Physical control of phytoplankton bloom development in the coastal waters of Jiangsu (China)

A large amount of phytoplankton blooms have occurred in the Jiangsu coastal waters since 2000. The trigger of the phytoplankton blooms responds to environmental factors. The present study aims to investigate the phytoplankton bloom development from the physical properties. To stress the significance of the phytoplankton, a vertical phytoplankton model is developed, coupling the characteristics of phytoplankton dynamics with a physical model. Combining with the analyses of the Delft3D model, the vertical phytoplankton model is well applied to the Jiangsu coastal waters. Significant correlations are established between chlorophyll a and phytoplankton biomass. The vertical stability threshold is strongly related to the specific growth rate, the loss rate and the euphotic depth, and critical depth is closely linked with light availability. The vertical stability provides a favourable living condition for the phytoplankton, while the shallower mixed layer depth promotes the accumulation of phytoplankton density in the water volume. All the observed blooms falling within the predictions demonstrate that the physical limitation can produce reliable blooms. The findings of this study contribute much to the understanding of the coastal ecosystem and the coastal management.