Climate change and poor land use have caused explosive growth of toxic algae around the world in recent years, putting more water-treatment plant operators on high alert and increasing anxiety of consumers.

Over the past two decades, the scourge has become so widespread, from the Arctic Circle to South America, that scientists were almost unfazed when they learned that trace amounts of the harmful algal toxin microcystin, the same one behind 2014’s Toledo water crisis, showed up for the first time a month ago on the west side of Columbus.

More cities and towns will be hit by outbreaks unless society fights harder to reverse the trend, scientists said.

“We are living in a time in which water quality is degrading worldwide rapidly,” said Tim Davis, a scientist at the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory who specializes in algae research.

In the Great Lakes region, one of the most freshwater-abundant places on Earth, water-treatment plant operators have for years battled algal outbreaks in western Lake Erie, the Maumee River, Lake Erie’s Sandusky Bay, and Grand Lake St. Marys in Ohio, as well as other hot spots across the region, such as Michigan’s Saginaw Bay and Wisconsin’s Green Bay.

This year, microcystis, the dominant form of toxin-producing algae in western Lake Erie and one of four chiefly responsible for producing microcystin, formed in the Scioto River in central Ohio.

For the first time, microcystin slipped into the Dublin Road water treatment plant that serves the west side of Columbus and several of the capital city’s nearby suburbs.

The untreated water had a concentration of 1.0 part per billion of microcystin on Aug. 28 and 0.97 ppb on Aug. 31.

That outbreak was mostly anecdotal: At levels that low, water-treatment plant operators can easily remove the toxin before it gets into the public drinking water system, Heidi Griesmer, Ohio Environmental Protection Agency spokesman, said.

The toxin’s presence was another sign of toxic algae’s continued expansion, though.

While much of North America has been on alert since last year’s Toledo water crisis, when nearly 500,000 metro area water customers were told to stay away from their tap water for three days after it was temporarily fouled by microcystin, Ohio EPA records show the threat has actually been much greater along the Ohio River, which rarely gets large algal blooms because of its depth and strong current.

In western Lake Erie, the concentration has hovered between 1.0 ppb and 3.0 ppb near the Toledo water-intake crib most of this summer, peaking at 4.9 ppb on Aug. 12.

NASA satellite images published in NOAA’s latest Harmful Algal Bloom bulletin, released Thursday, showed an intense hotspot of algae in a small area near the mouth of the Maumee River, with a large pocket of water that is largely clear or spotty for a few miles before thickening up just past Oregon. It is currently strongest in the Port Clinton-Sandusky area and up to the Canadian side of the lake just east of Pelee Island. Patches in the colder, deeper central basin have continued to break down, although there remains some algae in the Cleveland area — an area that hasn’t had much outside of the 2011 record bloom.

Algae season typically extends through late October.

NOAA said the toxicity remains relatively low in western Lake Erie “except in scums, where a significant risk continues to exist.” Concentrations are most prone to rise in calm water.

In general, though, western Lake Erie’s bloom hasn’t been that toxic this summer, especially given it is on pace to become the second-largest bloom on record.

Scientists have noted, though, that the size of a bloom doesn’t necessarily correlate with its toxicity.

The same can’t be said for the Ohio River and Grand Lake St. Marys.

Figures pulled from the agency’s online database show several instances in which microcystin levels spiked at 100 parts per billion or more. One reading on Aug. 27 recorded the Ohio River’s concentration near the Ohio shoreline at 630 ppb.

Readings in excess of 100 ppb, which can test the limits of modern technology and make water-treatment operators uncomfortable, also have been found in Grand Lake St. Marys.

The Ohio River Valley Sanitation Commission, which serves Ohio, Pennsylvania, Kentucky, West Virginia, Virginia, Indiana, New York, and Illinois, states on its website that it began coordinating an algae monitoring pilot program in 1999 “to address concerns with increased algal blooms and taste and odor problems with Ohio River drinking water.”

But this summer’s Ohio River outbreak was the first significant one since 2008, when Cincinnati dealt with harmful algal blooms near its water intake, Ms. Griesmer said.

“This is the largest bloom we’ve seen in the Ohio River,” she said.

No drinking water advisories have been issued, but water-treatment operators have been put to the test.

In a Sept. 4 news release, the Ohio EPA warned boaters to stay away from water on the river that looked “like spilled paint” or had “green globs floating below the surface.” Consumers also were warned to keep their pets away from the river water, and to remove the guts and liver of any fish they caught and planned to eat, as well as to wash the fillets in tap water, and to wash their hands if they came in contact with river water or shoreline debris.

“It’s not a continuous bloom. It’s intermittent. It tends to stay along the shoreline,” Ms. Griesmer said.

Other parts of Ohio with unexpected algal blooms this summer included the Lake Erie shoreline in Lake County. Blooms normally don’t migrate that far east.

The rise of toxin-producing algae on a global scale began about the same time one of the most notorious types of it, microcystis, came on strong in western Lake Erie back in 1995. Western Lake Erie had been plagued by various forms of algae for decades, but past blooms were not predominantly microcystis.

Then, after little or no algae since the mid-70s, microcystis came on strong. It has since been the dominant form of algae in western Lake Erie and in many other parts of the world.

Freshwater lakes and reservoirs in the Netherlands, northern Germany, even Nordic countries such as Sweden and Finland, now have toxic algae. Algae’s strong in the Baltic Sea. It’s strong in Brazil. It’s strong in New Zealand. It’s strong in Africa’s Lake Victoria. It’s strong in Canada’s Lake Winnipeg.

It’s strong in Florida’s Lake Okeechobee. It’s strong in Australia’s River Murray, the Pacific Northwest’s Klamath Lake, San Francisco Bay, and many other bays, lakes, and reservoirs around the world. Not all of the algae in those bodies of water is microcystis, but much of it is.

Believed to be some 3.5 billion years old, microcystis is now, for reasons scientists don’t fully understand, one of the fastest-growing organisms on Earth in addition to being one of the oldest.

China’s third largest lake, Lake Taihu, which is a source of drinking water for 10 million people, has especially bad blooms, some lasting nine months of the year. In May of 2007, in China’s Jiangsu province near the city of Wuxi, a massive bloom of toxin-producing microcystis did almost the same thing that happened in western Lake Erie near Toledo seven years later: Algae there made water unsafe for 2 million people for more than a week.

“Human activity’s a major driver,” said George Bullerjahn, a Bowling Green State University biology professor. “The demand for inexpensive food is really important. That’s resulted in a mobilization of nutrients into the land that haven’t been there before, at least not to the scale they are now.”

Mike McKay, another BGSU biology professor who studies algae on a global scale, agreed.

“One commonality with all of these events is they are occurring in large lakes with major agriculture,” Mr. McKay said.

According to the Woods Hole Oceanographic Institution in Woods Hole, Mass., the general problem of harmful algal blooms “has changed considerably over the last several decades in both marine and freshwaters.”

“Whereas 30 years ago the problem was scattered and sporadic, today virtually every state is threatened by harmful or toxic algal species,” according to the Woods Hole website. “Few would disagree that the number of harmful blooms, the economic losses from them, the types of resources affected, and the number of toxins and toxic species have all increased dramatically in recent years in the U.S. and around the world.”

The type of harmful algal bloom can vary from region to region, based on geography, water salinity, climate, nutrients, and other factors.

Hans Paerl, a distinguished professor at the University of North Carolina-Chapel Hill, has had more than a dozen monthlong expeditions in China to study its algae problems. He also has traveled to other parts of the world studying algae.

“We’re just leaving a bigger footprint. That leaves organisms like microcystis to take advantage of it,” Mr. Paerl said. “It’s certainly been one genus that’s been extremely successful at exploiting human activity.”

Why now?

The changes in climatic patterns, such as monsoonlike rain followed by drought, is a perfect one-two punch, researchers said, with a seemingly endless supply helping algae grow like mad.

And it’s not all farm runoff: About 30 percent of the nitrogen in China and along America’s East Coast is believed to come from air pollution that fell out of the sky. Phosphorus determines the size of a bloom, but nitrogen greatly influences its toxicity. Much of that nitrogen comes from coal-fired power plants and automobile exhaust.

“The only real knobs we have to tweak are the nutrient knobs,” Mr. Paerl said. “The bottom line is we’ve got to pay attention to both nutrients.”

The International Oceanic Commission, a United Nations commission created 55 years ago, plans to release a “Global HAB [Harmful Algal Bloom] Status Report” in late 2016. Linkages are expected to be made between the global rise in toxic algae and the latest climate research by the Nobel-winning Intergovernmental Panel on Climate Change.

HABs are “basically everywhere and everyone’s clamoring for solutions,” Mr. Paerl said.

Microcystis and several other harmful algae types, including anabaena and planktothrix, which also are in western Lake Erie, have a resiliency tougher than what meets the eye because of their longevity on Earth, he said.

“They’ve been through it all,” Mr. Paerl said. “They’ve experienced warming, cooling, ice ages, and periods when it was very dry. Their playbook is very rich.”

He said people should realize ancient organisms “are not necessarily organisms that are out of tune with modern times.”

“Dinosaurs are, but not algae,” Mr. Paerl said. “They’ve learned the trick of survival.”

Contact Tom Henry at: thenry@theblade.com, 419-724-6079, or via Twitter @ecowriterohio.

First Published September 27, 2015, 4:00 a.m.