Composition And Distribution Of Macrobenthos In A Riparian Restoration Pilot Area Of Taihu Lake

As a kind of aquatic-terrestrial ecotone, riparian area plays an important role in the lake basin ecosystem, and has high ecological, social and economic values. Its functions include lake buffer, conservation of biological diversities and special habitats, dike protection from soil erosion, and economic and esthetics values. The main factors inducting riparian area degradation are the anthropogenic activities that caused the converse succession of communities and the decline of ecological function. The theoretical basis of ecological restoration and reconstruction of degraded riparian area is restoration ecology; while the technologies are of three types, i. e., habitat restoration and reconstruction, species restoration and reconstruction, and structural and functional restoration.Macrobenthos is an important component of wetland ecosystems. Auatic Oligochaetes, mollusks and aquatic insects are the dominant groups of macrobenthos in freshwater. Macrobenthos in freshwater plays an important role in accelerating debris decomposition, regulating the material exchange on the interface water, and the promotion of self-purification of water. Macrobenthos is sensitive to the variation habitat due to the limited migration ability and the comparative long life. The distribution of macrobenthos will change significantly with different sediments of rivers and lakes, water environments and habitats. It has great significance to understand the structure, function and evolution of wetland ecosystems. Current researched had no enough attention on relationship between the macrobenthos composition and the habitat in ecological restoration pilot area. In this study, The T-Park ecological restoration project zone was taken as the study area. We wanted to study the macrobenthos composition, the habitat gradient, and the relationships between them, which had an important reference value on researches on the ecological restoration engineering.To examine the relationships between habitat gradient and macrobenthos composition, a field investigation was undertaken in three different habitats, riparian zone with emerged vegetation (zone Ⅰ), lake-bay zone with submerged vegetation (zone Ⅱ) and open water zone outside the weir (zone Ⅲ) in an ecological restoration pilot area of Gonghu Bay, Taihu Lake, during2010-2011. The result shows:(1) Collectively,18species of macrobenthos were identified from12sampling sites. Of those,7species were found in association with only one habitat type. Of the other11species,5ones showed significant differences in abundance across the habitat gradient.(2) By investigating the distribution of functional feeding groups of macrobenthos, significant differences were observed among the habitat types. For the scrapers, the highest relative abundance was shown in zone I, while that was present in zone II and III for gather-collectors and filter-collectors, respectively. In terms of species richness and relative abundance, the ratio between group of surface and group of surface below (GS/GSB) were the highest in zone I and the lowest in zone II.(3) Redundancy analysis was applied to examine the influence of water quality on macrobenthos composition. The results showed that annelids and aquatic insects were positively correlated with DO, NO3--N, PO43--P. Mollusks were negatively correlated with NO3--N and PO43--P. Some mollusks were able to endure the stress from low DO and correlated positively with NH4+-N and COD.Overall, the three distinctive habitat types were formed via the restoration project and varied in hydraulic conditions, water quality and substrates. As a result, they can lead to three different types of macrobenthos in terms of life form and feeding attributes.This study identified macrobenthos composition in three different habitats in an ecological restoration pilot area of Gonghu Bay, Taihu Lake; while by investigating distribution of functional feeding groups and life groups of the macrobenthos, revealed the communities difference among the three habitats. Redundancy analysis in the relationships between habitat gradient and macrobenthos composition showed the three distinctive habitat types lead to three different types of macrobenthos in terms of life form and feeding attributes. The results could provide a reference for protection on ecological restoration and reconstruction of degraded riparian area.