Effects of curlyleaf pondweed control on water quality and coontail abundance in Gleason Lake, Minnesota

Abstract

Three years (2007-2009) of early season lakewide endothall treatments to control curlyleaf pondweed (Potamogeton crispus) were followed by 4 years (2010-2013) of early season spot endothall treatments in 65 ha Gleason Lake, Plymouth, Minnesota. Endothall treatments controlled heavy growth of curlyleaf on an annual basis in all 7 years, but long-term control, where no future treatments would be necessary, was not achieved. During the curlyleaf control program, coontail (Ceratophyllum demersum) distribution and abundance increased dramatically as curlyleaf distribution and abundance decreased. None of the other 3 native submersed plant species found in Gleason Lake increased in frequency over the 7 years of treatment. It is not clear what triggered the rapid coontail expansion or if its heavy growth will be sustained. During the same time period, Gleason Lake transparency increased while phosphorus and chlorophyll concentrations decreased. Water quality improvements in Gleason Lake were likely related to nutrient uptake by coontail growth.