Figure 6: (a) Spatial distributions of the nutrient density and phytoplankton density on the 600th day, where the left vertical axis denotes the nutrient density, the right vertical axis denotes the phytoplankton density, (m^{2}·day^{−1}), (m·day^{−1}), and the other parameters are given in Table 1. (b) Relationship between nutrient density, phytoplankton density, and the sinking velocity , where the right vertical axis denotes the maximal nutrient density, and the left vertical axis denotes the maximal phytoplankton density. The purple field shows that the equilibrium state is stable, where (g·m^{−3}) and (m^{2}·day^{−1}).