Exploring the diversity of dissolved organic matter (DOM) properties and sources in different functional areas of a typical macrophyte - derived lake combined with optical spectroscopy and FT-ICR MS analysis.

Lake Baiyangdian is one of China's largest macrophyte - derived lakes, facing severe challenges related to water quality maintenance and eutrophication prevention. Dissolved organic matter (DOM) was a huge carbon pool and its abundance, property, and transformation played important roles in the biogeochemical cycle and energy flow in lake ecosystems. In this study, Lake Baiyangdian was divided into four distinct areas: Unartificial Area (UA), Village Area (VA), Tourism Area (TA), and Breeding Area (BA). We examined the diversity of DOM properties and sources across these functional areas. Our findings reveal that DOM in this lake is predominantly composed of protein - like substances, as determined by excitation - emission matrix and parallel factor analysis (EEM - PARAFAC). Notably, the exogenous tyrosine-like component C1 showed a stronger presence in VA and BA compared to UA and TA. Ultrahigh - resolution mass spectrometry (FT - ICR MS) unveiled a similar DOM molecular composition pattern across different functional areas due to the high relative abundances of lignan compounds, suggesting that macrophytes significantly influence the material structure of DOM. DOM properties exhibited specific associations with water quality indicators in various functional areas, as indicated by the Mantel test. The connections between DOM properties and NO3N and NH3N were more pronounced in VA and BA than in UA and TA. Our results underscore the viability of using DOM as an indicator for more precise and scientific water quality management.

A novel hierarchical network-based approach to unveil the complexity of functional microbial genome.

Biological networks serve a crucial role in elucidating intricate biological processes. While interspecies environmental interactions have been extensively studied, the exploration of gene interactions within species, particularly among individual microorganisms, is less developed. The increasing amount of microbiome genomic data necessitates a more nuanced analysis of microbial genome structures and functions. In this context, we introduce a complex structure using higher-order network theory, "Solid Motif Structures (SMS)", via a hierarchical biological network analysis of genomes within the same genus, effectively linking microbial genome structure with its function. Leveraging 162 high-quality genomes of Microcystis, a key freshwater cyanobacterium within microbial ecosystems, we established a genome structure network. Employing deep learning techniques, such as adaptive graph encoder, we uncovered 27 critical functional subnetworks and their associated SMSs. Incorporating metagenomic data from seven geographically distinct lakes, we conducted an investigation into Microcystis' functional stability under varying environmental conditions, unveiling unique functional interaction models for each lake. Our work compiles these insights into an extensive resource repository, providing novel perspectives on the functional dynamics within Microcystis. This research offers a hierarchical network analysis framework for understanding interactions between microbial genome structures and functions within the same genus.

Four new species of Cichlidogyrus (Platyhelminthes, Monopisthocotyla, Dactylogyridae) from Lake Victoria haplochromine cichlid fishes, with the redescription of C. bifurcatus and C. longipenis.

African cichlids are model systems for evolutionary studies and host-parasite interactions, because of their adaptive radiations and because they harbour many species of monogenean parasites with high host-specificity. Five locations were sampled in southern Lake Victoria: gill-infecting monogeneans were surveyed from 18 cichlid species belonging to this radiation superflock and two others representing two older and distantly related lineages. We found one species of Gyrodactylidae, Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, and seven species of Dactylogyridae. Four are described herein: Cichlidogyrus pseudodossoui n. sp., Cichlidogyrus nyanza n. sp., Cichlidogyrus furu n. sp., and Cichlidogyrus vetusmolendarius n. sp. Another Cichlidogyrus species is reported but not formally described (low number of specimens, morphological similarity with C. furu n. sp.). Two other species are redescribed: C. bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Our results confirm that the monogenean fauna of Victorian littoral cichlids displays lower species richness and lower host-specificity than that of Lake Tanganyika littoral cichlids. In C. furu n. sp., hooks V are clearly longer than the others, highlighting the need to re-evaluate the current classification system that considers hook pairs III-VII as rather uniform. Some morphological features of C. bifurcatus, C. longipenis, and C. nyanza n. sp. suggest that these are closely related to congeners that infect other haplochromines. Morphological traits indicate that representatives of Cichlidogyrus colonised Lake Victoria haplochromines or their ancestors at least twice, which is in line with the Lake Victoria superflock being colonised by two cichlid tribes (Haplochromini and Oreochromini).

Title: Quatre espèces nouvelles de Cichlidogyrus (Plathelminthes, Monopisthocotyla, Dactylogyridae) parasites d'haplochrominés (Cichlidae) du lac Victoria, avec la redescription de C. bifurcatus et C. longipenis. Abstract: Les cichlidés africains sont des systèmes modèles pour les études évolutives et les interactions hôtes-parasites, en raison de leurs radiations adaptatives et parce qu'ils hébergent de nombreuses espèces de monogènes parasites avec une spécificité d'hôte étroite. Cinq sites ont été échantillonnés dans le sud du lac Victoria, les monogènes infectant les branchies ont été étudiés chez 18 espèces de cichlidés appartenant à ce superflock et de deux autres espèces représentant deux lignées plus anciennes et éloignées. Nous avons trouvé une espèce de Gyrodactylidae, Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, et sept espèces de Dactylogyridae. Quatre sont décrites ici : Cichlidogyrus pseudodossoui n. sp., Cichlidogyrus nyanza n. sp., Cichlidogyrus furu n. sp. et Cichlidogyrus vetusmolendarius n. sp. Une autre espèce de Cichlidogyrus est signalée mais non formellement décrite (faible nombre de spécimens, similarité morphologique avec C. furu n. sp.). Deux autres espèces sont redécrites : C. bifurcatus Paperna, 1960 et C. longipenis Paperna & Thurston, 1969. Nos résultats confirment que la faune des monogènes des cichlidés du littoral du lac Victoria présente une richesse en espèces et une spécificité d'hôte inférieures à celles des cichlidés du littoral du lac Tanganyika. Chez C. furu n. sp., les crochets V sont clairement plus longs que les autres, ce qui souligne la nécessité de réévaluer le système de classification actuel qui considère que les crochets III-VII sont plutôt uniformes. Certaines caractéristiques morphologiques de C. bifurcatus, C. longipenis et C. nyanza n. sp. suggèrent que ceux-ci sont étroitement liés aux congénères qui infectent les autres haplochrominés. Les traits morphologiques indiquent que les représentants de Cichlidogyrus ont colonisé les haplochrominés du lac Victoria ou leurs ancêtres au moins deux fois, ce qui concorde avec le fait que le superflock du lac Victoria a été colonisé par deux tribus de cichlidés (Haplochromini et Oreochromini).

Effect of local and regional factors on the structure of the fish communities associated with aquatic macrophyte stands in oxbow lakes on the Amazon floodplain.

The Amazon floodplain is home to an extremely high diversity of fish, with lakes playing an important role in the establishment of this biological richness. These lacustrine environments are subject to constant fluctuations caused by the annual flood pulse, with local factors and other regional patterns also contributing to the variation in fish community structure. The present study verified how local (depth and transparency of the water, the size and species composition of the macrophyte stands) and regional factors (spatial distribution of the stands and the hydrological phase) influence the structure of the fish community of the floodplain lakes of the Môa River, in northern Brazil. Fish species richness was influenced by the depth of the water and the spatial distribution of the macrophyte stands. Fish species composition was influenced by local environmental variables, spatial structure, and the hydrological phase. However, variation partitioning indicated that only the hydrological phase explained the variation in fish composition. These findings indicate that the local environment, the spatial structure, and the hydrological phase drive changes in the structure of the fish communities associated with aquatic macrophytes in the floodplain lakes of the Amazon basin.

Environmental gradients and optimal fixation time revealed with DNA metabarcoding of benthic sample fixative.

Assessments of biodiversity and ecosystem status can benefit from DNA metabarcoding as a means to streamline sample processing and specimen identification. Moreover, processing the fixation medium instead of the precious material introduces straightforward protocols that allow subsequent focus on certain organisms detected among the preserved specimens. In this study, we present a proof of concept via the analysis of freshwater invertebrate samples from the Tatra Mountain lakes (Slovakia). Besides highlighting a match between the lake-specific environmental conditions and the results of our fixative DNA metabarcoding, we observed an option to fine-tune the fixation time: to prefer two weeks over a day or a month. This effect emerged from the presence/absence of individual taxa rather than from coarse per-sample records of taxonomic richness, demonstrating that metabarcoding studies-and efforts to optimize their protocols-can use the robust metrics to explore even subtle trends. We also provide evidence that fixative DNA might better capture large freshwater species than terrestrial or meiofauna.

Human activities-impacted lake dissolved organic matter (DOM) affects phycosphere microbial diversity and DOM diversification via carbon metabolism.

Photosynthetic carbon sequestration and microbial carbon metabolism are major processes of algae-bacteria interactions, affecting pollutant degradation as well as fundamental biogeochemical cycles in aquatic systems. Human-induced land-use changes greatly alter the molecular composition and input of terrestrial dissolved organic matter (DOM) in inland lakes. However, how the origin of DOM leads to varying effects on phycosphere microbial communities or molecular composition of DOM, e.g., via carbon metabolism, has been little studied in freshwater. Here, we incubated the cyanobacterium Microcystis aeruginosa and a bacterial community from natural lakes to establish an alga-bacteria model system. This allowed us to investigate how DOM from different sources affects phycosphere microbial diversity and DOM diversification. We showed that Suwannee River fulvic acid (SRFA), Suwannee River natural organic matter (SRNOM) and cropland lake DOM promote algal growth, whereas DOM from an urban lake inhibits algal growth. Algal metabolites and DOM together shaped the chemotaxis response of phycosphere communities. High-resolution mass spectrometry analysis demonstrated that DOM chemo-diversity tended to become uniform after interactions of diverse DOM sources with the algae-bacteria symbiosis system. Molecular thermodynamic analysis of DOM based on a substrate-explicit model further verified that microbial interactions render DOM less bioavailable and thus increase recalcitrant DOM formation. Metabolome analysis uncovered that DOM addition intensifies metabolic pathways related to labile and recalcitrant DOM utilization (mainly lignin/carboxyl-rich alicyclic molecule (CRAM)-like DOM, unsaturated hydrocarbon), whereby cofactor and vitamin metabolism represented an extremely strong activity in all metabolic pathways. Our results highlight covariation and interactions of DOM with microbial metabolism at the molecular level and expands our understanding of microbially mediated DOM shaping aquatic carbon cycling.

In search of the pH limit of growth in halo-alkaliphilic cyanobacteria.

Cyanobacteria have many biotechnological applications. Increasing their cultivation pH can assist in capturing carbon dioxide and avoiding invasion by other organisms. However, alkaline media may have adverse effects on cyanobacteria, such as reducing the Carbon-Concentrating Mechanism's efficiency. Here, we cultivated two halo-alkaliphilic cyanobacteria consortia in chemostats at pH 10.2-11.4. One consortium was dominated by Ca. Sodalinema alkaliphilum, the other by a species of Nodosilinea. These two cyanobacteria dominate natural communities in Canadian and Asian alkaline soda lakes. We show that increasing the pH decreased biomass yield. This decrease was caused, in part, by a dramatic increase in carbon transfer to heterotrophs. At pH 11.4, cyanobacterial growth became limited by bicarbonate uptake, which was mainly ATP dependent. In parallel, the higher the pH, the more sensitive cyanobacteria became to light, resulting in photoinhibition and upregulation of DNA repair systems.

Assessment of the ecological status of the river water system in European North under conditions of ultra-fresh humus waters using biotic indices (Suna River, Lake Onega Basin, Russia).

Protecting rivers and lakes from pollution is crucial for maintaining the health of aquatic ecosystems and ensuring the well-being of both wildlife and humans. Present study intends to examine the water quality of the Suna River (Eastern Fennoscandia in the European North of Russia) to assess the ecological risk. Widespread methods for assessing water quality based on macrozoobenthos and phytoperiphoton were applied. It was found that in conditions of ultra-fresh waters with high humus content, biotic indicators may indicate pollution of water bodies that do not actually experience significant anthropogenic impact. Ratings ranging from 'poor' to 'excellent' were obtained for different stations, reflecting the influence of natural features of different sections of the river. 'Good' water quality was noted at the river stones biotopes. In river gravel, sand and silt biotopes, as well as all lake biotopes, 'mediocre' water quality was found. The low anthropogenic income on the river catchment allows us to conclude that most indices for assessing water quality significantly underestimate the results in the natural conditions of Eastern Fennoscandia. Biotic indices EPT, BBI and EBI are most accurate for assessing the water quality of rivers and lakes in Eastern Fennoscandia.

Spatial differences of dissolved organic matter composition and humification in an artificial lake.

The depth-dependent dynamics of dissolved organic matter (DOM) structure and humification in an artificial lake limits the understanding of lake eutrophication and carbon cycling. Using fluorescence regional integration (FRI) and parallel factor analysis (PARAFAC) models to analyze the 3D fluorescence spectroscopy dataset, we revealed the depth-dependent structure and vertical distribution of DOM in the estuarine and center regions of Lake Hongfeng. The percentage fluorescence response (Pi,n) showed humic acid is an important part of DOM in Lake Hongfeng. Fluorescence results show that the fulvic-like and protein-like materials in HF1-DOM located at the estuarine position showed greater variation in the middle stage, probably due to human influence and sediment suspension. Fluorescence index (PI+II+IV,n/PIII+V,n and FIC4/FIC3) can be used to indicate the degree of humification of DOM in artificial lakes. Results of each index show that the estuary is more affected by human activities, and the humification degree is significantly lower than that of the center of the lake. The evaluation index system of the humification degree of artificial lake established in this study can effectively predict the eutrophication state of the typical area of artificial lake and deeply understand the possible important influence of human activities on the carbon cycle of lake.

Risk of capture is modified by hypoxia and interjurisdictional migration of Lake Whitefish (Coregonus clupeaformis).

Interjurisdictional migrations lead to seasonally changing patterns of exploitation risk, emphasizing the importance of spatially explicit approaches to fishery management. Understanding how risk changes along a migration route supports time-area based fishery management, but quantifying risk can be complicated when multiple fishing methods are geographically segregated and when bycatch species are considered. Further, habitat selection in dynamic environments can influence migration behavior, interacting with other management objectives such as water quality and habitat restoration. As a case study, we examined a novel acoustic telemetry data set for Lake Whitefish in Lake Erie, where they migrate through multiple spatial management units that are variably affected by seasonal hypoxia and host a variety of fisheries. Combining telemetry results with fishery catch and water quality monitoring, we demonstrate three exploitation risk scenarios: (i) high risk due to high residency and high catch, (ii) high risk due to high residency in time-areas with moderate catch, and (iii) low risk due to residency in time-areas with low catch. Interestingly, occupation of low risk refugia was increased by the development of hypoxia in adjacent areas. Consequently, fishery management goals to sustainably manage other target species may be directly and indirectly linked to water quality management goals through Lake Whitefish.

The interaction between warming and enrichment accelerates food-web simplification in freshwater systems.

Nutrient enrichment and climate warming threaten freshwater systems. Metabolic theory and the paradox of enrichment predict that both stressors independently can lead to simpler food-webs having fewer nodes, shorter food-chains and lower connectance, but cancel each other's effects when simultaneously present. Yet, these theoretical predictions remain untested in complex natural systems. We inferred the food-web structure of 256 lakes and 373 streams from standardized fish community samplings in France. Contrary to theoretical predictions, we found that warming shortens fish food-chain length and that this effect was magnified in enriched streams and lakes. Additionally, lakes experiencing enrichment exhibit lower connectance in their fish food-webs. Our study suggests that warming and enrichment interact to magnify food-web simplification in nature, raising further concerns about the fate of freshwater systems as climate change effects will dramatically increase in the coming decades.

Spatio-temporal analysis and prediction of land use land cover (LULC) change in Wular Lake, Jammu and Kashmir, India.

Landsat land use/land cover (LULC) data analysis to establish freshwater lakes' temporal and spatial distribution can provide a solid foundation for future ecological and environmental policy development to manage ecosystems better. Analysis of changes in LULC is a method that can be used to learn more about direct and indirect human interactions with the environment for sustainability. Neural network technology significantly facilitates mapping between asymmetric and high-dimensional data. This paper presents a methodological advancement that integrates the CA-ANN (cellular automata-artificial neural network) technique with the dynamic characteristics of the water body to forecast forthcoming water levels and their spatial distribution in "Wular Lake." We used remote sensing data from 2001 to 2021 with a 10-year interval to predict spatio-temporal change and LULC simulation. The validation of the calibration of predicted and accurate LULC maps for 2021 yielded a maximum kappa value of 0.86. Over the past three decades, the study region has seen an increase in a net change % in the impervious surface of 22.41% and in agricultural land by 52.02%, while water decreased by 14.12%, trees/forests decreased by 40.77%, shrubs decreased by 11.53%, and aquatic vegetation decreased by 4.14%. Multiple environmental challenges have arisen in the environmentally sustainable Wular Lake in the Kashmir Valley due to the vast land transformation, primarily due to human activities, and have been predominantly negative. The research acknowledges the importance of (LULC) analysis, recognizing it as a fundamental cornerstone for developing future ecological and environmental policy frameworks.

Limited Impacts of Water Diversion on Micro-eukaryotic Community along the Eastern Route of China's South-to-North Water Diversion Project.

The Eastern Route of the South-to-North Water Diversion Project (ER-SNWDP) represents a crucial initiative aimed at alleviating water scarcity in China's northern region. Understanding the dynamics governing the composition and assembly processes of micro-eukaryotic communities within the canal during different water diversion periods holds paramount significance for the effective management of the ER-SNWDP. Our study systematically tracks the dynamics of the micro-eukaryotic community and its assembly processes along the 1045.4 km of canals and four impounded lakes, totaling 3455 km2, constituting the ER-SNWDP during a complete water diversion cycle, utilizing high-throughput sequencing, bioinformatics tools, and null modeling algorithms. The primary objectives of this study are to elucidate the spatial-temporal succession of micro-eukaryotic communities as the water diversion progresses, to delineate the relative importance of deterministic and stochastic processes in community assembly, and to identify the pivotal factors driving changes in micro-eukaryotic communities. Our findings indicate notable variations in the composition and diversity of micro-eukaryotic communities within the ER-SNWDP across different water diversion periods and geographic locations (P < 0.05). This variation is influenced by a confluence of temporal and environmental factors, with limited impacts from water diversion. In essence, the assembly of micro-eukaryotic communities within the ER-SNWDP primarily stemmed from heterogeneous selection driven by deterministic processes. Water diversion exhibited a tendency to decrease community beta diversity while augmenting the influence of stochastic processes in community assembly, albeit this effect attenuated over time. Furthermore, our analysis identified several pivotal environmental parameters, notably including nitrite-nitrogen, nitrate-nitrogen, orthophosphate, and water temperature, as exerting significant effects on micro-eukaryotic communities across different water diversion periods. Collectively, our study furnishes the inaugural comprehensive exploration of the dynamics, assembly processes, and influencing factors governing micro-eukaryotic communities within the ER-SNWDP, thus furnishing indispensable insights to inform the water quality management of this important project.

Microplastics pollution in tropical lakes: water, zooplankton, and fish in Central Mexico.

The presence of microplastics in freshwater systems can have harmful effects on the food chain. Zooplankton, especially suspension and filter feeders, can ingest microplastics, which can cause adverse effects and transfer them to higher trophic levels. Here, we analyze the presence, abundance, and distribution of microplastics in surface water, zooplankton, and fish in two tropical lakes in central Mexico. We collected water samples in triplicate at three sites in each lake and 120 fish of the genus Chirostoma. From each water sample, 300 rotifers and 150 microcrustaceans were randomly isolated and processed independently. Of the particles found in the water, zooplankton, and fish from both lakes, the fragments were the predominant ones. The total abundance of microplastics in the water column of both lakes varied between 1.2 and 17.0 items L-1. In zooplankton, fragments were found predominantly with up to 0.1 items ind-1, while in fish, up to 4.5 items ind-1 was recorded. Our results confirm the presence of microplastics in different compartments of the food webs of freshwater bodies, water column, zooplankton, and fish. Further work is required on the possible effects of these stressors at the different trophic levels.

Centimetre scale functional dispersal limitation of freshwater copiotrophs.

The freshwater microbiome harbours numerous copiotrophic bacteria that rapidly respond to elevated substrate concentrations. We hypothesized that their high centimetre-scale beta diversity in lake water translates into pronounced metabolic variability, and that a large fraction of microbial 'metabolic potential' originates from point sources such as fragile organic aggregates. Three experiments were conducted in pre-alpine Lake Zurich over the course of a harmful cyanobacterial bloom: Spatially explicit 9 ml 'syringe' samples were collected in situ at centimetre distances along with equally sized 'mixed' samples drawn from pre-homogenized lake water and incubated in BIOLOG EcoPlate substrate arrays. Fewer compounds promoted bacterial growth in the syringe than in the mixed samples, in particular during the pre- and late bloom periods. Community analysis of enrichments on three frequently utilized substrates revealed both pronounced heterogeneity and functional redundancy. Bacterial consortia had higher richness in mixed than in syringe samples and differed in composition. Members of the Enterobacter cloacae complex dominated the EcoPlate assemblages during the mid-bloom period irrespective of treatment or substrate. We conclude that small-scale functional dispersal limitation among free-living copiotrophs in lake water reduces local biotransformation potential, and that lacustrine blooms of harmful cyanobacteria can be environmental reservoirs for metabolically versatile potential pathogens.

Assessment of health risks associated with heavy metal contamination in selected fish and crustacean species from Temsah Lake, Suez Canal.

Marine pollution caused by heavy metals has emerged as a significant environmental concern, garnering increased attention in recent years. The accumulation of heavy metals in the tissues of marine organisms poses substantial threats to both marine ecosystems and human populations that rely on seafood as a primary food source. Fish and crustaceans are effective biomonitors for assessing heavy metal contamination in aquatic environments. In this study, we determined the concentrations of several heavy metals, including cadmium (Cd), lead (Pb), nickel (Ni), mercury (Hg), and tin (Sn), in four fish species (Mugil cephalus, Mugil capito, L. aurata, and Morone labrax) and five crustacean species (S. rivulatus, Cerastoderma glaucum, Paratapes undulatus, R. decussatus, Callinectes sapidus, and Metapenaeus Stebbingi) from Temsah Lake during both winter and summer seasons. To evaluate the potential ecological and health risks associated with consuming these fish and crustacean species, we calculated the metal pollution index (MPI), weekly intake (EWI), target hazard quotient (THQ), and carcinogenic risk (CR) values. The results revealed a noticeable increase in metal levels during the summer compared to winter in the studied samples. Moreover, the concentration of heavy metals in the muscles of the species generally exceeded those in the liver and gills. The MPI values indicated that Morone labrax exhibited the highest values during winter, while L. aurata showed the highest values during summer. Mugil cephalus demonstrated the lowest MPI values in both seasons. The EWI values for the studied metals were found to be lower than the corresponding tolerable weekly intake (TWI) values. Additionally, under average exposure conditions, the THQ and HI data were generally below one for most study species in the area. The calculated CR values for investigated metals in the studied species indicated acceptable carcinogenic risk levels. Therefore, this suggests that consuming studied species within Temsah lake does not present any potential health hazards for consumers.

Origin of the Laurentian Great Lakes fish fauna through upward adaptive radiation cascade prior to the Last Glacial Maximum.

The evolutionary histories of adaptive radiations can be marked by dramatic demographic fluctuations. However, the demographic histories of ecologically-linked co-diversifying lineages remain understudied. The Laurentian Great Lakes provide a unique system of two such radiations that are dispersed across depth gradients with a predator-prey relationship. We show that the North American Coregonus species complex ("ciscoes") radiated rapidly prior to the Last Glacial Maximum (80-90 kya), a globally warm period, followed by rapid expansion in population size. Similar patterns of demographic expansion were observed in the predator species, Lake Charr (Salvelinus namaycush), following a brief time lag, which we hypothesize was driven by predator-prey dynamics. Diversification of prey into deep water created ecological opportunities for the predators, facilitating their demographic expansion, which is consistent with an upward adaptive radiation cascade. This study provides a new timeline and environmental context for the origin of the Laurentian Great Lakes fish fauna, and firmly establishes this system as drivers of ecological diversification and rapid speciation through cyclical glaciation.

Interactive and lag effects of environmental factors on the density of schistosome-transmitting Oncomelania hupensis: A twelve-year monthly repeated survey.

Schistosomiasis is a significant public health threat, and Oncomelania hupensis is the only intermediate host for schistosoma japonicum. We conducted 12-year monthly repeated surveys to explore the interactive and lag effects of environmental factors on snail density and to monitor their long-term and seasonal trends in a bottomland around the Dongting Lake region in China. Relevant environmental data were obtained from multiple sources. A Bayesian kernel machine regression model and a Bayesian temporal model combined with a distributed lag model were constructed to analyze interactive and lag effects of environmental factors on snail density. The results indicated the average annual snail density in the study site exhibited an increasing and then decreasing trend, peaking in 2013. Snail densities were the highest in October and the lowest in January in a year. Normalized Difference Vegetation Index (NDVI) and water level were the most effective predictors of snail density, with potential interactions among temperature, precipitation, and NDVI. The mean minimum temperature in January, water level, precipitation and NDVI were positively correlated with snail density at lags ranging from 1 to 4 months. These findings could serve as references for relevant authorities to monitor the changing trend of snail density and implement control measures, thereby reducing the occurrence of schistosomiasis.

How water stability relates with timing, size, and community successions of harmful algal blooms: A case study in the Three Gorges Reservoir.

Effective management of Harmful Algal Blooms (HABs) requires understanding factors influencing their occurrence. This study explores these dynamics in the Pengxi River, a tributary of the Three Gorges Reservoir, focusing on nutrient stratification and algal blooms. We hypothesized that nutrient levels in eutrophic waters with stable stratification correlate with HAB magnitude and that disruption of stratification triggers blooms due to nutrient shifts. A 38-day sampling campaign in Gaoyang Lake (April 16-May 23, 2022) revealed that consistent weather between April 26 and May 16 led to a surface density layer, restricting nutrient transfer and causing a bloom with 173.0 µg L-1 Chl-a on May 1. After a heavy rain on May 18, a peak bloom on May 20, dominated by Ceratium hirundinella, showed 533 µg L-1 Chl-a. There was a significant negative correlation between Cyanobacteria and C. hirundinella biomasses (r = -0.296, P < 0.01), highlighting nutrient availability and physical stability's roles in regulating HABs.

Water temperature and salt ions respectively drive the community assembly of bacterial generalists and specialists in diverse plateau lakes.

Plateau lakes (e.g., freshwater and saltwater lakes) are formed through intricate processes and harbor diverse microorganisms that mediate aquatic ecosystem functions. The adaptive mechanisms of lake microbiota to environmental changes and the ecological impacts of such changes on microbial community assembly are still poorly understood in plateau regions. This study investigated the structure and assembly of planktonic bacterial communities in 24 lakes across the Qinghai-Tibetan and Inner Mongolia Plateaus, with particular focus on habitat generalists, opportunists, and specialists. High-throughput sequencing of the 16S ribosomal RNA genes revealed that bacterial generalists had a lower species number (2196) but higher alpha diversity than the specialist and opportunist counterparts. Taxonomic dissimilarity and phylogenetic diversity analyses unraveled less pronounced difference in the community composition of bacterial generalists compared to the specialist and opportunist counterparts. Geographical scale (14.4 %) and water quality (12.6 %) emerged as major ecological variables structuring bacterial communities. Selection by water temperature and related variables, including mean annual temperature, elevation, longitude, and latitude, mainly shaped the assembly of bacterial generalists. Ecological drift coupled with selection by salt ions and related variables, including total phosphorus, chlorophyll a, and salinity, predominantly drove the assembly of bacterial specialists and opportunists. This study uncovers distinct bacterial responses to interacting ecological variables in diverse plateau lakes and the ecological processes structuring bacterial communities across various lake habitats under anthropogenic disturbance or climate change.