Foundational Studies On Effects Of Raft Culture Of Filter-feeding Bivalves On Coastal Ecological Environment

Owing to irrational exploitation, the shellfish raft culture industry has been continuously inflicted by casualties, which urgently needs to ascertain carrying capacity and culture methods in coastal areas. In this paper, studies on the characteristics of physiological ecology of sea raft-cultured bivalves and the processing of suspended particulate materials by bivalves, i. e. ingestion, absorption, excretion and defecation of particulate carbon, nitrogen and phosphorus nutrients by mollusks, are conducted in order to understand the role played by bivalves in material and nutrient circulation of coastal culture ecosystem. In addition, a more accurate and simplified ignition method is developed for determination of inorganic, organic and total phosphate in sediments and organisms. The main results are as follows.(ID Biodeposit production by the scallop Chlamys farreri in summer in raft culture areas of Sishili Bay, Yantai, has been determined in situ in eight stations. The result shows that biodeposit of 59.9mg is produced every day by a one-year-old scallop with shell height of 41.1?.1 mm and soft body dry weight of 0.48?.lOg/ind, and the mean biodeposition rates of POM, POC and PON by the scallops are 6.88, 3.09, 0.392 and 0.022 mg/ind?d, respectively. In one station, biodeposition rate of the bay scallop Argopecten irradians, whose shell height is 24.6?.3mm and soft body dry weight is 0.14 glind , is 24.3 mglind d or 179.2mg/g d. The biodeposition rates of the one-year-old Chlamys farreri vary in different areas of the bay, which is mainly related to total suspended particulate matter. The average biodeposition rate of two-year-old Chlamys farreri with shell height of 60.9?.2mm, soft body dry weight of 1.91?.32 g/ind is 112.7 mg/md d, and POM, POC, POON and POP deposition rates of the scallop are respectively 1.85, 1.68, 1.77 times as high as that of the one-year-old scallop. Compared to non-culture areas, theA慖deposition rate of particulate matter near the bottom in shellfish cultUre reas is．sl～3．47times ashighasm成oftheformeL he eveWd叮 biodepositprowctionbyall of＊theyallcultivated scallops In the Sishili bay in summer is 62 t(ry weight),or 86t POP, 8．37 tPOC,1．06t PON and 60kg PR It is estimated that'427t N and 98．ot P are circufored ndregenerated every year owing to blodeposlt production by scallops,which can meet heannual demands for．0％and 28．3％of N and P resPectively for pelagic pnm叼production of＊thetion whole bay ②Blodeposit production by Chb呗 fo册ri was also determined In semi－ieldwater－flowing systems within longer length of time(80dnys)．The results show that theblod聊sition rate Is negatlvelycorrelated to scallop,orPOsltlvelycorrelated to foodconceddatlon which vanes ith scallop density Boththe quantity andthe quality of＊theyblodeposit re related to肋d conce血tion．The hi归 the number ofscallops,the lowerthe o用amc m劝贸 comem orC,N and P coment of＊the＊＝ sediments,Which reflects t比scallop'sablllty to叨apt to de environment．In Lamln皿m仰onica andobp灿八polycultUre patterns,there Is no markea effect of the kelp on btrieposit production of hescallop,but in hehe ield,the kelp culture m叮 reduce the blodeposltlon rate of＊theosltlon scallopvia effects on phytopl讪on production． ＠N毗 P excretion by vanous ilter feeding orgamsms collected肋m coastalculture reas,Incfu41ngo2p加ri,Ampecten u'毗的us,蜘疗us eMIs,o删ostreagpo,！udmpes p》f帅Jn—urn咖5uhg Ofg一S——伽2C0ye,0OnO fnoof7na7KBahuns amPhi"it6 and丹aPezium liratum),were studied．InN excretion,NH4－N Is themain form,which accow吐s for more than 70％(mean 70．8～80．l％)ofhh excretion．Although anunonla is the domin恤 form ofnltrogen excretedbythe spedes,amlno acidsare the second main component of N excretion In all stUdwt ofganlsms,Which amounts to10－25％ofTN excret＊．Other forms ofN excretion by the spedes are urea,mme and...