Assessment Comments
1999 Biocriteria: Downstream Ankeny WWTP- Fish IBI= 24 (poor), 30(fair); BM-IBI= 55(fair), 49(fair); Upstream Ankeny WWTP - Fish IBI= 38 (fair), 37(fair); BM-IBI= 69(good), 75(good).
Basis for Assessment
The assessment was based on data collected in 1999 as part of the DNR/UHL stream biocriteria project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 Fish IBI scores upstream from the Ankeny WWTP were 38 (fair) and 37 (fair); the BM-IBI scores were 69 (good) and 75 (good). Downstream from the Ankeny WWTP, the Fish IBI scores were 30 (fair) and 24 (poor); the BM-IBI scores were 49 (fair) and 55 (fair). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
