Characteristics Of Strain In Procambarus Clarkii Ponds With Different Stocking Density And Plants Coverage

Sediment, an important part of the pond ecosystem, enrichment center of varieties of nutrition elements, places where a variety of biological habitats and feeding, pathogen of bacterial disease, provide water and a variety of biology with nutrient needed by the recycling process. Therefore, bottom is vital for the development of the aquaculture industry. But with the development of intensive farming, farmers blindly in pursuit of high yield, coupled with excretion of waste of breeding objects, have caused a lot of remnant sink and pollution to the bottom of the pond, and destroyed the ecological balance of aquaculture ponds. So, to improve substrate is an important section of steadying the development of crayfish industry.This experiment set up two kinds of stocking density(25kg/667m2, 40kg/667m2) and two kinds of aquatic vegetation coverage(20%, 35% respectively), four treatments groups in total, two repeats per group, in pond buried with biological bait medium under the bottom mud. To study the changes of the structure characteristics and diversity in pond with different grass coverage and density of livestock and analysisthe effect of grass coverage and stocking density on the pond bottom and micro ecological, provide reliable theoretical guidance for healthy breeding of procambarus clarkia, as result:1. Both grass coverage and stocking density have significantly influences on TOC, TN, TP in the bottom of the pond(P < 0.05), buried with biological bait medium under the bottom mud. It is found that the accumulation of TOC, TN, TP in the bottom of the pond covered with more aquatic plants were significantly lower than the pond covered with less aquatic plants in the stocking density under the same conditions compared treatment group A, Band C,D respectively(P < 0.05): the accumulation of TOC, TN, TP in the bottom of the pond covered with more aquatic plants were significantly lower than the pond covered with less aquatic plants in the stocking density in the group with a low density of livestock(P < 0.05); the accumulation of TOC, TN, TP in the bottom of the pond covered with more aquatic plants were significantly lower than the pond covered with less aquatic plants in the stocking density in the group with a high density of livestock(P < 0.05).The accumulation of TOC, TN, TP in the bottom of the pond covered with high density of livestockwere significantly higher than the pond covered with low density of livestock in the grass coverage under the same conditionscompared treatment group A, C and B, D respectively(P < 0.05): the accumulation of TOC, TN, TP in the bottom of the pond covered with high density of livestock were significantly higher than the pond covered with low density of livestock in the grass coverage in the group with a low grass coverage(P < 0.05); the accumulation of TOC, TN, TP in the bottom of the pond covered with high density of livestockwere significantly higher than the pond covered with low density of livestock in the grass coverage in the group with a high grass coverage(P < 0.05).2. Richness index and diversity index from different treatment groups in different times are obviously different in the view of time and space. In time, richness index and diversity index showed a trend of decline gradually with the passage of time cross the whole breeding cycle, and from maximum value, 30 and 2.78 respectively in April decline to the lowest gradually, namely 17 and 2.78 in September. In spaces different treatment groups behave differently, richness index and diversity index of the pond covered with more aquatic plants were higher in the stocking density under the same conditions; richness index and diversity index of the pond covered with high density of livestockwere higher in the grass coverage under the same conditions. These suggests that the grass coverage and stocking density have great influence on the richness index and diversity index. In terms of microbial community structure similarity, difference of samples from different months and different treatment groups is obviously, average of each cluster only 33% during the early stage of the breeding. In general, the similarity in time is higher than samples in space. By contrast, the diversity of the flora composite of Proteobacteria, Bacteroidetes, Chloroflexi, Verrucomicrobia, Spirochaetes, Actinobacteria, and other unknown bacterial flora cross the whole breeding cycle. Advantage bacterium group is Proteobacteria, account for 45% of the proportion of the total during the early stage of the breeding, and continue to the last stage of the breeding, account for 71%, absolute superiority. Proteobacteria and Bacteroidete are always the advantage bacterium group, but the classification to a finer level of species, flora species difference is more obviously. Spirochaetes and Bacteroidetes are disappeared, but two new kinds of bacteria, Chloroflexi and Verrucomicrobia, arise with the passage of time cross the whole breeding cycle. Through phylogenetic analysis, there are some flora in the sediment to play an important role in maintaining the pond ecosystem stability, such as Actinobacteria and Proteobacteria, playing an important role in material cycle and energy flow by resolving organic matter and inorganic matterin sediment of residual, like cellulose, aromatic compounds and wooden.Visibly, medium buried into the bottom of pond can improve the pond bottom at a certain extent, even so, grass coverage and density of livestock can also change the pond sediment physicochemical indexes and flora structure and composition of diversity. Therefore, to improve the pond bottom must consider many factors, not overly relying on improving a factor.