Benthic macroinvertebrates (i.e., bottom-dwelling animals that lack a backbone and are large enough to be visible with the naked eye) are commonly used as indicators of water quality conditions, as they are sensitive to pollution and spend most (if not all) of their time in water. The Louisville District Water Quality Team utilizes assessments of benthic macroinvertebrate communities to better understand the water quality conditions of tributaries flowing into reservoirs as well as conditions flowing out of reservoirs via tailwaters. The methods of these studies are consistent with the appropriate state water quality authorities for Kentucky, Indiana, and Ohio, depending on the jurisdiction of a reservoir. The results of these studies can be seen at Water Quality Data and Reports.

Left - Collecting benthic macroinvertebrates, including a stonefly larva and a hellgrammite. Right - Relic shells of freshwater mussels.

Fish communities are commonly used as indicators of water quality conditions, as they are sensitive to pollution and can be impacted by changes in water quality. The Louisville District Water Quality Team utilizes assessments of fish communities to better understand the water quality conditions of tributaries flowing into reservoirs as well as conditions flowing out of reservoirs via tailwaters. The methods of these studies are consistent with the appropriate state water quality authorities for Kentucky, Indiana, and Ohio, depending on the jurisdiction of a reservoir. The results of these studies can be seen at Water Quality Data and Reports.

Left - Collecting fish using a backpack electrofisher. Right - A captured Logperch (Percina caprodes).

Phytoplankton are free-floating aquatic microorganisms that are photosynthetic (convert light energy into chemical energy for food), such as algae and cyanobacteria (blue-green algae). Because phytoplankton compose much of the bottom of the food chain, aquatic ecosystems depend heavily on phytoplankton. Also, phytoplankton are sensitive to water quality conditions and make excellent indicators of water quality. Because of these reasons, the Louisville District Water Quality Team monitors phytoplankton communities at all Louisville District reservoirs annually. The results of phytoplankton assessments can be found in annual reports at Water Quality Data and Reports.

Various species of cyanobacteria.

Zooplankton are free-floating aquatic microorganisms that are consumers (consume other organisms for food), such as crustaceans and aquatic mites. Zooplankton serve as a critical link in the food chain by supporting organisms that then support larger organisms, such as fish. Also, zooplankton are sensitive to water quality conditions and make excellent indicators of water quality. Because of these reasons, the Louisville District Water Quality Team monitors phytoplankton communities at all Louisville District reservoirs annually. 

Left - Kemmerer bottle filled with water from a Daphnia lumholtzi bloom. Right - Daphnia lumholtzi female with eggs.