Foul-Water Season: Summer Algal Blooms

Increasing in size and severity, harmful algal blooms threaten both wildlife and people

  • Laura Tangley
  • Conservation
  • Jul 01, 2015
FRANK SZOLLOSI WAS ASLEEP in his Toledo, Ohio, home one Saturday morning last summer when a neighbor pounded on his front door. “Don’t drink the water!” the man shouted. “Don’t let your kids drink the water!”

Five hours earlier, at 2:00 a.m. on August 2, 2014, Toledo officials had warned residents not to drink from their taps after scientists detected high levels of microcystin—a potent liver toxin produced by algal blooms—at the city’s water-treatment plant on Lake Erie. For the next three days, nearly half a million residents were unable to consume tap water or even use it to cook, brush their teeth or bathe.

“We’d been warning all summer that something like this could happen,” says Szollosi, manager of regional outreach campaigns for the National Wildlife Federation. After ensuring his wife and children had enough bottled water, Szollosi joined NWF President Collin O'Mara to deliver cases of water and see the bloom up close. Two miles offshore, the thick green slime surrounding the city’s water intake was “astonishing—the most dense I’d ever seen,” O’Mara recalls. Sadly, it was just the latest in a series of harmful algal blooms that have been hitting western Lake Erie nearly every summer.

Green Monster Rerun

Four decades ago, when it was dubbed “North America’s Dead Sea,” Lake Erie was plagued by similar blooms, along with periodic fires on a tributary, the Cuyahoga River. Public outrage over these incidents helped spawn the nation’s environmental movement, in particular the U.S. Clean Water Act, which, along with billions in U.S. and Canadian investment, brought the waterway back to life. But since the late 1990s, Lake Erie has seen a resurgence in blooms of toxin-producing algae and other organisms. (Microcystis, the culprit behind last summer’s bloom, is actually a genus of chlorophyll-producing cyanobacteria commonly called blue-green algae.)

The lake is vulnerable in part because it is the shallowest of the Great Lakes, “particularly in the western basin where blooms occur,” says Jeff Reutter, special advisor to the Ohio Sea Grant College Program at Ohio State University and an expert on Lake Erie. Shallow water means warmer water, which fosters algal growth during late summer. In addition, the lake is naturally nutrient rich and productive, Reutter says, “often yielding more fish annually than the other four Great Lakes combined.”

But “it’s possible to have too much of a good thing,” Reutter adds—specifically nutrients such as phosphorus that fuel algal blooms. Phosphorus-rich manure and chemical fertilizers applied to more than 4 million acres of farmland—primarily planted with corn and soybeans—drain into the Maumee River Watershed and eventually empty into Lake Erie. Heavy spring rains worsen nutrient runoff, as do contributions from poorly treated wastewater as well as millions of suburban lawns, golf courses and other businesses that use fertilizers. The result: Algae can explode, leading to depleted oxygen and tainted water for humans and wildlife. 

Global Reach

Lake Erie may be particularly vulnerable, but algal blooms are a global problem. From California to Florida to Africa and Asia, “we have evidence that harmful algal blooms are increasing in frequency, duration and potential toxicity worldwide,” says Timothy Davis, research scientist for the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory. (A large algal bloom, left, stained the Gulf of Mexico green in 2007.) Culprits range from microscopic plankton like Microcystis to large seaweeds. While only a small percentage of these organisms produce known toxins, even innocuous species can wreak havoc when they reproduce on a huge scale, altering food webs and smothering habitat.

Because no international body tracks algal outbreaks, the full extent of the problem remains unknown. Even in the United States, the government does not monitor algae-related beach closures or health warnings, and only some states do so. To draw attention to the issue, NWF and Resource Media in 2013 produced a report, Toxic Algae: Coming to a Lake Near You?, providing the first nationwide map of health advisories issued in response to blooms the previous summer. Though more than 20 states reported beach closures or other warnings, harmful algal blooms “are still treated as a sporadic local concern, not a national water-quality problem,” note the authors.

Like last summer’s crisis in Ohio, all harmful algal blooms are driven by excess nutrients. Worsening the problem has been massive loss of forests, wetlands and other ecosystems that once filtered and slowed phosphorus and nitrogen runoff. In the United States, a boost in corn cultivation during the past decade—driven largely by federal mandates to produce more ethanol for fuel—also plays a role; more nutrients typically wash off corn fields than off other crops.

Climate change is exacerbating the blooms as well. Not only is water heating up and becoming more hospitable to algae, but heavy rains that flush nutrients into waterways are now more frequent and intense. According to a 2013 NWF report, Taken by Storm, the number of days with heavy precipitation in the Great Lakes region has increased 37 percent in the past five decades. The wettest spring on record, in 2011, triggered Lake Erie’s largest Microcystis bloom, which stretched along more than 100 miles of shoreline from Toledo to beyond Cleveland.

Wildlife Victims

While officials emphasize algal-bloom impacts on human health and the economy, the outbreaks also threaten wildlife, though these effects are not well known. “We need more research into the ecological impact of harmful algal blooms,” says NWF Staff Scientist Michael Murray. Some of the best-documented consequences are indirect: When algae die they sink to the bottom, where decomposition by bacteria sucks oxygen out of the water and creates what are known as dead zones. Animals that cannot swim away die, and even highly mobile fish may suffer. Dead zones that form each summer in central Lake Erie, for example, are blamed for disruptions to the normal movements and reproduction of commercially valuable species such as walleye and yellow perch.

Some dead zones become truly massive—most famously those that form annually in the Chesapeake Bay and northern Gulf of Mexico. Fueled by nutrient pollution draining off the nation’s heartland via the Mississippi River, the gulf’s summertime dead zone can cover more than 8,000 square miles depending on spring rainfall and other variables.

Biologists have documented direct effects of blooms on a handful of species, primarily wildlife living in marine habitats. Last year in northern California, hundreds of seals and sea lions were admitted to rehabilitation facilities, many sickened by domoic acid, a toxin produced by a diatom bloom that had concentrated in fish and shellfish the mammals eat. Similarly, southern sea otters (above) in the state’s Monterey Bay have succumbed to domoic acid-contaminated prey. Five years ago, scientists linked the deaths of more than 20 otters to microcystin, the toxin that shut down Toledo’s water supply. Microcystin also has been implicated in the deaths of great blue herons in the Chesapeake Bay.

Among the most beloved wildlife casualties to date is the endangered Florida manatee (below). Four years ago, a “superbloom” of a brown-tide algae—the latest in a series of blooms plaguing the state for a decade—blocked so much sunlight to northern reaches of the Indian River Lagoon that 60 percent of the sea grass died. Manatees, which eat sea grass, were forced to feed on a red seaweed, Gracilaria. “Ordinarily, Gracilaria does not produce toxins,” says Brian Lapointe, a research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute. But his lab discovered that the lagoon’s disturbed ecosystem—specifically an altered nitrogen-phosphorus ratio—triggered the plant to make a potent toxin that sickened and killed more than 100 manatees. Analyzing nitrogen ratios also allowed Lapointe to trace the nutrient pollution to sewage, specifically hundreds of thousands of septic tanks that line this biologically rich waterway.


Tipping Point?

To put a stop to harmful algal blooms in Lake Erie, scientists agree that phosphorus runoff must be reduced by at least 40 percent. Reaching that goal will be more difficult than it was four decades ago, when new laws and treaties brought about a 60 percent decrease in the lake’s phosphorus input by limiting point-source pollution from facilities like wastewater-treatment plants. Today’s main cause—farm runoff—is a nonpoint source not covered under the Clean Water Act or other laws.

To decrease the runoff, NWF has been urging farmers to voluntarily adopt “best management practices” that include applying only the precise amount of fertilizer needed at the right time: just before crops are planted rather than months ahead as is common now. Farmers also are encouraged to work fertilizers into the soil, as opposed to spreading them at the surface, and to make use of funds available through the U.S. Farm Bill to restore wetlands and forests that slow runoff. In addition, "we promote planting cover crops,” says Mike Shriberg, NWF’s Great Lakes regional executive director. He says this once-common practice of cultivating fields after the main crop is harvested “benefits not only soil and water but also the farmer’s bottom line.”

Though many farmers have begun following best practices, “they are still more the exception than the rule,” Shriberg says. “We need better incentives as well as new laws.” This March, the Ohio Legislature did pass a law setting limits on the use of fertilizer and manure on frozen or saturated ground, situations where nutrients run off into waterways without being absorbed by soil. Conservationists welcomed the legislation but agree it is not enough.

Shriberg doubts that even this modest law would have passed without last summer’s Toledo water shutdown, which he sees as a tipping point he hopes will lead to more meaningful steps to curb nutrient runoff. “Sometimes it takes a crisis to sharpen the attention and focus of decision makers,” Shriberg says.

Meanwhile, Szollosi and other Toledo residents warily await 2015’s foul-water season. Its severity depends on spring and early summer rainfall. “A wet spring means bigger algal blooms,” Reutter says. “Whenever it rains, I get pretty nervous.”


NWF Priority: Curbing Nutrient Pollution

For decades, NWF and its affiliates have been trying to raise awareness about harmful algal blooms and reduce the excess nutrients that trigger them, working at the national, regional and state level as well as with farmers to improve nutrient management in their fields. National efforts include supporting U.S. Farm Bill provisions that promote restoring nutrient-filtering wetlands and other habitats and, more recently, encouraging farmers who produce biofuels like ethanol to shift away from fertilizer-intensive corn to less-polluting sources such as grasses. “Expanding conservation practices and encouraging greater crop diversity—including growing less food for fuel—are essential to restoring America’s waterways,” says NWF President Collin O’Mara. To learn more, visit

Update: Victory for Lake Erie

As this issue went to press in June, the governors of Ohio and Michigan and the premier of Ontario, Canada, announced at the Council of Great Lakes Governors meeting in Quebec City that they would, within the next 10 years, cut the amount of phosphorus flowing into Lake Erie from their states and province by 40 percent—the percent reduction scientists agree is needed to curb harmful algal blooms in the lake. “This is a huge victory in our quest to clean up Lake Erie—and to restore healthy fish and wildlife populations,” said NWF President Collin O’Mara. “Our team has helped lead the effort in pushing for the 40 percent reduction for many years and really stepped up our advocacy since last August’s algal bloom poisoned drinking water for nearly half a million people in and around Toledo.”

The next challenge will be to fulfill the commitment. Officials from the two states and Canada are scheduled to develop plans soon on how to reach the 40 percent cut. (Indiana—which also produces runoff that empties into the watershed flowing into western Lake Erie—did not join the agreement, citing lack of baseline data in the state.) Meanwhile, they hope to reduce their runoff by 20 percent within five years. The full 40 percent cut would be “a game changer, an ambitious collective goal that—if met—could significantly reduce harmful algal blooms and the economic, social and environmental havoc they wreak,” says Mike Shriberg, NWF’s Great Lakes regional executive director.

Laura Tangley is senior editor of National Wildlife magazine.

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