Studies On The Water Quality And Nitrogen, Phosphorus Budget Of Seven Types Of Aquaculture Ponds In Suzhou Region

This paper relied on the study on 7 different aquaculture ponds near the east Taihu Lake, survey and experimental analysis was conducted to reveal the situation of water quality and the budgets of nitrogen and phosphorus in aquaculture. And comparative studies of the budgets of nitrogen and phosphorus about crab-farming ponds in which crab was feed with 3 different food composition have been conducted. The results were as follows:1. The water quality in crab-farming pond ware: total ammonia nitrogen (TAN) < 1.0 mg·L-1, total nitrogen (TN) < 3.0 mg·L-1, total phosphorus (TP) < 0.3 mg·L-1, permanganate index (CODMn) < 6.0 mg·L-1. These results suggested that the water quality in crab-farming pond was better than the third grade standard of environment quality standard for surface water as well as the discharge standard for pond culture in the Taihu Lake basin. The nitrogen budget equation of the crab-farming ponds was: fry 6.50 kg·hm-2+feeds 147.16 kg·hm-2=catch 30.60 kg·hm-2+effluence 18.82 kg·hm-2+elodea 144.00 kg·hm-2+unknown -39.76 kg·hm-2; the phosphorus budget equation was: fry 0.47 kg·hm-2+feeds 31.91 kg·hm-2=catch 1.75 kg·hm-2+effluence 2.10 kg·hm-2+elodea 18.00 kg·hm-2+unknown 10.54 kg·hm-2.2. The water quality in oriental river prawn-farming pond ware: TAN < 1.0 mg·L-1, TN < 2.0 mg·L-1, TP > 0.3 mg·L-1, CODMn < 12.0 mg·L-1. The water quality, except TP, in the pond was better than the third grade standard of environment quality standard for surface water as well as the discharge standard for pond culture in the Taihu Lake basin. The nitrogen budget equation of the oriental river prawn-farming ponds was: juvenile shrimp 6.77 kg·hm-2+feeds 167.01 kg·hm-2+fertilizer 33.83 kg·hm-2=catch 32.18 kg·hm-2+effluence 15.19 kg·hm-2+elodea35.20 kg·hm-2+unknown 125.04 kg·hm-2; the phosphorus budget equation was: juvenile shrimp 0.59 kg·hm-2+feeds 34.79 kg·hm-2+fertilizer 15.57 kg·hm-2=catch 2.78 kg·hm-2+effluence 6.07 kg·hm-2+elode 4.40 kg·hm-2+unknown 37.70 kg·hm-2.3. The water quality in whiteleg shrimp-farming pond ware: TAN < 1.0 mg·L-1, TN < 2.0 mg·L-1, TP < 0.3 mg·L-1, CODMn < 12.0 mg·L-1. The water quality in whiteleg shrimp-farming pond was better than the third grade standard of environment quality standard for surface water as well as the discharge standard for pond culture in the Taihu Lake basin. The nitrogen budget equation of the whiteleg shrimp-farming ponds was: juvenile shrimp 0.09 kg·hm-2+feeds 469.90 kg·hm-2+fertilizer 3.06 kg·hm-2=catch 154.83 kg·hm-2+effluence 30.07 kg·hm-2+unknown 288.16 kg·hm-2; the phosphorus budget equation was: juvenile shrimp 0.01 kg·hm-2+feeds 96.66 kg·hm-2+fertilizer 1.63 kg·hm-2=catch 14.62 kg·hm-2+effluence 5.00 kg·hm-2+unknown 78.68 kg·hm-2.4. The water quality in black carp-farming pond ware: TAN < 1.3 mg·L-1, TN > 3.0 mg·L-1, TP < 0.3 mg·L-1, CODMn < 12.0 mg·L-1. The water quality, except TN, in the pond was better than the discharge standard for pond culture in the Taihu Lake basin. The nitrogen budget equation of the black carp-farming ponds was: fry 68.11 kg·hm-2+feeds 1038.78 kg·hm-2=catch 243.67 kg·hm-2+effluence 93.94 kg·hm-2+unknown 769.28 kg·hm-2; the phosphorus budget equation was: fry 14.03 kg·hm-2+feeds 207.15 kg·hm-2=catch 54.39 kg·hm-2+effluence6.20 kg·hm-2+unknown 160.59 kg·hm-2.5. The water quality in grass carp-farming pond ware: TAN < 1.3 mg·L-1, TN < 3.0 mg·L-1, TP < 0.3 mg·L-1, CODMn < 12.0 mg·L-1. The water quality in whiteleg shrimp-farming pond was better than the discharge standard for pond culture in the Taihu Lake basin. The nitrogen budget equation of the grass carp-farming ponds was: fry 52.05 kg·hm-2+feeds 684.69 kg·hm-2=catch 204.58 kg·hm-2+effluence 86.55 kg·hm-2+unknown 445.60 kg·hm-2; the phosphorus budget equation was: fry 12.13 kg·hm-2+feeds 116.75 kg·hm-2=catch 48.76 kg·hm-2+effluence 10.21 kg·hm-2+unknown 69.90 kg·hm-2.6. The water quality in polyculture pond ware: TAN < 1.3 mg·L-1, TN < 3.0 mg·L-1, TP > 0.3 mg·L-1, CODMn > 12.0 mg·L-1. The concentration of TAN and TN was lower than the discharge standard for pond culture in the Taihu Lake basin, and the concentration of the TP and CODMn was higher than that standard. The nitrogen budget equation of the polyculture ponds was: fry 33.19 kg·hm-2+feeds 351.80 kg·hm-2=catch 148.40 kg·hm-2+effluence 166.14 kg·hm-2+unknown 70.45 kg·hm-2;the phosphorus budget equation was: fry 7.59 kg·hm-2+feeds 75.61 kg·hm-2=catch 35.03 kg·hm-2+effluence 32.94 kg·hm-2+unknown 15.23 kg·hm-2。7. The water quality in chinese soft-shelled turtle-farming pond ware: TAN < 1.3 mg·L-1, TN < 3.0 mg·L-1, TP > 0.3 mg·L-1, CODMn > 12.0 mg·L-1. The concentration of TAN and TN was lower than the discharge standard for pond culture in the Taihu Lake basin, and the concentration of the TP and CODMn was higher than that standard. The nitrogen budget equation of the polyculture ponds was: fry 57.73 kg·hm-2+feeds 912.64 kg·hm-2=catch 148.30 kg·hm-2+effluence 95.94 kg·hm-2+unknown 726.14 kg·hm-2; the phosphorus budget equation was: fry 84.91 kg·hm-2+feeds 222.08 kg·hm-2=catch 218.12 kg·hm-2+effluence 20.66 kg·hm-2+unknown 68.21 kg·hm-2.8. Crab feeding trial, in which the crabs were fed with trash fish replacement by different levels of formula feed, showed that: the deposition rate of nitrogen and phosphorus of the crab were fed with trash fish ware 10.62% and 2.02%, while that of the crab were fed with less than 1000 kg·hm-2 formula feed were 25.81% and 12.67%. The release of nitrogen and phosphorus via the tailrace discharge were decreased from 27.57 kg·hm-2·year-1 and 2.84 kg·hm-2·year-1 to 19.16 kg·hm-2·year-1 and 2.17 kg·hm-2·year-1, respectively.These results indicated that the different aquaculture object and model would cause different pollution intensity.The pollution intensity of nitrogen was: oriental river prawn