Lake Lily Fish Kill Blamed on Low Oxygen

CAPE MAY POINT — Low dissolved oxygen in Lake Lily is blamed for a fish kill here July 12 that caused public works employees to remove hundreds of pounds of dead fish from the freshwater lake.
Francine Nietubicz, chairwoman of the Lake Lily Committee, said she spoke at length with representatives of Clean-Flo which makes the aeration system used in the lake, Allied Biological which applied an herbicide to the lake May 27, representatives of two water analysis laboratories, the director of the Cape May County Mosquito Commission and a number of people at the state Department of Environmental Protection (DEP).
Nietubicz said all agree that the fish kill was probably caused by low dissolved oxygen (DO) in the lake. A DEP contact likened it to the fish kill here seven years ago.
“What caused the low DO will never be completely explained and there are many factors that could have caused it,” said Nietubicz. “I am convinced that it was a combination of causal events that I think of as a “perfect storm”:
• Warm water contains less oxygen than cold water and this is exactly when fish need more oxygen, not less; we were at the end of a severe heat wave.
• If it was solely due to the heat wave, the fish kill would have happened during the heat, not after it ended.
• A DEP Fish and Wildlife Freshwater Fisheries biologist, as well as the president of Clean-Flo, both think some external influence was involved. They both said that since there had not been rain in a significant period of time, the rain from the day before the fish kill washed something out of the storm drains into the lake, causing the low DO (there are 27 storm drains emptying into the lake) and/or contributing to the problem.
• We will never know exactly what it was that ran into the lake but analysis of water taken by public works during their clean-up showed extremely high levels of ammonia which can be created when storm drains sit idle with stagnant water over a long period of time. The level of ammonia found in the south end of the lake was in a range that is lethal for fish.
• The herbicide application on May 20 did not cause the fish kill but the resulting dead and decaying vegetation was probably a contributing factor. One third of lake area was treated with Reward, an herbicide that is not harmful to fish or other wildlife.
DEP made a visual inspection of the lake just after the fish kill and did not see anything of concern, said Nietubicz. Subsequent to the kill, fish have been seen swimming in the lake, so we know that they were not all eliminated, she said.
“More and more we learn how complicated a lake environment is, that we have to move forward with the storm drain filter pilot test project to be installed on three storm drains in August, that we have to continue to be mindful of how we treat the lake and that some things are beyond our control,” said Nietubicz.
Other than the fish kill, Lake Lily has been looking great this year, she said.
“The submerged weeds are gone, the filamentous algae is under control and now all we see is some planktonic algae and lots of green duckweed floating on top,” said Nietubicz.