Assessment Comments
Assessment is based on (1) a 1998 study of low DO/sediment oxygen demand, (2) a 1999 USGS report on ecological status and trends of the UMR, and (3) result of U.S. EPA/IDNR fish contaminant monitoring in 1998 and 2000-02.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW) aquatic life uses remain assessed (evaluated) as "fully supporting" based on an assessment of the ecological health of the Upper Mississippi River published in 1999. Fish consumption uses remain assessed (monitored) as "fully supported" based on fish contaminant monitoring in 1998 and from 2000-2002. The sources of data used for this assessment are (1) Sullivan and Endris (1998) and (2) results of U.S. EPA/DNR fish tissue (RAFT) monitoring downstream from Dubuque in 2000, 2001, and 2002.
EXPLANATION: The Class A uses remain "not assessed" due to lack of information on levels of indicator bacteria in this reach of river.
A study of dissolved oxygen levels in 1997 (Sullivan and Endris 1998; see assessment for the 1998 report), however, does suggest a concern with levels of dissolved oxygen in the main channel of the UMR. This study showed low levels of dissolved oxygen in the main channel of the Mississippi River during late June/early July 1997 during a period of high water temperatures and low river flow from Pool 9 downriver to Pool 12. Follow-up investigation suggested that these low levels of dissolved oxygen were due to high densities of zebra mussels in this river reach. These results suggest a concern regarding levels of dissolved oxygen in this reach of the Upper Mississippi River.
Chapter 16 of the USGS (1999) report ("Assessments and forecasts of the ecological health of the Upper Mississippi River System floodplain reaches"), identifies Pools 1-13 as a "moderately impacted" ecosystem with declining structural diversity and threats to native mussels from zebra mussels. They note, however, that the ability of this river reach to recover from disturbances has been demonstrated by improving populations of aquatic macroinvertebrates and aquatic vegetation. These authors suggests that the recovery of these aquatic communities is, at least in part, related to improved water quality over the last 25 years due to national clean water programs.
Fish consumption uses are assessed as "fully supported" based on the 2002 and 2004 EPA/IDNR fish tissue (RAFT) sampling on the Mississippi River downstream from Dubuque (at mouth of Catfish Creek). This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring. The results from the 2002 and 2004 sampling show low levels of the primary contaminants (chlordane, PCBs and mercury). The results for the 2002 sample are as follows: mercury: 0.066 ppm; total PCBs: 0.199 ppm; and technical chlordane: 0.063 ppm. The results for the 2004 sample are as follows: mercury: 0.05 ppm; total PCBs: 0.14 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 support of fish consumption uses in Iowa’s rivers and lakes. 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 2002 and 2004 RAFT samplings conducted in this assessment segment: the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
