Benthic Macroinvertebrate Community Analysis

Benthic macroinvertebrates were sampled quantitatively at up to six sites in Montezuma Creek and one site in Verdure Creek in 1995, 1996 and 1997. Qualitative samples were also made at selected sites (such as ponds) where quantitative approaches were inappropriate. Samples were processed in the laboratory to provide data on taxon richness and abundance.

The benthic macroinvertebrate community downstream of the Mill Site was characterized by:

No major differences observed among any sites in total taxonomic richness.

Low taxonomic richness of taxa typically sensitive to pollution (i.e., EPT richness) observed in 1995, but not 1996, relative to Verdure Creek. However, abundances of some of the more tolerant taxa within this group were high (e.g., Baetis).

Greater abundance of some of the most pollution tolerant taxa (e.g., Oligochaeta and Physella) observed at sites closest to the Mill Site (Figure 1).

A sharp increase observed in a few moderately-pollution intolerant taxa with increasing distance from the Mill Site (e.g., Baetis and Tanytarsini).

Most of these characteristics are often typical of streams with nutrient enrichment, but some may also be typical of streams with only small elevations in contaminants such as metals.

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Figure 1. Benthic macroinvertebrate data from sites in Montezuma Creek (MZ) and Verdure Creek (VD) surveyed in August 1995.

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Last Modified: April 17, 2001