Diel Patterns of Dissolved Oxygen and Select Chemical Parameters in three Lakes within Hoosier National Forest that have Experienced Recent Fish Kill

Abstract

Three lakes in Hoosier National Forest, Perry County, southern Indiana, were studied for changes in dissolved oxygen, temperature, pH, oxidation-reduction potential, salinity, specific conductance, and total dissolved solids because they have experienced recent fish kills. These lakes were evaluated for patterns in their chemical limnology over a 24–hr period during September 2005. The shallow nature of these three lakes has caused dramatic shifts in pH, dissolved oxygen, oxidation-reduction potential, and specific conductance. The largest changes in dissolved oxygen and pH occurred at dawn and dusk when aquatic plants switched from photosynthesis to respiration. Changes in oxidation-reduction and specific conductance were the result of the loss of dissolved oxygen in the lake sediment microzone. As the lake substrate changed from a reducing environment to an oxygenated environment, total dissolved solids and specific conductance increased as these materials were released into the water column. Low night-time dissolved oxygen levels and associated chemical stressors associated with aquatic plant respiration could explain the recent fish kills.