Can the establishment of a protected area improve the lacustrine environment? A case study of Lake Chaohu, China

Spatiotemporal dynamics of microcystin contamination in fish across the Lake Chaohu basin under the Yangtze River ten-year fishing ban: Ecological and human health implications

Microcystins (MCs), produced by harmful cyanobacterial blooms, pose a threat to aquatic ecosystems and public health in the Yangtze River basin, including Lake Chaohu, which implemented a ten-year fishing ban in 2021 for ecological restoration. This study provides the first basin-wide assessment of MC contamination in fish muscle tissues from Lake Chaohu and its major tributaries during the ban's initial phase (2022-2023), with comparisons to pre-ban data. Using UHPLC-MS/MS, we quantified MC-LR and MC-RR in fish from four trophic levels (planktivorous, omnivorous, herbivorous, and carnivorous). Results revealed that MC-RR was the predominant variant, and planktivorous fish exhibited the highest MC levels, followed by omnivorous, herbivorous, and carnivorous species, reflecting dynamics of trophic transfer. Overall, fish MC concentrations were significantly lower during the ban compared to pre-ban levels, demonstrating positive initial effects. Seasonal analysis revealed higher MC levels in warmer seasons, but detectable MCs persisted during cold seasons, reflecting ongoing contamination. Spatially, while fish in the lake exhibited higher MC concentrations, contamination was also detected in riverine fish, highlighting the basin-wide spread. Despite a lower overall health risk from fish consumption relative to the pre-ban period, high consumption of planktivorous species, especially during warm seasons and in lake regions, may still pose potential health risks. Additionally, MCs likely pose ecological risks to fish populations. These findings provide a crucial baseline for evaluating the long-term effectiveness of the fishing ban and underscore the need for integrated watershed management to safeguard both ecological and public health.

Niche partitioning and trait tradeoff strategies enable plants to coexist under interspecific competition in restored wetlands

Background

Niche partition and traits tradeoff theory were primary strategies for plants coexistence. However, specific strategies of plants remained to be verified to guide community configuration and biodiversity maintenance in ecological restoration.

Methods

The variation of plants composition and niche breath were utilized to examine the temporal and spatial niche partition strategies, respectively. Meanwhile, the chi-square (χ2), Spearman rank correlation coefficient (rij), Ochiai index (OI) were employed to analyze the interspecific relationship of 30 predominant species from species pool of 220 vascular plants. Besides, the Lotka-Volterra model was utilized to reveal the traits tradeoff strategies of predominant species from five vegetation formations.

Results

About 62.41% pairs of wetland species were niche partitioned while 37.58% of species pairs were niche overlapped. In temporal scale, 60.5% of species occurred either in spring or autumn while 39.5% occurred in both seasons. Meanwhile, significant change of relative height (RH) and relative coverage (RC) were observed in constructive species and auxiliary species. Height tradeoff strategy (Δ R H Δ R C > 1 ), coverage enlarge strategy (Δ R H Δ R C < 1 ), or both strategies (Δ R H Δ R C = 1 ) observed in wetland plants.

Discussion

Our finding testified that the temporal niche partition and traits tradeoff strategies are objectively observable in wetland plants. These findings on coexistence strategies can be used in the configuration of plants communities and the biological control of alien invasive plants.

Brownification increases the abundance of microorganisms related to carbon and nitrogen cycling in shallow lakes

Brownification in aquatic ecosystems under global change has attracted attention. The composition and quantity of dissolved organic matter transported from various land use types to lakes differ significantly, causing varying ecological effects of lake brownification by region. Bacterial communities make a significant contribution to the material cycle of ecosystems and are sensitive to environmental changes. In this study, a series of mesocosm systems were used to simulate forest lakes and urban lakes with different degrees of brownification, and a high-throughput amplicon sequencing technique was used to explore the changes in the composition, structure, and function of bacterial communities in shallow lakes undergoing brownification. Principal coordinate analysis (PCoA) and Jensen‒Shannon distance typing analysis both indicated significant differences in bacterial communities between forest lakes and urban lakes. The α diversity of bacterial communities in urban lakes increased with the degree of brownification. However, whether forest lakes or urban lakes, brownification increased the abundance of carbon cycling-related bacterial phyla (Proteobacteria, Poribacteria, and Chloroflexi) and nitrogen cycling-related bacterial genera (Microbacteriaceae, Limnohabitans, Comamonadaceae, Bacillus, and Rhizobiales_Incertae_Sedis). Additionally, the carbon and nitrogen cycling functions of bacterial communities in forest lakes are dominant, while those in urban lakes are dominated by functions related to light. Our study has preliminarily revealed that lake brownification promotes the growth of carbon and nitrogen cycling microorganisms, providing a new paradigm for understanding the response of lake ecosystems in different catchment areas to environmental changes and the carbon and nitrogen cycling processes in shallow lake ecosystems.

Restore polder and aquaculture enclosure to the lake: Balancing environmental protection and economic growth for sustainable development

The restoration of lakes and their buffer zones is crucial for understanding the intricate interplay between human activities and natural ecosystems resulting from the implementation of environmental policies. In this study, we investigated the ecological restoration of shallow lakes and buffer zones in the Yangtze-Huaihe River Basin, specifically focusing on the removal of polder and aquaculture enclosure areas within the lakes. By examining data from eight shallow lakes and their corresponding buffer zones, encompassing lake morphology, water quality parameters, and land use/land cover (LULC) data spanning from 2008 to 2022, which shed light on the complex relationships involved. During the process of restoring polder and aquaculture enclosure areas, we observed a general decrease in the extent of polders and aquaculture enclosures within the lakes. Notably, the removal of aquaculture enclosures had a more pronounced effect (reduction rate of 83.37 %) compared to the withdrawal of polders (reduction rate of 48.76 %). Linear regression analysis revealed a significant decrease in the concentrations of seven water quality parameters, including COD, CODMn, TN, TP, NH3-N, Chl-a, and F, while pH and DO factors exhibit a distinct increasing trend. The results of redundancy analysis and Pearson correlation analysis demonstrated significant correlations between the area of polders and aquaculture enclosures and the changes in lake water quality. Encouragingly, the withdrawal of polders and the removal of aquaculture enclosures had a positive impact on the lake water quality improvement. In contrast, the LULC in the buffer zones of the lakes experienced a gradual decline owing to land degradation, resulting in a reduction in ecosystem service value (ESV). These results offer valuable support for policymakers in their endeavors to restore lake water quality, mitigate the degradation of buffer zones land, and promote the sustainable development of land and water resources.

What drives the changing characteristics of phytoplankton in urban lakes: Climate, hydrology, or human disturbance?

Phytoplankton in shallow urban lakes are influenced by various environmental factors. However, the long-term coupling effects and impact pathways of these environmental variables on phytoplankton remain unclear. This is an emerging issue due to high urbanization and the resultant complex climate, lake hydrology and morphology, human interference, and water quality parameter changes. This study used Tangxun Lake, the largest urban lake in the Yangtze River Economic Belt, as an example to assess for the first time the individual contributions and coupled effects of four environmental variables and fourteen indicators on chlorophyll-a (Chla) concentrations under two scenarios from 2000 to 2019. Additionally, the influence pathways between the environmental variables and Chla concentration were quantified. The results indicated that the Chla concentration was most affected by lake hydrology and morphology, as were the total nitrogen, total phosphorus, and transparency. Especially after urbanization (2015-2019), the coupling effect of human interference, lake hydrology and morphology, and water quality parameters was strongest (18%). This is mainly due to fluctuations in the lake water level and an increase in the shape index of lake morphology, large amounts of nutrients were input, which reduced lake transparency and indirectly changed the Chla content. In addition, due to the rapid development of Wuhan city, the expansion of construction land has led to an increase in impervious surface area and a decrease in lake area. During periods of intense summer rainfall, a substantial amount of pollutants entered the lakes through surface runoff, resulting in decreased lake transparency, and elevated concentrations of nitrogen and phosphorus, indirectly increasing the Chla content. This study provides a scientific basis for aquatic ecological assessment and pollution control in urban shallow lakes.

Impacts of landscape pattern on plants diversity and richness of 20 restored wetlands in Chaohu Lakeside of China

The recovery of wetland function and biodiversity conservation aroused considerable interest in the past decades. Although many advances have been achieved in revealing disturbing factors on plants diversity, the knowledge of biodiversity manipulation, landscape configuration and ecosystem process in restored wetlands remains incomplete. To address this issue, the landscape of 20 restored wetlands' vegetation was classified into five vegetation formations including: upland plants, wet grassland, emergent plants, floating plants and submerged plants. Meanwhile, the configuration of landscape, plants' function traits and the structure of plants communities of each wetland were analyzed. A total of 142 herbaceous plants were identified from 399 samples of 20 lakeside wetlands. The top five predominant species were Typha orientalis, Alternanthera philoxeroides, Phragmites australis, Echinochloa caudata, and Erigeron canadensis. The highest of diversity index was observed in upland plants with Shannon-Wiener index (H) of 0.92 while higher richness of plants was obtained in wet grassland with species of 88. In dry year, the immigration of upland xerophyte and obligated aquatic species to facultative area increased the biodiversity of the ecotone. Meanwhile, this change may also aggravate the diffusion risk of exotic invasive species Erigeron canadensis. Additionally, the results indicated that number and evenness of landscape outweighed Shannon diversity index (SHDI) of wetlands in shaping the richness and diversity of wetland plants. Whereas, the high value of maximum proportion of landscape (Pmax) have reduced the landscape evenness and species richness. A suggested Pmax of <0.5 was benefit for the stability and biodiversity of restored wetlands.

A spatiotemporal optimization method for nutrient control in lake watersheds

Developing an efficient strategy for managing nutrients in less-developed lake watersheds that can balance the need for socioeconomic progress with the protection of aquatic ecosystems has become an urgent research subject for achieving sustainable development. This paper improves the optimization method for environmental and economic management of lake watersheds proposed in our previous research. A spatiotemporal optimization method based on a coupling model consisting of the Soil and Water Assessment Tool, system dynamics model, and objective programming model was applied to an agricultural non-point source (ANPS) pollution control program and a rural sewage treatment program at the Yilong Lake watershed as a case study. A simulation evaluation showed that the efficiency of the previous scheme was significantly improved after conducting spatiotemporal optimization. This scheme was dynamic and distributed, demonstrating an annual and high-resolution control program that can provide a basis for the precise management of ANPS. Although it still requires improvement, a framework for coupling simulation and two-step optimization was achieved in this study.