Distribution of heavy metals and benthic macroinvertebrates: Impacts from typical inflow river sediments in the Taihu Basin, China

Abstract

To characterize the distribution of heavy metals and benthic macroinvertebrates and to evaluate the relationship between metal pollution and benthic community structure, we collected samples of typical inflow river sediments from nineteen sites in the Taihu Basin in December 2012 and April and September 2013. The results showed that the mean concentration of heavy metals in the river sediments followed the order of Zn>Cr>Cu>Pb>Ni>As>Cd>Hg, and these metals may present moderate ecological risks. Compared to the background concentrations, it is likely that Cd and Cu pose much higher pollution than the other metals and should receive more attention. In terms of the distribution of the heavy metals, higher concentrations were found at the S1 and S2 sampling sites, while the other sampling sites exhibited relatively lower concentrations because of industrial wastewater containing heavy metals. The structure of the benthic macroinvertebrate community was also investigated, and the correlations between the heavy metals and the benthic communities were analyzed. The mean abundance and biomass of benthic macroinvertebrates in the study area were 49.22–117.23ind./m2 and 42.70–55.70g/m2, respectively, and 4 phyla and 8 classes were represented. The dominant groups were mollusks and arthropods. The FBI, BPI, GI values were low with means of 0.51, 0.41 and 0.16, respectively, and based on the GI and BPI values, most of the sampling sites were clean or slightly polluted with a minimal amount of the study area being moderately polluted. However, the FBI results indicated that all sampling sites were clean, but this may not be consistent with the pattern of pollution in the study area. The results of the correlation relationship analysis between the benthic community metrics and the heavy metal risk indices indicated that the abundance and biomass of Oligochaeta is the most sensitive to heavy metal contamination followed by Hirudinea, Gastropoda, Insecta, and the Goodnight–Whitley index because of significant correlation. And within a certain range, the Goodnight–Whitley index showed an increasing trend when pollution become more serious. However, some metals, such as Eri of Ni, Eri of Cd, Eri of Hg, Eri of Cu, Eri of As, and the RI significantly correlated with the benthic community metrics. Heavy metals in sediments may adversely impact the benthic community, and As and Cu have the greatest effect. Thus, the key influencing environmental factors may be As and Cu, and our results suggest that the benthic community, especially the abundance and biomass of Oligochaeta could be used in biomonitoring for heavy metal ecological risk from the studied area in the Taihu Basin, China.