Monday, July 6th, 2009
Low oxygen causes fish kills
By Nancy Allen
Low dissolved oxygen levels in manmade channels on Grand Lake caused large fish kills on June 28 and 29, said Craig Morton, manager of Grand Lake St. Marys State Park.
The low dissolved oxygen levels are caused in part by the excessive overabundance of blue-green algae in the lake, which uses up oxygen, wildlife officials say.
He spoke during Saturday's Lake Improvement Association meeting in Celina.
Morton said the state park office received several calls from residents reporting the water looked discolored, had a sewage-like smell and dead fish in some of them or fish gasping for air at the surface. Affected areas included channels at Harmon's Landing, Bayview Marina, Southmoor Shores subdivision, It's It Landing, Windy Point and the state park campground, Morton said. There were no complaints about any of the three public swimming beaches, he said.
"Most of this happened Sunday and Monday ," Morton said. "We had reports of bass, bluegill, walleye and catfish all dying.
Matt Hoehn, Auglaize County Wildlife officer responded to Rustic Haven, Southmoor Shores and Harmon's Landing after receiving calls of dead fish. At Rustic Haven there were about 300 dead fish with 60 percent being rough fish and 40 percent game fish, at Southmoor Shores there were about 200 dead fish with 80 percent rough and 20 percent game fish and at Harmon's Landing there were less than 80 dead fish with 60 percent game fish and 40 percent rough fish.
Hoehn took water samples at all three locations and they showed low dissolved oxygen levels.
Mercer County Wildlife Officer Ryan Garrison said he checked the channel at It's It Landing and it had no dead fish, but was discolored and had an odor.
Doug Maloney, a fish management supervisor with the Ohio Division of Wildlife, said reports of low dissolved oxygen levels in the lake and/or fish kills have become more common during the past four to five summers. They are more common during extremely hot calm weather where there is little agitation to the water.
The occurrences of low dissolved oxygen levels are the result of excessive algae blooms caused by an overabundance of nutrients (phosphorous and nitrogen) in the water.
Dissolved oxygen levels typically rise and fall in all lakes during a 24-hour period. In Grand Lake dissolved oxygen levels rise during daylight hours as the huge amounts of blue-green algae produce oxygen as a byproduct of photosynthesis. However, the levels can fall precipitously during nighttime as the overabundant algae uses oxygen. Additionally, large amounts of lake with little water circulation, such as the numerous manmade channels on the lake, are the most susceptible to these oxygen depletions.
These oxygen depletions are most likely to occur in the summer because warm water cannot hold as much dissolved oxygen as cooler water can, Maloney said.
Though nutrients in the lake's watershed come from many sources, the largest source is runoff from agriculture land, which is the major land use in the watershed, Ohio EPA water quality tests have shown. The Grand Lake Watershed has been deemed one of the most degraded in the state, water tests show.
Under other business, Buzz Goodwin, owner of Bayview Sun and Fun Marina, asked why the state didn't lift the no contact advisory on the lake even though the algae toxin levels were below levels for safety.
Goodwin said he realized some of his decreases in sales are likely due to the economy, but noted that his gas sales are down 60 percent, his personal watercraft sales are down 50 percent, boat and pontoon sales are down 35 percent and his dock sales are down 30 percent.
"If you say the toxin levels are down, why can't you take the signs down," he said. "What am I supposed to tell these customers. I get phone calls all week long."
Morton replied that because the algae toxin issue is so new and that levels can fluctuate so widely in just a few days, the state has kept the no contact warning in place. The Ohio EPA has said the algae toxin could cause skin rashes and if ingested, could cause nausea and diarrhea. The toxin also is particularly harmful to small animals like dogs, the EPA also said.
"Because it's an issue of public health and safety, we are playing it safe," Morton said.
Fielding a question from a man at the meeting, Morton noted that E.coli bacteria levels have been low all year. Though he noted that there have been no reports of any human or animal illnesses directly attributed to the algae toxin, he still advised caution.
"If you see a really bad algae bloom, scum or an oily residue on the surface, it's probably not a good place to swim or take your dog.
Brian Miller, assistant manager at Grand Lake St. Marys State Park said there is a lot of confusion over the algae toxin and the testing used to confirm it and suggested the LIA invite someone from the Ohio EPA to speak at the next LIA meeting.
The next LIA meeting is 10 a.m. Aug. 1 at the Loyal Order of the Moose Lodge in Celina.