Assessment Comments
Assessment based on results of IDNR/UHL biological (REMAP) sampling in 2002: FIBI = 45 (fair), BMBIB = 43 (fair). FIBI BIC = 31, BMIBI BIC = 54.
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life uses are assessed (monitored) as "partially supporting " based on results of biological monitoring. Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this river segment. The source of data used for this assessments is the results of the IDNR/UHL REMAP sampling in 2002.
EXPLANATION: This assessment was based on data collected in 2002 as part of the DNR/UHL REMAP 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 (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 FIBI score was 45 (fair) and the BMIBI score was 43 (fair). The aquatic life use support was assessed as partial supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 54. This assessment is considered evaluated because the drainage area (789 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the FIBI BIC and failed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.
As part of the REMAP project, diurnal dissolved oxygen/temperature monitoring conducted during September 2002 found substantial fluctuation of d.o. levels associated with high levels of seston and periphyton chlorophyll, and very high estimates of primary production. Levels of BMIBI metrics that are sensitive to organic enrichment suggest a nutrient enrichment/algal growth-related water quality problem. Habitat modification that has resulted in a wide and shallow stream channel with high solar input may contribute to algal growth. Additional sampling data are needed to evaluate the extent, causes and sources of this water quality problem.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this river segment.
