Damming has changed the migration process of microplastics and increased the pollution risk in the reservoirs in the Shaying River Basin

The impact of damming on river ecosystems has received increasing attention, but a comprehensive understanding of the occurrence, drivers and exposure risks of microplastic (MP) pollution in multigate dam-type rivers is lacking. We investigated the characteristics and abundance of MPs in water, sediment and biological tissues from samples collected in the vicinity of ten dams in the Shaying River basin and analyzed the effect of environmental and food web structural changes on MP accumulation in freshwater animals under the influence of dams. Dam construction affects the transportation, suspension, and deposition of MPs at different dam locations (upstream, reservoir, and downstream) by altering hydrodynamihas changed the migration process of MPs. The dams intercepted a large amount of MPs from upstream sediments in the reservoir but had no significant capturing effect on MPs in water. The structure of the food web in the reservoir was simplified and the animals in the reservoir had the highest risk of MP contamination. A high MP abundance (or high microplastic diversity integrated index (MDII) values) in the environment or simplification of the food web may have led to higher MP accumulation in animals. More effort is needed to monitor MP pollution in reservoirs and control it sources.