Distribution and changes in microplastics in Taihu Lake and cyanobacterial blooms formed by the aggregation of Microcystis colonies

As a new type of pollutant, microplastics have attracted much attention. As the third largest freshwater lake in China, Taihu Lake is characterized by severe eutrophication caused by external pollution and frequent occurrence of cyanobacterial blooms. Although there have been previous investigations into the spatial distribution of microplastics in Taihu Lake, research on the relationships among microplastics, pollutants, and cyanobacterial blooms, as well as the spatiotemporal distribution and changing characteristics of microplastics, is deficient. This study investigated the characteristics of microplastics, pollutants, and cyanobacterial blooms in the surface water and sediments of Taihu Lake. The abundances of microplastics were 0-3.7 items/L in the surface water and 44.42-417.56 items/kg (dry weight) in the sediments. Microplastics are most abundant in the western, southern, and northern lake areas. The northern and western lake areas are severely polluted, and cyanobacterial blooms are prone to occur in these areas. This study found that microplastics exist in the surface water of the southeastern lake area, which is a source of drinking water, and the microplastics may thus have adverse effects on drinking water quality. As the main organisms in the cyanobacterial blooms, Microcystis and microplastics have similar spatial distributions in Taihu Lake and are both affected by wind. Based on a combination of the investigations of this paper with the existing research on the microplastics in Taihu Lake, the spatiotemporal distribution of microplastics was obtained: the abundance of microplastics in surface water has continuously decreased, there are no obvious spatial distribution differences, and the spatial distribution of microplastics in the sediments is the same as that in the surface water.