EXPANDING LAKE HEALTH CRITERIA—AQUATIC MACROPHYTES, BEYOND PLANT MANAGEMENT

Jeremy Williamson, Polk County Land & Water Resources Department, Balsam Lake Wisconsin

Aquatic macrophytes play a major role in the dynamics of shallow lakes and often dominate the littoral zone of many large lakes. They provide food and habitat for a myriad of biota, anchor lake and river sediment, remove nutrients, and modify the current or seiche. Eutrophication and other anthropogenic impacts have caused dramatic changes to the structure and biomass of aquatic macrophyte communities. Sampling aquatic macrophyte communities and their taxonomy is relatively straightforward and interpretation of water quality and habitat impacts from aquatic macrophyte community data can be made with a reasonable amount of training and effort. The resulting data suggest that macrophyte community response to natural, human, and recovery processes is essential knowledge for lake management decisions rather and may be more informative than simple chemical (e.g. phosphorus) endpoints. Finally, the macrofossil remains of aquatic macrophytes in lake sediment cores can assist with the definition of pre-disturbance conditions and facilitate setting realistic restoration targets. The purpose of this presentation is to introduce inventory and monitoring of lake floras as a valuable index of lake quality and habitat disturbance and highlight projects in the St. Croix basin in which they have been used.

Suggestions for Reading

Carpenter, S.R. and D.M. Lodge. 1986. Effects of submersed macrophytes on ecosystem processes. Aquatic Botany 26: 341-370.

Jeppesen E, Jensen JP, Søndergaard M, Lauridsen T, Pedersen LJ, Jensen L. 1997. Top-down control in freshwater lakes: The role of nutrient state, submerged macrophytes and water depth. Hydrobiologia 342/343: 151–164.