| Some progresses about the ecology system of shellfish raft culture are introduced in this paper, especially work about the N and P cycling hi this system are mentioned. The natural sedimentation affected by biodeposit production and the flux between the seawater and sediments are also concerned in this paper. Sungo Bay is in the east of Shandong Peninsula where scallop, oyster and kelp have been cultured hi large scale over twenty years. The experiment on natural sedimentation hi aquaculture areas of Sungo Bay was made with sediment traps in 5 periods from Sep.2001 to Jul.2002. Scallop, oyster and kelp culture areas were chosed for the experiment, and the concentrations of TN, TP and POM in the particular matter both from the traps and from the sediments of the experimental areas were measured respectively. The experiment on NH/, NOs-, NCV and PCU3- of the overlying and interstitial water in Sungo Bay was made hi 4 cruises from May to July in 2002. The fluxes of dissolved inorganic N, P from the sediments were estimated by Pick's first law. The results are as follows:(1) The sedimentation rate of particular matter was 278.8 g.m-2.d-1 in these areas. One gram of sediment settled down to the bottom could carry 190.4ug of TN, 472.5ug of TP and 0.103g of POM. The peak value of the TN content in the sediment appeared in May, and the minimal value appeared in Dec. From Sep.2002 to Jan.2002, the differences of sedimentation rates in scallop, oyster and kelp-culture areas were not remarkable, but remarkable from May.2002 to Jul.2002.(2)The seasonal differences of TN (total nitrogen) and TP (total phosphorus) content of sediments are remarkable. The peak value of the TN content appeared in May and the minimal value appeared in Dec, but the TP content of sediments in Dec is apparently higher than that in May and July. This shows that the value of TP content of particular matter in cold season is higher than that in warm season. The N/Pratio of the sinking sediment was in the range of 0.67-2.0, but that on the bottom was in the range of 0.025~2.0. This shows that the bottom sediment constitutes are more complicated than sinking sediments. The specific gravity of the bottom sediment is 2.22 ~2.55(average 2.37), and the unit weight is 1.05-1.41g/mL(average 1.09), and the porosity is 0.46-0.57 (average 0.50). Because the porosity of sediments in Sungo Bay is smaller than that of some bays, the diffusion flux of nutrient between the seawater and sediments is maybe smaller than that of many bays.(3) Fluxes are 376.33, 33.02, 6.41, and 10.08 tmiol.m-2.d-1 for NH4+, NO3-, NO2- and PO43- respectively in Sungo Bay hi a long time scale. The diffusive matter of the inorganic N and P from the sediment of the Bay could supply 28.73% of the N requirement and 334.09% of the P requirement of the planktonic primary producers hi Sungo Bay in one year.These experiment data can be served as a basis for the studies of the nutrient flux and the carrying capacity of shallow sea for aquaculture. |
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