| Apostichopusjaponicus is the most economic aquaculture species in northern coastal areas of China. Annual variation of bottom water quality in culture ponds for Apostichopus japonicus in Laizhou, Shandong Province was studied by measuring11physicochemical indexes and bacterial numbers. The results show that the physicochemical indexes and bacterial numbers kept changing in the year. The variation ranges of the water temperature, dissolved oxygen levels, pH values, and salinity were4.97-29.73℃,3.81-9.03mg/L,7.83-8.37, and27.0-28.8, respectively. The concentrations of sulfide, nitrite nitrogen, ammonia nitrogen, total nitrogen, active phosphorus, total phosphorus and COD (Central Office District) varied in the ranges of0.010-0.049mg/L,0.023-0.051mg/L,0.002-0.156mg/L,1.941-3.813mg/L,0.024-0.047mg/L,0.031-0.111mg/L and6.17-47.73mg/L, respectively. The numbers of heterotrophic bacteria and vibrio were found to vary from1.91×103to2.71×104CFU/mL and2.92×101to4.50×103CFU/mL, respectively. The proportion of vibrio to heterotrophic bacteria appeared2peaks in November (22.92%) and April (21.60%). The study suggests that the water quality of the culture ponds keeps fluctuating during the test period. There are complicated and close relationship among the physicochemical indexes and bacterial numbers, and a slight change of external factors will bring consecutive reactions to different indexes of the culture ponds.Annual variation of sediment quality in the culture ponds for Apostichopus japonicus in Laizhou, Shandong Province was studied by measuring6physicochemical indexes and numbers of8bacteria. The results show that the physicochemical indexes and bacterial numbers kept changing in the year. The variation trends of pH value and redox potential of sediment in the ponds were similar, varying in the ranges of7.15-7.80and42.8--351.0mv, respectively. Meanwhile, that of the concentrations of sulfide was contrary to the former two ones, varying in the range of47.66-496.12μg/g. The variation ranges of concentrations of total nitrogen, total phosphorus and organic carbon were457.42865.83μg/g,166.83-241.32μg/g, and0.27%-0.37%, respectively. The numbers of heterotrophic bacteria, vibrios, and Bacillus varied in the ranges of3.27×105-6.41×106, 5.39×103-1.62×105, and1.31×104-7.57×104CFU/g, respectively. The numbers of ammonifying bacteria, denitrifying bacteria, and nitrite bacteria were6.80×1051.31×107,2.67×103-5.11×104, and8.08×101-1.45×103cells/g, respectively. The variation of ammonifying bacteria and denitrifying bacteria had the same trend. The numbers of sulphur reducing bacteria and presumptive sulphur oxidizing bacteria varied respectively in the ranges of5.62×102-7.22×104and6.50×101-1.00×104cells/g, and showed contrary variation trend. The study suggests that there are significant correlations and complex relationships among various physicochemical indexes and bacterial numbers in the culture ponds.The sediment improver for culture ponds was studied by using orthogonal program. Apostichopus japonicus were breeded in the plastic sink which had mud in bottom. The degradation rate of ammonia nitrogen, sulfide, COD in the water and sulfide in the sediment were detected after using sediment improver to make sure the optimum formula. THPS amount of15%, B component amount of7%and C component amount of78%was obtained by visual analysis, which was the optimum formula for sediment improver. THPS was the key effect factor of the sediment improver.The repairing and regulating effects of sediment improver on the quality of sediment and water in the culture ponds for Apostichopus japonicus were studied by measuring physicochemical indexes and bacterial numbers. There were6and3ponds in sediment improver treatment group and control group, respectively. The results show that,4months after using sediment improver, the concentrations of ammonia nitrogen, nitrite nitrogen and sulfide in treatment group were significantly lower than those in control group (0.037mg/L vs0.170mg/L,P<0.05,0.024mg/L vs0.044mg/L,P<0.05and0.008mg/L vs0.013mg/L,P<0.01, respectively). The concentration of active phosphorus in treatment group was significantly higher than that of control group (0.043mg/L vs0.027mg/L, P<0.05). There were no significant differences in other indexes of water quality between treatment and control group. The redox potential of the sediment was increased significantly (3.17mv vs-113.23mv,P<0.05), meanwhile, the concentrations of total nitrogen (417.33μg/g vs796.33μg/g,P<0.01) and sulfide (57.36μg/g vs171.33μg/g, P<0.05) were reduced significantly after using sediment improver, which would reduce some harmful deoxidized composites diffusing from soil surface to water. The numbers of presumptive vibrio and sulphur reducing bacteria in the sediment of treatment group were lower than those of control group. Our study suggests that sediment improver could increase redox potential of the culture pond sediment, reduce some harmful deoxidized composites. Therefore, the sediment improver treatment can effectively improve the quality of sediment and water in the culture ponds for Apostichopus japonicus and thus shows a great application prospect. |
PDF Full Text Request