ST. MARYS — Signs are going up at every beach at Grand Lake St. Marys to warn visitors that toxic blue-green algae has made the water unsafe for swimming.
State officials have been testing sites near beaches there this week after measurements of a liver toxin associated with the algae began to spike last month near where the city of Celina draws water into its treatment plant. By the end of April, readings of microcystin measured higher than 25 parts per billion, more than four times the state’s safety threshold of 6 parts per billion.
Matt Eiselstein, a spokesman for the Ohio Department of Natural Resources, said that, while exact measurements are still being calculated, the readings at the 13,000-acre lake in western Ohio are “definitely over the safety level.”
Blue-green algae, also called cyanobacteria, are common in most Ohio lakes. They grow thick by feeding on phosphorus from manure, fertilizers and sewage that rain washes from farm fields into nearby streams.
As many as 19 public lakes, including Erie and Buckeye in central Ohio, have been tainted in recent years by toxic algae.
Algae grew so thick in Grand Lake in 2010 that the state warned people not to touch the water. Officials say it likely caused seven people to get sick that year.
The Ohio Department of Natural Resources typically does not test for toxins unless someone reports a suspicious-looking bloom.
Microcystin in Grand Lake St. Marys reached its highest measured levels in October, at 100 parts per billion.
“Grand Lake St. Marys is probably the worst-case scenario,” said Jeff Reutter, director of the Ohio Sea Grant College Program and an expert on blue-green algae. “It’s a more-difficult situation than we have at Lake Erie.”
The phosphorus runoff from area farms is such a summertime problem at Grand Lake that nearby farmers now face state-mandated limits on the manure they spread on fields.
“We were finding that about 50 percent of the fields were oversaturated with phosphorus — they didn’t even need to be using it,” Eiselstein said.
This spring’s heavy rainfall isn’t helping, Reutter said.
The city of Celina spends about $450,000 a year to control algae at Grand Lake, and the state has spent more than $10 million trying to treat it.
Toxic algae outbreaks are a problem nationwide. Blooms are standard in 38 states that responded to a survey this year by Resource Media and the National Wildlife Federation. The majority of reporting states called the issue “serious.”
Ohio did not respond to the survey.
Kate Anderson, president of Guardians of the Grand Lake St. Marys, said the state needs to do more.
“The treatment obviously isn’t working,” she said. “We need to stop the phosphorus from coming into the lake.”
But the Ohio Environmental Protection Agency says that could take years.
“It didn’t get into this condition overnight,” said spokeswoman Dina Pierce. “It’s going to take long-term work to help it recover.”