Effects Of Bivalve Raft Culture On Environment And Their Ecological Regulation In Sanggou Bay, CHINA

The large scale cultivation of the filter-feeding bivalves, such as scallop, oyster, and mussel and so on, have caused serious problems in sustainable development in the cultures and impacted greatly on environmental condition and ecological balance in the coastal bays and shallow seas in many countries, including China. In this study, seasonal variations of the biodeposition, oxygen consumption, and ammonia and phosphorus excretion of some bivalves which are cultivated in Sanggou Bay are determined in site. Simultaneous, growth characters and ecological function of macroalgae Gracilaria lemaneiformis transplant from South Sea in China are studied. The aim of this study is to find out measures to maintain a sustainable development of mariculture in Sanggou Bay, in China.The results show that the biodeposition rates of bivalves change seasonally. The allometric relationship between biodeposition rates (BD) and dry tissue weight(DW) of bivalves are estimate using the formula: BD=aX Dwb.The bivalves can produce average circa 1.5 g biodeposite per individual every day, in which content average 7. 0 percent in OM, 1. 6 percent in OC, and 0.11 percent ON.There are seasonal variations of oxygen consumption rates, ammonia and phosphorus excretion rate of bivalves in Sanggou Bay. Oxygen consumption rates of these bivalves except bay scallop, general are high in July in summer, and low in January in winter. Oxygen consumption rates of bay scallop are high in September in summer and low in January in winter. Ammonia excretion rates of these bivalves are high in August in which the highest temperature occur and low in January in winter.In present study, experiments on growth characters and ecologicalfunctions of macroalgae Gracilaria lemaneiformis transplant from south china are conducted in polyculture areas of kelp and filter-feeding bivalve in Sanggou Bay in north china. Results of 116 clays cultivation show that, average wet weight of macroalgae increased 89 times from 0. 1 kg /meter of rope to8. 9kg/meter, with average of specific growth rate (SGRw) 3.9%/d (varying from9. 7%/d tol.2%/d). The photosynthesis of the macroaglae changed seasonally, with an average of 7.3mgO2 gdw-1h-1.In this study, the results also show that macroalgae Gracilaria lemaneiformis could act as effective biofilters in bioremediation lor deteriorating environment. Functions it plays include assimilating large amount of dissolved organic and inorganic nutrients, - releasing oxygen via photosynthesis, and establishing cleaner environment for shellfish in coastal hays and shallow seas.