PARENT SESSION
Oral Session 1: Aquatic Ecology I: Rivers, Nutrients, and Water Quality.
Presiding: D Kashian
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 105.
Using long-term monitoring data to understand spatial and temporal variability in the Upper Mississippi River System.
Houser, Jeffrey*,1, Rogala, James 1, Gray, Brian1, Fischer, James1, Johnson, Barry, 1 U.S. Geological Survey, La Crosse, WI, USA
ABSTRACT- Large river/flood plain ecosystems exhibit substantial large-scale spatial heterogeneity which is driven in part by seasonal changes in hydrology. We investigated variation in limnological variables among and within habitat types for the Upper Mississippi River System (UMRS) using quarterly data collected from 1993-2002 by the Long Term Resource Monitoring Program. The limnological data were derived from multiple habitat types (defined by hydrology and bathymetry) over a 1300 km stretch of the UMRS from Redwing, MN to Cairo, IL. Specifically we addressed the following questions: 1) How limnologically similar are habitat types (e.g. backwater areas, main channels, impoundments) and how do these similarities vary by season?, and 2) What proportions of the observed variation in limnological variables are associated with season, year, habitat type, and river kilometer? Limnological similarity among habitat types varied substantially by season. For example, correlations between main channel and backwater chlorophyll was highest in spring, intermediate in summer, and lowest in fall and winter (r= 0.91, 0.79, 0.53, 0.58 respectively). For suspended solids, correlations between main channel and backwater were highest in spring and fall (r= 0.53, 0.52), and were trivial in summer and winter (r=0.04, -0.17). Chlorophyll a and suspended solids increased from the upper reaches to the lower reaches of the UMRS. Variation within habitat-types differed substantially among habitats. For example, variation of chlorophyll a was generally highest within backwater areas and lowest within the main channel. These results contribute to our understanding of large river ecosystems by illustrating important characteristics of spatial and seasonal variability within the UMRS.
Key words: limnology, seasonal variability, river ecology, spatial variability