Nutrient enrichment destabilizes ecosystems globally, but the mechanistic pathways underlying this effect in multi-trophic communities remain unclear. To address this knowledge gap, we applied biodiversity-stability theory to multi-trophic communities by partitioning multi-trophic stability into two key components, within-trophic stability and cross-trophic asynchrony. We used two complementary datasets, a decade-long plankton time series from a large eastern Chinese lake (Lake Taihu) and time series from 30 geographically distinct lakes, to examine how total phosphorus (TP) concentration influences producer-consumer community stability. We found that increased TP consistently destabilized producer-consumer communities across both datasets. This destabilizing effect stemmed primarily from reduced within-trophic stability caused by reduced population asynchrony within each trophic level. Additionally, increased TP destabilized communities by reducing cross-trophic asynchrony, as elevated TP promoted phytoplankton biomass both directly and indirectly via diversity changes, thereby synchronizing dynamics across trophic levels by strengthening bottom-up forcing. The latter destabilizing pathway was particularly pronounced in Lake Taihu. Water temperature emerged as an additional destabilizing driver, independently reducing within-trophic stability by decreasing population stability across trophic levels. These findings advance our mechanistic understanding of how nutrient enrichment influences multi-trophic stability and inform effective conservation strategies.Read the free for this article on the Journal blog.

The long-term effectiveness of complete fishing bans in restoring lake ecosystems remains uncertain, particularly regarding ecosystem structure, stability, and the potential need for adaptive management, limiting precise management strategies. Here, we evaluated the ecological impacts and long-term effects of the ten-year fishing ban in Lake Taihu, China, as part of the Yangtze River Basin fishing-ban policy. We developed six Ecopath models for pre-ban (2018-2020) and post-ban (2021-2023) periods and used the 2020 Ecopath model to drive Ecosim calibrated with 2020-2023 data. The ban initially increased the biomass of tapertail anchovy (Coilia nasus) and filter-feeding fishes and enhanced the dominance of piscivores. Network indicators, including the Finn's cycling index, indicated an improvement in energy-flow-based stability during the early years of the ban. However, Ecosim predictions revealed that the fishing ban alone would have limited long-term effects. Projections showed declining biodiversity, pronounced stability fluctuations, and a potential increase in tapertail anchovy abundance. To sustain the ban's ecological benefits, adaptive management scenarios were tested. A combined strategy involving targeted harvesting of the functionally dominant tapertail anchovy (fishing mortality = 0.7), together with stocking of its predators, culters (6% of standing biomass), reduced tapertail anchovy dominance and improved fish community diversity and energy-transfer efficiency. These findings offer evidence-based guidance for optimizing fishing-ban policies. The modeling framework provides a transferable approach for restoring and sustainably managing disturbed freshwater ecosystems.

Toxic cyanobacteria can generate various bioactive metabolites, posing serious risks to aquatic organisms. Entire cyanobacteria cells-induced adverse influences on fish populations could be more complicated than cyanotoxins or extracts of cyanobacteria. Current scientific research usually focuses on the ecotoxicological effects of planktonic cyanobacteria or their cyanotoxins or their crude extracts while ignoring the harmful impacts of benthic cyanobacteria. This project investigated the harmful effects of two algal bloom-relevant densities (5 x 105 cells/mL and 10 x 105 cells/mL) of planktonic Microcystis aeruginosa (generating microcystin (MC)) and benthic Oscillatoria sp. (generating cylindrospermopsin (CYN)) on the filtering-feeding juvenile silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) under a short-time exposure (14 d). The data indicated that both silver carp and bighead carp can filtrate Microcystis rather than Oscillatoria by measuring the level of cyanotoxins. Both Microcystis and Oscillatoria can cause oxidative stress, neurotoxicity, apoptosis, and inflammation in the brain and liver of two kinds of filtering-feeding fish. Furthermore, both Microcystis and Oscillatoria can perturb many terms and pathways related to the immune responses in the liver of two types of fish based on the transcriptomics analysis, which could explain the observed inflammatory reactions in this study. Interestingly, the differentially expressed genes showed that both silver carp and bighead carp were more sensitive to benthic Oscillatoria than planktonic Microcystis. This study will contribute to a better mechanistic understanding of the harmful effects of different kinds of toxic cyanobacteria, suggesting that the adverse impacts and ecological risks of benthic cyanobacteria require further exploration.

Fish growth is closely related to environmental variables; however, how nutrient enrichment affects fish growth conditions remains unclear in subtropical polder rivers. We investigated the growth status of six fish species and nutrient concentrations at 40 sites in the subtropical polder rivers of the Lake Chaohu Basin, with the aim of evaluating how the fish condition factor (K) responds to nutrient enrichment across different feeding groups. We observed species-specific responses of growth conditions to nutrient enrichment. The omni-zooplanktivorous Hemiculter leucisculus and zooplanktivorous Toxabramis swinhonis exhibit better growth in nutrient-enriched rivers, with their K values showing a significant positive correlation with both total nitrogen (TN) and total phosphorus concentrations. However, the K values of the omni-benthivorous Carassius gibelio and Pseudobrama simoni exhibited no significant correlation with nutrient enrichment. Interestingly, the condition factor of the piscivorous Culter species also increased with rising TN levels. The growth patterns of H. leucisculus and C. gibelio were positive allometric, where the fish body weight increased at a faster rate than length. T. swinhonis and P. simoni showed isometric growth, in which both the body weight and length of them increased at approximately the same rates. These findings highlight the importance of considering fish functional traits (e.g., feeding guilds) when assessing the ecological impacts of eutrophication and provide insights for the management of subtropical polder river ecosystems under nutrient enrichment, such as predicting changes in fish community structure and developing targeted conservation strategies.

Biological invasions severely threaten ecosystems and their underlying drivers remain a subject of ongoing inquiry in ecology. Four mutually exclusive invasion hypotheses, biotic acceptance and resistance hypotheses and Darwin's preadaptation and naturalization hypotheses, have long drawn extensive attention. Furthermore, human activities and environmental factors are also widely recognized as key drivers of biological invasions. While integrative analyses of the aforementioned biotic and abiotic factors influencing biological invasions have been conducted previously, systematic global-scale analyses for freshwater fishes remain limited, constraining our understanding of large-scale invasion patterns in this taxon. Here, we leveraged a comprehensive database with taxonomic, functional, and phylogenetic data for 5245 freshwater fish species across 1411 global river basins to explore ecological correlates of non-native fish establishment. Specifically, we used taxonomic, functional, and phylogenetic facets of biodiversity to comprehensively quantify native communities (testing biotic acceptance and resistance hypotheses) and relatedness between native and non-native communities (testing Darwin's preadaptation and naturalization hypotheses). We further extracted environmental and anthropogenic variables across global rivers to assess external predictors of non-native fish establishment. Our results primarily supported Darwin's naturalization hypothesis: at the global level, native fish community invasibility peaked when non-native species exhibited great functional or phylogenetic distance from native communities, suggesting distantly related non-natives likely had unique traits or strategies to exploit vacant niches. Meanwhile, climatic factors also emerged as key drivers of global fish invasion patterns. At the biogeographic realm level, the determinants of fish invasions varied among the six realms, highlighting the complexity and regional specificity of biological invasions. However, our findings were based on correlational patterns of established non-native species at the basin scale and thus cannot establish definitive causal relationships between the identified drivers and establishment success. Future experimental manipulations at finer spatial and temporal scales are therefore required to validate the correlations observed in this study.

The concurrent presence of cyanobacterial blooms and cyanobacterial derivative pollution in natural freshwater poses serious threats to aquatic biota and human beings. To date, cyanobacteria, especially ignored benthic toxic cyanobacteria, may cause potential harmful impacts on benthic animals. Understanding benthic animals' possible responses to these toxic cyanobacteria is important for assessing cyanobacterial bloom-induced ecological risks. This study investigated the harmful impacts of planktonic Microcystis aeruginosa (generating microcystin) and benthic Oscillatoria sp. (generating cylindrospermopsin) on the feeding behavior, tissue structure, neurotoxicity, oxidative stress, and immunotoxicity of the freshwater macrobenthos clams Lamprotula leai and snails Bellamya aeruginosa under 14-d exposure. Firstly, two cyanobacteria can reduce the clearance rates of clams and snails, causing tissue damage in their digestive glands. Secondly, two cyanobacteria can induce neurotoxicity in clams and snails by altering acetylcholinesterase activities and acetylcholine levels in their digestive glands. Thirdly, two cyanobacteria can lead to oxidative stress in clams and snails by changing the antioxidant enzyme activities, glutathione levels, malondialdehyde levels, and reactive oxygen species levels in their digestive glands. Finally, two cyanobacteria can cause immunotoxicity in clams and snails by altering lysozyme activities in their digestive glands, while two cyanobacteria can also induce inflammatory responses in clams by increasing levels of interleukin-1β and tumor necrosis factor-α in their digestive glands. These data indicated that toxic cyanobacteria can threaten the health of macrobenthos, and the benthic cyanobacteria-induced adverse ecological impacts should not be ignored.

Hydrological variations in shallow temperate lakes act as sensitive barometers to climate change, affecting a broad spectrum of lake food web structure and function and may ultimately lead to ecological critical transitions. Yet, few investigations have described the effects of hydrological variations on the ecosystem scale due to the requirements of extensive field data and mechanistic modeling tools. Here, we investigated the long-term ecosystem dynamics in the largest freshwater lake in northern China (Lake Hulun) from the 1980s to the 2010s, which experienced substantial water level fluctuations (WLFs) with an approximate 4 m drop and then recovery over 5 years. We first established three steady-state food web models using ECOPATH corresponding to distinct hydrological conditions: 1982 (Wet), 2009 (Dry), and 2014 (Re-wet). The model suggests that the food web shifted from a pyramid to a truncated shape, with a significant loss of top predators and an increasing share of primary producers. This structural shift led to altered energy transfer efficiencies between trophic levels, suggesting an energy "short circuit" and an overall increase in ecosystem immaturity. These findings demonstrate that the lake suffered from a critical transition following the gradual change from wet to dry conditions and did not recover after re-wetting. Further, scenario analyses in PCLake determined that WLFs significantly altered the ecosystem state compared to the stable water level. Notably, despite the recovery of water level, ecosystem restoration was not achieved, pointing to a potential hysteresis response of the ecosystem to WLFs. Nevertheless, we would like to point out that the results of modeling analysis should be interpreted with caution, which serves as guiding hypothesis that requires further validation from more field observations. We summarized our findings by proposing a novel conceptual framework suggesting a hysteresis response to interannual WLFs in temperate shallow lake ecosystems. Our study reveals that the WLFs may have a much stronger and more persistent impact on lake ecosystems than previously anticipated, thus more attention is warranted on the associations between hydrological variation and ecosystem dynamics for lake management in a changing environment.

Cyanobacterial blooms can generate various toxic metabolites in freshwater, and pose serious threats to drinking water safety and human health. Although microcystins (MCs) have been detected in many freshwater ecosystems in China, little is known about the other cyanotoxins. An investigation of six eutrophic lakes (i.e. Hulun Lake, Wuliangsuhai Lake, Chaohu Lake, Taihu Lake, Xingyun Lake, and Dianchi Lake) in different geographical locations of China was performed during the summer of 2022 to determine the occurrence of various cyanotoxins (i.e. anatoxin-a (ATX), cylindrospermopsin (CYN), and MCs) in water column and their possible risks, and to evaluate the related environmental factors. MCs levels in sediment of these lakes were also investigated. MCs were the primary cyanotoxins in the water column of investigated lakes. The mean MCs contents in water column of Hulun Lake, Wuliangsuhai Lake, Chaohu Lake, Taihu Lake, Xingyun Lake, and Dianchi Lake were 3.61, 0.13, 3.60, 2.18, 0.57, and 2.56 mu g/L, respectively. The total MCs levels in water column exceeded 1 mu g/L in some areas of these lakes except Wuliangsuhai Lake. Replete nitrogen and/or phosphorus levels seemed to be related to MCs production. ATX can be detected in these lakes except Xingyun Lake at ng/L levels. CYN can be detected in all lakes at ng/L levels. However, the levels of ATX and CYN appear to be not significantly associated with environmental factors. MCs and CYN can pose a high or moderate risk for humans and aquatic organisms in some areas of these lakes, while ATX can pose a low or no risk for humans and aquatic organisms in most areas of these lakes. MCs can also be detected in sediment of all lakes at ng/g levels. This research emphasizes the necessity for long-term monitoring of different cyanotoxins in eutrophic lakes, and the implementation of nutrient control and management strategies.

With increasing anthropogenic activities, freshwater ecosystems around the world are becoming increasingly affected by various pressures, including eutrophication, overfishing, and irrational stocking, which may have a negative impact on the food web structure. Despite the extensive research and proposed management measures for eutrophic lakes, there are only few analysis on long-term monitoring data regarding fishery resources. Additionally, there is a lack of evaluation and prediction of the effectiveness of current fish management policies. To remedy this, we analyzed long-term monitoring data from Lake Taihu, China, a severely eutrophicated lake with a skewed fish size structure exhibiting dominance of small individuals. We first constructed 14 Ecopath models to investigate how trophic interactions and biomass fluxes changed from 2007 to 2020. Subsequently, the Ecosim model was used to predict how the biomass of fish and the ecosystem network respond to the initiated 10-years fishing ban. Our results demonstrate long-term changes in fish biomass and ecosystem stability. The analyses revealed that 1) the biomass development in different feeding types of fish is controlled by human activities (mainly catches and stocking) and trophic interactions and 2) the rate of decline in ecosystem network stability slows down during the fishing ban. The primary focus of this study was to fill the gap in long-term serial studies of fish monitoring data and ecosystem stability in the lake and, for the first time, to predict the outcome of the fishing ban from an ecosystem perspective using the Ecosim model. Overall, our results emphasize the importance of rational stocking and fishing policies and provide a better understanding of the changes in the ecological dynamics in Lake Taihu of relevance for the management and restoration of the lake.

Community structure and diversity of fish exhibit a strong correlation with environmental variables.We studied the spatial and temporal patterns of the fish community structure and diversity in both the small and main lake regions of Lake Hengshui throughout 2021.The relationships between fish community structure and environmental factors were analyzed.A total of 29 fish species across 15 families and 27 genera were recorded in Lake Hengshui.Cyprinid species contributed 98％to the total catch by weight.The dominant fish species in Lake Hengshui were Hemiculter leucisculus,Carassius carassius,Hypophthalmus molitrix and Pseudobrama simoni.There were no seasonal and spatial variations in Shannon-Wiener diversity index,Pielou's evenness index and Margalefs species richness index of fishes in the main region of the lake.However,permutational multivariate analysis highlighted significant temporal variations in fish community structure in the main lake region.Similarity percentage analysis revealed an aver-age seasonal difference over 40％in fish communities of the main lake,the spatial difference of fish community structure between the main lake and small lake regions was 41％.The abundance-biomass curve indicated that fish communities in the main lake re-gion was largely disturbed in all sampling seasons.In the small lake region,these disturbances were only observed in spring and summer,while not in autumn.Redundancy analysis indicated that the epilimnetic total phosphorus of the main lake explained most of fish community changes(36％).Total phosphorus,nitrite,secchi depth and total nitrogen were also the main contributors which influencing the fish community structure of the main lake.The fish community structure of Lake Hengshui is dominated by small omnivorous fish,such as H.leucisculus,C.carassius and P.simoni,while the abundance of piscivorous fish is relatively low.Therefore,in the context of enhancing water quality and ecological restoration,after the reduction of external nutrient loads,it is important to manipulate the fish community structure of Lake Hengshui.This involves strengthening the top-down effect by carnivo-rous fish,mitigating the potential adverse impacts of omnivorous fish and planktivorous fish on water quality,ultimately working to-wards the objective of improving water quality.

Arsenic (As) is a metalloid that can accumulate in eutrophic lakes and cause adverse health effects to people worldwide. However, the seasonal process and dynamic mechanism for As mobilization in eutrophic lake remains effectively unknown. Here we innovatively used the planar optodes (PO), high-resolution dialysis (HR-Peeper) combined with fluorescence excitation-emission matrix coupled with parallel factor (EEM-PARAFAC) analysis technologies. We synchronously investigate monthly O-2, As, iron (Fe), manganese (Mn), and naturally occurring dissolved organic matter (DOM) changes in sediments of Lake Taihu at high resolution in field conditions. We find high As contamination from sediments with 61.88-327.07 mu g m(-2) d(-1) release As fluxes during the algal bloom seasons from May to October 2021. Our results show that an increase in DOM, mainly for humic-like components, resulting in high electron transfer capacity (ETC), promoted the reductive dissolution of Fe and Mn oxides to release As. Partial least square-path modeling (PLS-PM) and random forest modeling analysis identified that Mn oxide reductive dissolution directly accelerated sediments As contamination, which is the crucial factor. Understanding crucial factor controlling As release is especially essential in areas of eutrophic lakes developing effective strategies to manage As-rich eutrophic lake sediments worldwide.

Invasive non-native freshwater fishes have long been recognized as a threat to biodiversity conservation and management. Non-native fishes with a high risk of becoming invasive can be identified using risk screening tools. Here, we used the Aquatic Species Invasiveness Screening Kit (AS-ISK) to identify the invasion risk of non-native fishes in Yunnan Province, China. AS-ISK scores were calibrated to distinguish between species with high and low-to-medium risks of invasiveness. Risk threshold was 17.25 for BRA (Basic Risk Assessment) and BRA+CCA (BRA+ Climate Change Assessment) in Yunnan Province. Based on BRA scores, 21 of the 37 screened species were classified as high risk, 13 as medium risk and 3 as low risk. Based on BRA+CCA scores, 22 of the 37 screened species were classified as high risk, 12 as medium risk and 3 as low risk. For both BRA and BRA+CCA, the highest-scoring species were Hypostomus plecostomus, Oreochromis aureus, Oreochromis mossambicus and Oreochromis niloticus. This study reliably assessed the risk of non-native fish invasion in Yunnan Province and identified priority non-native fishes for prevention and control, providing information for targeted monitoring and management decisions in the region.

Cyanobacterial blooms are worldwide distributed and threaten aquatic ecosystems and public health. The current studies mainly focus on the adverse impacts of planktonic cyanobacteria or pure cyanotoxins, while the benthic cyanobacteria-induced ecotoxic effects are relatively lacking. The cyanobacterial cell-induced toxic effects on aquatic organisms might be more serious and complex than the pure cyanotoxins and crude extracts of cyanobacteria. This study explored the chronic effects of toxin-producing planktonic Microcystis aeruginosa (producing microcystin) and benthic Oscillatoria sp. (producing cylindrospermopsin) on the behaviors, tissue structures, oxidative stress, apoptosis, and inflammation of the Asian clams (Corbicula fluminea) under 28-d exposure. The data showed that both M. aeruginosa and Oscillatoria sp. can decrease the behaviors associated with the feeding activity and induce tissue damage (i.e. gill and digestive gland) in clams. Furthermore, two kinds of cyanobacteria can alter the antioxidant enzyme activities and increase antioxidant, lipid oxidation product, and neurotransmitter degrading enzyme levels in clams. Moreover, two kinds of cyanobacteria can activate apoptosis-related enzyme activities and enhance the proinflammatory cytokine levels of clams. In addition, two kinds of cyanobacteria can disturb the transcript levels of genes linked with oxidative stress, apoptosis, and inflammation. These results suggested harmful cyanobacteria can threaten the survival and health of clams, while the benthic cyanobacteria-induced adverse effects deserve more attention. Our finding also indicated that it is necessary to focus on the entire algal cell-induced ecotoxicity when concerning the ecological impacts of cyanobacterial blooms.

Cultural eutrophication is the main cause of the decline of submerged plants in freshwater ecosystems. While many studies have focused on the nutrient uptake by the roots of these plants, less attention has been given to the effects of eutrophication on root structure. We designed a mesocosm experiment with Eurasian watermilfoil (Myriophyllum spicatum), a submerged plant indigenous to the Eurasian continent. The responses of plant functional traits, including growth traits, morphological traits and root topological indices, to different nitrogen (N) and phosphorus (P) concentrations were elucidated. We found that high P concentrations suppressed all the morphological traits and reduced the root topological traits, whereas N concentrations had a comparatively minor effect. Although the root branching of M. spicatum did not change, its root topology became more dichotomous with fewer exterior root links being formed in nutrient-rich habitats, and the root form changed from deep and thin to shallow and dense with increasing P concentrations. The root nutrient absorption ability of M. spicatum may decrease with cultural eutrophication, and this change most likely reduces its anchoring ability and increases its sensitivity to dislodge from the sediment if disturbed by hydraulic forces.

Carbamazepine (CBZ) is an anticonvulsant medication used to treat epilepsy and bipolar disorder. Due to its persistence and low removal rate in wastewater treatment plants, it is frequently detected in the environment, raising concerns regarding its potential adverse effects on aquatic organisms and ecosystems. In this study, we aimed to assess the impact of CBZ on the behavior and growth of juvenile yellow catfish Tachysurus fulvidraco, a native and economically important species in China. Fish were exposed to CBZ at three concentrations of 1, 10, or 100 µg/L for 14 days. The fish exposed to 10 and 100 μg/L of CBZ exhibited decreased feeding, and a significant increase in cannibalistic tendencies was observed in fish exposed to 100 μg/L CBZ. Acetylcholinesterase activity was increased in the brain of fish exposed to 100 μg/L CBZ. CBZ also inhibited the growth of yellow catfish. To better elucidate mechanisms of toxicity, transcriptomics was conducted in both the brain and liver. In the brain, gene networks associated with neurotransmitter dysfunction were altered by CBZ, as well as networks associated with mitochondrial dysfunction and metabolism. In the liver, gene networks associated with the immune system were altered by CBZ. The current study improves comprehension of the sub-lethal effects of CBZ and reveals novel insight into molecular and biochemical pathways disrupted by CBZ, identifying putative key events associated with reduced growth and altered behavior. This study emphasizes the necessity for improved comprehension of the effects of pharmaceutical contaminants on fish at environmentally relevant levels.

As global warming and water eutrophication, the multiple proliferation of harmful cyanobacteria can form algal blooms and cause serious ecological problems. In recent years, the large-scale and persistent cyanobacterial blooms occur frequently worldwide and have attracted widespread attention due to the harmful impacts. Among these harmful bloom-forming cyanobacteria, the ecological and toxicological impacts of planktonic cyanobacteria have been extensively studied. However, research on the ecological risks and adverse effects of harmful benthic cyanobacteria is lagging. Filter-feeding fish could suffer from more toxic stimuli than other fish due to their special feeding habits. To investigate and compare the complex toxic effects of different kinds of harmful cyanobacteria on fish, three different-sized (i.e. small, medium, and large) juvenile silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) were exposed to cyanobacterial blooms-related density (1 × 106 cells/mL) of Microcystis aeruginosa (i.e. generating microcystins) and Oscillatoria sp. (i.e. generating cylindrospermopsin) for 3 d, after which biomarkers of oxidative stress and inflammation in the liver of fish were detected. The silver carp and bighead carp can effectively ingest Microcystis cells but cannot effectively ingest Oscillatoria cells through the measurement of the levels of cyanotoxins. Both Microcystis and Oscillatoria cells can induce different levels of oxidative stress and inflammatory responses in the liver of these juvenile filter-feeding fish via altering the biochemical parameters of the antioxidant system (e.g. superoxide dismutase activity) and immune system (e.g. interleukin-1β level). Therefore, our research identified potential data gaps that how the different types of cyanobacteria induce toxic effects in the liver of juvenile filter-feeding fish in a short time. This study contributes to a better understanding of the short-term adverse effects of different cyanobacterial species on juvenile fish, suggesting that the benthic toxic cyanobacteria-induced ecological and health risks require further attention.

When restoring shallow lakes, the recovery of submerged macrophytes is of vital importance to obtain clear water conditions. However, post-restoration recovery of small omnivorous fish can increase water nutrient concentrations through excretion. The impact of these recycled nutrients on submerged macrophytes is not well-studied, and it may depend on fish food of varying nutrient contents. We studied the effects of Acheilognathus macropterus on the growth and nutrient stoichiometry of Vallisneria denseserrulata and Hydrilla verticillata . The experiment had six treatments: two controls without recycled nutrients and two nutrient treatments for each of the plant species, respectively. We found that fish released more phosphorus after consuming low N:P food and more nitrogen after high N:P food. The recycled nutrients significantly promoted the growth of both macrophyte species. Interestingly, macrophytes showed higher growth rates in treatments with nutrients from the low N:P food source. Our study, therefore, suggests that nutrient subsidy from fish excretion can significantly stimulate the growth of submerged macrophytes, the magnitude of the effect being determined by the N:P ratio of the fish food. The realization of this growth potential, however, also depends on the phytoplankton response to these nutrients, that expectedly will be weaker at high macrophyte coverage.

Utilizing data obtained from three surveys conducted in 2021 and historical records pertinent to fisheries,this study scru-tinized the alterations in the fish community structure within Lake Wuliangsuhai and elucidated its correlation with key environmen-tal factors.Comparative scrutiny with historical data unveiled substantial shifts in the fish community structure in Lake Wuliangsu-hai,typified by a decline in indigenous species,alterations in dominant species composition,and a discernible trend toward indi-vidual fish miniaturization.According to the distribution characteristics of fish communities,the lake was divided into three lake ar-eas:western,eastern and southern.ANOSIM and SIMPER results showed significant differences in fish community composition be-tween the lake regions.The mean difference was more than 70％and was mainly attributed to Carassius auratus,Pseudorasbora par-va and Cyprinus carpio.The results of biodiversity analysis showed that the diversity index of fish communities in the whole lake and each lake area was low(H'＜2).Mantel test analysis and CCA underscored turbidity and chlorophyll-a as key environmental factors influencing the fish community structure in the lake.The differences in fish communities and biodiversity among lake areas reflect the adaptation of fish community structure to the environmental characteristics of the lake.This paper proposes a reference direction for future fisheries management planning in the lake from different perspectives:1)the policy of fishing ban and stocking,2)make full use of the relationship between the fish community and environmental characteristics.

Biodiversity loss caused by biological invasions is an ecological problem on a global scale, and understanding the mechanism of biological invasion is the basis for managing non-native species. The biotic resistance hypothesis proposes that species-rich native communities are less susceptible to invasion because of the limited resources available to non-native species, therefore comparing the resource utilization patterns of different communities can reveal the invasion mechanisms of specific non-native species at the community level. We selected Lake Taihu, where icefish (Neosalanx taihuensis Chen) originated, and Lake Fuxian, where icefish invaded, as the research objects. We calculated the fish functional diversity indexes, including functional richness (FRic), functional evenness (FEve), and functional divergence (FDiv), to reflect differences in ecological niche and resource utilization based on four quarterly fish survey data from two lakes. The random forests model explored the relationship between functional diversity indexes and biotic and environmental variables. Our results showed that more diverse resource utilization (high FRic), more niche space (low FEve), and less competitive pressure (high FDiv) in Lake Fuxian were identified as the critical important factors for maintaining the current equilibrium state after successful invasion of icefish. The bottom-up effects mainly affected the functional diversity indexes in Lake Fuxian. They differed from those in Lake Taihu and were primarily influenced by top-down effects. Enhancing the top-down effects in Lake Fuxian and limiting the zooplankton available to icefish are critical to controlling the invasion of icefish. This study offers a new perspective for studying the non-native fish invasion mechanism, and provides scientific guidance for managing non-native fish in Lake Fuxian.