COMMUNITY METABOLISM IN A LARGE FLOODPLAIN RIVER:  HABITAT 
COMPARISIONS OVER TIME

Jackie L. Scherle and Michael D. Delong
Large River Studies Center, Biology Department, Winona State University, Winona, MN 
55987

While large floodplain rivers have been identified as highly productive systems, little is 
known about spatial and temporal patterns of community metabolism at levels below 
river-wide and annual scales.  Dissolved oxygen (DO) concentrations serve as a useful 
and easily measurable product of both primary production and respiration.  DO 
concentrations were measured in both main channel and backwater habitats in Reaches 5 
and 6 of the Upper Mississippi River over a 3-mon period (June - August 2005).  These 
measures will be used to estimate Gross Primary Production (GPP), Net Primary 
Production (NPP), and Respiration (R).  BioDevice Aqua 2002 dissolved oxygen and 
Temperature recorders were deployed at a depth of 1 m in main channel and backwater 
habitats.  Data were recorded every 1 – 3 min for a 7-d period.  Calculation of GPP, NPP, 
and R will be determined by using the calculations of Odum (1956) using a model 
developed for the U.S. Environmental Protection Agency.  Final calibration of the model 
has been completed and results will be presented.  Examination of DO concentration 
indicates ~0.4 mg/L daily fluctuations of DO in main channel and backwater in June and 
~1.5mg/L daily fluctuation of DO in main channel and backwater in August.  Diurnal 
patterns of DO over a 7-d sample period indicates that GPP exceeds R in both habitats, 
suggesting accumulation of fixed carbon in both habitats.  Rates of community 
metabolism may be similar in backwater and main channel habitats despite obvious 
physical, chemical, and biological differences.

Keywords:  dissolved oxygen, community metabolism, primary production, respiration, 
floodplain river, Mississippi River