The Effect of Macrophyte Removal on the Distribution of Selected invertebrates in a Littoral Environment

ABSTRACT

Submergent vegetation was removed from four locations in a shallow wetland lake containing a dense concentration of aquatic macrophytes. The distributions of selected species of zooplankton and macroinvertebrates were compared over a two month period between the vegetated sites and locations in which vegetation was removed. Chydorus, Al onella, Graptoleboris and Scapholebrus showed a preference for vegetated stations. Daphnia schodleri was collected mostly in the open water. Three macro invertebrate predators, Enallagma boreale, Notonecta unifasciata, and Hesperocorixa leavigata showed a significant attraction to submergent plants over sites where vegetation had been removed as was also the case with Hyallela azteca and Callibaetis. Chaoborus an open water predator did not occur in significant numbers at vegetated stations but was most commonly observed in the deep water stations over the shallow sites. It is thought that predation of D. schodleri by E. boreale is an important mechanism in reducing the number of this prey population especially during that time of year when dense concentrations of submergent plants are present in the lake.