HR: 11:30h
AN: NB52D-04    [Abstracts]
TI: Nutrients and chlorophyll a in the Upper Mississippi River System: What can we learn from spatial and temporal patterns?
AU: * Houser, J N
EM: jhouser@usgs.gov
AF: USGS Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Rd. , La Crosse, WI 54603 United States
AU: Rogala, J T
EM: jrogala@usgs.gov
AF: USGS Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Rd. , La Crosse, WI 54603 United States
AU: Gray, B R
EM: brgray@usgs.gov
AF: USGS Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Rd. , La Crosse, WI 54603 United States
AU: Gittinger, L A
EM: lgitting@inhs.uiuc.edu
AF: Illinois Natural History Survey, 8450 Montclair, Brighton, IL 62012 United States
AB: Variability in time and space is a defining characteristic of large river ecosystems. We investigated temporal and spatial variation in selected nutrients and chlorophyll a concentrations in 5 study reaches of the Upper Mississippi River System (UMRS) using quarterly data collected from 1993 to 2002. We addressed the following questions: 1) Are there consistent differences among aquatic areas (e.g. main channel and off-channel areas (backwaters))? 2) What temporal patterns occur within these aquatic areas? 3) What is the relative importance of spatial and temporal components in the total variance? Chlorophyll a concentrations were generally higher in backwaters than the main channel, whereas dissolved nutrient concentrations were generally lower in backwaters. These differences were most pronounced in summer. Seasonal patterns in nitrate (NO₃^{-) and soluble reactive phosphorus (SRP) showed that minimum [NO₃-] coincided with maximum [SRP] in late summer. Seasonal patterns in chlorophyll a concentration varied among study reaches, though minimum concentrations generally occurred in winter. Variance component analysis indicated that temporal components generally explained more variability than did spatial components. The proportion of variability explained by temporal vs. spatial components varied among study reaches. These patterns provide information for understanding chlorophyll a and nutrient dynamics in large river ecosystems.}
DE: 1845 Limnology
DE: 4227 Diurnal, seasonal, and annual cycles
DE: 4805 Biogeochemical cycles (1615)
DE: 4815 Ecosystems, structure and dynamics
DE: 4845 Nutrients and nutrient cycling
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly