Study On Community Structure Of Macrozoobenthos And Impact Factors In Lake Shahu Of Poyang Lake Nature Reserve

Lake Shahu is one of migratory birds wintering habitats in Poyang Lake and a typical floodplain lake due to seasonal floods submerged, The macrozoobenthos is an important aquatic taxa in floodplain ecosystem. To clarify community structure of macrozoobenthos and impact factors in the location of migratory birds wintering can provide a scientific basis for the protection and management of wetland habitat for migratory birds. An investigation of macrozoobenthos was carried out in November 2011 to December 2012. The main results are as follows:1. A total of 72 species belonging to 7 classes,25 families and 55 genera were identified in Lake Shahu. The dominant species are Spirosperma nikolskyi、Bellamya purificata、Alocinma longicornis、Bithynia fuchsiana、Parafossarulus eximius and Clinotanypus sugiyamay. The mean densityand biomass of macrozoobenthos which before and after migratory birds wintering were 422.08 ind./m2、80.99 g/m2 and 275.20 ind./m2、49.48 g/m2 in Lake Shahu.2. Environmental parameters and biodiversity before and after the migratory birds wintering were compared and the results showed that only the water temperature was a significant difference (F=12.73, P=0.02). In addition to the index of relative importance of most of Lumbricidae and Chironomidae increased trendly, other groups declined. Shannon-Wiener index (P> 0.05), Margalef index (P> 0.05) and Pielon index (P> 0.05) showed a non-significant difference, Non-parametric test results showed that the density and biomass of the macrozoobenthos were significantly decreased in Lake Shahu (P<0.05). On standing crop, vast majority of samples were decline, and the range of standing crop in coastal zone is greater than the center of lake. The density and biomass of scrapers was decline. According to individual size, after the wintering of migratory birds, dominant length group (0 to 2 cm) was decline, and standing crop with> 2cm individual increased. No significant changes in population structure of the dominant species was obsered. Submerged plant biomass had positively correlation with the density (R2= 0.246) and biomass (R 2= 0.206) of scrapers.3. The results showed that the physical and chemical parameters no significant difference (P> 0.05) in different flooded zone, but Shannon-Wiener diversity index and Margalef richness index showed intermittently-flooded zone IS (H’=2.56, D=6.44)> permanently flooded zone PT (H’=2.45, D=3.87)> intermittently-flooded zone IF (H’=1.60, D=2.08), and Pielou evenness index is permanently flooded zone PT (J=0.86)>intermittently-flooded zone IF (J=0.84) > intermittently-flooded zone IS (J=0.76). Standing crops showed permanently flooded zone PT> intermittently-flooded zone IS> intermittently-flooded zone IF, The density of the macrozoobenthos was no significant difference (P> 0.05), biomass showed a significant difference (P<0.05) in different flooded zone. Refering functional feeding groups, collector-gatherers and scrapers were dominant groups in intermittently-flooded zone IF and permanently flooded zone PT, and predators and scrapers were the dominant groups in intermittently-flooded zone IS.4. In the drains habitate of south of Lake Shahu, the dominant species were Bellamya purificata and Limnodrilus hoffmeisteri. Comparing sluice closing and sluice opening, when the gates opened macrozoobenthos in lower density and biomass increased, collector-gatherers, predators and scrapers were dominant groups in drainage. Standing crop of collector-gatherers significantly lower after the gates opened and density of scrapers decreased, but biomass increased, standing crop of predator increased.