Document: CAT-3-73-7

Cumulative impacts of two superfund sites and urban development upon a small watershed's streams.

ROGERS, C.E.* ¹, M.T.BARBOUR ², A.PETER ³ and H.F.HEMOND ⁴

U.S. EPA, Washington, DC 20460 ¹
Tetra Tech, Inc., Owings Mills, MD 21117 ²
Limnological Research Center, Kastanienbaum, SWITZERLAND ³
MIT, Cambridge, MA 02139 ⁴

Abstract:
Cumulative impacts of physical habitat degradation and metal contamination upon fish and aquatic macroinvertebrates were evaluated using spatial associations of potential cause and effect. The study area is a small watershed in Massachusetts that contains two Superfund sites and a mix of residential, commercial and industrial land uses. Sixteen sites in this watershed and four ecoregional reference sites were assessed. The predicted relationships of physical habitat degradation and contamination to biological impairment were observed. As expected, these relationships were only apparent when both chemical and physical stressors were considered. This result suggests the potential importance of including habitat assessment in field studies of contaminant impacts. For the evaluation of impacts upon fish, the number of native fish species caught (by electroshocking) at a site was used as the measure of biological condition, and habitat condition was a simple function of stream depth and instream cover score. As predicted, the biological condition of fish assemblages from minimally-contaminated sites varied from good to poor as habitat condition varied from good to poor. Biological degradation beyond that attributable to habitat degradation alone was observed at contaminated sites. Twelve benthic metrics were used to characterize the biological condition of macroinvertebrate assemblages and to relate biological impairment to chemical and physical degradation (using linear regression and t-tests comparing site categories). Similar levels of biological impairment were observed at sites with severe physical or chemical degradation, or moderate chemical and physical degradation. Individual benthic metrics were not diagnostic of impairment type. An aggregate macroinvertebrate index was developed that was more sensitive to chemical and physical degradation than any individual metric, illustrating the strength of a multimetric approach for detecting the cumulative impacts of physical habitat degradation and chemical contamination.

Keywords: macroinvertebrates, fish, aquatic, risk assessment, urban

This abstract is being presented at: 8:15 AM in session:
Oral Session #70: Aquatic Ecology.