Characterization of Macroinvertebrate and Fish Assemblages at 35 Streams in Southwestern Louisiana and an Assessment of Their Relations to Water-Quality and Physical Habitat

The U. S. Environmental Protection Agency (USEPA) requested that the USGS Lower Mississippi-Gulf Water Science Center (WSC) - Arkansas coordinate and conduct fish sampling at 35 sites in southwest Louisiana and, with assistance from USGS Lower Mississippi-Gulf Water Science Center (WSC) - Louisiana, evaluate relations between biological community and water-quality data collected to date by USGS, as well as to other historic water-quality data collected by other agencies. USEPA suspects that numeric water-quality criteria (particularly for dissolved oxygen) in the WGCP ecoregion of Louisiana are not attainable even in the highest quality waters and plans to use this study to investigate relations between water quality and biological communities.

Map showing monitoring sites of biota and DO in southwestern Louisiana.

The objective of this study is to provide a mechanism to evaluate the status of biological integrity and water-quality conditions across the WGCP in Louisiana. The approach for this study includes: 1) collect, identify, and enumerate fish species so that fish assemblages at the 35 sites can be characterized, 2) analyze all biological, chemical, and physical data collected at the 35 sites, 3) locate and analyze any historic water-quality data collected at the 35 sites by other agencies, and 4) write a final report that evaluates relations between biological communities and water-quality data. Sampling was conducted from mid August-October of 2007. Data analyses and report writing will be performed in 2008 and 2009 following data collection.