CLEVELAND, Ohio—As the summer winds down, much of western Lake Erie stinks. Green goo—miles and miles of it—floats on the surface, emanating a smell like rotting fish as it decays. 

The scum isn’t just unpleasant. It’s dangerous.

Harmful algal blooms are a health hazard in all 50 states. But Lake Erie, the shallowest, and therefore the warmest, of the five Great Lakes, is uniquely vulnerable to algal blooms. Like most other water bodies suffering from blooms, the lake is overloaded with nutrients, forming the perfect breeding ground for a bacteria known to poison pets, contaminate drinking water and create oxygen-deprived “dead zones” that kill aquatic life.

The lake’s immediate future looks grim: the blooms are worsening with climate change, and pose a threat to tourism and recreation. But research into the lake’s gunky plight is flourishing, and the findings are relevant worldwide. The blue-green “algae” smothering Erie, Microcystis—which is not really algae but a kind of photosynthetic bacteria—abounds in lakes on every continent except Antarctica.

“Why is it such a good competitor? That’s what we’re hoping to learn,” said Tim Davis, an associate professor of biological sciences at Bowling Green State University who has studied harmful algal blooms around the world. 

Toxic cyanobacteria, colloquially dubbed “toxic algae,” burst into the spotlight in the United States in 2014, after a drinking water plant in Toledo, Ohio, found dangerous levels of toxins during a routine test, and the city declared the tap water undrinkable. Hundreds of thousands of people were left scrambling to find safe water until Toledo lifted the ban more than two days later.

Once the emergency passed, the question on everyone’s minds was, “What do we need to do to make sure we’re safe?” said Pete Bucher, who began working as a legislative aide for the state assembly district representing southern Toledo a month after the city’s water crisis. Bucher is now the managing director of water policy at the Ohio Environmental Council.

At the time, testing for cyanotoxins, including the toxin produced by Microcystis, was not required by the Environmental Protection Agency (EPA). That changed after Toledo.

The EPA introduced mandatory national monitoring for cyanotoxins in 2016 with the Unregulated Contaminant Monitoring Rule. The rule took effect in 2018, and is set to end this year. Drinking water facilities in affected parts of Lake Erie have also introduced costly but effective treatments, including oxidation, filtration using activated charcoal and the physical removal or filtration of toxin-laden Microcystis cells, that can be implemented as soon as toxins are detected.

If the safeguards in place today—more frequent satellite monitoring with higher resolution images; instruments that detect blooms at drinking water intakes; and better modeling of the blooms themselves—had existed during Toledo’s 2014 bloom, the presence of the toxin would not have been a surprise, and “they would have been able to address it,” said Rick Stumpf, an oceanographer at the National Oceanic and Atmospheric Administration (NOAA). “It would not happen again.”

Stumpf is part of a team of NOAA researchers that began using satellites to estimate bloom size in Lake Erie in 2009. After the Toledo water crisis, NOAA switched from publishing weekly bulletins on Erie’s bloom using satellite imagery to releasing near-daily updates.

A Perfect Disaster

Lake Erie’s biggest tributary, the Maumee River, flows into Erie’s western basin, the shallowest part of the lake. More than 70 percent of the Maumee’s watershed is used for agriculture, and rainfall washes nitrogen and phosphorus—the two key nutrients for algae growth—from fertilizer used on farmland into the Maumee. The nutrients in that runoff are transported directly to the lake. 

Rainfall and nutrient levels are the two main factors that influence bloom size. The release of nitrogen and phosphorus from agriculture, the biggest source of nutrients entering Lake Erie, can be controlled. But heavier rainfall leads to increased nutrient loading from all sources, including natural ones, which is causing bigger blooms. Algae thrives in warmer water, and climate change is expected to bring warmer, wetter weather to the region, exacerbating existing factors.

“It’s like the worst case scenario,” said Laura Johnson, director of the National Center for Water Quality Research at Heidelberg University.

Researchers at Heidelberg have been studying nutrient loading in the Maumee River for decades. By comparing those records with NOAA’s algal bloom estimates, they linked phosphorus levels in the Maumee to bloom size in Lake Erie, and developed a seasonal bloom forecast for the lake.

The NOAA satellite monitoring program evolved into a project called the Cyanobacteria Assessment Network, or CyAN, named for cyanobacteria’s distinctive blue-green color and available as an app for Android. NOAA and other federal agencies now monitor for algal blooms in 2,000 U.S. lakes that could hold blooms big enough to be seen using satellite imagery, and they publicize bloom information from the lakes through the CyAN app. The agencies hope to support the development of local forecasting systems for the lakes they are currently monitoring, using the forecasting methods developed in Lake Erie.

But NOAA isn’t done with Lake Erie. Some Microcystis blooms are more toxic than others, and Stumpf sees Erie as the key to developing a toxicity forecast that doesn’t yet exist.

“We can’t do everything with satellites,” he said. “We can’t measure toxicity, because toxins aren’t pigments. They have no color.” 

At present, tracking toxicity requires regular water sampling, something researchers at Bowling Green do on a weekly basis. Their data helps explain how blooms change seasonally, but less is understood about how toxicity fluctuates each day. That’s where citizen scientists come in.

“We know that there’s a lot of dynamics that we’re missing on a day-to-day basis,” Davis, the Bowling Green professor, said. “So what we’re trying to do is, by incorporating citizen scientists, collect more data that will allow us to see some of these fine-scale trends in toxin concentrations, which will hopefully allow us to develop the toxin forecast model.”

Bowling Green partnered with several other universities and NOAA to recruit people who already work on the lake every day, like beach managers and charter boat captains. The researchers have received millions of dollars in state and federal grant money to support this and other algae research efforts. Standard toxin testing is complicated and takes hours to complete, but the citizen scientists will sample the water using newly-developed test cartridges that can measure toxicity in a fraction of the time.

Davis hopes that the simplified means of data collection will expand monitoring capabilities without overwhelming the citizen scientists. He plans to compare findings from Lake Erie to Microcystis found in Africa’s Lake Victoria and other lakes around the world, through a National Science Foundation-funded project that aims to unlock the mystery of the organism’s global dominance.

Despite Lake Erie’s size—it spans nearly 10,000 square miles, four states and two countries—the Great Lakes Water Quality Agreement, signed by the United States and Canada in 1972 and updated in 2012, facilitates consistent monitoring across borders. 

The agreement has been effective, Davis said. Though every lake is different, he said, “a lot of people do look to what’s going on in Lake Erie and the research coming out of the Lake Erie area in order to help guide them.”

Blooming Through Time

Exposure to cyanotoxins can cause anything from sore throats, headaches and exhaustion to severe symptoms such as vomiting, pneumonia and liver damage, according to the Center for Disease Control and Prevention. Though it was previously thought that exposure could only occur through waterborne contact, recent findings indicate that airborne cyanotoxins may be able to travel more than a mile inland.

“When you go to the beach and you’re sitting or recreating in a lake that has these algae toxins, you can come home with those kinds of symptoms that just last for a day or two,” said Anne Weir Schechinger, senior analyst in economics at the Environmental Working Group. “There’s also been some more research lately showing these longer-term impacts, like liver failure, and even some cancers that are starting to be associated with these toxins. But I would still say that health research is still early.”

Even if scum is present on a lake’s surface, it could be non-toxic. But the reverse can also be true. While avoiding potentially toxic scum altogether is the safest move, Schechinger cautioned against assuming that it’s safe to swim in rivers, lakes or ponds that appear algae-free.

“You don’t necessarily see a scummy bloom. That doesn’t mean there’s not (toxin) in the water,” she said.

A map of toxin advisories is available for Ohio’s public beaches through the state Department of Health. Many other states provide similar resources. Schechinger recommends an online search for nearby algae toxin advisories and, if nothing comes up, a call to the state agency that monitors blooms. 

Most research on Microcystis and cyanotoxins has emerged during the last decade. The relationship between nitrogen and toxicity is relatively well understood, although the field continues to develop.

The Microcystis dominating Lake Erie can only grow in size and toxicity until the bloom has used up all the available nitrogen or phosphorus in the lake. Early research identified phosphorus as the primary limiting nutrient, leading environmental regulations aimed at reducing algae to target only phosphorus.

Microcystis needs both phosphorus and nitrogen to grow, but it needs nitrogen directly to produce its toxin. So reducing phosphorus, but not nitrogen, would promote a bloom that is physically smaller but likely no less toxic. Reducing nitrogen, but not phosphorus, would promote a bloom that is just as large but composed of a different kind of algae that captures nitrogen from the air, which could be just as toxic.

“We need to focus on both, because really we’re looking at a holistic approach,” Davis said. “We want to reduce phosphorus and we want to reduce nitrogen so we have a healthy lake, because a healthy lake has a healthy balance of both nutrients.”

Though the EPA now recommends reducing nitrogen alongside phosphorus, states’ algae mitigation efforts have been slow to follow. In 2015, Michigan, Ohio and the Canadian province of Ontario signed the Western Basin of Lake Erie Collaborative Agreement, which requires a 40-percent reduction in the phosphorus—mostly from agricultural runoff—entering the lake by 2025. H2Ohio, which received funding as part of the Ohio budget last November, also focuses on limiting phosphorus runoff from agriculture to mitigate algal blooms.

Ohio has not achieved its preliminary goal of a 20 percent phosphorus reduction by 2020. When it comes to meeting the 40 percent target by 2025, said Bucher, from the Ohio Environmental Council, “I think we can get there. I think it’s just going to take a double-down on effort.” Having consistent funding will also be paramount, he said.

Most experts say reducing the quantity of nutrients released by farms is the only way to stop the blooms in a lake as large as Erie. Huichun “Judy” Zhang, a professor of civil and environmental engineering at Case Western Reserve University, wants to prevent phosphorus that has already been released by farms from making it to the lake. 

She is developing a phosphorus-capturing system to mitigate agricultural runoff, using filters packed with tiny structures, each the size of a sesame seed, that can absorb phosphorus from the water that passes through. She has received $200,000 in grant money to support this work.

Zhang and her research partner, Chad Penn, a soil scientist working for the U.S. Department of Agriculture, anticipate installing a pilot project demonstrating their technology in the near future. They plan to site the filters in places where runoff gathers naturally, such as drainage ditches.

“In the short term, to be able to cut down phosphorus release into the lake, this, we hope, is going to make a huge impact,” Zhang said. She expects the filters to serve as a temporary solution until the phosphorus released by agriculture can be significantly reduced.

An Israeli company, BlueGreen Water Technologies, has a different approach. Two years ago, it launched a form of algaecide that targets cyanobacteria, triggering a mass die-off of the toxic algae while allowing non-toxic forms of algae—and other aquatic organisms—to survive. The treatment has seen success in Israel, South Africa and China, as well as in Ohio’s Chippewa Lake, which had been plagued by toxic blooms for years. A year after BlueGreen applied its “LakeGuard” treatment, which took one day and cost about $20,000, Chippewa Lake remains algae-free.

Chief Technology Officer Moshe Harel is pleasantly surprised that algae has not returned to Chippewa Lake. “We write the book as we speak,” he said.

Algal blooms in ponds or small lakes are relatively easy to remedy. But treating larger lakes is challenging. Lake Erie is thousands of times larger than the biggest lake BlueGreen has treated, but unlike just about everybody else, the company isn’t put off by the scale. 

Harel, an environmental biologist and the creator of the LakeGuard treatment, which is USDA-approved and certified by the Ohio EPA, believes the treatment’s ability to float and follow water currents will translate effectively to any lake, no matter the scale. At some point, but not quite yet, he wants to take on Lake Erie.

“We are not aiming to treat the whole lake,” Harel said. “We do surgical treatments. So, for a lake such as Lake Erie, our aim will be to monitor where the bloom starts at the beginning of the season.” 

In the meantime, Harel’s sights are set on other big lakes, like Lake Okeechobee in Florida, the eighth-largest lake in the country, which is still 13 times smaller than Lake Erie.

“All these lakes are untreatable, left to bloom and for the blooms to get worse from year to year,” said Chief Executive Officer Eyal Harel, Moshe Harel’s brother, of the lakes BlueGreen has already treated. “I think we will treat Lake Erie. It’s just a question of time.”