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The importance of satellite altimetry for monitoring inland water bodies is increasing, with the increasing need for fresh water. With the addition of the Sentinel-6 Michael Freilich (MF) in 2020 to the satellite altimetry record, we have parallel high- and low-resolution inland water observations. In this study, we validate Sentinel-6MF low- and high-resolution lake water levels, as determined with a state-space model, with data from 124 gauges in 85 lakes (of size > 20 km2) from the United States, Canada, Sweden, and Australia. Furthermore, we estimate the scatter of the observations at 1330 globally distributed lakes. We address the difference in performance when using a physical (ocean) and empirical (OCOG) retracker. Using the 124 gauges as ground truth, we determine a best-case unbiased root mean squared error (u-RMSE) of 6.4 cm for Sentinel-6MF, when using the high-resolution mode and the OCOG retracker. The u-RMSE is between 6.4 and 12.3 cm when correcting for ice-covered lakes, and 15.6 to 31.3 cm for all data, depending on retracker and resolution mode. The corresponding median standard deviation of water surface elevations per transect from the 1330 lakes is 3.5 cm and 8.1 cm for high and low-resolution OCOG-based water levels, respectively. The corresponding median standard deviation of Sentinel-3A/B OCOG (enhanced measurement, 20 Hz mode, baseline-3/4) is 5.9 cm and 6.0 cm. We find a lower u-RMSE and standard deviation for high-resolution data, and the ability to observe more lakes, compared to the low-resolution mode. From this, we see that Sentinel-6MF yields valid estimates of the water surface elevation, including smaller lakes, and would provide additional value to future water level monitoring via remote sensing. [ABSTRACT FROM AUTHOR]

El'gygytgyn is the only ancient lake in the Arctic that avoided continental-scale glaciations. This lake is located on an arid mountain plateau, far from the main routes of post-glacial freshwater fish dispersal, and it is therefore challenging to consider the local fauna in a historical context. Here we present a study of the ecology and evolutionary history of the local charr complex (genus Salvelinus). We found that the endemic charrs exhibit extreme longevity, contrasting lifestyles and phenotypes. Salvelinus svetovidovi is a relic benthivorous species. The remaining charrs are descendants of Salvelinus taranetzi. Mitochondrial and microsatellite DNA polymorphisms analyzed in them and in charrs from surrounding basins indicate that S. taranetzi invaded the lake from Arctic Chukotka in the late Pleistocene as two distinct, previously diverged lineages. Descendants of both lineages occupied the pelagic food chain. The first lineage has flourished as a monomorphic planktivorous population since colonization. The second represents an example of a recent in-lake adaptive divergence, in which a deepwater piscivore specialist formed a new epilimnetic ecomorph of an impressive size (up to 9.0 kg). We suggest that this diversification was triggered by modern warming in the Arctic, which led to the formation of a productive littoral ecosystem. [ABSTRACT FROM AUTHOR]

The present study provides new insight into the key aspects of the early formative period of the ecosystem concept in aquatic ecology. Raymond Lindeman's trophodynamics is known to be a starting point for the development of the modern concept of ecosystem. The trophodynamic approach in ecology was proposed by Lindeman in his widely cited paper of 1942. Lindeman's views are analyzed in comparison with the contemporary production studies in aquatic ecology. It is shown that a similar theoretical system has been proposed in the USSR at the end of the 1930s by Georgiy G. Vinberg. He introduced the concept of biotic balance based on the wide appraisal of the dark and light bottles method. The study shows that both Lindeman's trophodynamics and Vinberg's concept of biotic balance relied on an energy-based approach in considering the wholeness of a water body. The two scientists, however, differed in several important aspects concerning the interpretation of the role of living organisms. The holistic interpretation of ecosystem by Lindeman and Vinberg can be seen as part of the dilemma between physicalism and organicism. At the same time, the main emphasis in the concepts of both Vinberg and Lindemann was on the primary production component, a feature that was common to the first holistic systems in production hydrobiology (e.g., E. Naumann's regional limnology). It is clear that modern problems of aquatic ecology should be addressed from the perspective of the organismocentric understanding of the ecosystem, but undoubtedly at the new level of development of this view. [ABSTRACT FROM AUTHOR]

In Büyük Akgöl, one of the most important lakes of Sakarya province in the Marmara region of Turkey, water and benthic sampling was carried out from five stations representing the lake seasonally between 2009 and 2010. As a result of the study, a total of 8736 individuals were collected from lake and that was a total of 24 species belonging to 36 taxa were identified. The benthic fauna community structure of the lake was classified with Turkish Biological Monitoring Working Party, Average Score Per-Taxon and Pielou's Evenness, Shannon–Wiener. According to the TR-BMWP scores were in the IV and the III class while the ASPT analysis was classified as moderate, and was as very poor. J' values ranged between 0.62 and 0.73, and H' values ranged from 1.74 to 2.14. The water quality parameters of the lake were classified as "unsuitable" by WQI and as "very polluted" according to HEI whereas the SAR, Na, and NPI were classified as 'excellent, good and no pollution.' According to the classification of water pollution control regulation it was showed 1st, 2nd and 3rd quality water characteristic. Pb, Hg, Al, Se, Cd concentrations and turbidity were exceeded the limit values set by WHO. [ABSTRACT FROM AUTHOR]

This study investigated the level of dissolved heavy metals in the water of Longhu Lake and focused on the speciation, mobility, and risks of heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb) in sediment. The levels of heavy metals in the water were found to be below the thresholds set by the Chinese safe drinking water standard. The highest average percentages of Cr, Ni, Zn, and As were bound with residual fractions, while Pb and Cu were bound with reducible fractions. Additionally, the highest percentage of Cd and Mn was bound to the acid-soluble fraction in the sediment. These findings suggest that Cd, Mn, Pb, and Cu likely originated from anthropogenic sources in the lake. There was a strong correlation between total organic carbon (TOC) and metal fractions in the sediment, indicating that TOC may play a role in transporting heavy metal fractions. Risk assessment code values for Cd and Mn indicated higher risks and mobility, while Ni, Cu, and Zn showed medium risks and mobility for aquatic biota. To mitigate heavy metal contamination, it is recommended to improve monitoring and regulation of urban runoff and inlet areas. [ABSTRACT FROM AUTHOR]

Lake Tennyson's basin and sedimentary record were assessed for multiple branches of paleoenvironmental research. A geophysical investigation of the lake depositional setting was supported by physical and chemical analysis of multiple sediment cores. The basin reaches 60 m depth and several subaerial landforms identified were likely deposited from seismic activity. Deformed sediments and turbidites in gravity cores are attributed to one or more large (pre)historic earthquakes, and episodic grain size changes in sediment cores are related to either seismic and/or climatic/meteorological processes. A hummocky slump deposit located on the western lake bed margin is linked to widespread sediment deformation that was likely caused by movement of the Awatere Fault. Radiocarbon dating constrains the most recent major deformation event between the late thirteenth century CE and mid-twentieth Century. Folded turbidites in the stratigraphy suggest multiple sedimentary deformation episodes occurred during the last millennium. Micro-XRF elemental signatures suggest proxies of past water column mixing (windiness proxy) can be reconstructed via identification of changing redox conditions. Records from Lake Tennyson show potential for several palaeoenvironmental research applications, and combining them with basin morphostratigraphy and land-based palaeoclimate and palaeoseismic evidence can enhance understanding of environmental change in the northern South Island. [ABSTRACT FROM AUTHOR]

The sources of thermophilic bacteria revealed in cold Lake Baikal sediments are considered. Comparative analysis of the taxonomic position of thermophilic microorganisms from four terrestrial hot springs at Lake Baikal coast and from the bottom sediments associated with hydrocarbon discharge was carried out. The sequences of thermophilic microorganisms with the same taxonomic position were revealed both in the hot springs and bottom sediments. Some microbial species occurred only in the hydrotherm samples or only in those from the sediments. Gas-saturated fluids from the hydrocarbon generation zone at the depth of 4‒6 km are the most probable source of thermophilic microorganisms in the bottom sediments. [ABSTRACT FROM AUTHOR]

The relic Lake Mogilnoe, separated from the Barents Sea by a sand and pebble dam, is located in the high Arctic on the Kildin island (Murmansk region). This lake is a classic example of a meromictic basin of marine origin. The data obtained during the 2018 expedition showed changes in the hydrochemical regime of the lake that have occurred over the past 20 years. Sulfide concentration in the monimolimnion of the lake was as high as 140 mg/L. A tendency for salinization of the surface waters to 7 g/L has been noted. The Lake Mogilnoe is characterized by a discrepancy between the halocline and thermocline levels. The chemocline zone in the lake is below the halocline level. In a narrow oxygen-containing layer between 3 and 7.5 m, aerobic microflora of the marine type and marine fauna were present. The bacterial plate was formed at the boundary of the sulfide layer at ~8 m and mainly consisted of green sulfur bacteria (GSB). Brown-colored GSB species containing bacteriochlorophyll e were predominant. The previously formed concept of anaerobic phototrophic bacteria (APB) biodiversity based on morphological characteristics was modified using metagenomic data obtained by analyzing DNA from two samples of lake water in the chemocline zone, and was also supplemented by identifying new GSB species. Molecular diagnostic data confirmed the absolute dominance of the brackish species of GSB Chlorobium phaeovibrioides. This is the first isolation and identification of brown- and green-colored Prosthecochloris aestuarii morphotypes from Lake Mogilnoe, as well as of bacteriochlorophyll c-containing Prosthecochloris sp. The taxonomic position of Pelodyction phaem, which was constantly present in the Lake Mogilnoe, is discussed in detail. Despite the partial isolation of the ecosystem of Lake Mogilnoe from the Barents Sea, the main properties of the dominant GSB species and Prosthecochlori aestuarii turned out to be similar to those of the phylotypes living in lakes on the White Sea coast. [ABSTRACT FROM AUTHOR]

Tajikistan is an area characterized by several lakes created after rockfalls and moraine deposits collapsed due to its geographic position on the collisional area of the Euro-Asian and Indian tectonic plates. In 1911, a violent earthquake generated the Usoi dam, which led to the creation of Lake Sarez. The purpose of the article is to provide an overview of the ground deformation of the two landslides that affect and threaten the area of Lake Sarez exploiting the combination of two different techniques, the interferometric synthetic aperture radar (InSAR) method with the SqueeSAR approach and optical image analysis through the use of COSI-Corr software. The combination of these two techniques turned out to be useful and provide more information because InSAR method balances lack the optical analysis and vice versa giving the possibility to obtain a complete overview of the displacement of the area. Moreover, InSAR data have been used to reconstruct the geometry and depth of the sliding surface of a potential landslide that could affect the lake, generating a wave that could overtop the dam and affect the villages downstream. [ABSTRACT FROM AUTHOR]

Coregonus populations across their Holarctic range have often undergone unexplained collapses. Here, we document causes of collapse for two of the largest Coregonus populations in the world, cisco (C. artedi) in Green Bay, Lake Michigan, and Saginaw Bay, Lake Huron, during the 1950s. We used simulation models, rank‐order correlations, and historical literature to evaluate effects of overfishing, interactions with introduced rainbow smelt (Osmerus mordax), and overwinter bottom hypoxia on both cisco populations. Fully selected exploitation rates for cisco were alarmingly high (0.82–0.84), correlations and anecdotal evidence suggested negative interactions with rainbow smelt, and extensive areas of hypoxia coincident with cisco declines suggested incubation of cisco embryos was impaired regionally. Our findings suggested that negative effects of rainbow smelt were mainly responsible for the cisco population collapse in Green Bay and that overfishing and hypoxia had suppressed the Saginaw Bay cisco population before rainbow smelt caused its final collapse. [ABSTRACT FROM AUTHOR]

Non-native species have invaded most ecosystems and methods are needed to manage them, especially in locations with sensitive species where they cannot be easily extirpated. Gillnetting for invasive lake trout [Salvelinus namaycush (Walbaum, 1792)] in Yellowstone Lake, Yellowstone National Park, USA began in 1995 and their carcasses are deposited into deep areas. This suppression method was recently supplemented by adding carcasses to shallow (< 20 m) spawning sites during the autumn spawning period to decrease dissolved oxygen through decomposition, suffocating lake trout embryos. We measured ammonium concentrations (shallow and deep sites), algal biomass, and ammonium uptake by phytoplankton and periphyton (shallow sites only) to investigate the degree to which carcasses caused bottom-up effects. Ammonium concentrations increased in autumn and were higher at deep sites than shallow sites. Algal biomass and ammonium uptake did not increase after adding carcasses, suggesting minimal effects. Periphyton biomass was 9 times higher than phytoplankton, but phytoplankton demanded 4.5 times more ammonium. Returning lake trout carcasses to deep areas of the lake may cause a second algal bloom. Assessing how novel management techniques alter the environment helps managers develop the most successful mitigation strategies that are effective without causing adverse effects to other portions of the ecosystem. [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]

Trophic polymorphism and temporal reproductive isolation are the drivers of sympatric differentiation in many fish taxa. We present a new case of ecologically based diversification of Arctic charr in a Transbaikalian mountain lake inhabited by reproductively isolated dwarf and normal forms. These forms differ in size, diets and morphology and breed, respectively, in April–May and in September–October representing a rare example of sympatric spring- and autumn-spawning charr pair. Microsatellite analysis reveals clear-cut genetic differences and low-level hybridization between them. Dwarf form charr are planktivorous and manifest uniform slow growth. Normal form charr, though genetically homogeneous, are highly heterogeneous in size-at-age. They are subdivided into omnivorous small-size and piscivorous large-size groups, which can be considered as incipient forms at an early divergence stage. As evidenced by back-calculated growth data, their size-at-age heterogeneity results from highly variable individual growth patterns, which include different combinations of slow and fast growth periods presumably associated with spawning and non-spawning years. Growth acceleration in late ontogeny may result in the transformation of some normal charr from the smaller into the larger group during their lifetime. [ABSTRACT FROM AUTHOR]

Nematodes disperse passively and are amongst the smallest invertebrates on Earth. Free-living nematodes in mountain lakes are highly tolerant of environmental variations and are thus excellent model organisms in dispersal studies, since species-environment relationships are unlikely to interfere. In this study, we investigated how population or organism traits influence the stochastic physical nature of passive dispersal in a topologically complex environment. Specifically, we analyzed the influence of female proportion and body size on the geographical distribution of nematode species in the mountain lakes of the Pyrenees. We hypothesized that dispersal is facilitated by (i) a smaller body size, which would increase the rate of wind transport, and (ii) a higher female proportion within a population, which could increase colonization success because many nematode species are capable of parthenogenetic reproduction. The results showed that nematode species with a low proportion of females tend to have clustered spatial distributions that are not associated with patchy environmental conditions, suggesting greater barriers to dispersal. When all species were pooled, the overall proportion of females tended to increase at the highest elevations, where dispersal between lakes is arguably more difficult. The influence of body size was barely relevant for nematode distributions. Our study highlights the relevance of female proportion as a mechanism that enhances the dispersal success of parthenogenetic species, and that female sex is a determining factor in metacommunity connectivity. [ABSTRACT FROM AUTHOR]

Constructed from a dataset capturing the seasonal and annual water body distribution of the lower Qarqan River in the Taitma Lake area from 2017 to 2022, and combined with the meteorological and hydraulic engineering data, the spatial and temporal change patterns of the Taitma Lake watershed area were determined. Analyses were conducted using Planetscope (PS) satellite images and a deep learning model. The results revealed the following: ① Deep learning-based water body extraction provides significantly greater accuracy than the conventional water body index approach. With an impressive accuracy of up to 96.0%, UPerNet was found to provide the most effective extraction results among the three convolutional neural networks (U-Net, DeeplabV3+, and UPerNet) used for semantic segmentation; ② Between 2017 and 2022, Taitma Lake's water area experienced a rapid decrease, with the distribution of water predominantly shifting towards the east–west direction more than the north–south. The shifts between 2017 and 2020 and between 2020 and 2022 were clearly discernible, with the latter stage (2020–2022) being more significant than the former (2017–2020); ③ According to observations, Taitma Lake's changing water area has been primarily influenced by human activity over the last six years. Based on the research findings of this paper, it was observed that this study provides a valuable scientific basis for water resource allocation aiming to balance the development of water resources in the middle and upper reaches of the Tarim and Qarqan Rivers, as well as for the ecological protection of the downstream Taitma Lake. [ABSTRACT FROM AUTHOR]

This work aims to show the potential of imaging spectroscopy in assessing water quality and aquatic vegetation in Lake Trasimeno, Italy. Hyperspectral reflectance data from the PRISMA, DESIS and EnMAP missions (2019–2022, summer periods) were compared with in situ measurements from WISPStation and used as inputs for water quality product generation algorithms. The bio-optical model BOMBER was run to simultaneously retrieve water quality parameters (Chlorophyll-a (Chl-a) and Total Suspended Matter, (TSM)) and the coverage of submerged and emergent macrophytes (SM, EM); value-added products, such as Phycocyanin concentration maps, were generated through a machine learning approach. The results showed radiometric agreement between satellite and in situ data, with R2 > 0.9, a Spectral Angle < 10° and water quality mapping errors < 30%. Both SM and EM coverage varied significantly from 2019 (135 ha, 0 ha, respectively) to 2022 (2672 ha, 343 ha), likely influenced by changes in rainfall and lake levels. The areas of greatest variability in Chl-a and TSM were identified in the littoral zones in the western side of the lake, while the highest variation in the fractional cover of SM and density of EM were observed in the south-eastern region; this information could support the water authorities' monitoring activities. To this end, further developments to improve the reference field data for the validation of water quality products are recommended. [ABSTRACT FROM AUTHOR]

For the lack of historical water ecology monitoring data and the limitations of traditional morphology-based water ecology reconstruction methods, the response mechanism of lake phytoplankton to climate change in the Tibetan Plateau remains unclear. In this study, we reconstructed the succession of phytoplankton community in Lake Gyaring, located in the northeastern Tibetan Plateau, since the 6th century by using sediment DNA metabarcoding. We found that the diversity and structure succession stages of phytoplankton community were consistent with the global temperature oscillation events, namely, the Medieval Warm Period (800–1300 CE). Little Ice Age (1300–1850 CE) and Current Warm Period (1850–2000 CE). The community structure dominated by Chlorophyta in the Medieval Warm Period gradually changed to that dominated by Bacillariophyta in the Little Ice Age. However, the Current Warm Period did not observe the dominant community structure of Chlorophyta similar to that of the Medieval Warm Period. This finding may be due to the climate change of the Current Warm Period was influenced by multiple human activities, such as increased anthropogenic aerosols, which promoted obvious weakening of the intensity of the summer monsoon, leading to decreased soil erosion and lake mixing, and thus may trigger a strikingly different aquatic ecosystem compared to that during the Medieval Warm Period. In this paper, the combination of genomics and palaeollimnology is helpful to explore the response mechanism of phytoplankton to climate change. [Display omitted] [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms have a strong impact on the food web structure, interactions and ecosystem functioning. The aim of this study was to describe the seasonal changes in composition and abundance of heterotrophic nanoflagellates, ciliates, rotifers, and crustaceans in relation to algae and nutrients in a shallow eutrophic lake (north-eastern Poland) dominated by cyanobacteria and exposed to the strong impact of cormorants. Our results showed that algae accounted for a small part of the total phytoplankton abundance (9–40%) and biomass (10–21%) and were dominated by diatoms and cryptophytes. All of the studied groups of planktonic organisms were quite rich in species (95 algal, 79 ciliate, 44 rotifer and 25 crustacean species) and relatively abundant. Copepods formed a substantial part (45–83%) of the total zooplankton biomass during all seasons. Relatively low algal to zooplankton biomass ratio (0.8–1.1) suggests that during spring, summer, and winter algae were not sufficient food resources for metazooplankton, which supplemented its diet with protists (heterotrophic nanoflagellates and ciliates). In a shallow lake dominated by cyanobacteria, winter (ice-covered period) may be a more favourable period for the growth of some groups of algae, ciliates and rotifers than other seasons due to decreasing abundance of cyanobacteria. [ABSTRACT FROM AUTHOR]

Understanding how metacommunity organization is structured in space and time is a long-standing challenge in community ecology. We aimed to explore the spatiotemporal beta diversity of macroinvertebrate metacommunities and their underlying drivers in two contrasting freshwater systems: streams and a lake. We observed that spatial beta diversity was higher than temporal beta diversity in both systems. Generalized dissimilarity modeling and dispersal-niche continuum index analyses suggested that this is probably because (i) environmental filtering was stronger in space than in time at least in streams, and (ii) dispersal was stronger in time than in space. The relative importance of spatial and seasonal drivers on metacommunity structures was notably different between stream and lake systems, as they have fundamentally different spatiotemporal structure of abiotic (i.e. environmental and hydrological) and biotic (i.e. aquatic insect diversities and life strategies) conditions. Our results shed light on spatiotemporal patterns in lake and stream metacommunities and may be useful for the management of freshwater ecosystems undergoing environmental changes. [ABSTRACT FROM AUTHOR]

The East African soda lakes are known worldwide for their huge populations of lesser flamingos. Their phytoplankton community is often dominated by the cyanobacterium Limnospira fusiformis, the main food of lesser flamingos. In the early 2010s, the population of the cyanobacterium collapsed and the picoplanktic green alga Picocystis salinarum became dominant in Lake Nakuru. Consequently, lesser flamingos had to migrate to other lakes in search of food. To establish the reasons for the success of P. salinarum, photosynthesis measurements have been performed on monoalgal cultures of both species. The examined environmental variables (temperature, light intensity) were not responsible for the dominance of P. salinarum either alone or in their any combination. Moreover, photosynthetic activity of the cyanobacterium was higher by an order of magnitude during all light and temperature treatments. Co-cultivation of L. fusiformis and P. salinarum in a chemostat revealed that a possible reason for the Limnospira replacement can be a rapid and remarkable increase of conductivity, as P. salinarum showed higher level of tolerance to this rapid change. Shortly after returning to the initial conductivity levels, the population of L. fusiformis recovered quickly. [ABSTRACT FROM AUTHOR]

The development of anthropic activities during recent years has led to an increase in nutrient fluxes in the Río Grande de Comitán and Montebello Lakes National Park, Mexico. In turn, this has modified the dynamics of the biotic community, specifically favoring the presence of cyanobacteria tolerant to contamination. The continual and massive presence of Planktothrix species (spp.) in the system suggests a potential detrimental impact for economic issues and human health. In this study, we identify the morphological and molecular characteristics of Planktothrix populations from seven tropical (1,380–1,740 masl, 23.0–25.5°C) and calcareous lakes and two ponds from a water treatment plant. We also assess the ecological drivers that could be related to the presence of cyanotoxins in the system. The ecological preferences, morphology, 16S rRNA structure, and 16S-23S rRNA internal transcribed spacer found evidence for three species: P. agardhii distributed in neutral to slightly basic water (pH = 7.7–8.7), and P. spiroides and Planktothrix sp. in alkaline waters (pH = 9.1). The presence of the mcyE gene and its validation by liquid chromatography confirmed the presence of two microcystin variants (MC-RR and MC-LR) in at least three populations of P. agardhii. These microcystins put the health of the ecosystem and its inhabitants at risk, a condition that should be addressed and resolved with a water management and detoxification strategy in the basin. [ABSTRACT FROM AUTHOR]

It is necessary to predict the critical transition of lake ecosystems due to their abrupt, non-linear effects on social-economic systems. Given the promising application of paleolimnological archives to tracking the historical changes of lake ecosystems, it is speculated that they can also record the lake's critical transition. We studied Lake Dali-Nor in the arid region of Inner Mongolia because of the profound shrinking the lake experienced between the 1300 s and the 1600 s. We reconstructed the succession of bacterial communities from a 140-cm-long sediment core at 4-cm intervals and detected the critical transition. Our results showed that the historical trajectory of bacterial communities from the 1200 s to the 2010s was divided into two alternative states: state1 from 1200 to 1300 s and state2 from 1400 to 2010s. Furthermore, in the late 1300 s, the appearance of a tipping point and critical slowing down implied the existence of a critical transition. By using a multi-decadal time series from the sedimentary core, with general Lotka-Volterra model simulations, local stability analysis found that bacterial communities were the most unstable as they approached the critical transition, suggesting that the collapse of stability triggers the community shift from an equilibrium state to another state. Furthermore, the most unstable community harbored the strongest antagonistic and mutualistic interactions, which may imply the detrimental role of interaction strength on community stability. Collectively, our study showed that sediment DNA can be used to detect the critical transition of lake ecosystems. [ABSTRACT FROM AUTHOR]

Background: Saline lakes are home to various archaea that play special and crucial roles in the global biogeochemical cycle. The Qinghai-Tibet Plateau hosts a large number of lakes with diverse salinity ranging from 0.1 to over 400 g/L, harboring complex and diverse archaea. To the best of our knowledge, the formation mechanisms and potential ecological roles of archaea in Qinghai-Tibetan Plateau saline lakes remain largely unknown. Results: Using High-throughput Illumina sequencing, we uncovered the vastly distinct archaea communities between two typical saline lakes with significant salinity differences on the Qinghai Tibet Plateau (Qinghai saline lake and Chaka hypersaline lake) and suggested archaea played different important roles in methanogenesis-related and nitrate reduction-related functions of these two lakes, respectively. Rather than the individual effect of salinity, the composite effect of salinity with diverse environmental parameters (e.g., temperature, chlorophyll a, total nitrogen, and total phosphorus) dominated the explanation of the variations in archaeal community structure in different habitats. Based on the network analysis, we further found the correlations between dominant archaeal OTUs were tight but significantly different between the two habitats, implying that archaeal interactions may also largely determine the shape of archaeal communities. Conclusion: The present study improved our understanding of the structure and function of archaea in different saline lakes on the Qinghai-Tibet Plateau and provided a new perspective on the mechanisms underlying shaping their communities. [ABSTRACT FROM AUTHOR]

Tropical marine lakes are small land-locked marine waterbodies occurring in karstic coastal areas. During biodiversity surveys in 12 marine lakes in Raja Ampat, Southwest Papua province, Indonesia, we recorded at least 37 species belonging to 29 genera of hard corals. Their observed associated symbiont fauna consisted of bivalve molluscs and polychaete worms. Marine lake temperature ranged from 30.0 to 32.5 °C, acidity from pH 7.6 to 8.1, and salinity from 26.4 to 33.2 ppt. This study provides the first inventory of the marginal coral communities in the extreme habitat of marine lakes, under chronic extreme environmental conditions of higher temperatures, land-based nutrient loads, and sedimentation. [ABSTRACT FROM AUTHOR]

This study surveyed freshwater mussels (family Unionidae) in 116 lakes and reservoirs east of the Missouri River in South Dakota, USA, during 2017. Using two-person–hour/site timed searches, evidence of a total of 1789 mussels, including 1053 live mussels, was obtained from 50 waters. Nine species, from two different orders, were found in lakes and reservoirs throughout five of the six major river drainages east of the Missouri River. The native species observed included Giant Floater Pyganodon grandis, Fatmucket Lampsilis siliquoidea, Threeridge Amblema plicata, White Heelsplitter Lasmigona complanata, Wabash Pigtoe Fusconaia flava, Deertoe Truncilla truncata, and Pink Heelsplitter Potamilus alatus. Giant Floater was the most widespread and abundant species observed, representing 63.3% of the live mussels sampled. Two non-native species, Zebra Mussel Dreissena polymorpha and Chinese Basket Clam Corbicula fluminea, were also documented from three water bodies in the lower Missouri River drainage. Overall, mussel abundance was negatively correlated with lake water conductivity and positively correlated with turbidity. No significant correlations were observed between species abundance and water temperature, pH, dissolved oxygen, or substrate particle size. [ABSTRACT FROM AUTHOR]

Lake St Lucia is one of the most important estuarine systems in South Africa, but the long history of anthropogenic intervention has threatened its integrity. With the exception of sporadic overtopping events and periodic marine connectivity via the uMfolozi River, the St Lucia Estuary remained closed off from the Indian Ocean since 2007. Due to the build-up of sediment and prolonged mouth closure, the beach berm was artificially breached in January 2021, fully reconnecting St Lucia to the Indian Ocean for the first time in 13 years. This study aimed to determine the effect of this breaching event on St Lucia's zooplankton community by analysing samples from March, May and August 2021, at five representative sites throughout the lake system. The mouth remained open for only five months, and the system was still largely oligo- to meso-haline due to high freshwater input. The patterns in the zooplankton were related more to the prevailing environmental conditions than to the breaching event itself. The composition of zooplankton in the system did change; however, the presence of marine taxa was not far-reaching nor long-lasting, most likely due to the limited tidal intrusion, strong outflow and predominant salinity regime. [ABSTRACT FROM AUTHOR]

With the increase in crude oil transport throughout Canada, the potential for spills into freshwater ecosystems has increased and additional research is needed in these sensitive environments. Large enclosures erected in a lake were used as mesocosms for this controlled experimental dilbit (diluted bitumen) spill under ambient environmental conditions. The microbial response to dilbit, the efficacy of standard remediation protocols on different shoreline types commonly found in Canadian freshwater lakes, including a testing of a shoreline washing agent were all evaluated. We found that the native microbial community did not undergo any significant shifts in composition after exposure to dilbit or the ensuing remediation treatments. Regardless of the treatment, sample type (soil, sediment, or water), or type of associated shoreline, the community remained relatively consistent over a 3-month monitoring period. Following this, metagenomic analysis of polycyclic aromatic and alkane hydrocarbon degradation mechanisms also showed that while many key genes identified in PAH and alkane biodegradation were present, their abundance did not change significantly over the course of the experiment. These results showed that the native microbial community present in a pristine freshwater lake has the prerequisite mechanisms for hydrocarbon degradation in place, and combined with standard remediation practices in use in Canada, has the genetic potential and resilience to potentially undertake bioremediation. [ABSTRACT FROM AUTHOR]

The overall impact of a crude oil spill into a pristine freshwater environment in Canada is largely unknown. To evaluate the impact on the native microbial community, a large-scale in situ model experimental spill was conducted to assess the potential role of the natural community to attenuate hydrocarbons. A small volume of conventional heavy crude oil (CHV) was introduced within contained mesocosm enclosures deployed on the shoreline of a freshwater lake. The oil was left to interact with the shoreline for 72 h and then free-floating oil was recovered using common oil spill response methods (i.e. freshwater flushing and capture on oleophilic absorptive media). Residual polycyclic aromatic hydrocarbon (PAH) concentrations returned to near preoiling concentrations within 2 months, while the microbial community composition across the water, soil, and sediment matrices of the enclosed oligotrophic freshwater ecosystems did not shift significantly over this period. Metagenomic analysis revealed key polycyclic aromatic and alkane degradation mechanisms also did not change in their relative abundance over the monitoring period. These trends suggest that for small spills (<2 l of oil per 15 m2 of surface freshwater), physical oil recovery reduces polycyclic aromatic hydrocarbon concentrations to levels tolerated by the native microbial community. Additionally, the native microbial community present in the monitored pristine freshwater ecosystem possesses the appropriate hydrocarbon degradation mechanisms without prior challenge by hydrocarbon substrates. This study corroborated trends found previously (Kharey et al. 2024) toward freshwater hydrocarbon degradation in an environmentally relevant scale and conditions on the tolerance of residual hydrocarbons in situ. [ABSTRACT FROM AUTHOR]

Cylindrospermopsis raciborskii- dominated harmful algae blooms have been reported globally in recent years. However, our understanding of the ecology of C. raciborskii in natural conditions is still poor. In this study, we collected the water samples from a C. raciborskii -blooming lake, Yilong Lake, in Yunnan province, China, and used both culture-dependent and culture-independent approaches to investigate their microbial communities and the interactions between C. raciborskii and the other bacteria. The composition and diversity of microbial communities were revealed with 16S rRNA gene high-throughput sequencing data analysis. Microbial co-occurrences analysis suggests C. raciborskii may have complex associations with other bacteria. Based on co-inoculation tests, we obtained 14 strains of bacterial strains from the water samples that exhibited either algicidal or promoting effects on a strain of C. raciborskii. Two bacterial isolates exhibited a consistent performance between co-occurrence analysis and experimental results. Effects of these bacteria-algae interspecies interactions on the bloom event are discussed. All these results may provide new insights into the C. raciborskii -dominated blooms and how its interspecies relationships with other bacteria may influence the bloom events in eutrophic waters throughout the world. [ABSTRACT FROM AUTHOR]

Aphanizomenon flos-aquae (AFA) is the dominant filamentous cyanobacterium that develops into blooms in Upper Klamath Lake, Oregon, each year. During AFA bloom and collapse, ecosystem conditions for endangered Lost River and shortnose suckers deteriorate, thus motivating the need to identify processes that limit AFA abundance and decline. Here, we investigate the relations between AFA and other members of the microbial community (photosynthetic and nonphotosynthetic bacteria and archaea), how those relations impact abundance and collapse of AFA, and the types of microbial conditions that suppress AFA. We found significant spatial variation in AFA relative abundance during the 2016 bloom period using 16S rRNA sequencing. The Pelican Marina site had the lowest AFA relative abundance, and this was coincident with increased relative abundance of Candidatus Sericytochromatia, Flavobacterium , and Rheinheimera , some of which are known AFA antagonists. The AFA collapse coincided with phosphorus limitation relative to nitrogen and the increased relative abundance of Cyanobium and Candidatus Sericytochromatia, which outcompete AFA when dissolved inorganic nitrogen is available. The data collected in this study indicate the importance of dissolved inorganic nitrogen combined with microbial community structure in suppressing AFA abundance. [ABSTRACT FROM AUTHOR]

Chlorophyll-a concentration (Chl-a) is commonly used as a proxy for phytoplankton abundance in surface waters of large lakes. Mapping spatial and temporal Chl-a distributions derived from multispectral satellite data is therefore increasingly popular for monitoring trends in trophic state of these important ecosystems. We evaluated products of eleven atmospheric correction processors (LEDAPS, LaSRC, Sen2Cor, ACOLITE, ATCOR, C2RCC, DOS 1, FLAASH, iCOR, Polymer, and QUAC) and 27 reflectance indexes (including band-ratio, three-band, and four-band algorithms) recommended for Chl-a concentration retrieval. These were applied to the western basin of Lake Ontario by pairing 236 satellite scenes from Landsat 5, 7, 8, and Sentinel-2 acquired between 2000 and 2022 to 600 near-synchronous and co-located in situ-measured Chl-a concentrations. The in situ data were categorized based on location, seasonality, and Carlson's Trophic State Index (TSI). Linear regression Chl-a models were calibrated for each processing scheme plus data category. The models were compared using a range of performance metrics. Categorization of data based on trophic state yielded improved outcomes. Furthermore, Sentinel-2 and Landsat 8 data provided the best results, while Landsat 5 and 7 underperformed. A total of 28 Chl-a models were developed across the different data categorization schemes, with RMSEs ranging from 1.1 to 14.1 μg/L. ACOLITE-corrected images paired with the blue-to-green band ratio emerged as the generally best performing scheme. However, model performance was dependent on the data filtration practices and varied between satellites. [ABSTRACT FROM AUTHOR]

We conducted an investigation into ghost fishing, a phenomenon in which abandoned fishing equipment remains operational for extended durations, in the southern region of Lake Tanganyika, Republic of Zambia. The perils associated with ghost fishing have achieved international recognition; however, there exists a conspicuous dearth of scholarly investigations in particular regions, notably inland aquatic environments and developing countries. Employing scuba diving for field observations, we discovered that ghost fishing was solely evident in monofilament nylon nets, despite the presence of four different net types in the littoral area of the lake. Notably, endemic crabs Platythelphusa armata and P. maculata from Lake Tanganyika constituted 65.2% of the organisms captured by abandoned nets, with the remainder comprising various fish species. The number of captured organisms exhibited a dependence on the interplay between the length and mesh size of the abandoned nets, indicating that the risk of ghost fishing is heightened when both net and mesh size are substantial. Furthermore, we encountered predatory Spiny Eels Mastacembelus moorii ensnared in nets around their jaws and teeth. Intriguingly, the digestive tract of one of the Spiny Eels contained a partially digested cichlid species entangled in the same nets, strongly suggesting the occurrence of secondary ghost fishing. [ABSTRACT FROM AUTHOR]

We applied an ensemble of climate warming models to an iconic protected landscape (Algonquin Park, Ontario) and the seasonal temperature profile model for lakes to assess changes in brook trout (Salvelinus fontinalis) thermal habitat volume (THV) among lakes of different sizes in 30-year periods under two climate warming scenarios (RCP 4.5 and 8.5). Bayesian beta regression models show that lake size (surface area) and morphometry (dynamic lake ratio) are important factors in THV loss. THV loss increases as a function of the dynamic lake ratio (transition from bowl-shaped to dish-shaped lakes). The magnitude of this effect depends on the lake size category and the RCP scenario. Small (<100 ha) and medium (100–500 ha) dish-shaped lakes are projected to have greater THV loss in 2071–2100 (60%–100% of brook trout THV under RCP 8.5; 40%–70% under RCP 4.5) than large lakes (>500 ha) of similar shape. Climate warming projections for the balance of this century, regardless of the RCP category, will result in the loss of brook trout THV in lakes that range widely in size and morphometry. [ABSTRACT FROM AUTHOR]

Rising temperatures, increasing hydroclimate variability and intensifying disturbance regimes increase the risk of rapid ecosystem conversions. We can leverage multi‐proxy records of past ecosystem transformations to understand their causes and ecosystem vulnerability to rapid change.Prior to Euro‐American settlement, northern Indiana was a mosaic of prairie, oak‐dominated forests/woodlands and beech‐dominated hardwood forests. This heterogeneity, combined with well‐documented but poorly understood past beech population declines, make this region ideal for studying the drivers of ecosystem transformations.Here, we present a new record from Story Lake, IN, with proxies for vegetation composition (pollen), fire (charcoal) and beech intrinsic water use efficiency (δ13C of beech pollen; δ13Cbeech). Multiple proxies from the same core enable clear establishment of lead–lag relationships. Additionally, δ13Cbeech enables direct comparisons between beech population abundance and physiological responses to changing environments. We compare Story Lake to a nearby lake‐level reconstruction and to pollen records from nearby Pretty and Appleman Lakes and the distal Spicer Lake, to test hypotheses about synchrony and the spatial scale of governing processes.The 11.7 ka sediment record from Story Lake indicates multiple conversions between beech‐hardwood forest and oak forest/woodland. Beech pollen abundances rapidly increased between 7.5 and 7.1 ka, while oak declined. Oak abundances increased after 4.6 ka and remained high until 2.8 ka, indicating replacement of mesic forests by oak forest/woodland. At 2.8 ka, beech abundances rapidly increased, indicating mesic forest reestablishment. Beech and oak abundances correlate with charcoal accumulation rates but beech abundance is not correlated with δ13Cbeech.Fluctuations in beech abundances are synchronous among Story, Appleman and Pretty Lakes, but asynchronous between Story and Spicer Lakes, suggesting regulation by local‐scale vegetation‐fire‐climate feedbacks and secondarily by regional‐scale drivers.Holocene forest composition and fire dynamics appear to be closely co‐regulated and may be affected by local to regional climate variations. The importance of extrinsic drivers and positive/negative feedbacks changes over time, with higher ecoclimate sensitivity before 2.8 ka and greater resilience afterwards.Synthesis: Overall, oak‐ and beech‐dominated ecosystems were highly dynamic over the Holocene, with multiple ecosystem conversions driven by shifting interactions among vegetation, hydroclimate and fire regime. [ABSTRACT FROM AUTHOR]

Microplastic contamination is ubiquitous across the globe, even in remote locations. Still, the sources and pathways of microplastics to such locations are largely unknown. To investigate microplastic contamination in a semi‐remote location, we measured microplastic concentrations in nine oligotrophic lakes within and around the International Institute for Sustainable Development—Experimental Lakes Area in northwestern Ontario, Canada. Our first objective was to establish ambient concentrations of microplastics in bottom sediments, surface water, and atmospheric deposition in semi‐remote boreal lakes. Across all lakes, mean shallow and deep sediment microplastic concentrations, near‐surface water microplastic concentrations from in situ filtering, and dry atmospheric microplastic deposition rates were 551 ± 354 particles kg−1, 177 ± 103 particles kg−1, 0.2 ± 0.3 particles L−1, and 0.4 ± 0.2 particles m−2 day−1, respectively. Our second objective was to investigate whether microplastic contamination of these lakes is driven by point sources including local runoff and direct anthropogenic inputs or nonpoint sources such as atmospheric deposition. Lakes were selected based on three levels of anthropogenic activity—low, medium, and high—though activity levels were minimal across all study lakes compared with highly populated areas. Whereas a positive correlation would indicate that point sources were a likely pathway, we observed no relationship between the level of anthropogenic activity and microplastic contamination of surface water. Moreover, the composition of microplastics in surface water and atmospheric deposition were similar, comprising mostly polyester and acrylic fibers. Together, these results suggest that atmospheric deposition may be the main pathway of microplastics to these remote boreal lakes. Environ Toxicol Chem 2024;43:999–1011. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Limnomonas gaiensis is a recently described green microalga inhabiting freshwater lakes in northern Europe (England, Sweden). There is little information on the species' tolerance to environmental factors and its capacity to spread to unconnected lakes. Using a barcoding approach, we investigated the phylogeography of L. gaiensis along a latitudinal gradient spanning 54–60°N. Experimental long-term exposure to a gradient of water temperatures, mimicking natural conditions, was performed to assess its thermal tolerance. Genetic analyses showed that this limnic species is easily identified at the species level. Phylogeographic analyses revealed the existence of two genetically similar haplotypes over the mitochondrial cytochrome C oxidase subunit 1 gene in different countries, suggesting that the range of L. gaiensis has recently expanded from a common source lineage, despite geographic isolation. Heterogeneity in the Helix III of the nuclear Internal Transcribed Spacer 2 region of the English strain suggested past hybridization. Physiological analyses showed that L. gaiensis can survive and reproduce asexually, potentially year-round. Optimal growth was observed at 15°C, with a doubling time of 1.1 days. The species is able to survive short periods of desiccation. The lack of connectivity between the lakes where the species was sampled rules out aquatic dispersal of this species. However, its physiological features make L. gaiensis a good candidate for propagule dispersal by either wind or human/animal-mediated transportation. Our study calls for further investigation into limnic systems, using rapid barcoding, with concurrent atmospheric and physiological analyses to establish its distribution over wider geographic scales and to understand how L. gaiensis disperses. Limnomonas gaiensis survives in a wide range of water temperatures. Phylogeographic analyses indicate its recent expansion in Northern Europe. Physiological features suggest airborne/animal-mediated dispersal between unconnected freshwater lakes. [ABSTRACT FROM AUTHOR]

Analysis of cyanobacterial diversity is an important step towards identifying new biological resources for production of bioactive compounds. In this study cyanobacterial surface coverage was assessed through satellite image analysis of Tehran drinking water reservoirs in late summer and early autumn of 2018. We also analysed freshwater cyanobacteria including seven local strains purified from surface water samples. Following a polyphasic taxonomic approach combining morphological and molecular methods the culturable strains were classified into Synechococcales and Oscillatoriales, representing at least three families and four genera. Similarity-based analysis of their partial 16S rRNA genes showed 93.4–97.0% sequence identity among the strains from different ecosystems. Considering 95–96% as the overall cut-off for discriminating bacterial species, strains UTMC6011 and UTMC6013 are likely to be new species. Physiological characterization of the new strains and nine others isolated previously by our group from another freshwater ecosystem led to identification of seven nitrogen-fixing, 11 sulphide-tolerant, three salt-tolerant and three heterotrophic strains. Further taxonomic analyses are needed to support investigation of their biotechnological potential. The biodiversity and physiology of cyanobacteria in the main drinking water reservoirs of the megacity, Tehran, were studied by remote sensing and sample analysis. Seven cyanobacterial strains were isolated from the two freshwater lakes. Similarity-based analysis of obtained 16S rRNA gene sequence showed 93.4–97.0% sequence similarity with the strains from other ecosystems. Cyanobacterial isolates of these freshwater reservoirs included seven N2-fixing, 11 sulphide-tolerant, three salt-tolerant and three heterotrophic strains. [ABSTRACT FROM AUTHOR]

Disappearance of lakes is one of the most dangerous processes affecting the entire natural environment, including soil. This phenomenon is considered natural, resulting from climate change, however in recent decades, a significant acceleration of this process has been observed due to the direct impact of human activity. In areas directly adjacent to lakes, organic soils usually predominate. Unfortunately, wetlands are increasingly being drained and used for agricultural purposes. Under such circumstances, changes in the physical and chemical properties of these soils are often irreversible, causing their degradation. As an effect of increased mineralization, a number of typical modifications occur in soils, such as carbon loss, increased degree of peat decomposition, and changes in soil structure. Long-term dehydration has led to muck formation. Additionally, lowering of lake water uncovers previously flooded areas and increases the intensity of soil-forming processes. However, the presence of the Subaquatic qualifier in the World Reference Base for Soil Resources (WRB) suggests that sediments in shallow water bodies no more than 200 cm deep can also be classified as soils. The progressive disappearance of lakes observed all over the world is therefore a process affecting not only the reduction of water bodies, but also changes in the properties and typology of soils and vegetation cover. [ABSTRACT FROM AUTHOR]

Testate amoebae are widely used as bioindicators in the study of modern ecotopes and as proxies in palaeoecological reconstructions of lacustrine environments. The metalimnion with thermocline in stratified water bodies strongly affects the species structure of a number of aquatic animals and often plays a role as an ecotone for pelagic animals, but our knowledge on the influence of the metalinmion on benthic organisms, especially on testate amoebae, is still limited.This study aims to describe the influence of the metalimnion and its thermocline on benthic testate amoebae assemblages along a temperature gradient in the stratified freshwater Lake Valdayskoe. Twenty‐eight samples from nine sites were collected along the transect starting in the littoral zone, passing through a long metalimnion and its thermocline and finishing in the hypolimnion on the bottom slope.We identified four species assemblages, six non‐attributed samples and five morphotrait compositions in the transect, including those corresponding to the area inside the metalimnetic zone. We observed similarities in the transitions in benthic species assemblages, morphotype compositions, and species and morphotrait structures from shallow to deep water, and two shifts corresponded well with the upper and lower limnological boundaries of the metalimnion. The combination of the observed biological and hydrological characteristics suggests that the metalimnion plays a role of an ecotone between shallow and deep water in stratified freshwater lakes, and maintains the integrity and sustainability of benthic communities of testate amoebae.We explored a multivariate approach to demonstrate that the combination of highly abundant species and dominant morphotypes may be an efficient indicator of related environmental conditions. Thus, the high abundances of Cylindrifflugia acuminata, Centropyxis aculeata, Difflugia lacustris, D. linearis and C. discoides in combination with the dominance of elongate‐spiky and flattened‐spiky shells are closely related to the littoral zone with sandy sediments covered by many macrophytes. The combination of a high abundance of D. petricola and D. penardi, and the dominance of pyriform, necked and oval shells are closely related to deep depth.The studied species and morphotrait transition from littoral to deep water provides additional information about the morphological adaptations of testaceans, and about the processes of forming and maintaining benthic testate amoebae assemblages along the depth gradient. The described species and morphotrait assemblages related to specific water depths may be useful for palaeoreconstructions. [ABSTRACT FROM AUTHOR]

Preserved assemblages of invertebrate remains in lacustrine sediment reveal temporal variations of community composition and environmental conditions. However, records for large tropical lakes are scarce. Lake Victoria, the largest tropical lake, has a dynamic history of changes in water level, biogeochemistry and fish community composition over the past ~17,000 cal yr BP.In order to quantify changes in the invertebrate assemblage of Lake Victoria from the late Pleistocene throughout the Holocene, we examined chitinous remains of Cladocera and larval dipterans (Chironomidae and Chaoboridae) from a sediment core (37 m water depth) dated from ~13,700 cal yr BP to present.We identified four major phases in the invertebrate assemblage throughout this period of lake history. Firstly, Chironomidae and Chaoboridae appeared at low abundances during the earliest stages of lake inundation in the late Pleistocene, at a time when Cladocera were notably absent. Secondly, chaoborids and chironomids increased in abundance during the mid‐Holocene, which coincided with high diatom production toward the end of the Holocene African Humid Period. Thirdly, starting ~4,700 cal yr BP, Alona, a predominantly littoral cladoceran genus, consistently appeared in the invertebrate assemblage alongside changes in mixing regimes and persisted throughout the late Holocene to the present. Fourthly, the arrival of both Chydorus and Bosmina longirostris marked the establishment of an abundant cladoceran assemblage at ~1,350 cal yr BP. The assemblage then gradually shifted toward the increasing dominance of B. longirostris, a planktonic cladoceran.Several of the observed changes in the invertebrate assemblage occurred concurrently with changes in climatic conditions in East Africa and diatom productivity that have been previously recorded in Lake Victoria. This multi‐millennial record of sedimentary invertebrate assemblages in Lake Victoria elucidates some of the temporal development of these communities throughout most of the dynamic modern history of the ecosystem. [ABSTRACT FROM AUTHOR]

Resting eggs are commonly produced by zooplankton inhabiting permanent and temporary lakes. Although resting eggs are acknowledged to survive varying harsh conditions, the effects of desiccation on the viability and hatching patterns of resting eggs are not fully understood and might be context‐dependent.This study simulated one long‐term (1 year) dry‐out episode in wet sediments originating from permanent and temporary lakes and compared hatching patterns through ex situ experiments.The abundance and species richness of hatchlings decreased in dry sediments compared to wet sediments. Hatchling composition differed between wet and dry sediments of each lake category, whereas community variability did not differ between wet and dry sediments of temporary lakes.Overall, there was no difference in the ability of rotifers and crustaceans to cope with desiccation, since all species decreased hatchling numbers after desiccation. Artemia was the only taxon that benefited from drying sediments.Long‐term desiccation may affect the contribution of resting egg banks to future active populations in the water column, even in temporary habitats which presumably select for drought‐resistant resting eggs. The ecological roles played by resting egg banks may be weakening because droughts are becoming more common worldwide, even in former permanent aquatic habitats. [ABSTRACT FROM AUTHOR]

Aim: Understanding the distance–decay relationship (DDR) has been considered important because it reflects a combination of several ecological processes such as dispersal limitation and environmental sorting. However, effects of human disturbances on DDR are poorly known, especially in freshwater lakes. This study is aimed to examine how anthropogenic eutrophication modified the relationships between three facets (taxonomic, functional and phylogenetic) of macroinvertebrate beta diversity and geographic and environmental distances across 30 freshwater lakes. Location: The Yangtze River floodplain, China. Methods: We used Mantel tests to examine the relationships between multiple facets of assemblage dissimilarities (overall beta diversity, replacement and richness difference components) and geographic and environmental distances. Distance‐based redundancy analysis (dbRDA) and associated variation partitioning procedures were applied to explore the relative contributions of environmental and spatial factors on the three facets of beta diversity. Results: We found that none of the three beta diversity facets was related to geographic distance, but all were significantly related to environmental distance, mainly mirroring eutrophication‐related variables. Based on the variation partitioning approach, the macroinvertebrate assemblages examined were almost exclusively structured by environmental factors associated with eutrophication, while spatial variables had a negligible effect. Nevertheless, the different facets of beta diversity did not decrease (i.e., no homogenization trend) in lake groups showing the highest eutrophication levels, implying complex influences of anthropogenic disturbances in driving homogenization or differentiation in assemblage compositional dissimilarity. Main Conclusions: Our findings suggested that the high degrees of eutrophication acted as an environmental filter to significantly modify the spatial distance–decay relationships, possibly via decreasing the importance of dispersal limitation in shaping macroinvertebrate assemblages in the studied lakes. Given the sensitivity of beta diversity patterns to eutrophication we found in this study, we recommend that the role of anthropogenic disturbances should be incorporated into research on general ecological patterns like the DDR. [ABSTRACT FROM AUTHOR]

The Laurentian Great Lakes region in North America is experiencing climate-driven disturbances that threaten the public safety of the region and is forcing communities to respond. Communities vary in their ability to respond to these disturbances based on their existing capacities and access to resources, but responses in the region are uneven and create vulnerabilities to disasters. A virtual workshop was conducted to understand the community responses to climate-driven disturbances in the Great Lakes and identify the essential capacities for effective responses. Results show that the region as a whole has not responded adequately, and although the resources exist to respond, they are not adequately organized, and inequalities between urban and rural communities can exacerbate these challenges. Community capacities identified as critical for resilience include leadership, scientific knowledge, and connection to broader regional networks to access additional resources, but there are challenges with the complacency of some communities and deficiencies in mental health services. [ABSTRACT FROM AUTHOR]

• Sediment OP and OC during the outbreak and decline of algal blooms were studied. • The changes in OC and OP in the sediment were synchronous. • Mono-P was the main component of OP during the decline of algal blooms. • The impact of the algal blooms on active OC in sediment was significant. In this study, sediment organic phosphorus (OP) and organic carbon (OC) in Lake Taihu, China, as well as their relationships, were analyzed during the outbreak and decline of algal blooms (ABs) over a five-month field study. The results showed synchronous temporal changes in the sediment OP and OC contents with the development of ABs. In addition, there was a significant positive correlation between the sediment OP and OC (p < 0.01), suggesting simultaneous deposition and consumption during the ABs outbreak. The sediment OP and OC contents decreased significantly at the early and last stages of the ABs outbreak and increased at the peak of the ABs outbreak and during the ABs decline. These temporal variation patterns suggest that the sediment OC and OP contents did not consistently increase during the ABs outbreak, even though algae are an important source of organic matter in sediments. The depletion or enrichment of OC and OP in sediments may also depend on the scale of the ABs outbreak. The obtained results revealed significant differences in the sediment OC and OP contents between the months (p < 0.05). In addition, OP in the sediments was dominated by orthophosphate diester (phospholipids and DNA-P) and orthophosphate monoester during the ABs outbreak and decline, respectively. The active OC contents and proportions in the sediments in the ABs outbreak were significantly lower than those observed in the ABs decline period, demonstrating the significant impacts of the ABs outbreak and decline on the sediment OC and OP in Lake Taihu. [ABSTRACT FROM AUTHOR]

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The concentration of colored dissolved organic matter (CDOM) in lakes is strongly influenced by climate, land cover, and topographic settings, but it is not known how drought may affect the relative importance of these controls. Here, we evaluate the controls of CDOM during two summers with strongly contrasting values of the Palmer drought index (PDI), indicating wet vs. dry conditions. We hypothesized that lake CDOM during a wet summer season is regulated mainly by the surrounding land cover to which the lakes are hydrologically connected, while, during drought, the lakes are disconnected from the catchment and CDOM is regulated by climatic and morphometric factors that govern the internal turnover of CDOM in the lakes. A suite of climate, land cover, and morphometric variables was assembled and used to explain remotely sensed CDOM values for 255 boreal lakes distributed across broad environmental and geographic gradients in Sweden and Norway. We found that PDI explained the variability in CDOM among lakes in a dry year, but not in a wet year, and that severe drought strongly decreased CDOM during the dry year. Large lakes, especially, with a presumed high degree of catchment uncoupling, showed low CDOM during the dry year. However, in disagreement with our hypothesis, climate, land cover, and morphometry all showed a stronger impact on lake CDOM in wet vs. dry years. Thus, drought systematically weakened the predictability of CDOM variations at the same time as CDOM was offset toward lower values. Our results show that drought not only has a direct effect on CDOM, but also acts indirectly by changing the spatial regulation of CDOM in boreal lakes. [ABSTRACT FROM AUTHOR]

Lake-effect snowfall (LES) occurs when cold air moves across open lakes. LES is expected to occur more frequently over the TP, due to the intensified lake expansion caused by intensified global warming. Thus, there is an urgent need to comprehensively assess the LES over the TP. Here, we revealed that the LES is triggered by westerly southward shift leading to the drop in air temperature and is positively correlated with lake area, wind speed and longitude across 12 large lakes (>300 km2) based on satellite observations and reanalysis data. Using a sensitivity model simulation, we determined that large lakes in the southern TP contributed to more than 50% of the snowfall in the downwind area in 2013. Projections indicate that the westerly-triggered LES will increase under the future RCP4.5 climate warming scenario, highlighting the importance of developing adaptive policies to address the growing risks associated with future LES. [ABSTRACT FROM AUTHOR]

Due to the rising concern about heavy metals in settled dust, a risk assessment of Arsenic (As), Cadmium (Cd), Copper (Cu), Lead (Pb), Nickel (Ni) and Zinc (Zn) has been conducted using multiple exposure paths, including oral ingestion, direct skin contact, and inhalation of dust around lake Urmia in Iran for the time period of 2020. Metal concentrations were assessed and sources were identified based on the enrichment factor and Pearson correlation coefficient. The metal concentrations were in the following order: Zn > Cu > Ni > Pb > Cd > As with arithmetic means of 3.5, 4.8, 57, 33, 25 and 83 mg/kg, respectively, which are within the range of Iran-EPA soil guideline values. A very weak correlation (r < 0.7) was found between the studied elements. The average enrichment factor (EF) for As, Cd, Cu, Ni, Pb, and Zn was 0.7, 4, 1.8, 0.5, 3.2 and 0.8, respectively, suggests minor enrichment for metals and influence from anthropogenic activity. The lifetime cancer risks (LTCR) due to exposure (three routes of inhalation) to metals were in the negligible risk category. The oral route had the highest hazard index (HI) between all of exposure paths. The HI was less than 1 for all three exposure paths. Moreover, the sensitivity analysis showed that exposure duration (ED) for As and Ni and exposure frequency (EF) for Cd and Pb had the highest impacts on LTCR values. Therefore, this study suggests the continuous monitoring of heavy metals in settled dust around the Lake Urmia as it is associated with the high health risk for the neighbourhood in the Lake Urmia's basin. [ABSTRACT FROM AUTHOR]

Slow and long-term variations of sea surface temperature anomalies have been interpreted as a red-noise response of the ocean surface mixed layer to fast and random atmospheric perturbations. How fast the atmospheric noise is damped depends on the mixed layer depth. In this work we apply this theory to determine the relevant spatial and temporal scales of surface layer thermal inertia in lakes. We fit a first order auto-regressive model to the satellite-derived Lake Surface Water Temperature (LSWT) anomalies in Lake Garda, Italy. The fit provides a time scale, from which we determine the mixed layer depth. The obtained result shows a clear spatial pattern resembling the morphological features of the lake, with larger values (7.18± 0.3 m) in the deeper northwestern basin, and smaller values (3.18 ± 0.24 m) in the southern shallower basin. Such variations are confirmed by in-situ measurements in three monitoring points in the lake and connect to the first Empirical Orthogonal Function of satellite-derived LSWT and chlorophyll-a concentration. Evidence from our case study open a new perspective for interpreting lake-atmosphere interactions and confirm that remotely sensed variables, typically associated with properties of the surface layers, also carry information on the relevant spatial and temporal scales of mixed-layer processes. [ABSTRACT FROM AUTHOR]

The spatial response mechanism of hydrology and water quality of large river-connected lakes is very complicated. In this study, we developed a spatial response analysis method that couples wavelet correlation analysis (WTC) with self-organizing maps (SOM), revealing the spatial response and variation of water level and water quality in Poyang Lake, China's largest river-connected lake, over the past decade. The results show that: (1) there was significant spatial heterogeneity in water level and quality during the dry seasons (2010–2018) compared to other hydrological stages. (2) We identified a more pronounced difference in response of water level and quality between northern and southern parts of Poyang Lake. As the distance increases from the northern lake outlet, the impact of rising water levels on water quality deterioration intensified during the dry seasons. (3) The complex spatial heterogeneity of water level and quality response in the dry seasons is primarily influenced by water level fluctuations from the northern region and the cumulative pollutant entering the lake from the south, which particularly leads to the reversal of the response in the central area of Poyang Lake. The results of this study can contribute to scientific decision-making regarding water environment zoning management in large river-connected lakes amidst complex environment conditions. [ABSTRACT FROM AUTHOR]