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.

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.

Periphyton plays a critical role in the progress of the regime shift between macrophytes and phytoplankton in shallow lakes, since its overgrowth could trigger metaphytic blooms and lead to the collapse of submerged macrophytes. Understanding the mechanisms of metaphytic blooms and the subsequent prediction are important for lake managers to prevent ecological disaster. In this study, a one-year field survey on periphyton was conducted in Lake Ulansuhai to explore the driving factors of metaphytic blooms. The result revealed that the filamentous chlorophyta Mougeotia was identified as the key genus involved in metaphytic blooms. Structural Equation Modeling showed that Mougeotia biomass was positively correlated with total nitrogen, temperature, and submerged vegetation density. While phytoplankton biomass was primarily positively correlated with total phosphorus and temperature. A logistic regression model indicated that when the biomass of Mougeotia reached 1.78 g m−2 (95

Aquaculture ponds have emerged as a significant contributor to greenhouse gas (GHG) emissions. We measured methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions in ponds, all located in Jiangsu Province, with different fish and management practices over an entire cycle. All ponds emitted these gases, with higher CH4 and N2O levels during fish growth than stocking period. The highest CH4 and N2O fluxes were found in the Crucian carp (Carassius auratus) pond with up to 16,512 ± 3015 µmol/(m2·h) and 5.54 ± 0.31 µmol/(m2·h), respectively. CH4 was the primary contributor to the global warming potential in traditional earthen ponds, accounting for an average contribution rate of 87.7 %. The dissolved oxygen (DO) concentration was the water quality parameter that most significantly influenced the CO2 flux, while pH acted as its primary regulator. The GHG emission intensity per unit of fish production in traditional earthen ponds was 197 times higher than that in-pond raceway systems. Largemouth bass (Micropterus salmoides) and Crucian carp ponds exhibited CH4 diffusion fluxes at the sediment-water interface, which were > 20 times higher than those at the water-air interface. Our results further suggest that stocking density and feed amount significantly influence the variations in GHG emissions among the ponds with the in-pond raceway system having low carbon emissions and being high yield aquaculture system compared to traditional earthen ponds. The water depth and DO concentration can be manipulated to reduce GHG emissions across the various interfaces.

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.

Rapid expansion of China’s aquaculture ponds (APs) has significantly contributed to food security and economic development, yet simultaneously triggering ecological degradation. However, the absence of high-resolution national datasets has constrained systematic analyses of APs’ spatiotemporal dynamics and their transboundary environmental footprints. To fill this gap, we developed a robust approach for accurately monitoring APs across China and elucidating the spatiotemporal dynamics and underlying mechanisms driving their changes. The Optical-SAR Aquaculture Pond Mapper (OS-APM) was developed, a novel framework integrating spatiotemporal-spectral signatures to synergistically leverage multi-sensor time series for precision AP mapping. The OS-APM comprised a hierarchical segmentation strategy for large-scale AP delineation, multi-modal feature fusion to distinguish spectrally ambiguous classes, and an ensemble classifier integrating optical, SAR, geometric, and topographic features. The framework achieved individual-pond-scale extraction accuracy (OA > 90 %) and generated China’s first 10-m resolution annual AP dataset (China_AP), derived from 119,882 Sentinel-1 and 579,436 Sentinel-2 scenes (2016–2023). This dataset revealed previously undocumented spatiotemporal patterns, indicating a 2023 AP inventory of 19,919.52 km2, with inland systems (55.56 %) now surpassing coastal ones (44.44 %) to dominate China’s aquaculture landscape. Spatially, four provinces (Jiangsu, Hubei, Shandong, Guangdong) collectively host 56 % of national APs, with 58 % clustered in the Yangtze-Huaihe River corridors. Temporally, the AP area exhibited an inverted-U trajectory, increasing from 20,685.20 km2 (2016) to a peak of 23,256.84 km2 (2019), then contracting below initial levels to 19,919.52 km2 by 2023. This reversal strongly correlates with China’s ecological civilization initiatives, notably the 2017 Aquaculture Water and Tidal Flat Plan. This study establishes multi-sensor data for national AP monitoring, quantifies inland AP expansion patterns under policy regulation, and delivers a scientific foundation for reconciling aquaculture intensification with wetland conservation.

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.

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.

Aquaculture ponds (APs) are rapidly expanding globally and are considered crucial for guaranteeing the supply of food, population growth, and economic development. However, the rapid expansion of aquaculture not only brought benefits but also a series of eco-environmental issues, such as water eutrophication. To achieve sustainable development, it is essential to gain a profound understanding of the spatiotemporal evolution of APs, the drivers behind their dynamics, and their relationship with the aquatic environment. Jiangsu Province (JS) in China, a historically significant aquaculture region, encompasses two prominent river basins: the Huai River Basin (HRB) and the Yangtze River Basin (YRB). In light of the construction of an ecological civilization, JS serves as a demonstration and pioneering area for basin protection and development. Therefore, this study focuses on JS, aiming to elucidate the spatiotemporal dynamics of APs, the corresponding relationship with basin management policies, and the impact on water eutrophication. The results revealed that: (1) in 2022, APs in JS were unevenly distributed, with a total area of 3278.78 km2, of which 79 % was located in the HRB. (2) During 2016-2022, APs exhibited an initial growth trend before 2019, followed by a decrease. (3) Due to policy interventions, AP changes within different basins showed opposite trends, and the corresponding water eutrophic

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.

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.

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.

The risks of planktonic cyanobacteria blooms have been the focus of much scientific research, but studies on the ecotoxicological effects of benthic cyanobacteria are lagging. The impacts of cyanobacteria cells on fish populations might be more complex in contrast to purified cyanotoxins or cyanobacteria extracts. This study systematically compared the chronic effects of benthic Oscillatoria sp. (producing cylindrospermopsins) and planktonic Microcystis aeruginosa (producing microcystins) on the growth and reproduction of zebrafish through life-cycle exposure (5- 90 days post fertilization). The results showed that both Oscillatoria sp. and M. aeruginosa exposure caused growth inhibition and fecundity reduction in F0 generation by disrupting sex hormone levels, delayed ovarian and sperm development, and induced pathological lesions in zebrafish gonads. Furthermore, exposure to Oscillatoria sp. or M. aeruginosa in adult zebrafish increased mortality and teratogenicity in F1 embryos (without exposure), indicating a parental transmission effect of developmental toxicity. The difference was that M. aeruginosa exposure led to significant alterations in pathways, such as tissue development, redox processes, and steroid hormone synthesis. In contrast, Oscillatoria sp. exposure primarily disrupted the PPAR signaling pathway, cell adhesion molecules, and lipid transport pathways. Interestingly, the differentially expressed genes revealed that male fish were more sensitive to harmful cyanobacteria than females, whether exposed to Oscillatoria sp. or M. aeruginosa. These findings contribute to a better mechanistic understanding of the chronic toxic effects of distinct types of harmful cyanobacteria, suggesting that the ecological risk of benthic cyanobacteria requires further attention.

The Taihu Lake ecosystem has been subjected to numerous anthropogenic stressors during the past decades, leading to substantial changes in nutrient dynamics and habitat quality. For instance, the northwestern lake bays receive large amounts of nutrient-rich wastewater and have frequently experienced algal blooms, while the eastern lake region is still dominated by submersed macrophytes. Such changes in environmental characteristics can greatly impact benthic macroinvertebrate communities. We used a 15-year monitoring data series collected by the Taihu Laboratory for Lake Ecosystem Research to examine the spatial and temporal variations of the benthic invertebrate fauna and evaluate its status and trends. We found that three major communities could be distinguished based on taxonomic group composition and abundance, and these corresponded well with three lake habitat types: algal-dominated, macrophyte-dominated, and open-lake zone. An analysis of temporal trends showed major changes in the macroinvertebrates during the study period, largely driven by a lake-wide and significant decline in the abundance of pollution-tolerant taxa. The spatial and temporal variations of macroinvertebrate communities were mainly explained by nutrients (e.g., total nitrogen and ammonium concentrations) and habitat factors (e.g., sediment substrates and macrophyte biomass) as indicated by Random Forests regression, but the major drivers of macroinvertebrate density differed among the three lake zones at the temporal scale. Moreover, our findings suggest that benthic invertebrates were more sensitive to the improvement of the lake's environmental conditions than the pelagic community was. This study provides insights into the responses of macroinvertebrates to ecological dynamics in lakes and highlights the importance of continued monitoring for tracking long-term changes.

Lake Fuxian has the largest reserves of high-quality water resources in China, and understanding its ecological health status is the basis of its environmental protection. Based on a seasonal field investigation of the plankton community, we established a planktonic index of biotic integrity (P-IBI) evaluation system to assess the lake’s ecosystem health. The biological integrity of Lake Fuxian was relatively good during winter and spring, but gradually deteriorated from summer to autumn. Areas with poor biological integrity were mainly distributed near tourist attractions along the lake’s west coast. Redundancy analysis (RDA) was performed to explore the relationships between the P-IBI, its selected indicators, and the environmental variables. Water temperature (WT), pH, ammonia nitrogen (NH3-N), and dissolved oxygen (DO) significantly influenced the P-IBI and its selected indicators. NH3-N and DO were significantly positively correlated with the P-IBI, indicating that it could be used as a water quality indicator to indirectly reflect lake biological integrity. We demonstrated that the P-IBI can effectively reflect temporal and spatial variations of biological integrity and could be used as a potential tool to evaluate Lake Fuxian ecosystem health.