Largest Freshwater Lake In China Research Articles

Assessment of heavy metal accumulation in freshwater fish of Dongting Lake, China: Effects of feeding habits, habitat preferences and body size

We measured the concentrations of Cr, Fe, Ni, Cu, Zn, Cd, Pb and Hg, and the stable isotope ratios (δ13C and δ15N) in 87 fish samples within 12 economic fish species collected from the Dongting Lake, the second largest freshwater lake in China. With few exceptions in concentration of Cr, most of fish species showed lower concentrations of the 8 metals than legislation thresholds. Piscivorous fishes had significantly higher values of δ15N (possessing higher trophic level) and metal concentrations than planktivorous and herbivorous fishes. Moreover, demersal fishes showed higher concentrations of Cu, Zn, Cd and Pb than pelagic and benthopelagic fishes. We found positive correlations between concentrations of Fe, Pb and Hg and δ15N ratio, confirming the biomagnification of the three metals through trophic transfer. In contrast, fishes showed clear growth dilution effect for Ni, Zn, Cu, Pb and Hg, indicated by the negative correlations between their concentrations and fish weight or length. Multiple regression analysis demonstrated that growth dilution and biomagnification effects simultaneously governed the metal concentrations in fish muscle, and the two effects' importance varied among different metals. The human health risk assessment indicated that all 8 metals gave target hazard quotient (THQ) values < 1.0, i.e., the estimated daily intake (EDI) of metals did not exceed the oral reference dose (RfD), indicating a safe consumption of these fish species for consumer. Our study provides comprehensive approaches to better understand the determining processes and potential risk of heavy metals in freshwater lake fishes.

Spatiotemporal Dynamics of Water Body Changes and Their Influencing Factors in the Seasonal Lakes of the Poyang Lake Region

Poyang Lake is the largest freshwater lake in China, an internationally important wetland and the largest migratory bird habitat in Asia. There are numerous seasonal lakes in the Poyang Lake region, and these lakes create a complex and diverse wetland landscape and serve as the main activity area for migratory birds. Seasonal lakes have significant effects on hydrological and ecological processes and are highly susceptible to various changes, but research on seasonal lakes is relatively limited. Based on long-term remote sensing images, this study analyzed the spatiotemporal variation characteristics of seasonal lakes and their influencing factors and ecological effects. The conclusions were as follows: the average water area of seasonal lakes showed a unimodal change during the year, reaching a maximum in July and a minimum in January. The interannual water area fluctuated greatly, and the overall water area showed a small downward trend. In terms of spatial variation, the seasonal lakes were connected with the main lake in the wet season and separated from the main lake in the dry season. Among the natural factors, the influences of temperature, evaporation, and rainfall on the water area of the seasonal lakes were successively reduced. In addition, the incoming water from the Yangtze River had an important influence. Among the human factors, the traditional fishing method “enclosing sublakes in autumn” had the greatest impact on the water area in a specific period, followed by the indirect impact of the Three Gorges Project.

Evaluating the landscape ecological risk based on GIS: A case‐study in the Poyang Lake region of China

AbstractInfluenced by human activities, the largest freshwater lake in China, Poyang Lake is suffering from landscape degradation and increased ecological risks. However, the specific landscape ecological risk in Poyang Lake region remains unknown. The impact of land use change on landscape pattern and ecological risk around Poyang Lake has not been revealed. In order to analyze the spatio‐temporal distribution characteristics of landscape ecological risk in Poyang Lake region, this study constructed a landscape ecological risk index model based on GIS, geostatistics, and landscape ecology theory. The results show that: (a) all land use types in Poyang Lake region had been changed during the period 2010–2018. While large tracts of farmland and woodland were converted into construction land, farmland and woodland have seen the largest decrease and construction land has increased greatly. (b) On the whole, the low and medium‐low landscape ecological risk area accounted for about 60% of the total area, while high and medium‐high risk area increased during 2010–2018. The landscape ecological risk has seen a downward trend with increased low and medium‐low ecological risk areas during 2010–2018. Spatially, ecological risk in the core waters of Poyang Lake was higher, while in the surrounding waters was lower. (c) The landscape ecological risk in Poyang Lake Region in each period shown positive spatial correlation and tended to be spatially agglomerative. The high‐high risk clusters were mainly located in the core waters of the Lake area, while the low‐low risk clusters were mainly located far away from the core waters, including county and city areas. (d) In 2018, farmland, woodland, grassland, and unutilized land were dominated by medium and medium low risk, the landscape ecological risk in the water area was the highest, and that of construction land was the lowest. The decrease rate of ERI in water areas was the largest, indicating that the change of water area contributed the most to the reduction of landscape ecological risk. During the process of ecological risk management in Poyang Lake Region, attention should be paid to the changes of the water area's structure and quality.

Numerical study of hydro-environmental processes of Poyang Lake subject to engineering control

Abstract Poyang Lake, the largest freshwater lake in China, plays a key role in regulating the hydrology, water quality and ecosystem in the middle reaches of the Yangtze River. Recent industrialization and urbanization in Jiangxi province have led to rapid increase in water consumption and water quality deterioration. In this research, a numerical model is developed to simulate the hydrodynamics and water quality evolutions in Poyang Lake and its surrounding river network. The study links an in-house one-dimensional river network model with a MIKE multi-layered three-dimensional hydro-environmental model. The validated model is used to investigate the impact of a proposed downstream barrage on Poyang Lake's flow and ecosystem. All of the five considered barrage operation schemes demonstrate the capability of increasing the water level and inundation area during the dry period, especially in the lake's downstream region. The barrage schemes help reduce the lake's nutrient concentrations, due to the enhanced dilution at higher water levels. Nonetheless, the barrage leads to DO depletion which could pose a threat to the aquatic wildlife and habitats. This study's findings contribute to a better understanding of the hydro-environmental influence of the proposed barrage and thus the optimisation of its operation to mitigate the adverse influence.

A New Algorithm for Monitoring Backflow from River to Lake (BRL) Using Satellite Images: A Case of Poyang Lake, China

Backflow from river to lake (BRL) usually happens in inland lakes and affects water exchange, matter migration, and variations in the water quality and eco-environment. However, at present, discharge data derived from hydrological stations are the only way to monitor BRL, and the influence scope of BRL has not been monitored through hydrological stations. To address this problem, we propose a novel algorithm to monitor BRL using satellite images of Poyang Lake (the largest freshwater lake in China). The following results were obtained: (1) According to the difference in suspended sediment from rivers and lakes, an algorithm using the total suspended sediment (TSS), which was used as a tracer, was designed for monitoring BRL in Poyang Lake. (2) An innovative extraction method for the mutation line using the TSS was developed to analyze BRL via satellite images. A gradient variation method was developed to extract the mutation line accurately. (3) The satellites with daily acquisition or higher-frequency resolution images (e.g., Moderate-Resolution Imaging Spectroradiometer (MODIS)) were satisfactory for monitoring the characteristics of BRL. The MODIS-derived band combination Rrs(645) − Rrs(859))/(Rrs(555) − Rrs(859) yielded a higher fitting accuracy (R2 = 0.858, RMSE = 10.25 mg/L) derived from an exponential model, which was helpful to highlighting the mutation line. (4) The important parameters of BRL, such as the beginning time, the duration, the end time, and the influence scope, were quantitatively determined by judging the movement of the mutation line. This algorithm was applied to quickly and effectively extract the information of two instances of BRL in Poyang Lake in July 2000 and July to August 2007, and the results were accurate and reasonable. This algorithm can save a great deal on monitoring costs. A BRL monitoring algorithm using remote sensing is an efficient government measure supplement to address the limitations of hydrological stations. These results provide technological support for lake management and can serve as a valuable reference for water bodies similar to Poyang Lake worldwide.

Different storm responses of organic carbon transported to Lake Taihu by the eutrophic Tiaoxi River, China

Low-frequency high-magnitude storms can flush disproportionate amounts of terrigenous dissolved organic carbon (DOC) and particulate organic carbon (POC) into rivers during a short period. However, previous studies focused on the impacts of storms on organic carbon transport in headwater streams that are minimally influenced by human activities and are far from lakes. To better estimate the lake carbon budget and manage lake water environments, we need to understand the transport of storm-induced organic carbon into lakes by eutrophic rivers. Based on daily and hourly time-series monitoring data, this paper systematically studied the influences of storm precipitation on DOC and POC transport in the eutrophic Tiaoxi River entering Lake Taihu, the 3rd largest freshwater lake in China. The results showed that seven storms transported 59% of the annual total organic carbon into Lake Taihu in 2019, and all storms resulted in transport peaks. During the storm period on August 9–16, 2019, DOC was negatively related to the water level (r = −0.44, p < 0.05), but POC responded positively (r = 0.52, p < 0.05); allochthonous organic carbon contents were elevated, but the autochthonous components were diluted. Moreover, the storm-induced input of riverine organic carbon influenced the lake water environment across a large region, and the impacts lasted more than 10 days. These findings have important implications for accurately estimating riverine organic carbon fluxes into lakes and making better-informed decisions about when to pump drinking water from lakes.

Variation of water body in Dongting Lake from in situ measurements and MODIS observations in recent decades

ABSTRACT Identifying the spatiotemporal dynamics of the water body in Dongting Lake, the second largest freshwater lake in China, is crucial for water resource management. In this study, the variations of the water body were comprehensively analyzed based on remote sensing images and in situ measurements from 2000 to 2019. Four breakpoint detection approaches were integrated to analyze the change trends and explore the related driving forces behind the changes. The results showed that significant intra– and inter–annual fluctuations of the water body were found from 2000 to 2019. The water area and volume decreased at rates of 1.26 km2/a and 16.65 × 106 m3/a, respectively. During the entire study period, the outflow at Chenglingji station (CLJ), the inflow from three outlets of the Yangtze River (Inflow2), and the inundation conditions during the last period (Arealag) made the largest relative contributions to the water area variation (around 25%, 27% and 24%, respectively). A breakpoint was detected around 2004, corresponding to the operation period of the Three Gorges Dam (TGD). The regulation of TGD profoundly affected the hydrological characteristics at the three outlets and CLJ, and may have indirectly caused the water area to expand by 2.41 km2/a during the dry seasons between 2004 and 2019. These results provide valuable insight into how natural and anthropogenic factors affect water body variation and may offer a practical reference for the local government to adjust management strategies.

Social resilience to climate and water-related disasters in the Poyang Lake area (East China) over the past 2000 years

The largest freshwater lake in China, the Poyang Lake, experienced a long history of evolution with combined influences from both climate factors and human activities. Along with the dramatic changes of water related disasters such as flood and drought, local society developed various strategies to cope with the water problems. This paper investigated the evolution of the Poyang Lake area, the flood and drought disasters, and the society resilience using statistical analysis, spatial analysis, and a combination of qualitative and quantitative approaches. Historical data on climate, population, flood and drought, water engineering, and social economics were collected to support a detailed examination of the climate-hazard-society relationships. The results indicate that: (a) the lake area was mainly influenced by the warm and rainy climate and expanded significantly before the Yuan Dynasty (1271–1368 AD). Since the large-scale southward population migration in the Yuan Dynasty, intensive reclamation of wetlands surrounding the lake plus the effects of a colder climate shrank the lake area sharply. (b) The frequency of water-related disasters was gradually increasing during the past 2000 years, especially since 12th century, as a result of climate change and population growth. (c) Despite significant change in climate and increasing flood and drought, local people in Poyang Lake area adopted various water engineering to prevent flood and coast training measures to protect farmland, which enabled the social surviving and continuous economic development. Social resilience in Poyang Lake was highly correlated with lake changes and associated water hazards. (d) Presently, more ecological strategies have been adopted to mitigate the risk of flood and drought at the Poyang Lake area. The study emphasizes the influences of climate and water environment and the coping activities of human society, and thus contributes to a specific understanding of resilient living with big lakes.

Hydrodynamics, Sediment Transport and Morphological Features at the Confluence Between the Yangtze River and the Poyang Lake

AbstractConfluences act as critical nodes in a river network as they affect flow, sediment transport, water quality, and ecological patterns. A complete knowledge about hydro‐morpho‐sedimentary processes at river confluences is still incompleted and it has been usually accepted that secondary flows are weak because of the significant role of form roughness in large rivers. In this study, two field surveys were conducted on the flow structure, suspended sediment transport and morphology of the confluence between the Yangtze River (the largest river in China) and the Poyang Lake (the largest freshwater lake in China). Dual counter‐rotating cells were observed during high flow conditions and a single secondary cell appeared in low flow conditions. These helical cells restricted the core size of high sediment concentration and downwelling flows acted as a barrier hindering the exchange of sediment between the two rivers. Furthermore, the observed large scour hole was likely related to the downwelling and upwelling flows caused by helical motions. In low flow conditions, the scour hole looked like a deep channel, which was likely related to a long‐surviving helical cell. The scour hole disappeared further downstream, when either the helical motion got weak during low flow conditions, or when a reverse helical cell occurred during high flow conditions. Hydrodynamics, suspended sediment transport and morphological features observed at such a large confluence demonstrated that river planform geometry and discharge ratio affected the flow structure, especially the helical motion. This in turn affected sediment transport as well as the local bed morphology.

Water Ecosystem Service Quality Evaluation and Value Assessment of Taihu Lake in China

Taihu Lake is the third largest freshwater lake in China. Water ecosystems play an important role in the survival and development of human society. The evaluation of water ecosystem services is helpful to understand and grasp the changing rules of Taihu Lake’s ecosystem services value in recent years. First, we used the Water Environment Qualities Index (WQI) to evaluate the water ecological quality of Taihu Lake; second, on the basis of the survey data from 2010 to 2018, we combined economic and ecological methods to evaluate the water ecosystem of Taihu Lake. The evaluation system includes four major service functions, 11 second-class evaluation indicators and 19 index factor. Research indicates that, (1) in the past 8 years, the WQI of Taihu Lake increased year by year and Taihu Lake changed from moderate pollution to light pollution; (2) provisioning services are the main service of Taihu Lake’s water ecosystem and the order of various service values was provisioning service value &gt; regulation service value &gt; cultural service value &gt; support service value, with water supply as the core function of provisioning services; and (3) the total values in 2010, 2014, and 2018 were 115.39 billion yuan, 113.31 billion yuan, and 119.96 billion yuan, respectively, showing a trend of first decreasing and then increasing. To a certain extent, the improvement in Taihu Lake’s water ecological quality has led to an increase in the value of regulation services.

Spatial heterogeneity of vegetation extent and the response to water level fluctuations and micro-topography in Poyang Lake, China

Wetland vegetation dynamics are vital but difficult to understand due to complex impact factors and their spatial heterogeneities. Poyang Lake, the largest freshwater lake in China, is well-known for its ecological importance as a floodplain wetland. However, heterogeneity in vegetation extent and its response to water regimes across different geomorphic units of Poyang Lake remain unclear to date. To address this gap, Landsat images acquired during dry seasons from 1987 to 2018 were selected to explore vegetation extent and its response to water level fluctuations across multiple elevation bands and four wetland types, namely Riparian Wetland (RW), Delta Wetland (DW), Dish-shaped Wetland (DSW), and Fan-shaped wetland (FSW). Results show that vegetation extent in lower elevation bands of the four wetland types increased remarkably with an average increase rate of 0.53 km2/year between 2003 and 2018 compared to −0.17 km2/year−1 during 1987 to 2002. Hydrological variables indicating high-flow events negatively affected vegetation extent in DSW while variables indicating low-flow events appear to be positive for vegetation extent in RW, DW, and FSW. Over-long floods as happened in 2016 has caused fatal damage to vegetation extent in DSW. In addition, extreme droughts in recent years caused by the Three Gorges Dam promoted significant (p < 0.05) vegetation expansion in lower elevation bands of RW, DW, and FSW, but a deterioration of vegetation extent in higher elevation bands, making Poyang Lake at risk of shrinkage and degradation. Human impacts on the evolution Poyang Lake system have caused wide concern, which also contribute to the proposal of Poyang Lake water control structure. Heterogeneity in vegetation extent and their response to water regimes across Poyang Lake provide precise spatial information for restoration efforts of the wetland ecosystem.

Research on Protective Development of Wetland Ecological Resources in Poyang Lake

As one of three major ecological regulatory systems in the world, wetlands play an important role in protection of ecological environment and biodiversity. As the largest freshwater lake in China, Poyang Lake is also one of the areas with the most abundant biological resources in wetland ecosystem in China, which has great ecological and economic benefits. In recent years, a string of problems inevitably exist in the further development of Poyang Lake wetland ecological resources. Based on comprehensive introduction of Poyang Lake wetland ecological resources, this paper makes a comprehensive analysis of its development and utilization status and existing problems. Besides, it also puts forward a series of strategies for protection and development of Poyang Lake wetland, in an effort to further protect ecological resources of Poyang Lake wetland and realize the sustainable utilization of resources.

Linking macrophyte community structure with food chain length: A case study in the largest freshwater lake in China and ecological restoration implications

Food chain length is a significant ecosystem index and it greatly affects ecosystem processes and their outcomes. In recent decades, determinants or indicators of FCL have been investigated in different ecological contexts, but few studies analyzed the relationships between macrophyte community structure and the food chain length of freshwater ecosystems despite the crucial role of macrophyte community in determining food web structure. This study investigated the influence of macrophyte community structure on food chain length by conducting a field survey in Lake Poyang, the largest freshwater lake in China. Plant volume inhabited (PVI), Shannon-Wiener diversity index and Pielou’s evenness index were used to indicate macrophyte community structure. Our results suggested that intermediate levels of PVI and diversity (PVI 44% and diversity 0.61) with greater evenness could support longer food chain in sub-lakes of Lake Poyang. We proposed that macrophyte community structure indexes could be useful indicators in indicating food chain length in freshwater ecosystem. These novel findings also highlight that within suitable ranges of PVI and diversity, better restoration effect could be achieved by higher macrophyte evenness in lake management. Our findings provide new insights for the restoration and management of macrophytes in freshwater ecosystems.

Aquatic Ecosystem Health Assessment of Poyang Lake through Extension Evaluation Method

Freshwater lakes encounter a series of problems, such as a decline in lake water quality, a sharp decrease in biodiversity, and ecological degradation. As such, lacustrine studies by highly skilled professionals and managers with water resources at home and abroad have focused on assessing the aquatic ecosystem health status of lakes. In this study, the health status of the aquatic ecosystem in the largest freshwater lake in China (Poyang Lake) was assessed, and its temporal and spatial characteristics were illustrated. The index contained three element layers, including hydrologic characteristics, trophic status, and aquatic organisms. The health status of the aquatic ecosystem was classified into three categories: ‘good’, ‘moderate’ (subhealthy), and ‘bad’. It was examined through extension evaluation method. Results showed ‘moderate’ health status, whereas remarkable seasonal and spatially variations. The annual changes in the health status were remarkably due to the influence of complex hydrological and hydrodynamic conditions. This study provides an overall understanding of the aquatic ecosystem evaluation in Poyang Lake. Such an understanding is vital for environmental conservation and identification of causes of the aquatic ecosystem degradation in Poyang Lake.

Spatiotemporal Distribution, Partitioning Behavior and Flux of Legacy and Emerging Per- and Polyfluoroalkyl Substances (Pfas) in Surface Water and Sediment from the Largest Freshwater Lake in China

Spatiotemporal Distribution, Partitioning Behavior and Flux of Legacy and Emerging Per- and Polyfluoroalkyl Substances (Pfas) in Surface Water and Sediment from the Largest Freshwater Lake in China

基于深度神经网络算法的水体透明度反演方法

水体透明度能够直观反映湖泊水质状态，掌握长时间大尺度湖泊水体透明度是控制和改善湖泊水生态环境的关键。由于滇池的水质原位监测工作起步较晚，导致长时间序列的历史湖泊水体透明度数据的缺失。为此，以滇池为研究区，以深度神经网络算法为理论基础，以原位监测和MODIS遥感影像为数据，对2001年1月1日-2018年12月31日滇池水体透明度进行反演，并利用地理空间分析方法探讨了滇池湖泊水体透明度时空变化特征。研究结果表明：（1）提出的反演模型具有较好的性能（RMSE=0.1359，MAE=0.1134），能够客观反映湖泊水体透明度状况；（2）时间变化特征分析结果表明，滇池水体透明度总体呈现下降趋势，综合变化率为-0.08 m/10 a；（3）空间变化特征分析结果表明，水体透明度较高的区域下降率较大，水体透明度较低的区域变化趋势相对稳定，距离城区及居民区较近的水体透明度相对较低；人类活动将成为影响滇池水体透明度变化的重要因素，同时也是造成滇池水体污染的主要因素。;Lake is an important ecological resource, which not only determines the quality of regionally ecological environment, but also guarantees the sustainable development of the city. Lake ecological environment can reflect the environmental situation of the region. Secchi depth (SD) can directly reflect the state of lake water quality, and mastering long-term and large-scale lake SD is the key to control and improve the lake water environment. Dianchi Lake, located in the middle of Yunnan Guizhou Plateau, is the sixth largest freshwater lake in China. It is the main water area for irrigation in Kunming area, and it is also the basic condition for urban development. Therefore, Dianchi Lake is chosen as the research area. Because the in-situ monitoring of lake water quality for this study area was started late, there are few historical SD data. So, it is necessary to simulate and estimate SD by remote sensing images. In this paper, deep neural network algorithm was used to invert the SD of Dianchi Lake from January 1, 2001 to December 31, 2018 based on in-situ data and MODIS remote sensing images, and explored its spatial-temporal variation characteristics by geospatial analysis. The in-situ data was the daily monitoring values of 10 stations (Baiyukou, Caohai Center, Dianchi South, Duanqiao, Guanyinshan East, Guanyinshan West, Guanyinshan Center, Haikou West, Huiwan Center, and Luojiaying) from 2001 to 2010 and the monthly monitoring values of 2 regions (Caohai and Waihai) from 2018, which was provided by Yunnan Academy of Environmental Sciences; MODIS data was provided by NASA LAADS Web, with daily time resolution and 500 m spatial resolution. The methods used in this paper included Grey Relational Analysis (GRA), Long-Short Term Memory (LSTM), and Theil-Sen slope estimation. In the construction of SD inversion estimation model, the main methods include Correlation Analysis (C), Outlier Processing (O), Denoising Processing (D), and estimation model (COD-LSTM). The results showed that (1) the inversion model proposed in this paper had better performance (RMSE=0.1359, MAE=0.1134), which can objectively reflect SD status. (2) The analysis of temporal variation characteristics indicated that the SD of Dianchi Lake presented a downward trend with an average comprehensive change rate of -0.08 m/10 a. (3) The analysis of spatial variation characteristics indicated that the rate of decline in the region with higher SD was larger, and the trend in the region with lower SD was relatively stable. The SD near the urban and residential areas was relatively low. Human activities would become an important factor affecting the SD changes in Dianchi Lake, and it was also the main factor causing lake pollution.

Lake Poyang ecosystem services changes in the last 30 years

鄱阳湖是我国最大淡水湖，在维持区域生态安全和生态平衡中发挥重要作用.为了解近30年鄱阳湖生态系统服务变化情况，本文对已有文献与监测数据进行收集整理，直接获取鄱阳湖水资源供给、渔业资源供给、水环境净化服务数据，通过输沙量法、Berger-Parker优势度指数计算泥沙淤积调控和生物多样性维持服务，利用RMSD方法分析1992—2014年鄱阳湖生态系统服务关系.结果表明：（1）渔业资源供给和水环境净化服务不断下降，水资源供给和泥沙淤积调控服务在2010s有所恢复；（2）冬候鸟种类和数量增加，鱼类种群结构逐渐恢复，但Berger-Parker指数总体上升；（3）浮游植物、底栖动物多样性上升，浮游动物多样性下降；（4）不同时间尺度各服务间均为高权衡关系，水环境净化服务相对收益始终高于其他服务.;As the largest freshwater lake in China, Lake Poyang plays a vital role in maintaining regional ecological security and ecological balance. Due to natural changes and human activities, the hydrology and hydrodynamics of Lake Poyang changed, and the ecosystem of Lake Poyang was seriously threatened, which directly led to the degradation of ecosystem services. In order to capture ecosystem services changes of the Lake Poyang in the past 30 years, the existing literature and monitoring data were systematically collected and sorted to obtain data on Lake Poyang's water supply, fish supply, and water depuration services directly. Sediment transport method and Berger-Parker index were used to estimate sedimentation control and biodiversity protection services. The root mean square deviation (RMSD) method was applied to explore the temporal change of the trade-off relationships of Lake Poyang from 1992 to 2014. The results show that: (1) Fish supply and water depuration services continued to decline. Water supply and sedimentation control services recovered gradually in the 2010s. (2) The biodiversity of winter migratory birds and fish biodiversity increased slightly, characterised by the increased species and number of winter migratory birds and the fish population composition. (3) The biodiversity of phytoplankton and benthic animals increased, and the biodiversity of zooplankton decreased. (4) All the ecosystem service pairs had high trade-off relationships, and water depuration service always had a relatively higher benefit than other services.

Integration of α, β and γ components of macroinvertebrate taxonomic and functional diversity to measure of impacts of commercial sand dredging.

Effects of commercial sand mining on aquatic diversity are of increasing global concern, especially in parts of some developing countries. However, understanding of this activity on the diversity of macroinvertebrates remains focused on the α component of species diversity, rather than community functioning. Thus, there remains much uncertainty regarding how each component of taxonomic (TD) and functional (FD) diversity respond to the activity both in freshwater and marine environments. Here, we assessed the effect of sand dredging on α, β and γ components of TD and FD during different dredging periods based on the response of macroinvertebrate communities over 4 years in the second largest freshwater lake in China. After three years of active dredging, substantial reductions in each component (α, β and γ) of TD and FD were observed within the dredged area. Moreover, after one year of natural recovery, a distinct restoration was observed with an obvious return in multiple facets of TD and FD indices. No such changes were observed within the adjacent and reference areas. Decreases in the multiple components of TD and FD within the dredged area were most likely associated with the direct extraction of substrate and associated benthic fauna and indirect variations of the water and sediment environment (e.g., increases in water depth and decreases in %Clay). Furthermore, dispersal processes and mass effects mainly contributed to the maintenance of TD and FD during the dredged and recovery stages. In addition, the fast recovery of TD and FD was also related to the simple taxonomic structure and highly connected nature of the study area. Our results suggest that a more precise experimental design (BACI) should be pursued to avoid potentially confounding effects (e.g., natural disturbance) because the sensitivity of diversity indices depends upon different experimental designs. Moreover, measurement of the impacts of sand dredging on macroinvertebrate diversity can be undertaken within a rigorous framework for better understanding the patterns and processes of each component of TD and FD under the sand dredging disturbance.

The effects of water-level changes on periphytic algal assemblages in Poyang Lake

Poyang Lake, which is the largest freshwater lake in China, has a seasonal flooding cycle that significantlychanges the water level every year. The aim of this study was to research the effects of water-level changeson periphytic algal assemblages in Poyang Lake. Dynamic shift of periphytic algal biomass were studied fromNovember 2016 to July 2019. Periphytic algal biomass and species composition were analyzed microscopically, andphysicochemical conditions were measured. There were significant seasonal variations in the community distributionof periphytic algae. The biomass of the periphyton ranged from 8 to 22,636 mg m-2. Periphytic algal biomassranged from 30 to 622 mg m-2 with the average of 204 mg m-2 in the LWL phase; periphytic algal biomass rangedfrom 8 to 21,839 mg m-2, with the average of 3,399 mg m-2 in the IWL phase. It ranged from 166 to 22,636 mgm-2, with the average 4,320 mg m-2 in the HWL phase and from 16 to 3,231 mg m-2 with the average of 585 mgm-2 in the DWL phase. There were temporal variations in periphytic algal community structure in Poyang Lake.Cryptophyceae dominated in algal periphyton from November 2016 to February 2017. Bacillariophyceae dominatedfrom March to July 2017 (increasing water-level phases). Pyrrophyceae and Euglenophyceae were dominant fromAugust and September (high-water-level phase) in 2017. Bacillariophyceae dominated through 2018 with occasionaldominance of Cryptophyceae from January to June and the occasional dominance of Chlorophyceae fromJuly to December. Chlorophyceae dominated from January to July in 2019 with occasional dominance of Bacillariophyceae.The water-level variations led to environmental heterogeneity in Poyang Lake, creating heterogeneoushabitats for algal periphyton. Our study revealed the primary importance of water level, water temperature, conductivity,total nitrogen, nitrite and total phosphorus as abiotic local factors structuring the periphytic algal communityin Poyang Lake. The water-level changes did not prevent growth of periphytic algae, but it did change the periphyticalgal community assemblages. This research provides data on the periphytic algae in Poyang Lake and will beuseful for establishing biological indicators of environmental changes and protecting Poyang Lake in the future.

A review on the driving forces of water decline and its impacts on the environment in Poyang Lake, China

Abstract The recession of water levels of natural lakes and their associated impacts on wetland ecosystems is a serious issue worldwide. Poyang Lake (the largest freshwater lake in China) has experienced a heightened and prolonged water decline since the year 2000, which causes concern for associated ecological impacts. In particular, climate change, operation of the Three Gorges Dam (TGD), and high magnitude sand mining appear to be well-correlated with the occurrence of water decline in Poyang Lake. Though the above factors have been analyzed in previous studies, a comprehensive summary has never been compiled. This paper provides a detailed literary review highlighting the driving forces and possible impacts of the consistent water decline in Poyang Lake. We conclude here that the operation of TGD is a fundamental cause for the lake water decline, aggravated by climate change and sand mining. The water decline has caused a deterioration of water quality, as well as having given rise to a potential threat to the habitat of migratory birds and Yangtze finless porpoises. The paper intends to offer constructive references that can be used in decision-making for effective protection of water resources and lake ecosystems.