Microstratification of water chemistry in a littoral population of Elodea canadensis.

Abstract

The data presented in this paper was collected in an effort to study the biogenically produced microstratification in the water column of a macrophyte-dominated aquatic community. A dense stand of macrophytes may effect microstratification in shallow waters in a number of ways. Physical factors of the system are altered by the presence of a dense vegetation stand. Currents are reduced, and mixing of the water column from wind stress is greatly inhibited. Lack of mixing allows establishment of vertical gradients which would not occur in open water. Solar radiation produces sharp temperature stratification. Biological activity of organisms in the community sets up chemical gradients. In the zone of active photosynthesis oxygen concentration increases while carbon dioxide levels drop, affecting the pH of the surrounding water. Ruttner has shown that actively photosynthesizing Elodea canadensis can produce a marked rise in pH of water by utilization of HCO- ions, with the consequent release of OH- ions to solution. The epiphytes and benthic organisms in assocation with the macrophytes produce chemical changes in the water of the unlighted zone beneath the plant mat. In this study the chemistry of these lower waters appears to have been heavily affected by the oscillations in chemical content of the water coming into the system from upstream. Effects of the Elodea community on downstream water were evaluated in an effort to predict effects of macrophyte removal on water quality in the lake under study.