THE RESPONSE OF MACROPHYTE COMMUNITIES TO DROUGHT-INDUCED REDUCTION OF NUTRIENT LOADING IN A CHAIN OF LAKES

During a 2 year period of unusually low precipitation and reduced stream flow through a chain of lakes, the submersed aquatic plant community of eutrophic Shoe Lake changed qualitatively and quantitatively to one more similar to that of the less productive East Graham Lake, downstream in the lake chain. In Shoe Lake, the previously dominant non-rooted species declined along with phytoplankton biomass, and the abundance and diversity of submersed rooted plants increased. Also, the free-CO2-requiring macrophyte species present in Shoe Lake declined in favor of some previously restricted bicarbonate users. These changes appear to have been caused by a decrease in nutrient loading to the lake chain and by the consequential greater light availability in Shoe Lake.