Primary production mechanism in a bay with cultivation of pearl oyster Pinctada fucata martensi (Dunker)

本研究旨在阐明马氏珠母贝养殖海湾的初级生产机制。结果表明：1)夏季马氏沼虾对浮游植物的捕食量为0.11个/小时/克湿重；2)夏季马氏沼虾对海水的捕食量为171个/小时/个(43g)海水；(3)0.50个/小时/L的叶绿素a含量随湾内巨洲的升高而增加；4)马氏沼虾通过过滤海水间接促进浮游植物生长的假说，是基于泵升机制增加捕食量与捕食量减少的比较而得出的。(5)过滤后海水中P_(04-P)和NH_4-N浓度增加，6)马氏沼虾在过滤后的海水中存在生长物质，在促进海湾浮游植物生长的同时，也通过捕食阻碍了浮游植物的生长。这是褐藻对浮游植物捕食的一种缓解作用。这些结果表明，在水生生态系统中存在着一种重要的捕食-捕食关系。

The object of this study was to clarify the primary production mechanism in the bay where pearl oysters Pinctada fucata martensi (Dunker) were cultivated. The results obtained were as follows : 1) the amount of predation of P.fucata martensi on phytoplankton in summer was 0.11 mug/hr/g of wet weight, 2) P.fucata martensi filtrated 171/hr/individual (43g) of sea water in summer, 3) 0.5 mug/l of chlorophyll a increased with the Kyucho in the bay, 4) a mitigation hypothesis, that P.fucata martensi indirectly favored the growth of phytoplankton by filtrating sea water, was induced based on the comparison of the increase by the pump up mechanism and the decrease by predation of P.fucata martensi predation, 5) the concentrations of P04-P and NH4-N increased in the filtrated sea water, 6) growth substances existed in the filtrated sea water by P.fucata martensi.It was found that while P.fucata martensi favored the growth of phytoplankton in the bay it also hindered its growth by its predation. This is a mitigation effect of P.fucata martensi on its predation on phytoplankton.These results indicated an important prey-predatory relationship in an aquatic ecosystem.