STUDY ON THE SUSTAINABLE OYSTER CULTURE IN HIROSHIMA BAY WITH SPECIAL REFERENCE TO THE ROLE OF OYSTER CULTURE ON NITROGEN AND PHOSPHORUS CYCLES

广岛湾每年生产约2万吨鲜重牡蛎，约占日本牡蛎总产量的60%。从生态学的角度来看，牡蛎由于具有较高的过滤能力，在河口海岸生态系统的物质循环中可能发挥重要作用。本研究的目的是估计量的碳，氮，磷处理养殖牡蛎在广岛湾和评估的作用，养殖牡蛎悬挂在筏上的循环，这些元素在这个海湾。为实现上述目标，在野外调查的基础上，建立了广岛湾牡蛎的生理和生物量模型，结果表明，牡蛎排对颗粒物的吸收和释放速率在夏季和秋季高于冬季。悬浮牡蛎养殖对颗粒物和汇中C：N：P原子比没有显著影响 ...更多信息 但显著影响养殖区水体中的物质浓度和沉降颗粒物质量。用该模型模拟的牡蛎鲜重与实测值吻合较好，表明该模型能够较好地模拟牡蛎的生理活动和生长。利用生理模型估算了筏下养殖牡蛎的滤水率和生物沉积率，其结果与筏上的观测结果吻合较好;利用生物量模型估算了广岛湾养殖牡蛎的生物量。结果表明，水质参数可用于估算牡蛎的实际生长和累积死亡率。与生物量模型，在整个研究期间，估计在海湾养殖的活牡蛎的总数，并与生理模型一起用于估计牡蛎处理的C，N和P的量。结果表明，过滤后的C、N和P分别为9，360，1，560和210 g m-2 yr-1。约42%的过滤材料作为生物沉积物材料（粪便和假粪便）释放，其中31%至48%被代谢。滤出的C、N和P分别占滤出量的7%、19%和20%。以北方广岛湾为例，研究了牡蛎养殖对该湾碳、氮、磷循环的影响。此外，研究结果还表明，大量的材料（即4.7吨N和1.0吨P d-1）被保留在海湾的牡蛎的显着加工。从物质向陆地的转移和能量转移来看，广岛湾牡蛎养殖的能量转移和可转移物质C、N、P均高于其他渔业。少

Hiroshima Bay produces oysters of about 20,000 tons of fresh meat weight annually, which is ca.60% of the total oyster production in Japan. From the ecological point of view, oysters may play an important role on material cycling in the estuarine and coastal ecosystems due to the high filtering capacity. The objectives of the present study are to estimate the amounts of carbon, nitrogen and phosphorus processed by cultured oysters in Hiroshima Bay and to evaluate the role of the cultured oysters suspended from the rafts on the cycling of these elements in this bay. In order to achieve these objectives, in addition to the field investigation, the physiological and biomass models of oyster in Hiroshima Bay were developed.The results from field investigation showed that the rates of particulate uptake and release at an oyster raft were higher in summer and autumn than in winter. The suspended oyster culture did not significantly affect C : N : P atomic ratio in particulate matter and sink … More ing particles, but significantly affected the concentration of materials in water column and the mass of sinking particles in the culture area. The simulated fresh meat weight of an oyster (summed from the estimated growth) using physiological model was in good agreement with observed values, indicating that this model is suitable to simulate the physiological acitivities and growth of oyster. With the physiological model, the filtration and biodeposition rates by cultured oysters under the raft were estimated and these results also showed a good agreement with the results observed at the raft.Biomass of the cultured oysters in Hiroshima Bay was estimated using the biomass model, which is based on the variation of growth and mortality of oysters and the harvested loss. Our results showd that water quality parameters could be used for the estimation of actual growth and cumulative mortality of oysters. With the biomass model, total number of living oysters cultured in the bay was estimated throughout the study period and was used together with physiological model for the estimation of the amounts of C,N and P processed by oysters. The results revealed that filtered C,N and P were 9,360,1,560 and 210 g m-2 yr-1, respectively. About 42% of the filtered materials were released as biodeposit materials (feces and pseudo-feces), and 31 to 48% of them were metabolized. The amounts of 7,19 and 20% of the filtered C,N and P were harvested as oysters. The role of suspended oyster culture on C,N and P cycles was evaluated for northern Hiroshima Bay.The results from the present study revealed that oysters play a significant role on the cycling of carbon, nitrogen and phosphorus in the bay. In addition, the results also revealed that high amount of materials (i.e.4.7 ton N and 1.0 ton P d-1) were retained in the bay by the significant processing of oysters. In term of the removal of materials from the bay to the land and energy transfer, the results of the present study demonstrated that the eneregy transfer and removable materials i.e.C,N and P through oyster culture in Hiroshima Bay are higher than those through the other fisheries. Less