Cedar Creek IA 04-LDM-1054

Assessment Comments

Five stream use assessments between 1990 and 1994.

Basis for Assessment

Used a review of the  DNR stream use assessments with data for aquatic species evaluation to downgrade the assessment of support of the Class B(LR) aquatic life use from FST to PS due to presence of reltively low fish diversity at all sampling locations (although sampling was hindered by habitat features at several locations) (e.g., (species/families, dstr->upstr:  5/3, 2/1 (2 fish total), 4/2 (6 fish total), 2/2).   This relatively low diversity is unusual given the presence of above-average habitat quality at most locations.   In addition, none of the sample sites contained a majority of the eight expected fish taxa for streams in the Central Irregular Plains subecoregin (40).   The most likely explanation for the depressed diversity of the fish communities of this stream is low pH resulting from coal mine runoff.   This stream reach was identified in 1992 by DNR fisheries biologists as impaired by resource extraction impacts (see page 3-106 of the 1996 Section 305(b) report) and Detroy et al.  (1983:40) identify Cedar Creek as having pH values less than 6.0 units.   Most of the data used to develop this assessment are more than 5 years old.   Follow-up monitoring is needed to better determine the status of the aquatic communities of these streams and to determine the degree to which the Class B(LR) uses may be impaired.