Mississippi River IA 01-NEM-71

Assessment Comments

Assessment is based on (1) a special study of low DO/sediment oxygen demand (Sullivan and Endris 1998), (2) a report on ecological status and trends of the UMR by USGS (1999), and result of U.S. EPA/IDNR fish contaminant monitoring downstream from Dubuque from 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 / threatened" based on the 1997 study of dissolved oxygen levels by Sullivan and Endris (1998) of the Wisconsin DNR and based on summary information in USGS (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.  

The Class B(WW) uses remain assessed (evaluated) as "fully supporting / threatened" based on the 1997 study of dissolved oxygen levels by Sullivan and Endris (1998) of the Wisconsin DNR (see assessment for the 1998 report).   The study by Sullivan and Endris (1998) 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.   However, because the data from Sullivan and Endris (1998) are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is changed from "monitored" (indicating an assessment with relatively high confidence) to "evaluated" (indicating an assessment with relatively low confidence).  

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 (monitored) as "fully supported" based on results of U.S.  EPA/DNR fish tissue (RAFT) monitoring in 2000, 2001, and 2002 downstream from Dubuque that showed levels of contaminants were less than ½ the respective FDA action levels and DNR levels of concern in the composite samples of whole-fish common carp in 1998, 2000 and 2002 and in the composite samples of fillets from common carp and white crappie in 2001.   The sample of whole-fish common carp collected in August 2002 did not contain levels of contaminants that approached even one-half the respective FDA action levels or IDNR levels of concern.   Levels of primary contaminants in the sample were as follows: mercury: 0.066 ppm; total PCBs: 0.199 ppm; and technical chlordane: 0.063 ppm.   For information on fish contaminant (RAFT) monitoring conducted in 2000 and 2001, see the assessment developed for this assessment segment for the 2002 report.