capacity of Sanggou Bay：observation and modeling

Abstract:

The background and themes of dynamic study on mariculture carrying capacity of Sanggou Bay were described. The method used for this study was based on the fine processes observation, using physical oceanography theory and numerical model to examine the interaction between mariculture and hydrodynamics in Sanggou Bay. Design proposal and purposes for two cruises were introduced. Based on the observation we found that the kelp and the raft influenced the current vertical structure greatly, and the maximum velocity was at the lower layer with strong phase delay. It was also found that the damped current was too weak to mix the sediment detritus and nutrients into the upper layer. Based on these discoveries a double drag boundary hydrodynamic model was proposed by adding the aquaculture drag at surface. The mechanism of kelp influence on the current profile was studied numerically by a one dimension model. Considering the kelp drag in the water column besides the boundary drag, a three dimension hydrodynamic model was adopted to quantify the influence of the aquaculture on hydrodynamics and water exchange of Sanggou Bay. A physical biological coupled aquaculture ecosystem model was established using DIN, POM concentration and phytoplankton with kelp biomass as variable. The simulation and numerical experiments showed that polyculture was a useful method for healthy and high efficiency aquaculture. Sanggou Bay has nearly reached its capacity under present aquaculture mode. By cutting down aquaculture density to 0.9 fold of the present density, the total production of kelp will slightly increase and the cost will be reduced. Cutting down the kelp density at the mouth of the bay could greatly enhance the amount of nutrients and biomass in the kelp bivalve culture area in the inner side. Artificial mixing might bring more nutrients from seabed in the bay.