Distribution of Benthic Macroinvertebrates in Relation to Environmental Variables across the Yangtze River Estuary, China

This article reports on a study of the spatial and seasonal distribution of benthic macroinvertebrates and reveals the correlation between benthic macroinvertebrate community and environmental variables in the Yangtze River Estuary, China. A total of 75 species from seven phyla were identified during sample collection in May, August, and November of 2010 and February of 2011; among which, Annelida and Mollusca were found to be the predominant phyla. No significant difference in the community parameters (species, abundance, biomass, Shannon-Winner index, distinctness) of benthic macroinvertebrates was observed among survey trips. In contrast, an increasing tendency of abundance and biomass from river channels to the east waters was observed, and the differences between different geographic zones or community clusters were confirmed with a Kruskal-Wallis test. Compared with the data of the 1980s in the Yangtze River Estuary, the species richness, biomass, and abundance has decreased greatly. Distinct groups were classified based on clusters and nonmetric multidimensional scaling (nMDS) analysis. Corbicula fluminea, Potamocorbula amurensis, Nassarius variciferus, and Notomastus latericeus were the dominant species in abundance in clusters I, II, IIIa, and IIIb, respectively. The most abundant species during all four survey trips were Glycera chirori, Notomastus latericeus, Heterospio sinica, and Cossura longocirrata, all of which belong to the polychaetes. Our study demonstrated that the distribution of benthic macroinvertebrates in the Yangtze River Estuary was closely related to environmental variables. Salinity, bottom water temperature, sand content (C-S), silt content (C-T), and pH were explanatory variables for the spatial and seasonal distribution across the Yangtze River Estuary. Salinity was the factor that most determined the spatial distribution of the species, temperature determined the species occurrence on the entire estuarine scale, and the high content of silt favored the abundance of polychaetes.