Response of silver lake trophic state to artificial circulation

Abstract

Artificial circulation is a lake management technique which can sometimes improve the quality of eutrophic impoundments. While improvements associated with extension of oxygenated habitats are common, other benefits such as reduction of algal biomass and changes in phytoplankton and zooplankton species composition are less certain. Circulation was implemented from June through October 1982 in eutrophic Silver Lake, Summit County, Ohio. Dissolved oxygen was maintained at the bottom of most stations, with a concomitant increase in zooplankton and benthic macroinvertebrate ranges. Negative results included increases of surface phosphorus, chlorophyll, and algal biomass, a slight decline in transparency, and the continued predominance of blue-green algae at the surface. One station was partially isolated by basin morphometry and functioned as an in-lake control which remained physically, chemically, and biologically stratified. The overall trophic state of the lake as measured by phosphorus, transparency and chlorophyll declined. Reasons for these undesirable results include failure of the system to maintain isothermal conditions, failure to achieve a pH and phytoplankton shift, and mixing of sediments into the water column from placement of the diffuser directly on the lake bottom. © 1987 Taylor & Francis Group, LLC.