Assessment Comments
Assessment based on (1) a 1998 study of low levels of dissolved oxygen conducted by Wisconsin DNR, (2) results of U.S. EPA/IDNR fish tissue monitoring in 2000, and (3) a 1999 USGS publication on the ecological health of the UMR.
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 2000. The sources of data used for this assessment are (1) Sullivan and Endris (1998), (2) results of U.S. EPA/DNR fish tissue (RAFT) monitoring in 2000 downstream from Guttenberg, and (3) a report on ecological status and trends of the UMR by USGS (1999)
EXPLANATION: An assessment of support of the Class A (primary contact recreation) uses was not developed due to lack of sufficient data on levels of indicator bacteria in this river reach.
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 were assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring downstream from Guttenberg in 2000. 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 protective and compatible with the various protocols used by adjacent states, the Iowa Department of Public Health (IDPH), 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 impairment of, fish consumption uses.
Although this scenario does not apply to the fish contaminant data generated from the 2000 RAFT sampling conducted in this assessment segment, levels of contaminant are sufficiently high for at least some concern and justify follow-up monitoring. The levels of at least one contaminant now slightly exceeds one or more advisory trigger levels, thus suggesting the need for additional (follow-up) monitoring to determine whether a consumption advisory should be issued. The composite samples of fillets from the 2000 RAFT sampling had generally low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.072 ppm; total PCBs: 0.207 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.125 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. The level of mercury in the sample of common carp fillets, however, exceeds the IDNR/IDPH trigger level of 0.2 ppm for a one meal per week consumption advisory. According to the IDNR/IDPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory. Thus, additional monitoring will be conducted in 2008 to determine whether an advisory is needed for this waterbody. According to IDNR’s assessment methodology, the occurrence of contaminant slightly above an advisory trigger level does not suggest impairment of the fish consumption uses but does suggest the need to conduct additional fish contaminant monitoring.
