Stable organic carbon (OC) burial into lacustrine sediments was the important C fixation path for atmospheric C reduction. However, OC retention effect and stability mechanisms in sediments was still unclear at the molecular scale during the burial period. Chronology and OC fractions were measured for the sediments from two freshwater lakes. Three-dimensional fluorescence and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were used to detect the change in the forms and molecular structure of soluble OC (SOC). Remarkably increasing TOC and total nitrogen (TN) concentrations along with the decreasing TOC/TN (C/N) values upwards occurred in the sediment columns indicated the weakened terrigenous OC and N inputs from about the 1980s. The OC mineralization contributed to the decrease of C burial in deeper sedimentary layers. However, higher SOC concentrations was found in deeper depths, suggesting that SOC facilitated the OC accumulation and fixation in the sediments and triggered the higher OCBR values over time. Additionally, obvious fluorescence intensity existence throughout the the whole sediment cores suggested the synchronous accumulation of both humic acid-like and fulvic acid-like materials over time as dominant SOC fractions. Higher fluorescence intensity at upper sediment layers indicated the SOC burial as humic acid-like materials with stronger sequestration potential. The persistence of fluorescence signal suggested that fulvic acid-like materials dominated the SOC immobilization and resistance to mineralization in the sediments. Finally, FT-ICR-MS analysis showed that remarkable accumulation of lipids with abundances from 31 to 44 % of organics was attributed to the decomposition of lignins and dominated CHO and CHON formulas and OC compounds. Lipids and lignins with higher abundances dominated the SOC burial and fixation over time even though mineralization occurred. Our work testified that lipids and lignins contributed to the majority of humic acid-like materials and subsequent OC retention in the lacustrine sediments at the geological time scale.

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.

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.

Regime difference induced by nutrient load regulation can alter microbial community structure and interaction in the sediments of lakes. However, the mechanism, processes and effect of bacterial community regulation on organic phosphorus (Po) mineralization in different regimes remains highly uncertain. Different Po pools in the sediments from Cyanophyta-dominated and macrophyte-dominated regimes of Taihu Lake, China were obtained using multiple extraction procedures. Alkaline phosphatase activities (APA) and three-dimensional fluorescence spectra for Po fractions were obtained. The abundances of functional gene phoD and diversity of bacterial communities encoding Po mineralization in the sediments were also assessed using high throughput sequencing. The results showed that different P fractions including Po compounds in the sediments had higher concentrations in Cyanophyta-dominated regime than macrophyte-dominated regime, indicating higher mineralization potential of sedimentary P. Higher APA values detected in macrophyte-dominated regime indicated noteworthy mineralization efficiency of Po into bioavailable P. However, the accumulation of bioavailable P via Po mineralization due to extensive Po stock especially Mono-Po contributed to the higher reactive P load in Cyanophyta-dominated regime. Higher phoD gene abundance (2.38-6.74 × 106 Copies/g) and community structure diversity were found in Cyanophyta-dominated regime, suggesting that regime difference differentiated the aggregation of phoD-encoding bacteria in Cyanophyta-dominated regime (1.6-5.90 × 106 Copies/g). Community structure regulation triggered by abundant and rare taxa demonstrated that regime difference regulated the phoD gene abundance and subsequent Po mineralization pathway and effects in the lake ecosystems. Generally, abundant and rare microflora responded to the regime regulation and synchronously contributed to the phoD gene abundance and mineralization effect. Our findings implied that Cyanophyta-dominated regime had higher Po mineralization potential via microbial activities and eutrophication risk activated by extensive P accumulation relative to macrophyte-dominated regime.

Tracing footprint and risk of microplastics and microfibers is crucial to managing plastic and fiber waste. We identified microfibers from microplastics, quantitatively apportioned the sources of microplastics and microplastics in 102 lakes across China by field work, and developed a novel index (IMRI) to assess the risk based on human footprint and the abundance, size, shape, color, and residual monomers and chemical additives. The abundance in the sediments of these lakes ranged from 0.3 to 66.7 items g-1. Microfibers and fiber-shaped microplastics accounted for 45% and 32% of the abundance. The risk levels assessed by IMRI indicated that microplastics and microfibers in the sediments of 33.3%, 28.4%, 27.5%, and 9.8% of the lakes had moderate, extremely high, high, and low risk, respectively, which was more consistent with the real situation of Chinese lakes compared with PLI, PHI, and RI and independent of background abundance. Secondary and tertiary industry-related activities and aquaculture activities contributed 64% and 36% to the abundance, posing extremely high risk and high risk, respectively. Artificial cellulosic microfibers mainly derived from aquaculture activities contributed 61% to the risk due to the residual toxic chemical additives. Residual monomers and chemical additives and size contributed 42.7% and 42.3% to the risk.

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.

Different nutrient load in the lake ecosystems trigger the regime difference and change of predominant biotype. The regulation of carbon (C) sequestration mode in the lacustrine sediments in response to this process need prudent clarification. Fluorescence measurements and high-throughput sequencing for functional genes cbbL and cbbM encoding C-fixing bacteria genus were executed for sediments from two representative regimes dominated by macrophyte and Cyanophyta, respectively. The results showed that humic-like and fulvic-acid like materials dominated the dissolved organic matter (DOM) from the algae and macrophyte-dominated lake regions, respectively. Microbial assimilation played critical influence on C fixation into the sediments in both of the two regimes. However, higher diversity was detected in macrophyte-dominated regime compared to that in Cyanophyta-dominated regime, suggesting that moderate nutrient levels facilitated the species richness of bacteria encoding functional genes concerning C fixation. Bacterial species and diversities varied between two regimes including predominant and rare taxa, suggesting that community structure alteration due to regime difference triggered the regulation the C sequestration mode and stability. Predominant genera manipulated the abundance of C-fixing bacteria genes in response to the regulation of nutrient levels. Noted that rare genera also responded to the regime difference and played key role in C sequestration into lacustrine sediments. Our results suggest that more abundant macrophyte-dominated regime facilitated the C sequestration in the lake ecosystems for atmospheric C reduction.

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.

Lake sediments play a critical role in organic carbon (OC) conservation. However, the biogeochemical processes of the C cycle in lake ecosystems remain limitedly understood. In this study, Fe fractions and OC fractions, including total OC (TOC) and OC associated with iron oxides (TOCFeO), were measured for sediments from a eutrophic lake in China. The abundance and composition of bacterial communities encoding genes cbbL and cbbM were obtained by using high-throughput sequencing. We found that autochthonous algae with a low C/N ratio together with δ13C values predominantly contributed to the OC burial in sediments rather than terrigenous input. TOCFeO served as an important C sink deposited in the sediments. A significantly positive correlation (r = 0.92, p < 0.001) suggested the remarkable regulation of complexed FeO (Fep) on fixed TOC fractions, and the Fe redox shift triggered the loss of deposited OC. It should be noted that a significant correlation was not found between the absolute abundance of C-associating genera and TOC, as well as TOCFeO, and overlying water. Some rare genera, including Acidovora and Thiobacillus, served as keystone species and had a higher connected degree than the genera with high absolute abundance. These investigations synthetically concluded that the absolute abundance of functional genes did not dominate CO2 fixation into the sediments via photosynthesis catalyzed by the C-associating RuBisCO enzyme. That is, rare genera, together with high-abundance genera, control the C association and fixation in the sediments.

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.

Freshwater lakes undergo substantial alterations of the phosphorus (P) cycle in the water-sediment ecosystem due to thermal change. The impact process of seasonal fluctuation on P cycling in sediments has been scarcely investigated. P forms in sediments from a freshwater lake in China were analyzed using sequential extraction technique. The vertical distribution of soluble reactive P (SRP), Fe2+, and S2-in the interstitial water was measured using diffusion gradient technique (DGT). Fick's Law and DIFS model were used to obtain the diffusion fluxes of SRP and the kinetic parameters in the water-sediment system. The results showed that total P (TP) concentrations in the solid sediments varied from 207.5, 266.6 and 130.3 mg/kg to 614.7, 1053.1, and 687.6 mg/kg in winter, spring, and summer, respectively. The concentrations of individual P forms in spring were higher than those in other seasons, with Fe-bound P (Fe-P) concentration being the highest across all seasons. Notably, significant variations of SRP concentrations were found in the interstitial water between sedimentary depths of approximately 2 cm and 6 cm, particularly in the summer. Furthermore, higher diffusion fluxes of SRP through the interface were found in summer. A stable anaerobic environment failed to develop in spring with high water level, preventing the desorption of solid Fe-P and diffusion of Fe2+ into the water due to the afflux and deposition of P-containing particulate into deeper sediment layers along with organic material. Under extreme high-temperature in summer, decreased rainfall and rising temperatures boosted the activity of aquatic organisms in the water, thereby reducing P fixation by sediments and leading to P release. This process increased the risk of P excess and potential eutrophication in the water. Generally, clarifying the resupplying processes of endogenous P in sediment systems experiencing seasonal variations is critical for eutrophication management of lakes.

Microbial communities play a critical role in aquaculture ecosystems. To identify the influence of sediment nutrient levels on microbial communities, sediment and water samples were collected from Chinese mitten crab Eriocheir sinensis culture ponds with different nutrient enrichment levels. Relevant physicochemical properties were measured, and 16 S rRNA gene sequencing was applied to identify relevant bacterial communities in the sediments. The results showed that the diversity and composition of microbial communities in sediments with different levels of nutrient enrichment varied considerably. Proteobacteria was the most abundant phylum in all samples, followed by Bacteroidetes, and Desulfobacterota with relative abundances of 23.5-40.9%, 9.8-21.5%, and 9.6-18.1%, respectively. Notably, total nitrogen (TN), organic matter (OM), and pH were important factors driving sediment bacterial community aggregation, the TN concentration explaining 61.5% of the microbial community variation. This study highlights that long-term culture activities alter the degree of sediment nutrient enrichment, which in turn affects microbial community composition and may ultimately have an impact on culture efficiency.

Coastal aquaculture ponds (CAPs) are of great importance for food security, ecosystem health, and greenhouse emissions. However, existing data often lacks geographic information on both national and international scale spatial data. Satellite remote sensing makes large-scale monitoring of CAPs more efficient. This is especially true when using synthetic aperture radar (SAR) data, which can provide all-day acquisition as a high-quality data source for large-scale CAP mapping. In this study, focusing on CAPs in China and Vietnam, a novel method of large-scale CAPs mapping using Sentinel-1 images was developed. Moreover, high-resolution (10 m) CAP datasets in 2015 and 2020 were produced, and spatiotemporal changes and drivers were analyzed. The key results are as follows: (1) the overall accuracy of the mapping method proposed was >90%. (2) In 2020, CAP area in China was 8774.93 km2 (69.43%) and it was 3864.10 km2 (30.57%) in Vietnam. (3) CAPs showed an opposite trend in China and Vietnam. The CAP area decreased by 891.29 km2 with a change rate of about-9.22% in China, while the CAP area increased by 920.35 km2 with a change rate of about 31.26% in Vietnam. China had made unprecedented ecofriendly efforts to restrict expansion for improving the ecological environment. Vietnam focused more on increasing production than on environmental protection, leading to significant expansion. Our results offer some new insights on satellite remote sensing and its use in coastal eco-environmental management and contribute to Sustainable Development Goals 2, 6 and 14.