Assessment Comments
Assessment is based on results of (1) 2000 and 2004 IDNR/UHL biocriteria monitoring [(FIBI ave (n=3) = 54.3 (good); BMIBI ave (n=4) = 70 (good)], (2) ISU statewide survey of freshwater mussels in 1998-99 and (3) EPA/IDNR fish contaminant monitoring in 2003.
The FIBI riffle BIC = 65 and the BMIBI Hess sample BIC = 70.
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life uses remain assessed (monitored) as "partially supported" based on (1) results of IDNR/UHL biocriteria/REMAP monitoring in 2000 and 2004 and (2) results of the 1998-99 statewide assessment of freshwater mussels in Iowa streams by Arbuckle et al. (2000). Fish consumption are assessed as “fully supported” based on results of fish contaminant monitoring in 2003 conducted as part of the U.S. EPA/IDNR (RAFT) fish tissue monitoring program.
EXPLANATION: Results from the IDNR/UHL biocriteria sampling in 2000 and 2004 suggest that the Class B(WW) uses should be assessed (monitored) as "partially supported." This assessment is based on data collected in 2000 and 2004 as part of the DNR/UHL stream biocriteria and REMAP projects. The 2000 FIBI score was 62 (good) and the BMIBI score was 47 (fair). The 2004 REMAP FIBI scores were 46 (fair), 55 (good); and BMIBI scores were 86 (excellent), 77 (excellent), and 70 (good). The FIBI average for this segment was 54.3 and the BMIBI average was 70. The aquatic life use support assessment was changed from fully supporting / threatened (=FST) (see 2000 assessment comments) to partially supporting (= PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI riffle BIC for this ecoregion is 65 and the BMIBI Hess sample BIC for this ecoregion is 70.
Results from the 1998-99 statewide assessment of freshwater mussels in Iowa streams also suggest a potential impairment to the aquatic life uses of this stream segment and are consistent with the assessment based biocriteria monitoring in 2000. As part of this study, sampling results from 1998 and 1999 (Arbuckle et al. 2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987). In general, this comparison showed sharp declines in the numbers of mussel species ("species richness") from the mid-1980s to the late 1990s. For purposes of Section 305(b) reporting, results of this comparison were used by staff of the Iowa DNR Water Quality Bureau to assess the degree to which the aquatic life uses of the sampled stream segments are supported. This assessment included the following factors: (1) the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey and (2) the number of mussel species found in the 1998-99 survey. Greater than a 50% decline in species richness from the 1984-84 to the 1998-99 period suggests an impairment of the aquatic life uses. In addition, low species richness in the 1998-99 survey suggests potential impairment. Species richness of freshwater mussels at the two sample sites in this segment of the Wapsipinicon River were 10 and 9 in the 1984-85 period and were 2 and 6, respectively, in the 1998-99 period for a percent change of -56%. These results suggest that the Class B(WW) aquatic life uses are "partially supported." As presented by Arbuckle et al. (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high instream levels of nutrients (phosphorus and nitrogen). Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness. Additional monitoring is needed to better define the biological status of this stream segment.
Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Twin Ponds Park in 2003. The composite samples of fillets from channel catfish and walleye had low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.142 ppm; total PCBs: 0.094 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.095 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.
The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 2003 RAFT sampling conducted in this segment of the Wapsipinicon River: the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
