Griffy Lake will receive chemical treatment in May

Griffy Lake will undergo the equivalent of about a $71,500 de-weeding this summer. \nStarting May 1, the chemical Sonar, an Environmental Protection Agency -approved herbicide, will be dumped directly into the water to combat the invasive aquatic weed Brazilian elodea, said Doug Keller, the aquatic invasive species coordinator for the Indiana Department of Natural Resources. \nKeller said the plant has been eliminating Griffy Lake’s native plant diversity and making many recreational activities impossible since 2004. \nThis summer will in fact be the second year in a row that the lake will be treated with this chemical, which is funded by the Department of Natural Resouces.\n“We first found the evidence of the plan in 2004 and when we began treatment in 2006, it was already covering 30 percent of the lake,” Keller said. \nLast year’s treatment was successful, Keller said, but to fully rid the lake of all plant fragments, it will be repeated this year.\nBut introducing a chemical to a natural ecosystem inevitably has both positive and negative effects.\nHeather Reynolds, an assistant professor in the biology department and the chair of the Bloomington Environmental Commission, said that though the chemical is used in amounts that are too low to be toxic to animals, it still kills certain native plants.\n“There’s no silver bullet here,” Reynolds said. “The system has been disturbed and you can’t really try to put it back without causing further disturbance.”\nAccording to Reynolds, there are generally five ways that an invasive plant is treated in an ecosystem: through hand-pulling; introducing a biological control like an animal or plant to attack the invasive plant; mechanical eradication; draw-downing, where the lake is literally drained; or chemical treatment. \nThe elodea was too widely spread to hand-pull the weed, Reynolds said. The only biological control considered was introducing grass carp, but Keller said the carp would not specifically eat the elodea and might escape from the lake through the spillway. Keller also said to eliminate the elodea by drawing the lake would require 90 percent of the lake’s volume drained, which would virtually eliminate the ecosystem entirely. The Department of Natural Resources decided not to use mechanical eradication, or dredging, because it would fragment the plant stems, spreading it further. Chemical treatment is the most appropriate alternative, Keller said. \n“I know there are a lot of people who are really afraid of dumping chemicals in the water,” Keller said. “But the chemical is in such trace amounts that the water could be used for drinking water. There are no fishing restrictions when the chemical is in use. There are no restrictions at all.”\nKeller said the highest concentration of the chemical Sonar that is legal to introduce to a natural ecosystem is 150 parts per billion. The strongest concentration ever introduced last summer at Griffy Lake was 20 parts per billion. The average concentration used in Griffy is 7 to 8 parts per billion. \n“It’s a tough call,” said Reynolds. “In this case, for example, it is essential that the native vegetation in Lake Griffy (which is also killed by the chemical at the concentrations used), be restored to its former levels of diversity. If not, this simply leaves a huge vacant niche in the lake for elodea and other exotic invasives to fill.”