Sediment pollution and predation affect structure and production of benthic macroinvertebrate communities in the Rhine-Meuse delta, The Netherlands

Most floodplain sediments of the rivers Rhine and Meuse in The Netherlands are moderately polluted with trace metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other chemicals. The effects of these sediment-bound contaminants on the productivity of benthic macroinvertebrates are unclear. Sixteen locations along a pollution gradient were investigated in creeks in the Biesbosch floodplain area. Sediment samples were analyzed for bulk sediment characteristics and contaminants (total and bioavailable concentrations of trace metals, PAHs, and PCBs). Exclosures were used to study the effect of predation by fish and birds on macroinvertebrates. Macroinvertebrates were sampled and identified to species level, and production was estimated from biomass increases inside the exclosures during a 1-mo interval in spring
Most floodplain sediments of the rivers Rhine and Meuse in The Netherlands are moderately polluted with trace metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other chemicals. The effects of these sediment-bound contaminants on the productivity of benthic macroinvertebrates are unclear. Sixteen locations along a pollution gradient were investigated in creeks in the Biesbosch floodplain area. Sediment samples were analyzed for bulk sediment characteristics and contaminants (total and bioavailable concentrations of trace metals, PAHs, and PCBs). Exclosures were used to study the effect of predation by fish and birds on macroinvertebrates. Macroinvertebrates were sampled and identified to species level, and production was estimated from biomass increases inside the exclosures during a 1-mo interval in spring. Benthic macroinvertebrate species richness was negatively affected by sediment contamination. Production of oligochaetes and chironomids was not correlated with levels of contamination, but production of gastropods was negatively correlated with contamination. Environmental variables that reflected food availability (seston and sediment organic C) were positively correlated with contamination. Predation significantly reduced invertebrate biomass, but the effects of predation and sediment contamination were not correlated with each other. Our study suggested that the moderate levels of contamination affected the structure but not the productivity of the benthic macroinvertebrate community, probably because of the counteracting effects of contamination and associated surplus of food.