Chironomid Deformities, Benthic Community Composition, and Trace Elements in the Buffalo River (New York) Area of Concern

Deterioration of ecosystem health is often reflected by changes in benthic community structure, but specific community metrics may differ widely in their usefulness as environmental monitors. We investigated the association of several of these metrics with concurrently measured sediment trace element levels at 15 sites within the Buffalo River, New York from 1990 to 1993. Site mean concentrations (9 sample dates) of As, Cd, Cu, Fe, Hg, Mn, Ni, Pb, and Zn were subjected to principal component analysis, yielding 1 factor describing a spatial gradient in trace element levels. Community metrics were then regressed on this factor. The mean density of the family Chironomidae decreased (R² = 0.41, p = 0.01) with increasing factor scores (i.e., higher trace element concentrations). However, the mean density of tubificid oligochaetes, which accounted for >80% of the benthic community, was not linearly associated with trace elements (R² = 0.22, p = 0.08). Mean richness and diversity of the chironomid community were strongly negatively associated with factor scores (R² = 0.77 and 0.76, respectively, p < 0.001), while the prevalence of the tolerant genera Procladius and Chironomus increased with trace element levels (R² = 0.55, p = 0.002). Mouthpart deformities in larvae of Chironomus thummi group also increased with higher trace element levels (R² = 0.72, p < 0.001). Benthic community metrics can be very useful in ranking the health of specific sites, but our study shows that more detailed metrics (e.g., taxonomically detailed chironomid data, Chironomus mouthpart deformity frequencies) provide additional information on community health that justifies the extra effort required for their assessment.