| 12th June to September 26 of 2013,the rice-crab ecosystem was studied in Pan Shan county,Liao Ning province. Rice-crab paddy was set as experiment group feeding bait with different protein contents(the percent content of protein in bait were 45%,35%,25%,which were called experiment group 1,2,3),and nomal paddy was set as control group as well. The study included the change of physical and chemical factors and the relationship between those factors, plankton and zoobenthos. During the whole investigation, Comparison results of temperature, salinity, p H, content of DO, COD, Chl-a, TN, TP, NH3-N, NO2-N and eight main ions among groups had no significant differences in efferent dates.226 species of 7 classes of phytoplankton were checked out. Chlorophyta was the predominant species, and the advantage index of dominant species was Cyanophyta. Density and biomass of phytoplankton during the whole investigation ranged from 182.81×104 ind·L-1 to 3349.06×104 ind·L-1 and from 0.95 mg·L-1 to 21.71 mg·L-1 in experimental group 1, ranged from 264.53×104 ind·L-1 to 3714.38×104 ind·L-1 and from 1.51 mg·L-1 to 26.08 mg·L-1 in experimental group 2, ranged from 133.91×104 ind·L-1 to 2436.25×104 ind·L-1 and from 0.92 mg·L-1 to 10.78 mg·L-1 in experimental group 3, ranged from 358.13×104 ind·L-1 to 3325.63×104 ind·L-1 and 2.47 mg·L-1 to 16.32 mg·L-1 in control group. Diversity index and evenness index of phytoplankton during the whole investigation ranged from 1.36 to 2.67 and from 0.40 to 0.70 in experimental group 1, ranged from 2.09 to 2.74 and from 0.58 to 0.78 in experimental group 2, ranged from 1.50 to 2.55 and from 0.52 to 0.67 in experimental group 3, ranged from 1.50 to 2.72 and from 0.50 to 0.77 in control group, which means that the structure of phytoplankton community was integrated and stabilized.119 species of 4 main categories were checked out. Rotifer is the predominant species in each group during the whole investigation. Density and biomass of zooplankton during the whole investigation ranged from 838.13 ind·L-1 to 5836.25 ind·L-1 and from 8.27 mg·L-1 to 66.83 mg·L-1 in experimental group 1, ranged from 721.25 ind·L-1 to 5642.50 ind·L-1 and from 3.84 mg·L-1 to 83.62 mg·L-1 in experimental group 2, ranged from 411.25 ind·L-1 to 3751.25 ind·L-1 and from 16.80 mg·L-1 to 84.01 mg·L-1 in experimental group 3, ranged from 1435.00 ind·L-1 to 5755.00 ind·L-1 and 5.14 mg·L-1 to 197.48 mg·L-1 in control group. Diversity index and evenness index of zooplankton during the whole investigation ranged from 1.91 to 2.61 and from 0.63 to 0.75 in experimental group 1, ranged from 1.36 to 2.53 and from 0.50 to 0.71 in experimental group 2, ranged from 1.51 to 2.53 and from 0.57 to 0.77 in experimental group 3, ranged from 1.41 to 2.71 and from 0.48 to 0.78 in control group.8 species of zoobenthos were checked out consisted of Branchiura sowerbyi, Limnodrilus sp., Cipangopaludina chinensis, Hippeutisum bilicalis, Bellamya aeruginosa, Pelopia sp., Chironomus plumosus and Chaoborus sp.. According to IRI, Branchiura sowerbyi,Cipangopaludina chinensis and Hippeutisum bilicalis became dominant species in zoobenthos. Density and biomass of zoobenthos during the whole investigation ranged from 108.97 ind·L-1 to 2879.56 ind·L-1 and from 3.45 mg·L-1 to 59.87 mg·L-1 in experimental group 1, ranged from 92.86 ind·L-1 to 2053.33 ind·L-1 and from 1.91 mg·L-1 to 33.02 mg·L-1 in experimental group 2, ranged from 164.29 ind·L-1 to 2278.11 ind·L-1 and from 4.44mg·L-1 to 58.10 mg·L-1 in experimental group 3, ranged from 119.64 ind·L-1 to 1112.50 ind·L-1 and 3.07 mg·L-1 to 28.70 mg·L-1 in control group. Diversity index and evenness index of zoobenthos during the whole investigation ranged from 0.39 to 0.97 and from 0.51 to 0.87 in experimental group 1, ranged from 0.53 to 1.07 and from 0.51 to 0.82 in experimental group 2, ranged from 0.25 to 0.92 and from 0.32 to 0.93 in experimental group 3, ranged from 0.16 to 0.83 and from 0.23 to 0.70 in control group. |
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