Effects of saltmarsh dike project on benthic community in Chongming Dongtan of the Yangtze Estuary

Chongming Dongtan saltmarsh serves as an important habitat for both migratory and resident birds. However, the exotic plant of Spartina alterniflora has changed the community structure and function of the saltmarsh. Diking at the Chongming Dongtan saltmarsh is an ecological restoration project aiming to eradicate Spartina alterniflora. In order to discuss the influence of human interference on the structure and function of estuarine saltmarsh ecosystem, this study analyzed the change of macroinvertebrates in diversity and composition of species before and after diking project construction, since macrobenthos are considered as important environmental indicators. The quantitative sampling of macrobenthos were carried out in June 2013 and June 2016 to assess the ecological influence of the diking project on the macrobenthos of an Yangzte Estuary. The surveys were conducted each year in three sample lines from inside and outside the dyke. In total, 25 and 27 species were recorded from all sample lines in 2013 and 2016, respectively. All species belonginged to Anopla, Polychaeta, Gastropoda, Bivalves, Crustacea and Insecta respectively. In the mudflat area of outside dyke, 21 and 27 species occurred from 2013 and 2016 respectiely. All lines showed the increased number of species. However, in the inside the dyke area, the number of species changed from 12 to 6 in sample line 2 and 3(completely closed), and from 7 to 12 in sample line 1(semi closed) after diking project construction. In addition, the average density of macrobenthos in the inside dyke area were(75±0) ind./m~2 in 2013 and(288±111) ind./m~2(P=0.091) in 2016 from sample line 1, whereas those were decreased significantly(P