桑沟湾水动力特征及其对养殖容量影响的研究——观测与模型

capacity of Sanggou Bay：observation and modeling

关键词:  养殖容量  水动力影响  精细过程观测  双阻力边界层

Key words:  Aquaculture capacity  Hydrodynamic effects  Fine processes observation  Double drag boundary model  Physical biological coupled aquaculture ecosystem model  Sanggou Bay

摘要:

主要介绍了从动力学研究桑沟湾养殖容量的主要思路、方法及结果。研究以精细过程观测为基础，以数值模型为手段，从物理海洋学角度考察养殖海区水动力特征，研究水动力对物质循环的影响、对颗粒态/溶解态营养物质的补充和对养殖生物量的影响，探寻不同养殖模式效果的技术路线；介绍了两个航次设计方案与目的。通过观测发现养殖对水动力垂直结构有很大影响，底层流速最大并滞后表层，发现弱动力条件下海底颗粒物和营养盐无法进入水体上层的事实。据此提出双边界层动力模型，建立一维数值模型进行机制探讨，将养殖阻力三维化建立水动力数值模型，定量给出养殖对水动力和水交换的阻碍；以此驱动三维养殖生态模型，充分考虑养殖对水动力的影响、水动力对生源要素的输运。建立了一个真正的物理 生物过程耦合模型。利用该模型进行的数值模拟和实验表明，贝藻兼养多元养殖是健康、高效养殖的有利措施；桑沟湾在现有养殖模式下，目前已基本达到了它的养殖容量，养殖品种分布不变，减少养殖密度至目前的0.9倍会略微提高产量，降低成本；减少湾口海带养殖密度，会大幅度提高贝藻兼养区的营养盐总量和养殖生物产量，从海带与贝类经济价值对比会有更高的效益。人为提高水动力混合或许是解决湾内营养盐缺乏的途径。

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.