Abstract：
Lake Taihu, an inland lake, frequently experiences Cyanobacterial blooms that have historically posed severe threats to its aquatic ecosystem. Combining field observations and satellite remote-sensed data, factors that influence algal bloom intensity in Lake Taihu over an eight-year period, from 2016 to 2023, are examined, and changes in phytoplankton community composition, climate, water quality, economic activities, and food web dynamics are reported. Sentinel-2 MSI data analysis reveals a dramatic decrease in Cyanobacterial blooms in 2023, with a reduction in the annual maximum bloom area of 76.90 % from 2016 values. From 2016 to 2022, the ratio of Cyanobacteria to other phytoplankton ranged 82.09 %-98.29 %, but in 2023, this dropped to 60.98 %. Concurrently, Cyanobacteria density dropped to an historic low of 2.29 × 107 cells/L (16.4 % of 2021 peak values). Redundancy and random forest analyses indicated that nitrogen has a greater influence on phytoplankton than phosphorus, with temperature and permanganate index being the important parameters to affect phytoplankton community structure. We attribute the decrease in Cyanobacterial blooms in Lake Taihu in 2023 to be largely caused by shifts in phytoplankton community structure, particularly the sharp decline in Microcystis sp. density, a genus often linked to bloom formation. Meteorological conditions such as reduced rainfall and wind speed during the winter and spring of 2023 also contributed to diminishing Cyanobacterial blooms. Ongoing improvements in water quality, reduced economic activities because of pandemic restrictions, and implementation of a fishing ban since 2020 have likely further contributed to reductions in bloom frequency. These results improve our understanding of the processes that affect algal blooms in Lake Taihu, and potentially other eutrophic inland lakes.
摘要：
太湖,一个内陆湖泊，经常经历蓝藻水华，这些水华在历史上对其水生生态系统构成了严重威胁。结合实地观测和卫星遥感资料,影响太湖水华强度8年的因素,从2016年到2023年，进行了检查，浮游植物群落组成的变化，气候,水质,经济活动,和食物网动态报告。Sentinel-2MSI数据分析显示，2023年蓝藻水华显着减少，年最大水华面积比2016年减少了76.90％。从2016年到2022年，蓝藻与其他浮游植物的比例为82.09%-98.29%，但在2023年，这一比例下降到60.98%。同时,蓝细菌密度降至2.29×107细胞/L的历史低点（2021年峰值的16.4％）。冗余和随机森林分析表明，氮对浮游植物的影响大于磷，温度和高锰酸盐指数是影响浮游植物群落结构的重要参数。我们将2023年太湖蓝藻水华的减少归因于浮游植物群落结构的变化。特别是微囊藻的急剧下降。密度,一个通常与水华形成有关的属。2023年冬季和春季降雨和风速减少等气象条件也导致蓝藻水华减少。水质不断改善，由于大流行的限制，经济活动减少，自2020年以来实施的捕鱼禁令可能进一步有助于减少开花频率。这些结果提高了我们对影响太湖藻华的过程的理解，和其他潜在的富营养化内陆湖泊。
