Mississippi River IA 01-NEM-75

Assessment Comments

Assessment is based on (1) results of ambient monitoring conducted by Illinois EPA from 2000-02, (2) 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 (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2000 and 2002.

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."  Fish consumption uses remain assessed (monitored) as "fully supported."  The sources of data used for this assessment are (1) Sullivan and Endris (1998), (2) results of monitoring conducted from July 2000 to November 2002 by the Illinois Environmental Protection Agency at station M  13 at Lock and Dam 11 at Dubuque, (3) results of U.S.  EPA/DNR fish tissue (RAFT) monitoring in 2000 downstream from Guttenberg and in 2002 near Dubuque, and (4) 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.   During the period 2000 through 2002, only two samples were analyzed for indicator bacteria at the Illinois EPA station (M  13).   This amount of data is not sufficient to develop an assessment of support of the Class A uses.  

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 downstream from Guttenberg and in 2002 near Dubuque.   RAFT sampling in 2000 downstream from Guttenberg that showed levels of contaminants in composite samples of fillets from channel catfish and smallmouth bass were less than ½ the respective FDA action levels and DNR levels of concern.   Similarly, RAFT sampling in 2002 at Mud Lake near Dubuque also showed very low levels of contaminants:  composite samples of fillets from common carp and largemouth bass had very low levels of contaminants.   Neither sample contained levels of contaminants that approached even one-half the respective FDA action levels or IDNR levels of concern.   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.