Long-term response of plankton assemblage to differentiated nutrient reductions in Laizhou Bay, China

Nutrient reductions are considered effective methods to control eutrophication; however, our understanding of how plankton assemblages respond to nutrient reductions is limited. In the present study, we used a long-term dataset between 2004 and 2018 from Laizhou Bay, China, to describe the main characteristics of plankton assemblage response to nutrient reduction, and to compare the differences in plankton response between the different nutrient reduction regions. The results showed that plankton abundance showed obvious decreasing trends in response to nutrient reductions. The phytoplankton abundance decline rate was directly proportional to the magnitude of nutrient reductions. The large-scale shellfish culture may disrupt the response of mesozooplankton to nutrient reductions. Positive recovery signs in the plankton community were observed with species dominance decreasing for small individuals and increasing for large ones. The results suggested that the reduction in nitrogen and phosphorus positively affected plankton abundance and community recovery in Laizhou Bay.