April Arroyo Monroe
Griffy Lake winter drawdown simulation: how long does it take to kill Egeria densa.
BSES Senior Research 2006

Egeria densa is an invasive aquatic plant native to South America. It was introduced into the US in 1893. It was first found in Griffy Lake in Monroe County, IN, in 2001. Griffy Lake is the only lake on public land in Indiana to contain it. Due to the species ability to reproduce vegetative through drifting fragments, it is of major management concern. One suggested method of control is winter drawdown, during which the pond or lake water is drained, drying and freezing the plants. I simulated winter drawdown by transplanting E. densa plants and Griffy Lake sediment to containers in an environmental chamber. I drained the containers through holes in the bottom and set the environmental chamber to 0°C. The lights were set on 10 hour days. Plants were frozen for 7, 10, or 15 days, after which they were allowed to thaw and then were transferred to a common aquarium where they rehydrated. One plant from the 7-day group survived this process; all other plants died. Clearly, winter drawdown has potential to control E. densa in natural settings. Expense and ecological impacts to other species may affect the decision to conduct a drawdown.