottage and those who were not (p > 0.05). Participants expressed concerns about the impacts of algae blooms on the health of their pets, and wildlife. While climate change was the most frequently identified cause of algae blooms, there was substantial heterogeneity in the responses. In addition, the reporting of the presence and frequency of algae bloom varied between respondents who lived on the same lake. Taken together, the findings from our survey suggest that cottage owners in New Brunswick are aware and concerned about the impacts of algae blooms, however, there is a need to provide additional information to them about the occurrence and causes of these blooms. [ABSTRACT FROM AUTHOR]

Caohai Lake is a typical natural lake-type karst plateau wetland, which is sensitive to environmental changes, and the release of dissolved organic nitrogen (DON) in sediment is a potential factor of nitrogen pollution in this lake. Therefore, we aimed to reveal the temporal and spatial distribution characteristics and source analysis of DON in karst lake sediment. Surface sediment samples were collected from Caohai Lake in southwest China, and the sample locations were distributed across almost the entire wetland area, during both the wet and dry seasons. The DON content and fluorescence spectroscopy were determined and analysed using a three-dimensional fluorescence-parallel factor analysis (3DEEM-PARAFAC) model. The mean DON content in the sediment during the dry season (67.79 ± 42.96 mg/kg) was higher than that in the wet season (28.57 ± 20.97 mg/kg). There were four fluorescent components of DON in the sediment: C1 (tyrosine-like protein), C2 (terrestrial humus), C3 (tryptophan-like protein) and C4 (terrestrial humus). The DON in the surface sediment of Caohai Lake was influenced by terrestrial sources and biological activities. These findings help reveal the circulation mechanism of endogenous nitrogen in the lake and provide theoretical support for the prevention and control of nitrogen pollution in Caohai Lake. [ABSTRACT FROM AUTHOR]

In the present study, the cadmium, lead, and zinc levels in the blood and shell of Caspian pond turtles (Mauremys caspica) were investigated at five stations in Zarivar International Wetland in Kurdistan Province. All specimens were released at their capture locations within 2 h of capture. Water samples were collected at each station. Heavy metal concentrations were determined using an atomic absorption spectrometer. The mean cadmium, lead, and zinc concentrations were 0.04, 32.10, and 11.45 mg/l in blood samples; 1.82, 16.91, and 89.22 mg/l in shell samples; 0.005, 1.30, and 0.07 mg/l in water samples, respectively. In this study, the highest metal adsorption was zinc and was observed in shell. According to the results of this study, the shell of the Caspian Pond Turtle can be used to estimate the concentration of heavy metals. Our results suggest that Caspian pond turtle can be used as a biological indicator to estimate heavy metals. [ABSTRACT FROM AUTHOR]

Nutrient inputs to northern freshwaters are changing, potentially altering aquatic ecosystem functioning through effects on primary producers. Yet, while primary producer growth is sensitive to nutrient supply, it is also constrained by a suite of other factors, including light and temperature, which may play varying roles across stream and lake habitats. Here, we use bioassay results from 89 lakes and streams spanning northern boreal to Arctic Sweden to test for differences in nutrient limitation status of algal biomass along gradients in colored dissolved organic carbon (DOC), water temperature, and nutrient concentrations, and to ask whether there are distinct patterns and drivers between habitats. Single nitrogen (N) limitation or primary N-limitation with secondary phosphorus (P) limitation of algal biomass was the most common condition for streams and lakes. Average response to N-addition was a doubling in biomass; however, the degree of limitation was modulated by the distinct physical and chemical conditions in lakes versus streams and across boreal to Arctic regions. Overall, algal responses to N-addition were strongest at sites with low background concentrations of dissolved inorganic N. Low temperatures constrained biomass responses to added nutrients in lakes but had weaker effects on responses in streams. Further, DOC mediated the response of algal biomass to nutrient addition differently among lakes and streams. Stream responses were dampened at higher DOC, whereas lake responses to nutrient addition increased from low to moderate DOC but were depressed at high DOC. Our results suggest that future changes in nutrient availability, particularly N, will exert strong effects on the trophic state of northern freshwaters. However, we highlight important differences in the physical and chemical factors that shape algal responses to nutrient availability in different parts of aquatic networks, which will ultimately affect the integrated response of northern aquatic systems to ongoing environmental changes. [ABSTRACT FROM AUTHOR]