Simulation Of Responses Of Plankton Ecosystems To Typhoons In The Northern Part Of South China Sea

Plankton is the most basic component of marine ecosystem.It plays an important role not only in the material cycling and energy flowing, but also in the global climate change. In recent years, due to an increasing of typhoon in frequency and intensity, more attention has been paid to its influence on phytoplankton bloom.In this stduy an one-dimensional Modular Ecosystem Model (MEM-1D) was used to understand the seasonal variation of the plankton ecosystem's vertical profile in the northern of South China Sea. Based on the simulation, this stduy analyzes the relations among the elements, the influencing factors and mechanism of the subsurface chlorophyll-a maximum, the controlling factors of winner bloom. Results show that sea surface chlorophyll-a concentration exhibited an evidently seasonal variation. The minimum occurred in summer (<0.05 mg m-3), while the maximum occurred in winter (0.38 mg m-3). The vertical profile of zooplankton and bacteria were similar to each other and both of their maximum appeared in winter, which were 24 mg C m-3 and 12 mg C m-3 respectively.A case study is performed to how the marine plankton ecosystem in the South China Sea (SCS) responsed to the typhoon (Damrey). Our studys show that:1) Nutrient concentrations in the sea surface were enhanced by the typhoon and subsequently induced the plankton bloom, i.e. silicate concentration in the sea surface increased by approximately four times.2) The concentration of plankton didn't increase immediately because of turbulence effect caused by the typhoon, and it could explain that there was a time lag between phytoplankton bloom and occurrence of typhoon.3) The new primary production caused by typhoon contributed about 7% to the primary production of the northern South China Sea in a year.Sensitivity anlysis is also conduted to further study the influence of individual factor on the plankton ecosystem response to typhoon. Intensity and speed of typhoon have various impacts on the upper ocean:i.e., the greater intensity and longer duration of typhoon would cause more heat transferring from the upper to deeper water. At the same time more nutrients will be taken to the surface, providing more nutrients for the growth of the phytoplankton. Although strong typhoons could cause higher concentration of phytoplankton and longer duration of the bloom, the larger time lag between phytoplankton bloom and typhoon passage. Vertical profile of zooplankton and bacteria varied similar to that of phytoplankton,but the former lagged for a phase after the growth of phytoplankton.When the same intensty typhoon passed over the ocean subject to different nutrient Imitation, the time lag was almost the same, but strength of the bloom was different...