| Many artificial larval rearing of grouper failed due to the deterioration of water quality (the accumulation of harmful substance). The conventional solution was to refresh water. However, the early fries could mass mortality for the ecosystem changing and the screen cloth adhibiting during the water refreshing process. So, the stabilization of the water quality was expected in the first 20 days. Two strategies could be choiced in the larval rearing productive practice. One was to use unicellular algae to keep the stabilization of the water quality, the algae can absorb the harmful substance in the rearing pool. The other was to add shrimp chip and living bacteria timingly and quantitatively, because living bacteria can breakdown the residual bait, excreta, residues of animal and plant, and noxious gas(ammonia, hydrogen sulfide etc.). This article quantitatively analyzed the changes of ecological factors in two industrialized breeding ecosystem. The main results were shown below:1. Influences on physical and chemical factors in water. The results were as following: when the photosynthesis was in process, absorbion of the CO2 by algae raised the pH of the water; algae could decrease the nitrite content of water when they grew well in the rearing pool; algae also reduced the content of ammonia nitrogen significantly. Adding effective macrobes (EM) and shrimp to the rearing water could reduce the pH; EM could also reduce the content of nitrite, ammonia nitrogen, and inorganic phosphate.2. Influence on phytoplankton and zooplankton. The results were as following: adding EM and shrimp could significantly increase both the species number and quantities of phytoplankton and zooplankton in water.3. Influence on the respiration rate and primary productivity of plankton in different fraction. The results were as following: in the ecosystem added with EM 1, the mean respiration rate of minitype, microscale and ultramicroscale were 0.012, 0.177 and 0.347mg/(dm3·d) respectively, and the mean primary productivity were 0.006, 0.027 and 0.052mg/(dm3·d) respectively; in the ecosystem added with EM 2, the mean respiration rate of minitype, microscale and ultramicroscale were 0.009, 0.226 and 0.433mg/(dm3·d) respectively, and the mean primary productivity were 0.055, 0.033 and 0.054mg/(dm3·d) respectively; in the ecosystem added with microalgae 1, the mean respiration rate of minitype, microscale and ultramicroscale were 0.024, 0.031 and 0.260mg/(dm3·d) respectively, and the mean primary productivity were 0.034, 0.047and 0.124mg/(dm3·d) respectively; in the ecosystem added with microalgae 2, the mean respiration rate of minitype, microscale and ultramicroscale were 0.089, 0.067 and 0.336mg/(dm3·d) respectively, and the mean primary productivity were 0.084, 0.135 and 0.191mg/(dm3·d) respectively.4. Influence on the population growth and productivity of protozoa. The results were as following: in the rearing pool added with bacteria, the protozoa grow well, the biomass and productivity were higher than the pool added with algae. In the rearing pool added with bacteria, the mean population growthrate of the main dominant species such as Gymnodinium coeruleum,Mesodinium,Strobilidium gyrans Stokes and Actinophrys sol were 0.013～0.067,0.008～0.043,0.009～0.049 and 0.016～0.036/hr respectively; in the pool added with microalgae, the mean population growth rate of the main dominant species such as Mesodinium and Cyclidium Litomesum Stoke were 0.005～0.021 and 0.007～0.008/hr respectively. Measured by the in-situ experimental bottle test, the protozoa cumulation productivity were 736.48 mg/m3·d and 46.91mg/m3·d respectively, and the P/B were 1.38 and 0.70 respectively.
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