The crisis may have eased in Toledo, but the toxic algae in Lake Erie that contaminated the water supply for 500,000 people in Ohio continues to plague lakes and rivers across the country, including here in Maryland.
Lake Williston, a swimming hole for a Girl Scout camp in Caroline County, is off limits this summer because of dangerous levels of a toxin in its water. So is 75-acre Lake Needwood in Rock Creek Regional Park in Montgomery County. Same for Northwest Creek, a 100-acre impoundment on Kent Island in Queen Anne's County.
They're all suffering from microcystis, the same toxin-producing blue-green algae that got into the Toledo area's water system last weekend and prompted warnings to residents not to drink from their taps for two days.
Harmful algal blooms are a major problem in all 50 states, according to the Environmental Protection Agency. Variously known as red tides, blue-green algae or cyanobacteria, they can have severe impacts on human health, aquatic ecosystems and the economy.
Lake Erie and many other fresh-water bodies suffering from blue-green algae have something in common with the ailing Chesapeake Bay. All are polluted by runoff of farm and lawn fertilizer, inadequately treated sewage and other nutrient-rich wastes. The influx of nutrients spurs algae growth, which in the bay's case leads to formation of a vast "dead zone" incapable of sustaining oysters, fish or crabs. Some of the algae, though, can cause direct harm by releasing toxins.
Microcystis, commonly known as blue-green algae. is actually a type of bacteria that relies on sunlight to grow, as plants do. It grows in fresh water, feeding on nutrients, and releases toxins that can damage the liver and nervous systems of animals, and unwary people.
Microcystis blooms like the one that contaminated Toledo's water have occurred in the fresh-water portions of several rivers in the Chesapeake region, including the Potomac, Sassafras and Transquaking. The blooms tend to pose greater problems in ponds, lakes and reservoirs, where their toxins can become more concentrated.
Unlike Toledo, the Baltimore region's drinking water does not appear to be in jeopardy -- for now. Officials with the city's Department of Public Works say they check twice a week and haven't seen blue-green algae in any of the three reservoirs -- Loch Raven, Liberty and Prettyboy -- that furnish water to 1.8 million residents of the city and surrounding counties.
"To the best of my knowledge, we haven't had that issue," said James Price, chief of environmental services for the city public works agency. The only algae of note have been diatoms, he said, which are not toxic, though they can clog filters at the water treatment plants.
Charles Poukish, with the Maryland Department of the Environment, said blue-green algae have been detected in the region's reservoirs, just not at levels of concern. Indeed, according to reports by the city, the Baltimore Metropolitan Council and the U.S. Geological Survey, blue-green algae blooms have appeared regularly in one or more reservoirs every summer, as recently as 2007. While those apparently were not of the type or intensity to cause problems for the region's drinking water, a month-long bloom in Loch Raven in 1981 did trigger widespread complaints from residents about the odor and taste of their tapwater, the reports noted.
All three of the reservoirs are impaired by nutrient pollution, though, making them potentially vulnerable to algae blooms, including harmful ones. City officials are working with their counterparts in Baltimore County to reduce nutrient runoff from suburban development and farms that could drain into the reservoirs, said Kimberly Grove, chief of environmental compliance for the city.
City officials note that the normal water treatment process removes nearly all algae, and if necessary to avoid problematic blooms, they can pull raw water from below the reservoirs' surface with submerged intake pipes.
But experts warn that as long as nutrient pollution remains widespread, harmful algae blooms will be a problem, and drinking water contamination is not out of the question.
"The trajectory is, it's probably going to happen here," said Allen Place, a biochemist with the University of Maryland Center for Environmental Science who's specialized in harmful algae. "It is a national problem."
Place, a professor at the Institute of Marine and Environmental Technology at the Columbus Center, has been studying the state's microcystis-infested lakes. While short-term remedies have been found, he said, the only long-term solution is to reduce the flow of nutrients from the land into the water.
Case in point, he said, is Lake Williston near Denton. The 64-acre impoundment at the Girl Scouts' Camp Todd was closed a few years ago to swimming and kayaking after dangerous levels of toxin from blue-green algae were measured in the water. In an attempt to clean out the lake, it was drained, and barley straw laid on the bottom -- an unconventional remedy that had seemed effective in preventing algae growth in other cases.
Regular draining and barley straw applications worked for a couple years, allowing the Scouts to resume swimming at the lake, Place said. But this year microcystis returned "with a vengeance," he said, contaminating the lake with toxin 100 times the level that prompted do-not-drink warnings in Toledo.
Bob Foote, manager for Camp Todd, said he believes the problem this year stemmed from delays in refilling the lake, which likely prevented the barley treatment from working. He said he's hopeful to get the lake back next year with a better-timed treatment.
Meanwhile, he said, "the week before last I had 150 girls here, and they're looking at the lake but can't get on it." Camp officials had to haul the camp's kayaks to Martinak State Park nearby, he said, so the girls could paddle on the Choptank River.
While regular treatments may help, Place cautioned that unless the flow of nutrients into Lake Williston is reduced, there will always be a threat blue-green algae could come back.
It's the same challenge confronting Maryland and other states attempting to restore the Chesapeake's water quality, Place said. Only in lakes and reservoirs, he noted, the algae blooms triggered by nutrient pollution can pose additional threats to pets and people.
"I don't want to be Chicken Little ... but we really do have to do something about this," he said, "because it's not just going into the bay."