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Microorganisms can both indicate the water quality characteristics and the health of the aquatic environment, which have an important influence on the cycling of organic carbon, nitrogen (N), and phosphorus (P) in nature. In this study, we took Taihu Lake, a typical eutrophic lake in China, as the research object, and monitored the northern (Changzhou City) and southern (Changxing County) regions of Taihu Lake for three consecutive years (2019–2021), respectively. We also analyzed the microbial diversity in sediments, and then summarized the effects of different nutrient environments on microorganisms in the aquatic environment. The results showed that the pollution level in the northern part of Taihu Lake was higher than that in the southern region of Taihu Lake, where the pollution was mainly in summer (June–July). The pollution in the southern region of Taihu Lake is relatively stable between 2019 and 2021; the changes in the northern part of Taihu Lake are relatively significant. Microbial diversity in the study area was negatively correlated with the degree of eutrophication of water bodies; microbial abundance was positively correlated with nutrient levels. The functional difference analysis indicated that the microorganisms in the sediments of Taihu Lake in the study area were involved in the nutrient transport and transformation, and played an important role in the purification of the lake water body. This study reveals the relationship between water eutrophication and microbial diversity, and then provides a theoretical basis for the management of eutrophic lakes.

The rapid rise of microcystins (MCs) poses a serious threat to global freshwater ecosystems and has become an important issue of global public health. MCs have considerable stability and are the most widely distributed hepatotoxins. It cannot only accumulate in aquatic organisms and transfer to higher nutrients and levels, but also be degraded or transferred during the resource utilization of cyanobacteria. No matter which enrichment method, it will lead to the risk of human exposure. This review summarizes the research status of MCs, and introduces the distribution of MCs in different components of aquatic ecosystems. The distribution of MCs in different aquatic organisms was summarized, and the potential risks of MCs in the environment to human safety were summarized. MCs have polluted all areas of aquatic ecosystems. In order to protect human life from the health threats caused by MCs, this paper also proposes some future research directions to promote MCs control and reduce human exposure to MCs.

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