| Conventional freshwater aquaculture species including Black Carp, grass carp, silver carp, variegated carp, carp, crucian carp and parabramis pekinensis of China, which produces accounted for seventy percent of the national farmed freshwater fish, and the annual output of grass carp is the largest of the total. Aimed at the establishment of aquaculture system with optimized structure and efficient function, which the water substance will have good cycle, the primary productivity can be fully utilized, and theoretical basis for the ponds ecosystem function can be provided, we investigated and analyzed the tendency of water quality, the community structures phytoplankton, the relationship between phytoplankton community structure and environmental factors, the primary productivity and the energy conversion efficiency in the ponds during May to October,2012, where Ctenopharyngodon idellus were predominant stocking fish species in Central China. And then in the same region ponds, microzooplankton grazing conditions were also studied during June to October,2013. The results are as follows:(1) During the experiment, the physical and chemical indicators of the ponds were studied including WT, SD, DO, pH, TN, TP, NO2--N, N03--N, NH4+-N, PO43--P, COD and SS, and the changes of them were18.18℃～33.48℃,0.07m～0.29m,4.41mg/L～11.91mg/L,7.54～9.32,0.63mg/L～2.72mg/L,0.13mg/L～0.33mg/L,0.004mg/L～0.31mg/L,0.12mg/L～2.39mg/L,0.41mg/L～2.39mg/L,0.03mg/L～0.11mg/L,8.35mg/L～9.13mg/L and12.08mg/L～92.17mg/L, respectively.(2) Present study showed that phytoplankton identified from the ponds belonging to240species,102genera and8phyla. Specifically, phytoplankton included Chlorophyta (114species,44genera), Cyanophyta (44species,20genera), Bacillariophyta (19species,12genera), Euglenophyta (38species,10genera), Chrysophyta (7species,5genera), Xanthophyta (8species,5genera), Pyrrophyta (6species,4genera), and Cryptophyta (4species,2genera). The phytoplankton density ranged from1.77x107ind/L to8.83*107ind/L and the average was4.23×107ind/L. The phytoplankton biomass ranged from12.24mg/L to298.58mg/L and the average was44.13mg/L. Shannon-Wiener diversity index was1.80～3.69, Margalef diversity index was3.12～6.74and Pielou evenness index was0.31-0.61. The CCA final results showed that WT, SD, DO, pH, NO2’-N and SS were the main factors affecting the number of phytoplankton. (3) The ponds showed vertical and seasonal changes of primary productivity. In the0cm～30cm aquifer, the gross oxygen had the highest yield, and the average of three ponds were11.57g/m2·d,11.00g/m2·d,9.58g/m·d, respectively. Between May and August, the primary productivity rose month by month and between July and August it reached the maximum. The average compensation depth was111.83cm. The result shows that spoutnet oxygen production of three ponds were7.38g/m·d,6.21g/m2·d,6.84g/m2·d. The photosynthetic energy effciency reached0.956%～0.805%of solar radiation. The ecological efficiency of converting solar radiation to fish production was0.10%～0.12%.(4) Phytoplankton growth and microzooplankton herbivory studies showed that in different months, the content of Chl-a were0.17g/m3,0.15g/m3,0.17g/m3,0.16g/m3,0.37g/m3, respectively, and the average were0.20g/m3. Phytoplankton growth rates were0.96d-1,1.52d-1,0.82d-1,0.50d-1,1.34d-1, and the average was1.03d-1. Microzooplankton grazing rates were1.31d-1,1.58d-1,0.33d-1,1.29d-1,1.40d-1, and the average was1.18d-1.In conclusion, Phytoplankton plays an important role in the Grass Carp pond ecosystem, the physical and chemical indicators of the ponds interacts with phytoplankton.Having good ponds quality control can improve the material recycling, the microcirculation between plankton and the energy conversion efficiency in the ponds, so as to establish a good pond aquaculture system. |
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