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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]

The high-elevation plateaus of the inter-Andean valleys are home to shallow lakes that have become eutrophic. These lakes share similarities with shallow lakes in temperate and subtropical areas. Because native species diversity is low, invasive species dominate the fish and macrophytes communities. The study aimed to investigate the behavioral response of the local Daphnia pulex from the Andean shallow Lake Yahuarcocha to the exotic submerged macrophyte Egeria densa and the exotic fish Poecilia reticulata. Laboratory habitat choice experiments revealed that D. pulex from Lake Yahuarcocha strongly avoid E. densa, irrespective of the presence of the fish P. reticulata or chemical cues indicating fish predation on D. pulex. This observation could be explained by the fact that P. reticulata displayed a strong attraction to E. densa during the daytime, probably to avoid bird predation. D. pulex from the nearby Lake San Pablo where P. reticulata is absent but where the fish community is dominated by Oncorhynchus mykiss displayed the same avoidance behavior to submerged macrophytes as D. pulex from Lake Yahuarcocha. These results indicate that macrophytes in these high-elevation shallow lakes may not facilitate top-down control of phytoplankton, since plants do not offer refuge to D. pulex from fish predation. [ABSTRACT FROM AUTHOR]

We consider the stochastic control problem of the shallow lake and continue the work of Kossioris, Loulakis, and Souganidis. First, we generalise the characterisation of the value function as the viscosity solution of a well-posed problem to include more general recycling rates. Then, we prove approximate optimality under bounded controls and we establish quantitative estimates. Finally, we implement a convergent and stable numerical scheme for the computation of the value function to investigate properties of the optimally controlled stochastic shallow lake. This approach permits to derive tails asymptotics for the invariant distribution and to extend results of Grass, Kiseleva and Wagener. https://www.sciencedirect.com/science/article/pii/S1007570414004754] beyond the small noise limit. [ABSTRACT FROM AUTHOR]

Small shallow ponds are widespread but understudied water bodies in agricultural landscapes. Agricultural run‐off (ARO) transports pesticides and nutrients into adjacent aquatic ecosystems where they occur dissolved in the water column or are bound to sediments. Consequently, aquatic communities are affected by ARO via different exposure pathways. We hypothesize that sediment‐bound ARO mainly affects submerged rooted macrophytes, while phytoplankton and periphyton are more prone to ARO in water. These primary producers compete for resources resulting in a regime shift between alternative stable states of macrophyte or phytoplankton dominance. We hypothesize that warming increases nutrient release from sediments and thereby facilitates the occurrence of phytoplankton dominance.Using a full‐factorial microcosm design, we exposed aquatic primary producers to either sediment or water application of a mixture of common pesticides (terbuthylazine, pirimicarb, tebuconazole and copper) and nitrate at two concentrations and two temperatures (22°C and 26°C) for 4 weeks. Initial and final concentrations of pesticides and nitrate, final biomass of macrophytes, periphyton and phytoplankton, pesticide accumulation in macrophytes and changes in carbon, nitrogen and phosphorus content and selected exoenzyme activities in the sediment were measured.We found lower final macrophyte biomass for both ARO treatments compared to controls, indicating a prevalence of negative effects by herbicides and competition for light with other phototrophs. In contrast, phytoplankton and periphyton biomass increased, but only when exposed to ARO via the water column, indicating a prevalence of positive effects by nutrient supply. Microbial carbon and nutrient cycling in sediments was not affected by ARO. Higher temperature mitigated ARO‐related effects on macrophytes under sediment exposure.Synthesis and application. ARO poses a strong risk of submerged macrophyte loss and establishment of turbid conditions with phytoplankton dominance in aquatic ecosystems. In conclusion, exposure pathways as well as indirect and interacting effects of multiple stressors need to be considered when designing appropriate mitigation measures. Under climate change, we suggest to prioritize local measures as buffer strips a reduced use of pesticides and fertilizers, and sediment removal as appropriate measures to protect these vulnerable but widespread aquatic systems, which are highly relevant for biodiversity in agricultural landscapes. [ABSTRACT FROM AUTHOR]

In lentic ecosystems (e.g., lakes and ponds), anthropogenic shoreline alterations, such as concrete embankments, severely degrade habitat, affecting fish assemblage structure. Since fishes have a significant influence on lake ecosystems, it is, however, also essential to assess the response of fish behavior to this degradation to better understand the impact of shoreline alteration on lake ecosystems. Here, we investigated freshwater fish migration behavior in 12 small lakes of norther Japan, in which shorelines are environmentally altered, to assess how the habitat alterations can affect fish emigration from the lake to its connecting channels. We collected fishes using traps installed in lake inflow channels and five focal species were selected for the analysis. A generalized linear mixed model showed that emigration of three of five focal fish increased with the increasing proportion of concrete embankment on the lake shorelines. This result suggests that anthropogenic alteration of a lake shoreline structure significantly impacts fish behavior and affects to their emigration from lakes. Further, this finding indicates that behavioral changes caused by anthropogenic alteration are important for understanding the dynamics of small lake ecosystems. [ABSTRACT FROM AUTHOR]

The present study investigated the distribution, sources, bioavailable fractions, and ecological risks of nine metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn) in water, sediment, and vegetation samples collected from a shallow lake within the industrial town of Ranipet, India. The lake water samples exceeded the concentrations of Al, Cd, Cr, Cu, Fe, Mn, and Pb beyond BIS (Bureau of Indian Standards) limits for drinking water with Cr to be highest as 6.73 mg/L. The Geo-accumulation index for lake bed sediment samples were in the order of Cr>Cu>Co>Mn>Zn>Pb. The bioavailability of the metals in sediment samples determined through Sequential Extraction Procedure (SEP) showed Cr>Co>Zn>Cu>Pb>Mn>Fe>Al. The sediment samples collected from the root zone of different plant species (Cynodon dactylon, Sida acuta, and Eclipta prostrata) exhibited varied bioavailable fractions than lake bed sediments, which indicated the influence of plants in mobilising and fixing the metals. The plant samples had metals concentration in the order of Root>Stem>Leaves and showed the possibility of phytoremediation. Principle Component Analysis (PCA) and Pearson Correlation Matrix (PCM) in the lake bed sediment samples identified the clustering of Al and Fe which indicated probable lithological origin. The lone clustering of Cr from Co, Mn, and Cu indicated separate anthropogenic sources. Further Al, Fe, and Mn showed strong correlations with TOC (Total Organic Carbon) substantiate their distribution under influence of TOC. The study indicated elevated metals pollution is water, sediment, and plants samples from lake area which require immediate attention from all the stakeholders. The assessment of pollution in small and shallow lakes amidst industrial belts need to be prioritised as they often become victims of industrial encroachment and cease to exist in long run. [ABSTRACT FROM AUTHOR]

Vertical transport caused by mixing is essential for understanding physical processes in lakes. However, mixing processes in shallow lakes are not well understood because of the lack of turbulence measurements. This study presents observations of vertical mixing and oxygen flux in a shallow lake, Lake Kitaura of the Lake Kasumigaura continuous lake system, which is located along the central eastern coast of the Japanese mainland. Mooring and microstructure surveys were conducted in August 2020. The vertical eddy diffusivity was estimated from the Ellison scale using high-frequency sampled temperature data from the mooring location, and the estimations were consistent with those observed from the microstructure profiler. The estimated eddy diffusivity revealed a mixing structure and oxygen flux in the lake during the study period. The daily cycle of stratification and mixing was caused by daily heating due to solar radiation and by winds from daily sea breezes, respectively. The daily stratification maximum occurred around noon, which suppressed vertical mixing. Vertical mixing was intensified due to sea breezes in the afternoon, which led to movement of oxygen from the surface layer to the bottom layer. The maximum vertical mixing was observed at 18:00. The oxygen concentration did not increase during nighttime when the negative surface heat flux was observed; thus, nighttime cooling may not primarily contribute to the vertical oxygen supply. [ABSTRACT FROM AUTHOR]

Water‐level drawdowns are a management option for improving water quality in shallow, eutrophic lakes, but how much water levels should be reduced and what abiotic and biotic mechanisms can be expected to reduce the adverse effects of eutrophication are unclear.We conducted a study with two experimental pools (10 m wide, 30 m long, and approx. 2.5 m water depth) in a before‐after‐control‐impact design to examine whether water‐level drawdowns could influence surface water quality and bottom‐water conditions, as well as how physicochemical and biological variables contributed to improvements. In the experiment, we fertilised the pools to increase productivity and induce hypoxia, and then reduced water levels four times in increments of 0.5 m.Our experiment using high‐frequency sensors showed that water‐level drawdowns could decrease cyanobacterial blooms and alleviate hypoxia relatively quickly by changing physicochemical conditions. Water‐level reductions quickly increased bottom light illuminance, increased bottom‐water temperatures, and weakened stratification. The result was a dramatic increase in bottom‐water dissolved oxygen concentrations.Water‐level drawdowns also decreased the relative fluorescence of chlorophyll and phycocyanin, probably because of a decrease of internal nutrient loadings from sediment. Total nitrogen and NH4‐N concentrations in the water column decreased after water‐level reductions, and NH4‐N and PO4‐P concentrations in sediment pore waters were reduced in the water‐level treatment.Periphyton biomass did not change after the water‐level drawdowns. Water‐level manipulations increased the abundance of cyclopoids and calanoids but not large cladocerans. These biological processes responded slowly to water‐level drawdowns and are unlikely to have contributed to water quality improvement.Overall, the size of the water‐level reduction required to start changing water quality was 0.5–1.0 m. Our results suggested that a temporary reduction in water‐level of 20%–40% of the depth might help to suppress cyanobacterial blooms and hypoxia in shallow lakes, reservoirs, and agricultural ponds. Such water‐level management may help resolve conflicting demands for water and may be incorporated into management plans for flood control. [ABSTRACT FROM AUTHOR]

• Seasonal DOM changes at the sediment–water interface in Lake Chaohu were analyzed. • Mineralization of DOM results in the nitrogen and phosphorus release. • Cyanobacterial growth and decline contribute to the DOM components in Lake Chaohu. • The strongest P release from sediments occurs during the early growth stage. The seasonal changes in dissolved organic matter (DOM), and its correlation with the release of internal nutrients during the annual cycle of cyanobacteria in the eutrophic Lake Chaohu, China, were investigated from four sampling periods between November 2020 and July 2021. The DOM fluorescence components were identified as protein-like C1, microbial humic-like C2, and terrestrial humic-like C3. The highest total fluorescence intensity (F T) of DOM in sediments during the incubation stage is due to the decomposition and degradation of cyanobacteria remains. The lowest humification of DOM and the highest proportion of C1 in waters during the initial cyanobacterial growth indicate that fresh algae are the main source. The highest molecular weight of DOM and F T of the C2 in sediments during cyanobacterial outbreaks indicate the concurrent deposition of undegraded cyanobacterial remains and microbial degradation. The components of DOM are affected mainly by the dissolved total phosphorus in waters, while the temperature drives the annual cycle of cyanobacteria. The decreasing C1 in sediments and increasing nutrients in waters from the cyanobacterial incubation to outbreak indicate that mineralization of algal organic matter contributes importantly to the release of internal nutrients, with the strongest release of phosphorus observed during the early growth of cyanobacteria. The humic-like C2 and C3 components could also affect the dynamics of internal phosphorus through the formation of organic colloids and organic–inorganic ligands. The results show that the degradation of DOM leads to nutrients release and thus supports the continuous growth of cyanobacteria in eutrophic Lake Chaohu. [Display omitted] [ABSTRACT FROM AUTHOR]

Beyşehir Lake, located in one of the important karstic discharge basins of the Anatolian Plate, is Turkey's largest freshwater lake with a surface area of 650 km2, and is a very important wetland in terms of bio-ecological, socio-economic, and cultural aspects. Although the first records on Beyşehir Lake fishery date back to the 1910s, the first scientific findings on fisheries began in the 1950s. Although it is challenging to reach reliable data about the fishery of Lake Beyşehir, the main processes that have been effective in fishing from the 1950s to the present are: i) used fishing gear and methods, ii) changes in the trophic structure of the lake, iii) foreign fauna elements entering the lake, iv) the lake water level changes, v) fishermen's socio-economic and awareness level, vi) fisheries management strategies. The lake's catch yield was nearly 3 kg/ha in the 1950s, and it was determined as 13.34 kg/ha in 2021. While there have been significant changes in the fauna in the intervening time, it has been determined that there has been a substantial increase in the number of fishermen with the increasing amount of catch. Today, 23 fish species, 14 of which are endemic, live in the lake, which is at the mesotrophic-eutrophic level in terms of trophic status. The average catch amount between 2010 and 2021 was 669.051 kg/year. 67.41% of this amount was composed of Carassius gibelio (Prussian carp), 20.17% of Sander lucioperca (pike-perch), and 12.42% of Cyprinus carpio (carp). In 2021, the last fishing season, 75.41% of the caught species were Prussian carp, 21.47% pike-perch, and 3.11% carp. 385 fishermen are actively fishing in the lake, and according to the data of 2021, it has been determined that the fishermen have earned 13,970 TL/year in return for 2.252 kg/year of catch. As another result of this study, it has been understood that the most significant factor in the fishing ecosystem of Beyşehir Lake is untimely and excessive fishing. [ABSTRACT FROM AUTHOR]

Climate change is enhancing the frequency of cyanobacterial blooms not only during summer but also in spring and autumn, leading to increased ecological impacts. The bacterioplankton community composition (BCC), in particular, is deeply affected by these blooms, although at the same time BCC can also play important roles in blooms' dynamics. However, more information is still needed regarding BCC during species-specific cyanobacterial blooms. The goal of this study was to assess BCC succession in a hypereutrophic shallow lake (Vela Lake, Portugal) during a warm spring using a metagenomic approach to provide a glimpse of the changes these communities experience during the dominance of Aphanizomenon-like bloom-forming species. BCC shifts were studied using 16S rRNA gene metabarcoding and multivariate analyses. A total of 875 operational taxonomic units (OTUs) were retrieved from samples. In early spring, the dominant taxa belonged to Proteobacteria (mainly Alphaproteobacteria—Rickettsiales) and Bacteroidetes (Saprospirales, Flavobacteriales and Sphingobacteriales). However, at the end of May, a bloom co-dominated by cyanobacterial populations of Aphanizomenon gracile, Sphaerospermopsis aphanizomenoides and Synechococcus sp. developed and persisted until the end of spring. This led to a major BCC shift favouring the prevalence of Alphaproteobacteria (Rickettsiales and also Rhizobiales, Caulobacteriales and Rhodospirillales) and Bacteroidetes (Saprospirales, followed by Flavobacteriales and Sphingobacteriales). These results contribute to the knowledge of BCC dynamics during species-specific cyanobacterial blooms, showing that BCC is strongly affected (directly or indirectly) by Aphanizomenon-Sphaerospermopsis blooms. [ABSTRACT FROM AUTHOR]

Dissolved inorganic nitrogen (DIN) plays an important role in aquatic ecosystems as an available source of nitrogen (N). Despite recent advances in our understanding of the effects of climate change on DIN in coastal waters, shallow high-latitude lakes exposed to large seasonal temperature differences have received limited research attention. Therefore, in the present study, Baiyangdian Lake (BYDL) was selected as the study area, as a typical high latitude shallow lake in North China. Based on water and sediment samples collected in spring, summer and winter seasons, DIN accumulation in sedimentary pore water and DIN diffusion fluxes at the sediment-water interface were quantified under different temperature conditions. Correlation analysis was used to establish the effects of temperature on DIN concentration and diffusion in different media. Results show that the diffusion of DIN at the lake sediment-water interface exhibited a strongly positive relationship with temperature, suggesting that high temperature conditions lead to greater DIN release from sediments. Cold temperatures cause DIN accumulation in sedimentary pore water, providing sufficient substrate for N-related bacteria in the sediment under cold temperature conditions. Temperature controls the vertical distribution of DIN by affecting its migratory diffusion and transformation at the sediment-water interface. These findings are valuable for understanding the impact of climate change on the distribution of N in inland shallow lakes, especially in high latitude shallow lakes subjected to large seasonal temperature differences throughout the year. [Display omitted] [ABSTRACT FROM AUTHOR]

The existence of alternative stable states and hysteresis underpinned by positive feedback mechanisms explains why it is often difficult to restore submerged macrophytes in shallow lakes. It is especially difficult to restore water quality of turbid tropical lakes. It has been speculated that transplanting macrophytes tolerant of high turbidity may help the system escape from the turbid state, but systematic assessments are so far largely lacking. Here we conducted a mesocosm transplanting experiment in a shallow lake of subtropical China to mimic macrophyte restoration. We transplanted three common native turbidity-tolerant submerged macrophyte species in shallow-water mesocosms and monitored water quality within one growing season. Our experiment demonstrated that following artificial recolonization, the submerged macrophytes could indeed persist in turbid shallow water. However, the persistence of submerged macrophytes cannot significantly improve water quality, and cannot reverse the ecosystem state of tropical shallow lakes within one growing season. Our results thus provide useful implications to the current lake restoration practices. In real-world situations, it may not be realistic to anticipate rapid restoration through macrophyte transplantation only. Monitoring the long-term effects of macrophyte transplantation is imperative for lake restoration. Our work highlights the need to harness the nuanced hidden complexity for tropical lake restoration and calls for attention to alternative stable states among practitioners of lake management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wave disturbance is the main factor leading to the low transparency in shallow lakes. • Artificial shoals can greatly alter hydrodynamic characteristics of shallow lakes. • Suitable terrain reshaping is a key basis for grass-type lake formation. This paper focuses on a typical shallow lake, Lake Changdanghu, which is subject to frequent hydrodynamic disturbances and suspended sediment deposition, resulting in reduced water clarity and the degradation of the grass-type ecosystem. Using a combination of long-term systematic observations and numerical simulations, the impact of terrain modification on the hydrodynamic characteristics of Lake Changdanghu and its resulting environmental improvements are systematically analyzed. The results indicate that there is a significant correlation between the wind wave intensity, suspended solids concentration of the water, and water clarity. The artificial shoal project effectively reduces the local wind wave intensity, increases the water area of the weak waves, and alters the flow structure and transport path of the lake. The wave reduction effect of the artificial shoal significantly improves the transparency of the local water, especially under high wind wave conditions, with a 60% increase in the sheltered area, significantly improving the physical habitat environment. Additionally, the flow resistance and guidance roles of the artificial shoal concentrate the impact of the poor water quality of the inflow in a local area, reducing its adverse effects on the main body of the lake. Our research demonstrates that for shallow lakes, the water transparency can be improved, the physical habitat conditions for aquatic vegetation can be enhanced, and grass-type ecosystems can be gradually restored through artificial intervention and vegetation recovery projects by reducing the wave energy, flow resistance, and guidance through the construction of artificial shoals. This approach achieves long-term maintenance of eutrophication control and water quality improvement in shallow lakes. [ABSTRACT FROM AUTHOR]

The jute mattings of two different densities were tested to control growth of Elodea canadensis Michx. and Myriophyllum spicatum L. in the Velký Bolevecký pond (West Bohemia, Czechia) during fourteen months. Both jute densities prove to be effective, permeable and stayed intact for one year. Results showed significant interaction among species, jute density and date in both abundance and length of Elodea and Myriophyllum fragments. When tested separately, we found the significant difference between abundance of Elodea and Myriophyllum fragments on the jute mattings, among the sites, and in time, but not between the two jute densities. Elodea dominated the sites due to spread of fragments from mowing that continued at the pond. However, the fragment length of given species varied between the two jute densities. They might easier root, but it could be also explained by the variability of sampled quadrats. Fragment lengths of Elodea and Myriophyllum were also changing in time but the length did not significantly differ between the two species or among the sites. Although Elodea and Myriophyllum dominated the jute mattings by the end, their progress was slower than in control sites. This study proved the positive effect of jute mattingson growth control of native and invasive macrophytes in shallow clear-water ponds. Result also showed significant interaction among jute density and time on abundance and length of Elodea and Myriophyllum fragment. [ABSTRACT FROM AUTHOR]

After introduction, the invasive bivalve dreissenids became key species in the biota of Lake Balaton, the largest shallow lake in Central Europe. The contribution of dreissenid soft tissue and shell, as biotic phases, in element distribution and its interaction with the water and upper sediment phases were examined in two basins with different trophic conditions in spring and autumn. Six metals (Ba, Cu, Fe, Mn, Pb, Zn) were detected in all investigated phases. In general, metals were abundant in the water and soft tissue in the eastern basin in spring, and in the sediment and shells in the western basin in autumn. This might be associated with the more urbanized surroundings in the eastern, and the enhanced organic matter production in the western basin. High relative shares of Ba, Cu, Mn, and Pb were associated with the water and shell samples, whereas high shares of Fe and Zn were noted in the soft mussel tissue and sediments. Results suggest that dynamics of metal uptake by dreissenids depend on the seasonal change in metabolic activity. Shell metal content is less changeable; shells might absorb metals from both the soft tissue and water phases. Metallothionein peptides, the scavengers of intracellular metals, were determined to be biomarkers of the bulk contaminants rather than only metals. The present study shows that invasive bivalves, with high abundance, filtering activity, and storing capacity can significantly contribute to element distribution in the shoreline of a shallow lake ecosystem. [ABSTRACT FROM AUTHOR]

Although the combined pollution of trace elements and antibiotics has received extensive attention, the fate and toxicity risk of trace elements with high antibiotic risk are still unclear. The multimedia distributions, partitioning, sources, toxicity risks and co-occurrence network characteristics of trace elements in surface water (SW), overlying water (OW), pore water (PW) and sediment (Sedi) samples of 61 sites from Baiyangdian (BYD) Lake were investigated. The trace elements in the SW and OW are derived mainly from traffic and agricultural sources, and those in PW and Sedi samples are primarily from lithogenic and industrial sources. The total toxicity risk index (TRI) of nine trace elements (ΣTRI) in Sedi samples showed a very high toxicity risk (18.35 ± 8.84), and a high combined pollution toxicity risk (ΣΣTRI) was observed in PW (149.17 ± 97.52) and Sedi samples (46.37 ± 24.00). The co-occurrence network from SW to PW became more vulnerable. Generally, total antibiotics and TP may be keystones of trace elements in water and sediment. The high antibiotic risk significantly influenced ΣΣTRI in water samples but not in Sedi samples. The findings provide new implications for the monitoring and control of combined antibiotic-trace element pollution in shallow lakes. [Display omitted] • River inflow and agriculture affected the spatial distribution of trace elements in multimedia. • Agricultural source was primary sources in water and sediments. • The co-occurrence network from surface water to pore water became more vulnerable. • Total antibiotics and TP may be keystone for the fate of trace elements in water and sediment. • The high antibiotic risk influenced combined pollution toxicity risk in water not in sediments. [ABSTRACT FROM AUTHOR]

Ecological water replenishment is a crucial and effective measure to improve the water quality and ecological function of lakes. However, the effects of ecological water replenishment on the pollution characteristics and ecological risks of trace elements and bacterial communities in lake surface water are still kept unclear. We investigated the pollution levels and potential ecological risks for trace elements, as well as variation of the bacterial community in surface water in the BYD lake before and after ecological water replenishment. Our results revealed that higher levels and pollution indexes (I geo) of trace metals (e.g., As, Cd, Co, Cu and Ni; p < 0.05) after ecological water replenishment were observed than before ecological water replenishment and their total potential ecological risk (∑RI) were increased. In contrast, the network complexity of these trace elements, including nodes, edges, average diameter, modularity, clustering coefficient and average pathlength showed a decrease after ecological water replenishment than before. The diversity (community richness, community diversity and phylogenetic diversity decreased) and community structure of the bacterial community in the surface water (p < 0.05) were greatly changed after ecological water replenishment than before, with the increase in heavy metal-resistant phylum (e.g., Acidobacteriota). Moreover, the concentration of trace elements and ∑RI were significantly correlated with the alpha diversity of bacterial community, as well as dissolved organic carbon (DOC) and ORP, after ecological water replenishment. The findings indicate that it is very necessary to continuously monitor trace metal pollution levels and heavy metal-resistant phylum and identify their potential pollution sources for water environment control and lake ecosystem health. [ABSTRACT FROM AUTHOR]

• A 3.5 °C warming of lake has marginal effect on dissolved CO 2 and CH 4 concentrations. • Monthly temperature and nutrient changes drive seasonal lake water carbon. • The dependence of CO 2 and CH 4 on temperature and nutrients is different. • The temperature threshold affecting aqueous CO 2 is likely to be around 9 °C. Shallow lake ecosystems are highly sensitive to temperature fluctuation because of their high water surface-to-volume ratios. Shallow lakes have been increasingly identified as a hotspot of CO 2 and CH 4 emissions, but their response to temperature variation remains unclear. Here, we report from a 5-month outdoor mesocosm experiment where we investigated the impacts of a projected 3.5 °C future warming and monthly temperature changes on lake CO 2 and CH 4 , as well as the key drivers affecting the lake carbon cycling. Our results show that CO 2 and CH 4 concentrations had a significantly positive correlation with monthly temperatures. CH 4 concentration was primarily regulated by monthly temperature, while nutrients effects on CO 2 concentration overrode climate warming and temporal temperature changes. These findings imply the varied roles that temperature and nutrient levels can play on CO 2 and CH 4 dynamics in shallow lake systems. The relationship between temperature and CO 2 concentration was nonlinear, showing a threshold of approximately 9 °C, at which CO 2 concentration could be strongly modified by nutrient level in the lake systems. Understanding this complex relationship between temperature with CO 2 and CH 4 concentrations in shallow lakes is crucial for effective lake management and efficient control of greenhouse gases (GHGs) emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

The Barra Velha Formation, representing the uppermost Aptian formation of the Santos Basin, predominantly comprises dolomudstones, intraclastic grainstones, and rudstones. Additionally, spherulitic and Mg-rich claystones suggest deposition in a shallow alkaline lacustrine environment. Despite the significance of reworked deposits within the Barra Velha Formation, limited attention has been given to understanding their origin, provenance, and their link to high well productivity. This study aims to characterize the reworked carbonate facies and establish their diverse genesis using a multi-scale approach. Through the analysis of core samples retrieved from the upper 19 m of the Upper Barra Velha Formation, we identified eight sedimentary facies, including microfacies grouped into two distinct associations: back-barrier deposits and foreshore-shoreface transition deposits. Back-barrier deposits consist of shrubstones, laminated shrubby spherulitestone, laminated mudstone, massive grainstone, and massive rudstone facies, composed of in situ facies and carbonates reworked by wave and distal hyper-concentrated flow. Foreshore-shoreface transition deposits comprise laminated grainstone, pebble grainstone, and massive rudstone. The facies analyses provide insights into swash-backwash effects, hyper-concentrated flow, and high wave reworking deposits. Detailed interpretation of seismic reflectors in the Uppermost interval of Barra Velha Formation revealed two distinct geometric patterns: high-amplitude onlapping seismic reflectors toward the basement and bidirectional high-amplitude reflectors on the platform edge. These patterns primarily consist of spherulitestones, shrubstones, and grainstones-packstones BHI facies. Gravity flow deposits of a fan-delta in the Lowermost interval of the Barra Velha Formation were interpreted as rudstones-grainstones and mixed reworked carbonates/volcanic rocks BHI facies, associated with low-amplitude sheet-like shape reflectors dipping toward the slope seismic reflectors. Based on the constructed onlap curve derived from the seismic lines in the study area and the described facies associations, it is evident that the lake margins are expanding, conducive to the formation of reworked facies mainly associated with wave action. • Integrating BHI, seismic, and core samples for comprehensive Barra Velha Formation reworked deposit analysis. • Identified seismic architecture in Upper Barra Velha Formation, yielding two reworked deposit models. • Well core analysis reveals two facies associations influenced by wave-reworked clastic deposits and gravity flows. • In lower interval, seismic patterns match BHI facies, indicating reworked facies from fan-delta gravity flow. • Upper reworked deposits: high exploration potential, low silicification, high porosity, good pore connectivity. [ABSTRACT FROM AUTHOR]

Submerged macrophytes play important roles in nutrient cycling and are widely used in ecological restoration to alleviate eutrophication and improve water quality in lakes. Epiphytic microbial communities on leaves of submerged macrophytes might promote nitrogen cycling, but the mechanisms and quantification of their contributions remain unclear. Here, four types of field zones with different nutrient levels and submerged macrophytes, eutrophic + Vallisneria natans (EV), eutrophic + V. natans + Hydrilla verticillata , mesotrophic + V. natans + H. verticillata , and eutrophic without macrophytes were selected to investigate the microbial communities that involved in nitrification and denitrification. The alpha diversity of bacterial community was higher in the phyllosphere than in the water, and that of H. verticillata was higher compared to V. natans. Bacterial community structures differed significantly between the four zones. The highest relative abundance of dominant bacterioplankton genera involved in nitrification and denitrification was observed in the EV zone. Similarly, the alpha diversity of the epiphytic ammonia-oxidizing archaea and nosZ I-type denitrifiers were highest in the EV zone. Consist with the diversity patterns, the potential denitrification rates were higher in the phyllosphere than those in the water. Higher potential denitrification rates in the phyllosphere were also found in H. verticillata than those in V. natans. Anammox was not detected in all samples. Nutrient loads, especially nitrogen concentrations were important factors influencing potential nitrification, denitrification rates, and bacterial communities, especially for the epiphytic nos ZI-type taxa. Overall, we observed that the phyllosphere harbors more microbes and promotes higher denitrification rates compared to water, and epiphytic bacterial communities are shaped by nitrogen nutrients and macrophyte species, indicating that epiphytic microorganisms of submerged macrophytes can effectively contribute to the N removal in shallow lakes. [Display omitted] • In shallow freshwater lakes, the epiphytic bacterial community maintained higher diversity than that of bacterioplankton. • The epiphytic microorganisms of submerged macrophytes contribute significantly to nitrogen removal. • The ability of epiphytic microorganisms to N removal is related to N nutrients and plant species. [ABSTRACT FROM AUTHOR]

Rosette‐type submerged macrophytes are widely distributed across a range of water depths in shallow lakes and play a key role in maintaining ecosystem structures and functions. However, little is known about the rapid adaptive responses of such macrophytes to variations in water depth, especially at the juvenile stage. Here, we conducted a short‐term in situ mesocosm experiment, in which the juveniles of Vallisneria natans were exposed to a water depth gradient ranging from 20 to 360 cm. Twenty‐two leaf‐related traits were examined after 4 weeks of growth in a shallow lake. Most (18) traits of V. natans generally showed high plasticity in relation to water depth. Specifically, juveniles allocated more biomass to leaves and had higher specific leaf area, leaf length‐to‐width ratio, chlorophyll content, and carotenoids content in deep waters, displaying trait syndrome associated with high resource acquisition. In contrast, V. natans juveniles in shallow waters had higher leaf dry matter content, leaf soluble carbohydrate content, carotenoids per unit chlorophyll, and peroxidase activity, pertaining to resource conservation. Notably, underwater light intensity was found to be the key factor explaining the trait plasticity along the water depth gradient, and 1.30 mol photons m−2 d−1 (at 270 cm) could be the optimal irradiance level based on the total biomass of V. natans juveniles. The present study highlights the significance of leaf trait plasticity for rosette‐type macrophytes in response to variations in water depth and sheds new light on the differences between trade‐offs in deep‐ and shallow‐water areas. [ABSTRACT FROM AUTHOR]

Palygorskite-bearing claystones and mudstones were deposited in a salt lake in the middle and lower parts of the Neogene Baiyanghe Formation in the Yangtaiwatan Basin, China. The petrological, mineralogical and geochemical characteristics of the sediments were investigated to determine the factors controlling palygorskite formation. The palygorskite claystones and mudstones have distinctly varying mineral compositions. The claystones are composed of detrital minerals, palygorskite and illite, whereas the mudstones consist mainly of mixed-layer illite/smectite and illite. The palygorskite crystals were intact with sharp edges and interwoven with other minerals, indicating an authigenic origin. The chemical characteristics indicate that the palygorskite claystones in the middle part of the Baiyanghe Formation were deposited in a salt lake environment in an arid and hot climate. As the salinity of the lake gradually increased, the detrital minerals such as quartz, feldspar, dolomite and detrital clay minerals dissolved in the alkaline medium, thus providing Si4+, Mg2+ and Al3+ for the crystallization of palygorskite. The palygorskite coexists with certain amounts of detrital quartz and feldspar with limited roundness and sorting, indicating that the shallow lake of the basin under an oxidation environment may represent a favourable environment for the crystallization of palygorskite. [ABSTRACT FROM AUTHOR]

In recent years there has been a growing interest in detecting, delimit and inventory wetlands under an ecohydrogeomorphic approach to expand the knowledge of these ecosystems and enable the development of management guidelines for their use. The aim of this article is detect and delimit those sectors that reflect favorable ecohydrogeomorphic conditions to define them as wetlands in a sector of the Alsina basin located in the southwest of the province of Buenos Aires, Argentina. A complementary methodology was applied between optiand radar images, consisting of the use of a digital AlosPalsar elevation model and Sentinel 2 A and Sentinel 1 images. A flood pulse was addressed in the shallow lake that occurred in 2017. The wet events reflect the operation of the shallow lake and the wetland systems. Biophysical changes that occurred in the perilaguna sectors were analyzed in reference to the entry of precipitations. The results verified the presence of different types of wetlands between the shallow lake and its perilagunar area that during a flood function as a hybrid ecosystem. [ABSTRACT FROM AUTHOR]

We monitored lake surface water temperatures from 1992 to 2019 in Lake Kasumigaura, a shallow lake in Japan. We hypothesized that increases of shortwave radiation had increased surface water temperatures and heat fluxes more than had the increases of air temperature. We used the heat flux analyses and the sensitivity analyses to test the hypothesis. The fluxes of solar radiation gradually increased during the study period in a manner consistent with the phenomenon of global brightening. The increase was especially apparent in the spring. The rate of increase of surface water temperature was especially significant in May. Air temperature did not significantly increase in May, but it increased significantly in June (0.40 °C decade-¹). A sensitivity analysis of the heat fluxes at the lake surface (shortwave radiation, longwave radiation, latent heat flux, and sensible heat flux) revealed that surface water temperature was more sensitive to changes of shortwave radiation than to air temperature during the spring. Although other factors such as inflows of groundwater and river water may also have impacted surface water temperatures, the increase of solar radiation appeared to be the major factor responsible for the increase of surface water temperature during the spring in Lake Kasumigaura. [ABSTRACT FROM AUTHOR]

In alluvial plains, where shallow lakes are subject to inputs of sediments, the impact of turbidity on predator–prey interactions needs to be studied. We conducted an in situ mesocosm study in a shallow floodplain lake during 36 days to evaluate the main and interactive effect of fish predation and turbidity on the abundances, composition and habitat selection of a natural aquatic assemblage, including zooplankton and plant-associated invertebrates, and the cascading effect on phytoplankton biomass. Four treatments were involved: clear water (C), clear water plus fish (CF), turbid water (T), and turbid water plus fish (TF). In each mesocosm, free-floating macrophytes were included to provide environmental heterogeneity, so organisms could display habitat selection. Fish predation was the main factor in structuring the abundances and assemblages composition regardless of turbidity condition. This was explained in part, because turbidity alone did not cause structural changes in the assemblage composition, but produced disorientation of prey organisms, weakening the effect of macrophyte roots as a refuge and favoring the consumption by fish in TF. Therefore, the trophic link between fishes and their prey was the same for zooplankton and stronger for amphipods and chironomids under turbid conditions than in clear waters. Fish caused a cascading effect on phytoplankton biomass, but it was partially counterbalanced under turbid condition due to the negative effect of clay particles on the planktonic algae due to light attenuation. Our results suggest that, within a specific turbidity range, there should be no mismatch in the trophic link between fish and phytoplankton. [ABSTRACT FROM AUTHOR]

Plutonium and 137Cs deposited in lacustrine sediments have been used for dating and radionuclide source identification. In order to determine if the radionuclides can be applied to chronogram in shallow lakes with disturbances, we investigated the vertical distribution profiles and loss ratio of plutonium isotopes and 137Cs in sediment cores from Lakes Taihu and Dianchi. We obtained that the inventory of 239+240Pu and 137Cs were lower than those for global fallout for the corresponding latitude and the loss ratios of 137Cs in Lake Taihu was 96%, evident that the loss of 137Cs inventory led to invalid chronological time scales. [ABSTRACT FROM AUTHOR]

We investigated the composition and dynamics of the zooplankton community in a Pampean seepage lake (Buenos Aires, Argentina) under different environmental (rainfall, hydrometric level, conductivity, transparency) and biotic (phytoplankton biomass and presence of submerged macrophytes) conditions. In the annual cycle analyzed, the shallow lake evidenced alternating turbid- and clear-water periods associated with changes in phytoplankton biomass and the extent of colonization by submerged macrophytes. Thirty-five species were identified (21 rotifers, nine cladocerans and five copepods). Only six species were perennial: the rotifers Brachionus caudatus, Keratella tropica; the cladoceran Ceriodaphnia dubia; and the copepods Notodiaptomus incompositus, Metacyclops mendocinus, and Microcyclops dubitabilis. The zooplankton manifested a similar annual-abundance pattern in the three sampling stations established. Density and biomass peaks occurred in autumn during the clear phase without submerged macrophytes, whereas minimum values were obtained during the turbid phase. The presence of submerged macrophytes favored the zooplankton community, as evidenced by an increased abundance (twice that recorded during the turbid period) and species richness (from 20 to 30 species), with both parameters being associated with increased possibilities for zooplankton refuge plus an incorporation of periphytic and benthic species. Rotifers always predominated numerically. The copepod contribution prevailed throughout the annual cycle with respect to biomass except in spring when the cladocerans were more prevalent. These findings demonstrated that the zooplankton community responded positively to the changes that occurred in the environmental conditions of the lake between the turbid- and the clear-water states. [ABSTRACT FROM AUTHOR]

For the management of eutrophic lakes, watershed nitrogen and phosphorus control is oriented to future water quality. Assessing future nutrient dynamics and the risk of lake eutrophication is necessary. However, current assessments often lack integrated consideration of socioeconomic and climatic factors, which reduces the reference value of the results. In this study, a typical large shallow lake Chaohu, which is highly influenced by human activities, was selected as the study area, and the current and future total nitrogen (TN) and total phosphorus (TP) loading in the basin were analysed using the improved MARINA model, and the risk of water bloom were assessed. The results showed that socioeconomic factors alone varied future TN and TP loading by −24% to 32% and −40% to 34%, respectively, under different development patterns. After considering the effect of increased precipitation, the changes of TN and TP loading became −10% to 163% and −29% to 108%, respectively. The effect on loading reduction under the sustainable development pattern was weakened (58% and 28% for TN and TP loading, respectively) and the increase in loading under the brutal development pattern was significantly amplified (409% and 215% for TN and TP loading, respectively). The adoption of active environmental policies remained an effective way of loading control. However, the risk of water bloom in local lake areas might persist due to factors such as urbanization. Timely and comprehensive assessments can provide managers with more information to identify key factors that contribute to the risk of water blooms and to develop diverse water quality improvement measures. The insights from our study are applicable to other watersheds around the world with similar socio-economic background and climatic conditions. • Analysis of the compounding effect of socio-economic and climatic factors on loading. • Complex impact of precipitation on loading under different development scenarios. • Improved MARINA model to enhance model accuracy and applicability. • Assessing the risk of future water bloom from a local perspective in the lake. [ABSTRACT FROM AUTHOR]

• Construct a phenological map of the submerged aquatic vegetation groups. • Analyze the frequency of the existence and stable growth areas from 1986 to 2021. • Analysis of the long time series distribution and trends of submerged aquatic vegetation. Submerged aquatic vegetation (SAV) is a key functional group for the restoration of wetlands and aquatic ecosystems. It plays a vital role in the stability of ecosystem structure and function in shallow lakes and reservoirs. With Baiyangdian Lake as the research area, Landsat TM/ETM+/OLI and Sentinel-2 imagery datasets were used to explore the phenological characteristics of SAV over different time scales and construct a phenological map of the SAV groups. The long-term spatial distribution characteristics and trends of SAV from 1986 to 2021 were analyzed. The results show the following: (1) the harmonic analysis of time series (HANTS) eliminated abnormal observations and noise. Normalized difference vegetation index (NDVI) time series curves generated after HANTS accurately reflected the phenological characteristics of SAV. The early spring submerged aquatic vegetation (SAV1), such as Potamogeton crispus, entered the germination period in late February at the earliest (DOY = 53). The mature period ran from April to May, after which SAV1 began to decline gradually. The length of the growing season (LOS) was about 110 days. SAV2, which was represented by Ceratophyllum demersum , Myriophyllum verticillatum , and Potamogeton pectinatus , germinated in early April (DOY = 99). The mature period ran from July to September. The length of the growing season was 210 days. (2) The decision tree constructed based on the NDVI and modified normalized difference water index (MNDWI) identified SAV with an accuracy of 89.7%. (3) The distribution range of the SAV changed dramatically during 1986–2021. According to the area change, it can be divided into a shrinkage period, expansion period, degeneration period, and initial period of recovery. The succession trend of SAV provide a theoretical scientific basis and technical support for the ecological restoration and management of shallow lake ecosystems. [ABSTRACT FROM AUTHOR]

Lake Balaton, the largest lake in Central Europe, underwent severe eutrophication from the 1960s to the 1990s, due to phosphorus loadings from external anthropogenic sources. The subsequent and complex eutrophication control and lake restoration program resulted in a significant decrease in the external phosphorus loading to the lake. Consequently, Lake Balaton has been returning to its former meso-eutrophic character. In this paper, we explore the long-term dynamics of chlorophyll a (Chl a) concentration, a proxy for phytoplankton biomass, and zooplankton biomass in Lake Balaton during its re-oligotrophication period from 2001 to 2017, and attempt to draw some conclusions on the subsequent changes in the fish stock. We found a proportional decrease in zooplankton and phytoplankton biomasses at moderate phytoplankton levels. However, below a certain phytoplankton concentration (< 10 μg l−1 Chl a), the decrease in phytoplankton biomass was not coupled with a further decline in zooplankton biomass because the fraction of small phytoplankton, edible for zooplankton, showed a much smaller decrease in biomass compared with large non-edible phytoplankton. Thus, improvements in water quality (i.e., reduced nutrient loading), partly via concomitant changes in the phytoplankton size distribution, did not cause a large difference in the fish stock in this shallow lake. [ABSTRACT FROM AUTHOR]

Little is known about the detailed community composition of heterotrophic bacterioplankton in macrophyte-dominated littoral systems, where a considerable amount of dissolved organic carbon originates from aquatic macrophytes instead of phytoplankton. The aim of the present study was to reveal the effect of macrophytes on the microbial community and to elucidate their role in a macrophyte-dominated shallow soda lake, which can be characterised by a mosaic of open waters and reed marsh. Therefore, 16S rRNA gene amplicon sequencing, the most probable number method, cultivation of bacterial strains, EcoPlate and cultivation-based substrate utilisation techniques were applied. Differences in the structures of microbial communities were detected between the water and the sediment samples and between vegetated and unvegetated water samples. Planktonic bacterial communities of an inner pond and a reed-covered area showed significant similarities to each other. Woesearchaeia was the dominant archaeal taxon in the water samples, while Bathyarchaeia, 'Marine Benthic Group D' and 'DHVEG-1' were abundant in the sediment samples. The most probable number of heterotrophic bacteria was lower in the open water than in the reed-associated areas. The vast majority (83%) of the isolated bacterial strains from the water samples of the reed-covered area were able to grow on a medium containing reed extract as the sole source of carbon. [ABSTRACT FROM AUTHOR]

Water level fluctuations (WLF), one of the most affected ecological drivers by climate change, are dominant forces controlling submerged macrophyte performance and distribution in freshwater ecosystems. Submerged macrophytes are prominent components of shallow lakes, predicting their response to WLF is therefore crucial for the management and conservation of these valuable and vulnerable ecosystems. We conducted an experiment in 15 outdoor mesocosms to explore the influence of WLF on the performance of Vallisneria spinulosa. We subjected V. spinulosa to WLF of two amplitudes and two frequencies, with stable water level as a control, and measured variations in 20 traits related with growth, sexual and asexual reproduction and resource allocation. Generally, compared with the control plants, fluctuations in water level adversely affected macrophyte biomass and growth, but increased both height and specific leaf area, which are helpful for adaptation of V. spinulosa to high-water level periods. Changes in the WLF frequency had little effect on the growth and reproduction of V. spinulosa plants apart from their leaf mass. In contrast, increased amplitude not only inhibited aboveground and root growth of V. spinulosa, but also decreased investment in sexual reproduction by influencing fruit production. V. spinulosa held a relatively stable allocation to overwintering asexual propagules in response to both components of WFL, which can maintain a capacity for clonal propagation following WLF. Moreover, as WLF amplitude increased, V. spinulosa invested a higher fraction of resources to belowground mass at the expense of their allocation to leaf mass. Our results suggest that shifts in WFL and especially magnified WLF amplitude due to climate change, may severely affect the growth and reproduction of submerged macrophytes with implications for other biota and the ecological state of shallow lakes. [ABSTRACT FROM AUTHOR]

Both runoff and water diversion can interfere with the physical and chemical environment of a lake and affect aquatic organisms. In this study, previously obtained data were used to analyze the phytoplankton community, water quality, water level, and temperature in Dongping Lake (DPH) before, during, and after the water diversion caused by the South-to-North Water Transfer Project. The results showed that the total density and diversity index of phytoplankton decreased in the water transfer period, and was related to low temperature. Temperature also affected the recovery of phytoplankton community structure when the water transfer period ended. In a water transfer cycle, changes in dominant genera were more drastic than that of a whole phytoplankton community, and dominant genera were sensitive to total phosphorus (TP) and total nitrogen (TN) changes. Water transfer alleviated the deterioration of water quality in DPH, but water transfer process increased the risk of water pollution. Runoff from Dawen River carried TN, TP, and chemical oxygen demand (COD) into DPH in the rainy season, which indirectly affected phytoplankton, while it also carried phytoplankton directly into DPH. Overall, these findings provide a clear understanding of the impact of water transfer projects on ecology in shallow lakes. [ABSTRACT FROM AUTHOR]

Dormancy is an essential component of the life cycle for populations that disappear from the plankton during winter. The hatching of resting eggs is the main mechanism for restoring active population components. Here, we analyzed the hatching dynamics of zooplankton from sediments of a shallow lake as affected by temperature. Sediment samples collected every other month were incubated at in situ temperatures and at 20°C. The highest number of individual's hatchings was observed for copepod nauplii, the cladoceran Bosmina sp., and the rotifer Brachionus havanaensis. Temperature showed a positive significant effect on the hatchlings of B. havanaensis. Other zooplankton species were less affected by temperature, and there was no relationship between their emergence from the incubated sediments and occurrence in the water column. We also tested the effect of short-term (6 and 12 weeks) and long-term (a year) storage duration on hatching success. The hatching success of B. havanaensis was not affected by the storage time. In contrast, the hatchlings of Bosmina sp. and nauplii increased after short storage time. The evidence collected here suggests that many zooplankters were not affected by temperature, while for B. havanaensis temperature turned out to be a master variable that links planktonic and passive phases. [ABSTRACT FROM AUTHOR]

We aimed to investigate the influence of environmental factors and predict zooplankton biomass and abundance in shallow eutrophic lakes. We employed time series of zooplankton and environmental parameters that were measured monthly during 38 years in a large, shallow eutrophic lake in Estonia to build estimates of zooplankton community metrics (cladocerans, copepods, rotifers, ciliates). The analysis of historical time series revealed that air temperature was by far the most important variable for explaining zooplankton biomass and abundance, followed, in decreasing order of importance, by pH, phytoplankton biomass and nitrate concentration. Models constructed with the best predicting variables explained up to 71% of zooplankton biomass variance. Most of the predictive variables had opposing or antagonistic interactions, often mitigating the effect of temperature. In the second part of the study, three future climate scenarios were developed following different Intergovernmental Panel on Climate Change (IPCC) temperature projections and entered into an empirical model. Simulation results showed that only a scenario in which air temperature stabilizes would curb total metazooplankton biomass and abundance. In other scenarios, metazooplankton biomass and abundance would likely exceed historical ranges whereas ciliates would not expand. Within the metazooplankton community, copepods would increase in biomass and abundance, whereas cladocerans would lose in biomass but not in abundance. These changes in the zooplankton community will have important consequences for lake trophic structure and ecosystem functioning. [ABSTRACT FROM AUTHOR]

The use of deconstructive approaches, such as functional classification models, can be an important tool for understanding aquatic systems. This study aimed to evaluate the distribution and community structure of mixotrophic flagellates in lakes of four large Brazilian floodplain systems, those of Amazon River, Araguaia River, Pantanal and upper Paraná River, in contrasting hydrological periods. A partial redundancy analysis (pRDA) was used to estimate the relative roles of environmental, spatial and biogeographic factors on both the entire community and a deconstructive approach using Reynolds' mixotrophic flagellate functional groups (RFGs). High environmental variability was found between the rainy and dry periods, mostly for the Amazon floodplain system. We identified 135 taxa and seven RFGs of mixotrophic flagellates: E, Lo, Q, W1, W2, Ws and Y. A permanova evidenced that biomass of mixotrophic flagellate RFGs reflected differences among floodplains and between hydrological periods. Our results showed that the use of RFGs better summarises the mixotrophic phytoplankton metacommunity structure when compared to the use of the entire community. The pRDA showed that explanatory matrices explained up to 37% of variation in the community. Environmental, spatial and biogeographic factors were important to explain the structure of the mixotrophic flagellates; however, the importance of the different components seemed to depend on the hydrological period and the traits of each RFG. [ABSTRACT FROM AUTHOR]

Shengjin Lake is a typical Yangtze River-connected lake, that is also a national nature reserve and a Wetland of International Importance. In order to evaluate the eco-environmental evolution of Shengjin Lake, a210Pb- and 137Cs-dated sediment core collected from the upper part of the lake was analyzed. Based on a biological indicator (subfossil cladoceran) and geochemical indicators (loss on ignition (LOI), total organic carbon (TOC), δ13C of bulk sediments (δ13C org), total phosphorous (TP) and total nitrogen (TN)), we revealed the changes in the cladoceran assemblages and eco-environmental processes of Shengjin Lake. The results showed that there was a healthy ecological environment with low nutrient levels in Shengjin Lake before the 1980s. However, the increasing levels of the eutrophic species B. longirostris , nutrients (TN and TP) and organic matters (LOI and TOC), and the decreasing δ13C org in recent decades indicated that the trophic state of Shengjin Lake has increased since the 1980s. This corresponded with increasing anthropogenic effects, including land reclamation, chemical fertilizer application, and sluice construction. In addition, the droppings of water birds also promoted increases in nutrient and organic matters levels in Shengjin Lake. [ABSTRACT FROM AUTHOR]

Lake Ludaš has been under a strong anthropogenic influence for a very long time, so the history of fruitful scientific investigation was very often connected with the evaluation of a human impact and potential rehabilitation measures. Unfortunately, attempts to improve the lake's natural status remain more in the field of theoretical models than concrete practical solutions. Aiming to better understand the potential of different rehabilitation measures for Lake Ludaš, we combined our ecological analyses (unpublished results) and the literature survey. The continuous massive cyanobacterial bloom and the formation of a thick sediment layer rich in different organic and inorganic pollutants represent two major challenges in the lake's rehabilitation. The unknown ecological role of invasive species that have already colonised Lake Ludaš will make the attempts to improve conditions in the lake even more challenging. The reduction of nutrient load, changes in the intensity and directions of water circulation, as well as top sediment layer removal in the lake, are measures under consideration for several decades. But their combination, order of implementation and possibilities of successful execution are still under debate. However, there is no doubt that the restoration of a natural hydrological regime should be a key step in the rehabilitation of Lake Ludaš. [ABSTRACT FROM AUTHOR]

To elucidate the patterns and characteristics of dissolved oxygen (DO) decline near bottom in shallow polymictic eutrophic lakes, we conducted a statistical analysis of monthly measurements for 12 years at 14 stations and hourly observation for 8 years at two stations in Lakes Kasumigaura and Kitaura. Results indicated that DO decline (hereafter, <2 mg/L) was negligible at stations with a depth of <5 m. Thus, we consider this depth to be critical depth for studying DO decline conditions in these lakes. The collected data revealed that DO decline events lasting more than 2 days occurred a few times a year. During these events, wind blew weakly (usually, <2 m/s), and diurnal stratification was formed by solar radiation. The averaged DO declining rate leading up to these events was 4.3 (±2.7) mg L−1 d−1, suggesting that within a few days, DO can fall into a declined state. The occurrence probability of DO declined events in the respective summer increased significantly with the proportion of weak wind hours (<2 m/s). Significant correlations between wind velocity and DO change rate (1 hr difference in DO) supported the importance of wind on DO changes in polymictic lakes. The influence of mean air temperature on DO decline events was insignificant. [ABSTRACT FROM AUTHOR]

Positive feedbacks are generally related to the interactions between biotic processes and abiotic drivers and may lead to the emergence of alternative stable states in ecosystems. Understanding the mechanisms of self-reinforcing feedbacks in a macrophyte-dominant clear state is critical for lake management. Based on a survey of 35 lakes in the Yangtze River floodplain and canonical correspondence analysis (CCA) with forward selection, the results showed that water clarity is the most limiting factor that influences the community structure and biomass of submerged macrophytes. The canopy length of tall macrophytes (i.e. , Myriophyllum spicatum L. and Potamogeton malaianus Miq.) showed positive allometry with plant height, while the canopy length of small macrophytes (e.g. , Potamogeton maackianus A. Benn.) showed isometry. Our results indicated the existence of positive feedbacks between macrophyte vegetation and water clarity in a "more vegetation, higher water clarity" pattern. We found that the relationships between monospecific community biomass and water clarity differed among community types, indicating that the strength of the positive feedback was interspecific. Furthermore, we found significant differences in the Secchi depth (SD), chlorophyll a (Chl a), light attenuation coefficient (K) and dissolved oxygen (DO) associated with monospecific macrophyte patches. Plant height had significant relationships with the mean values of SD, Chl a, total phosphorus (TP) and K, suggesting that plant height was one of the mechanisms underlying the positive feedbacks. In management practices, efforts to build and maintain the resilience of an ecosystem should be trait-based rather than merely focusing on vegetation abundance. Unlabelled Image • Light availability is a limiting factor that influences submerged macrophytes. • Our results indicate the presence of a positive feedback loop between more vegetation and increased water clarity. • Small macrophytes exhibit stronger positive feedbacks than large macrophytes. • Trait-based management is recommended rather than focusing on only plant abundance. [ABSTRACT FROM AUTHOR]

The release of pharmacologically active compounds (PhACs) into aquatic ecosystems poses an environmental risk resulting in a chronic exposure of non-target organisms. A great variety of PhACs, of generally low concentrations, and the complicated sample preparation, makes circumstantial the accurate detection and quantification. Additionally, there is little information published about the spatiotemporal variation of the PhAC load in a larger catchment area utilised for touristic purposes. In addition to the natural biotic and abiotic changes, the seasonal variation of tourism also has a dramatic impact on water quality and the natural ecosystem in larger catchment areas. Therefore, our aim was to develop a reliable solid-phase extraction (SPE)-supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS) method for simultaneous multi-residue analysis of drugs to reveal the spatiotemporal changes in the PhAC contaminations in the waters of an important touristic region, the catchment area of the largest shallow lake in Central Europe, Lake Balaton (Hungary). The environmental application of the developed method revealed 69 out of the traced 134 chemical compounds, including 15 PhACs, which were detected from natural waters for the first time. Wastewater treatment plant (WWTP) loads have a major role in the PhAC contamination of the studied area; at the same time, the mass tourism-induced PhAC contamination was also detectable. Furthermore, the impact of tourism was indicated by elevated concentrations of recreational substances (e.g., caffeine and illicit drugs) in the touristic season affecting the water quality of this important summer holiday destination. Unlabelled Image • The SPE SFC-MS/MS method offers multi-residue analysis from surface water sample. • Investigation of spatiotemporal variation of the PhAC load in a large catchment area • Effect of mass tourism is detectable in the seasonal changes of drug contamination. • The wetlands can play a significant role in reducing PhACs concentrations. [ABSTRACT FROM AUTHOR]

Habitat complexity drives aquatic community attributes, including the beta diversity components. We tested the hypothesis that community diversity, richness and density are higher on complex artificial substrates than on simple ones. Additionally, we hypothesised that the species occurrence would change from the simplest substrates to the more complex ones because complex habitats provide more niches and methods of exploiting environmental resources, thereby supporting larger numbers of organisms. We expected that the periphytic community would present a nestedness pattern when considering the quantitative index and turnover for the qualitative index. The effect of habitat complexity on the beta diversity was mediated by the relative species abundances. The periphytic algae density was higher on the complex substrates, but contrary to our expectations, the species richness and diversity did not increase on the complex substrates. Based on our findings, we suggest that habitat complexity can play a crucial role in structuring beta diversity patterns. However, we highlight that the responses of species turnover and nestedness to the variation in habitat complexity contrasted with the abundance and species occurrence approach. Additionally, we suggest that the species richness patterns in the periphytic community are independent of increases in the number of individuals. [ABSTRACT FROM AUTHOR]

Mixed siliciclastic–carbonate sediments were well developed in the BZ‐X block as a subunit in the Huanghekou Sag in the southeastern part of the Bohai Bay Basin (China) during the Member 1 of the Shahejie Formation. An integrated approach based on detailed microscopic observation and core descriptions was applied to characterize the lithofacies types, facies associations, and depositional environment of the mixed sediments system. A detailed sedimentary facies analysis suggests that various lithofacies types can be grouped into four facies associations: mixed bioclastic sandy beaches (FA1), mixed clastic bioclastic shoal (FA2), mixed sandy oolitic shoals (FA3), and mixed distal bioclastic sandy beaches (FA4). These facies associations are interpreted to be deposited in varying depositional environments ranging from foreshore to shoreface setting in a shallow lake setting. An interplay of the climate regime, nearshore carbonate productivity, and current activity was proved to control the lithofacies types, dispersion and depositional environment change of mixed sediments in different depositional phases. Meter‐scale mixed cycles were found in this shallow lake setting and their features seem to differ from the classical mixed sediment models. It is suggested that these particular cycles in the stratigraphic record might indicate a typical mark of mixed sediment system in shallow areas of the lacustrine basin. [ABSTRACT FROM AUTHOR]

Antibiotics are widely found in aquatic ecosystems and pose a serious threat to human and the ecological system. Samples of surface water (SW), overlying water (OW), pore water (PW) and sediments (Sedi) were collected to investigate the spatial variability, potential sources, ecological risk (RQs) and health risks (HQs) of nine common antibiotics in Baiyangdian Lake using positive matrix factorization (PMF), and Monte Carlo simulation. Significant spatial autocorrelation of most antibiotics were observed in PW and Sedi samples rather than in SW and OW samples, and higher antibiotic levels were found in the northwest of waters and the southwest of sediments. Livestock (26.74–35.57%) and aquaculture (21.62–37.70%) were identified as primary sources of antibiotics in the water and sediments. Norfloxacin and roxithromycin showed high levels of RQ and HQ in more than 50% of samples, respectively. The combined RQ (ΣRQ) in the PW can be used as a sign of across multimedia risk. Notably, appreciable health risks were observed for the combined HQ (ΣHQ) in about 80% of samples, indicating the importance of taking health risk of antibiotics into consideration. The findings of this work provides a reference for antibiotics pollution control and risk management in shallow lake. [Display omitted] • The three quinolones were common dominant antibiotics in water and sediment. • Higher antibiotic levels were found in northwest water and in southwest sediment. • Aquaculture and livestock were the main sources of antibiotics. • Combined ecological risk in porewater can be used as a sign of across multimedia risk. • Combined health risk remains a concern due to 80% sites posed appreciable health risks. [ABSTRACT FROM AUTHOR]

Antibiotics are ubiquitous pollutants that are widely found in aquatic ecosystems, where the bacterial community of aquatic plants is influenced by antibiotics. However, differences between endophyte and phyllosphere bacteria of Lotus from above and below surface water remains unclear. Lotus samples from above and below the surface water were collected to investigate the differences in endophyte and phyllosphere bacteria and dominant environmental factors in regions with low (L-) and high (H-) total antibiotic levels. There were significant differences in Shannon diversity between endophyte and phyllosphere bacteria except between the below-surface water phyllosphere bacteria and below-surface water endophytes in both L-antibiotic and H-antibiotic regions, with higher values for phyllosphere bacteria. The dominant phylum in all phyllosphere samples was Proteobacteria (76.1%–92.5%), while Cyanobacteria (47.8%–81.1%) was dominant in all endophyte samples. The dominant source of above-surface water endophytes was below-surface water endophytes (83.68–91.25%), below-surface water phyllosphere bacteria (48.43–55.91%) for above-surface water phyllosphere bacteria, and above-surface water endophytes (53.83–61.80%) for below-surface water endophytes, while the dominant contributor to the below-surface water phyllosphere bacteria was also below-surface water endophytes (52.96–61.00%) in two regions, indicating that antibiotic stress changed the sink‒source relationship between endophytes and phyllosphere bacteria. The physical-chemical properties of surface water and sediments could be responsible for the variations in the above- and below-surface water endophytes and phyllosphere bacteria in both regions. It is suggested that antibiotics may have a substantial effect on endophyte and phyllosphere bacterial community. • Phyllosphere showed higher Shannon diversity than endophyte under antibiotic stress. • Antibiotics stress changed the sink-source relationship of aquatic plants bacteria. • The main phylum in phyllosphere and endophyte was Proteobacteria and Cyanobacteria. • High concentration of antibiotic shaped below-surface water phyllosphere bacteria. [ABSTRACT FROM AUTHOR]

• High-turbidity events are triggered by wind waves with wind speeds of > 7 m s−1. • Sediment erosion and deposition are synchronous during HTEs. • Synchronism causes a near-lakebed turbid water layer and sustains the lutocline. High-turbidity events (HTEs) frequently occur in shallow lakes and can deeply influence lake ecosystems. However, the processes of sediment erosion and deposition are not fully understood. To investigate these processes, two investigative campaigns that integrate bed sediment measurements, sediment settling experiments, in-situ observations, or a hydrodynamics-sediment model were conducted to quantitatively study wind-induced HTEs in Lake Taihu, China. Cohesive sediments were massively entrained from the lakebed by wind waves when the wind speed exceeded its critical value of 7 m s−1, as estimated by water depth, triggering HTEs with turbidity waves of > 100 nephelometric turbidity units. The suspended sediment concentration was the net sediment flux of erosion (average: 5.9 mg m−2 s−1) and deposition (average: 5.5 mg m−2 s−1), which occurred synchronously for most of the HTEs and resulted in high temporal variation in suspended sediment concentration. This synchronism was determined by the critical erosional stress of lakebed sediments, which was spatially heterogeneous (0.017–0.055 N m−2) in a large lake. Equations for erosion and deposition processes were derived following the investigative campaigns and used to develop a cohesive sediment transport model for simulating HTEs in Lake Taihu. Simulations indicate that the synchronism of sediment erosion and deposition led to a near-lakebed turbid water layer during an HTE, which sustained the sediment lutocline in Lake Taihu. Further investigation should be conducted on the role of the near-lakebed turbid water layer during endogenous pollution in large eutrophic lakes. [ABSTRACT FROM AUTHOR]