Effects of Intermittent Artificial Circulation in Summer Months on Chlorophyll a Concentration in a Small Eutrophic Impoundment

Abstract

Impact of artificial circulation on total algal biomass (as chlorophyll a integrated over depth) in a small eutrophic impoundment in the Northern Great Plains, was monitored over three consecutive summers. Chlorophyll a concentration and nutrient concentrations were measured at depths along water columns under aerated and non-aerated conditions at four sampling locations. Aeration destratified the water column, which resulted in homogenous chlorophyll a concentration throughout the water column and across the four sampling locations. The non-aeration resulted in concentration gradient along the water column at all sampling locations. Overall, the artificial circulation resulted in an overall reduction of chlorophyll a concentration along the water column and across sampling locations. Reduced chlorophyll a might be attributed to a shift in dominant phytoplankton species. For example, increased mixing by aeration may have favored dinoflagellates or green algae over cyanobacteria. In conclusion, the artificial circulation in this impoundment was effective in reducing total algal biomass.