Lower Mississippi River National Rivers and Streams Assessment

The data will be used by States to assess the condition of biological assemblages, water quality, and physical habitat in the Mississippi River from the confluence of the Ohio River near Cairo, IL to the Arkansas-Louisiana state-line. The specific objectives are to collect water quality, fish, phytoplankton, macroinvertebrate, and riparian physical habitat information as indicators of biological condition from 30 sites on the Lower Mississippi River.

Map showing Lower Mississsippi River National Rivers and Stream Assessment reach.

Sampling sites on the Lower Mississippi River are a sub-set of the NRSA sample design. The NRSA design is a stratified probability design that distributes sites across the country by state and stream order. The probability design sampling sites were sampled in July-October, 2008. Sampling was conducted in 10, 400-meter transects located on alternate sides of the river. At each sampling site, physical habitat characteristics were measured, and macroinvertebrates and sediment samples were collected. A 3-person Fish Crew was responsible for collecting fish and some physical habitat measurements. Fish were collected by electrofishing a minimum of 2000 meters within the 4000 meter reach. A 4-person River Crew was responsible for sampling water quality, algae, macroinvertebrates, sediment, and physical habitat. At three cross-channel stations, along a transect passing through the sampling site and perpendicular to the main-channel, the River Crew collected depth-integrated water samples. The three samples were combined to create a single site-composite sample from which numerous sub-samples were taken.