草鱼–鳙–鲫零换水池塘有机碳、氮、磷收支研究

Study on organic carbon, nitrogen and phosphorus budgets of zero-water exchange ponds of grass carp, bighead carp and crucian carp

中文关键词: 草鱼  鳙  鲫  零换水  营养盐收支

英文关键词: Ctenopharyngodon idella  Aristichthys nobilis  Carassius carassius  Zero-water exchange  Nutrient

中文摘要:

      为研究草鱼(Ctenopharyngodon idella)–鳙(Aristichthys nobilis)–鲫(Carassius carassius)零换水池塘营养盐收支状况，阐明其零换水机制，以草鱼–鳙–鲫零换水池塘为实验组，以草鱼–鳙–鲫常规换水池塘为对照组，开展了为期2年的池塘有机碳(TOC)、氮(N)、磷(P)收支的研究。结果显示，2组池塘TOC、N、P的主要来源均为饲料投入，分别为77.06%和81.00%，92.08%和92.77%，94.18%和95.63%；TOC、N、P的主要输出途径均为底泥积累，分别占输入营养盐的43.32%和22.10%，61.40%和52.82%，78.71%和79.58%。2组池塘养殖鱼类收获分别占输入碳(C)、N、P的10.08%和13.05%，21.00%和25.57%，15.41%和18.60%。零换水池塘的C、N、P水体积累量和积累率均显著低于常规池塘(P<0.05)，其积累率分别降低92.91%、88.52%和87.12%。零换水池塘的N、P底泥积累量显著高于常规池塘，但C、N底泥积累率显著低于常规池塘(P<0.05)，分别降低了48.99%和13.97%。零换水池塘养殖鱼类的C、N、P利用率均显著高于常规池塘(P<0.05)，分别提高了29.49%、21.72%和20.65%。研究表明，零换水模式能降低营养盐积累，有效提高系统物质利用率，是一种绿色高效养殖模式，具有较好的推广价值。

英文摘要:

      Presently, aquaculture production is increasing to meet the increasing demand for protein, and the total area of aquaculture ponds worldwide was 5.4 million hectares in 2016. However, pond aquaculture causes serious environmental problems. Animals generally use only 20%~30% of the input nutrients in feed, and the majority of the remainder are dispersed in the aquaculture system, leading to an increasing waste load inside the aquaculture pond system. The conventional way to improve the aquaculture pond environment is by changing water, however, wastewater drainage is not in accordance with the water shortage situation in China. Additionally, aquaculture wastewater discharge affects the surrounding environment. It showed that China’s seawater ponds discharge 4.77×104 and 3.75×103 tons of nitrogen and phosphorus, respectively, into surrounding seas annually. According to our previous research results, it is estimated that China’s freshwater aquaculture ponds discharge 2.79×105 and 2.89×104 tons of nitrogen and phosphorus, respectively, into the surrounding waters annually. To reduce the impact of aquaculture wastewater on the environment, our research team built a zero-water exchange aquaculture mode based on the polyculture system of grass carp (Ctenopharyngodon idella), bighead carp (Aristichthys nobilis), and crucian carp (Carassius carassius). At present, this mode has achieved zero-water exchange for four years, and the annual yield is 96 000 kg/hm2. However, the mechanism of zero-water exchange is unclear. In aquaculture ponds, the organic carbon, nitrogen, and phosphorus contents can directly reflect changes in the aquaculture environment, and the budget of organic carbon, nitrogen, and phosphorus can reflect the nutrient accumulation and utilization efficiency of nutrients by aquaculture animals. Quantifying the budget of organic carbon, nitrogen, and phosphorus can aid the understanding of the system from the material cycle and energy flow, and is of considerable significance for the management and optimization of the system at the ecosystem level. Therefore, this study used the zero-water exchange pond of grass, bighead, and crucian carp as the experimental group, and a common pond for grass, bighead, and crucian carp as the control group. The carbon, nitrogen, and phosphorus budget characteristics of these two groups were studied to provide a theoretical reference for optimizing the zero-water exchange culture mode. This study was conducted between January, 2017 and November, 2018. The results showed that feed was the main source of organic carbon, nitrogen, and phosphorus in the experimental and control groups, contributing 77.06%, 92.08%, and 94.18% in the experimental group, and 81.00%, 92.77%, and 95.63% in the control group, respectively. The main output of organic carbon, nitrogen, and phosphorus was sediment accumulation, which accounted for 43.32%, 61.40%, and 78.71% of the input nutrients in the experimental group and 22.10%, 52.82%, and 79.58% of that in the control group, respectively. Harvesting the fish in the experimental and control groups accounted for 10.08% and 13.05% of input carbon, 21.00% and 25.57% of input nitrogen, and 15.41% and 18.60% of input phosphorus, respectively. The water accumulation amount and accumulation rates of carbon, nitrogen, and phosphorus in the zero-water exchange ponds were significantly lower than those in the common pond (P<0.05), and the water accumulation rates decreased by 92.91%, 88.52%, and 87.12%, respectively. The sediment accumulation of nitrogen and phosphorus in the zero-water exchange pond was significantly higher than that in the common pond; however, the sediment accumulation rates of carbon and nitrogen in the zero-water exchange pond were significantly lower than those in the common pond (P<0.05), decreasing by 48.99% and 13.97%, respectively. The carbon, nitrogen, and phosphorus utilization rates of the zero-water exchange pond were significantly higher than those of the normal pond (P<0.05), increasing by 29.49%, 21.72%, and 20.65%, respectively. These results indicate that the zero-water exchange mode can effectively reduce nutrient accumulation and improve the material utilization rate, representing a green and efficient aquaculture mode. Considering the nutrient emissions of Chinese aquaculture, the zero-water exchange mode has a good application potential.