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Dukerschein J.T.,Mississippi River Monitoring Field Station | Bartels A.D.,Mississippi River Monitoring Field Station | Ickes B.S.,U.S. Geological Survey | Pearson M.S.,U.S. Environmental Protection Agency
River Research and Applications | Year: 2013

We applied an Index of Biotic Integrity (IBI) used on Wisconsin/Minnesota waters of the upper Mississippi River (UMR) to compare data from two systemic sampling programmes. Ability to use data from multiple sampling programmes could extend spatial and temporal coverage of river assessment and monitoring efforts. We normalized for effort and tested fish community data collected by the Environmental Monitoring and Assessment Program-Great Rivers Ecosystems (EMAP-GRE) 2004-2006 and the Long Term Resource Monitoring Program (LTRMP) 1993-2006. Each programme used daytime electrofishing along main channel borders but with some methodological and design differences. EMAP-GRE, designed for baseline and, eventually, compliance monitoring, used a probabilistic, continuous design. LTRMP, designed primarily for baseline and trend monitoring, used a stratified random design in five discrete study reaches. Analysis of similarity indicated no significant difference between EMAP-GRE and LTRMP IBI scores (n=238; Global R=-0.052; significance level=0.972). Both datasets distinguished clear differences only between 'Fair' and 'Poor' condition categories, potentially supporting a 'pass-fail' assessment strategy. Thirteen years of LTRMP data demonstrated stable IBI scores through time in four of five reaches sampled. LTRMP and EMAP-GRE IBI scores correlated along the UMR's upstream to downstream gradient (df [3, 25]; F=1.61; p=0.22). A decline in IBI scores from upstream to downstream was consistent with UMR fish community studies and a previous, empirically modelled human disturbance gradient. Comparability between EMAP-GRE (best upstream to downstream coverage) and LTRMP data (best coverage over time and across the floodplain) supports a next step of developing and testing a systemic, multi-metric fish index on the UMR that both approaches could inform. © 2011 John Wiley & Sons, Ltd. Source


Giblin S.M.,Mississippi River Monitoring Field Station | Houser J.N.,U.S. Geological Survey | Sullivan J.F.,550 Mormon Coulee Road | Langrehr H.A.,Mississippi River Monitoring Field Station | And 2 more authors.
Wetlands | Year: 2014

Duckweed and other free-floating plants (FFP) can form dense surface mats that affect ecosystem condition and processes, and can impair public use of aquatic resources. FFP obtain their nutrients from the water column, and the formation of dense FFP mats can be a consequence and indicator of river eutrophication. We conducted two complementary surveys of diverse aquatic areas of the UpperMississippi River as an in situ approach for estimating thresholds in the response of FFP abundance to nutrient concentration and physical conditions in a large, floodplain river. Local regression analysis was used to estimate thresholds in the relations between FFP abundance and phosphorus (P) concentration (0.167 mg l-1), nitrogen (N) concentration (0.808 mg l-1), water velocity (0.095 m s-1), and aquatic macrophyte abundance (65 % cover). FFP tissue concentrations suggested P limitation was more likely in spring, N limitation was more likely in late summer, and N limitation was most likely in backwaters with minimal hydraulic connection to the channel. The thresholds estimated here, along with observed patterns in nutrient limitation, provide river scientists and managers with criteria to consider when attempting to modify FFP abundance in offchannel areas of large river systems. © Society of Wetland Scientists 2014. Source

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