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Biological Assessments

Biological assessments are commonly used by scientists not only to understand water quality but also to evaluate the condition of aquatic ecosystems. The Louisville District Water Quality Team has utilized the following biological assessments for understanding the water quality of reservoirs and their associated tributaries and tailwaters: benthic macroinvertebrates, fish, phytoplankton, and zooplankton. Results of biological assessments can be seen at Water Quality Data and Reports or can be provided upon request by emailing louisvillewaterquality@usace.army.mil.

Benthic Macroinvertebrates

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. Each year, a subset of the 20 Louisville District reservoirs are assessed.

In 2016, the four Green River Basin reservoirs (Barren River Lake, Green River Lake, Nolin River Lake, and Rough River Lake) were assessed using benthic macroinvertebrate communities. The results of this study can be seen at Water Quality Data and Reports. In 2017, Brookville Lake and Cecil M. Harden Lake were assessed using benthic macroinvertebrate and fish communities (these results are pending).

 

      

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

Fish

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. Each year, a subset of the 20 Louisville District reservoirs are assessed.

Fish sampling began in 2017 with the assessments of Brookville Lake and Cecil M. Harden Lake (these results are pending).

 

           

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

Phytoplankton

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 20 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

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 20 Louisville District reservoirs annually. Zooplankton sampling began in 2016 and reports of these results are pending.

 

  

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

Water Quality