桑沟湾营养盐及浮游植物对水产养殖活动的响应

Responses of Nutrients and Phytoplankton to Aquaculture Activities in Sanggou Bay

为了解水产养殖活动对营养盐循环及浮游植物结构的影响以及微型浮游动物的摄食压力,本文在桑沟湾进行了现场培养实验。结果显示,NO_(3)^(-)是秋季浮游植物生长的限制因子。栉孔扇贝养殖会引起NH_(4)^(+)的累积,实验结束时NH_(4)^(+)浓度为初始浓度12.8倍;同时栉孔扇贝会对甲藻选择性摄食,从而改变浮游植物的群落结构;而大型藻类通过与浮游植物竞争营养盐,限制浮游植物的生长繁殖,使浮游植物粒径向小型化转变。此外,浮游植物还受到微型浮游动物的上行控制,调查期间湾内浮游植物生长率为0.39 d^(-1),微型浮游动物摄食率为0.79 d^(-1);微型浮游动物对浮游植物现存量和初级生产力的摄食压力分别为54.6%和169%。本研究有助于加深营养盐及浮游植物对水产养殖活动响应机制的理解并为水产养殖的可持续发展和生态环境管理提供理论支持。

Nutrients are essential elements for the growth of phytoplankton and macroalgae.In aquaculture activities,shellfish excretion will increase the nutrient loads in the water column and promote the growths of phytoplankton and macroalgae,however,the filter feeding effect of shellfish and nutrient competition from macroalgae will lead to a decrease in phytoplankton biomass;moreover,the feeding of microzooplankton may change the structure of the phytoplankton communities.To understand the effects of aquaculture activities on nutrient cycling and phytoplankton community structure as well as the grazing of microzooplankton,experiments of enclosure and dilution culture were conducted in Sanggou Bay.The results showed that NO_(3)^(-) was the limiting factor for phytoplankton growth in autumn.Chlamys farreri causes accumulation of NH+4,with NH_(4)^(+) concentrations 12.8 times higher than the initial concentration at the end of the experiment.Chlamys farreri selectively fed on dinoflagellate,thereby altering the phytoplankton community structure.Macroalgae could compete with phytoplankton for nutrients,thereby limiting the growth and reproduction of phytoplankton and a shift in phytoplankton size to miniaturization.In addition,phytoplankton were controlled by the top-down effect of microzooplankton.During the study period,the growth rate of phytoplankton in the bay was 0.39 d^(-1),and the feeding rate of microzooplankton was 0.79 d^(-1).The feeding pressures of microzooplankton on the current stock and primary productivity of phytoplankton were 54.6%and 169%,respectivety.This study contributes to a broader understanding of the mechanisms by which nutrients and plankton respond to aquaculture activities,and provides theoretical support for the sustainable development and ecological environment management of aquaculture.