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Evidence for alternate states in shallow prairie lakes.
Jackson, Leland1, 1
ABSTRACT- Abundant macrophytes have been hypothesized to be key to keeping shallow lakes in a relatively clear state. This is because macrophytes should reduce sediment resuspension, provide refuge for large-bodied zooplankton, and harbour nutrients that otherwise would be available for phytoplankton growth. I sampled 32 shallow (1-13 m depth) lakes in central Alberta to search for evidence of alternate states and if they exist, determine whether or not macrophytes differ among lakes of different states. The lakes sampled separated into 1) relatively clear, stratified lakes, 2) shallow, relatively clear lakes with abundant macrophytes, and 3) shallow, relatively turbid lakes with low macrophyte biomass. Macrophyte biomass and % littoral zone were key variables that classified lakes into the different categories. Thus, alternate states exist and macrophyte biomass and cover differs within the unstratified lakes. However, high macrophyte biomass is also a source of that could lead to high rates of oxygen decay under ice, and anoxia. The implications of high macrophyte biomass and food web processes to the potential stability and functioning of these lakes will be discussed.
KEY WORDS: alternate stable states, submerged aquatic macrophytes