Studies On The Transport And Transformation Of Particulate Organic Matter In Aquaculture Water Area Of Sungo Bay

Investigation was conducted on the transport and transformation process, including sedimentation, release, degradation and resuspension, of particulate organic matter (POC, TN and TP) in aquaculture water areas of Sungo Bay in Aug. and Nov., 2003. The flux of sedimentation, release rate, degradation rate and proportion of resuspension in different species culture areas (scallop, kelp and oyster) and different seasons were determined, using the methods of measurement on-the-spot and simulation test in lab. The followings were the main results:(1) The flux of sedimentation and amount of resuspension in the aquaculture water areas of Sungo Bay were measured by using suspended sediment traps. It was indicated that the flux of sedimentation was affected greatly by resuspension and differed significantly among areas with seasonal variation. After deducting the effects of resuspension, the flux of sedimentation in scallop and oyster aquaculture water areas was larger than that in kelp culture areas. The sedimentation fluxes of total particulate matter, POC, TN and TP in summer were 42.39g/m2/d, 0.56g/m2/d, 0.059 g/m2/d, and 0.010g/m2/d, respectively. In autumn, the values were 65.51g/m2/d, 0.85g/m2/d, 0.091 g/m2/d, and 0.030g/m2/d, respectively.(2) By using columnar mud-picker, the columnar sediment samples were collected in scallop, kelp and oyster aquaculture water areas of Sungo Bay. Laboratory incubation method was employed to simulate the releasing process of POC, TN and TP from sediment. Release rates were calculated with sequential function and non-linear fitness. It was indicated the release rates of POC, TN and TP from sediment manifested obvious region diversity and seasonal variation. The release rates of POC, TN and TP in scallop and oyster aquaculture water areas were larger than those in kelp culture areas. In summer, the average release rates of POC, TN and TP were 144.5mg/d/m2, 27.82 mg/d/m2 and 6.32 mg/d/m2, respectively, larger than the values in autumn, which were 72.7 mg/d/m2, 3.61 mg/d/m2 and 1.59 mg/d/m2,3respectively. The release rates of POC, TN and TP were in the sequence of POC > TN > TP. All of the values increased with the increase of POC, TN and TP content in sediment.(3) Columnar sediment samples were collected, by using the same method as above-mentioned, and delaminated on-the-spot. Using the dynamics equation ( Inc = In Co - k-id ) to fit the content variations of POC, TN and TP in sediment, the degradation rate constant could be obtained. It has been shown that POC, TN and TP in sediment mainly degraded in the surface layer, and the degradation rates were in the sequence of TN ^ TP > POC. The degradation rates of POC, TN and TP in sediment in summer were larger than those in autumn, manifesting obvious seasonal variations. The values also displayed distinct region diversity, large in scallop and oyster aquaculture water areas and small in kelp culture areas. The reason is likely to the fact that intensive shell aquaculture resulted in organic pollution in sediment, consequently, the abnormal benthic environment promoted the growth and metabolism of microorganisms.(4) Sediment samples in middle and bottom water were collected with sediment traps. Taking aluminum as indicate substance, the resuspension proportion in eachWr (Cl ?Cs)layer could be estimated by the formula: = - . The results were indicatedthat the resuspension proportion of paniculate organic matter in Sungo Bay aquaculture water area was very high, the resuspension quantity in bottom and middle water accounting for 97% that 80% of total sedimentation quantity, respectively. The suspension proportion did not manifest evident seasonal difference. The suspension quantity in oyster aquaculture water areas was smaller than that in scallop and kelp aquaculture water areas. It was mainly due to the fact that the oyster aquaculture water areas had less wind effect, accordingly less agitating action.