Species composition and long-term variation of macrobenthos in intertidal zone and offshore areas of the yellow river delta

Abstract

The Yellow River Delta wetlands play a major role in protecting the biodiversity and ecological function of the Bohai Sea. To understand the species diversity and spatial-temporal dynamics of macrobenthic community in this region, five surveys were carried out in intertidal zone and offshore areas in August and November 2016, May, August and November 2017, respectively. Results showed that 187 macrobenthic species were identified in surveyed areas, of which, 119 species were found in the intertidal zone and 99 in offshore areas. Obvious variation was found in the spatio-temporal distribution pattern of species composition. Compared to historical records, individuals of certain species presented a miniaturization trend in body size. The dominant species composition also has undergone an obvious change from large-sized crustacean and mollusc species toward small-sized polychaete, bivalve and crustacean species. Possible factors responsible for these changes are complex, including a decrease of water inflow and sediment transport by the Yellow River combined with human activities (overfishing and increasing exploitation) and other factors, e.g., salinity decrease and the invasion of Spartina alterniflora happened in the Yellow River Delta.