Ecological Responses of macrobenthic community to freshwater replenishment in the tail wetland of old Yellow River

Selectingthe tail wetland of old Yellow River as the study area, in order to freshwater replenishment project, we have collected sediment and macrobenthos samples before (April-May) and after (September-October) freshwater replenishmentfrom 2014 to 2016. The sediment salinity was used to represent the effect of freshwater replenishmenton habitat environment, and the composition, abundance and biomass of macrobenthic communitywas used to represent the effect of freshwater replenishment on macrobenthic community. We found that the sediment salinity in areas I-IV (from land to sea) increased firstly and then decreased; what’s more, there is a high sediment salinity zone in area III before freshwater replenishment. While, after freshwater replenishment, the implementation of freshwater significantly reduced the high sediment salinity in area III, and the sediment salinity increased along with from land to sea in areas I-IV.The composition of macrobenthiccommunity in the freshwater replenishment area, dominated by class of Insecta and Crustacea, is relatively simple comparing with that in the intertidal wetland (area VI). Before freshwater replenishment, the relationship between sediment salinity and macrobenthosanbundance showed “U” type, while the sediment salinity had an inverted “U” relation with macrobenthos biomass. After freshwater replenishment, the abundance of macrobenthos decreased slightly along with the increase of sediment salinity, in contrast, the biomass of macrobenthos increased gradually with the salinity of the sediment. Analysis of themacrobenthicresponses to freshwater replenishment project is of great significance to guide the ecological restoration in the estuary wetland.