养殖水体溶氧平衡的实验分析及泛塘成因再探讨

在江汉平原荆州市分别在植物培养箱和自然条件下模拟高密度养殖水体，利用多参数水质监测仪，采用完全开放式对养殖水体溶氧、水温等要素的变化进行自动连续观测，结合养殖水域中溶解氧动态平衡方程分别计算出水-气界面溶氧速率、水呼吸耗氧速率、草鱼呼吸耗氧率及光合作用产氧量；并对低溶氧条件下草鱼生存时间等进行实验监测。结果显示：鱼塘水呼吸耗氧率1.22~1.83 mg/(L·h)；在水体溶氧在1.5 mg/L以上时，草鱼的代谢呼吸耗氧率为78.6~210.0 mg/(L·h)；在高密度养殖塘内水呼吸是鱼呼吸耗氧4倍以上。阴到多云天气下光合作用产氧量为3.47~4.33 mg/(L·h)，大于鱼呼吸与水呼吸量之和，但阴雨天光合作用产氧量不能维持鱼塘良好的溶氧环境。草鱼在0.1~0.4 mg/L低溶氧环境中有浮头出现，但能存活长达到5天时间。分析还表明：缺氧引起浮头，也造成底层H₂S、CH₄有毒物质增加，雨水进入鱼池形成水上下层对流，水体上部有毒物质浓度升高是泛塘死鱼的主要原因。

Analysis of DO Balance in Aquaculture Water Experiment and Reanalysis of Suffocation Reason

Water environment with high density of fish feeding was simulated under Biotron Open Type and natural condition in Jingzhou of Jianghan Plain, and day-night aquaculture water observation of DO (dissolved oxygen) and water temperature variation were carried out by using water quality multi-parameter monitoring system in a totally open way. Dynamic balance formula was used to calculate water-atmosphere DO rate, oxygen production of photosynthesis, oxygen consuming rate of grass carp and water body; grass carp survival time under low oxygen condition was also observed. The result shows that, oxygen consuming rate of water body in pool is 1.22-1.83 mg/(L·h), while oxygen consuming rate of grass carp is 78.6-210.0 mg/(L·h) when water body DO is above 1.5 mg/L. The oxygen consuming rate of aquaculture ponds in high density fish feeding environment is more than 4 times of the oxygen consuming rate of fish. The oxygen dissolution rate of water-atmosphere interface is low. And oxygen production of photosynthesis is 3.47-4.33 mg/(L·h) in rainy or cloudy days, which is more than the total oxygen consuming rate of fish and aquaculture ponds, while oxygen production of photosynthesis in rainy days cannot maintain favorable environment in aquaculture ponds. The grass carp would gasping for air but still survive 5 more days in low DO environment as 0.1-0.4 mg/L. The result also indicates that lacking oxygen could cause the increase of H₂S and CH₄ in the bottom of aquaculture ponds; water convection in aquaculture ponds and increase of toxic substances caused by rain is the main reason of suffocation.