Abstract

Data from ecological and ecotoxicological research were analysed together in order to gain more insight into the biological effects caused by sediment pollution in the delta of the rivers Rhine and Meuse. Information from the following three sources was integrated: surveys of the macroinvertebrate assemblages, chemical analyses in sediment and bioassays. On the basis of cluster analysis and multivariate analysis of a dataset consisting of macrofauna samples from 283 sampling points, it was concluded that the most important factors determining species composition are: presence of solid substrates, depth, current velocity, erosion caused by wind or shipping, and grain size distribution and organic matter content of the sediment. In order to evaluate the role of sediment toxicity in more detail, subsets of the dataset were formed that corresponded with more homogenous clusters of sampling points with regard to sediment characteristics. The degree of sediment toxicity was based on the effects observed in three bioassays with whole sediment or sediment pore water. Further multivariate statistical analysis was performed for four sediment types. Direct linear gradient analysis indicated that for the sediment types fine sand, sandy silt and silt, sediment toxicity can explain part of the variation in species composition. Sediment toxicity was positively correlated with the levels of heavy metals, mineral oil, hexachlorobenzene and/or endrin. It is concluded that the approach followed in this study can contribute to our understanding of the influence of chemical pollution on macroinvertebrate communities.

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