NOAA photograph of blue green algae floating on water next to a dock.
NOAA photograph of blue green algae floating on water next to a dock.

By Catherine Clabby

Harmful algal blooms, particularly the periodic explosive growth of cyanobacteria species, appear to be increasing in frequency and severity globally, researchers from the EPA and the Centers for Disease Control and Prevention say.

While most algae pose no risk, harmful algal blooms, whether green or reddish masses floating on the surface of water, can produce toxins that even in tiny amounts can harm people.

Young children are likely at greatest risk.

Swallowing or swimming in water during a dangerous bloom can produce skin rashes, liver injury and neurological changes. Toxic algae metabolites can also harm or kill pets and livestock.

The North Carolina Department of Environmental Quality confirmed the presence of potentially harmful cyanobacteria algae 19 times across North Carolina during the summer of 2016 alone.

How many potentially harmful blooms occurred in North Carolina in 2016 is unknown. State officials did detect cyanobacteria toxins called microcystin at five locations: Pamlico Sound, Albemarle Sound, a Brunswick County storm water pond, a Davie County pond and Greenfield Lake in New Hanover County, said Cobey Culton, a state Department of Health and Human Services spokesman.

The same uncertainty exists nationally. Blooms occur unpredictably and are not always documented, never mind assessed for their full chemical content.

“We need more data to inform prevention and mitigation of harmful-bloom health effects,” said Lorri Backer, a senior CDC environmental epidemiologist who spoke this week at a meeting of the North Carolina One Health Collaborative at Research Triangle Park.

a series of four photos, two showing green slime floating on waterways, the other two are microscopic views of algae organisms
A DEQ analysis of algae blooming in the Tuckasegee River where it reaches Lake Fontana last June tentatively identified the mass as a bloom of a Dolichospermum species, which may be capable of making toxins. Photos courtesy: NC Dept. of Environmental Quality

To achieve more clarity on this risk nationally, the CDC has launched a surveillance program, One Health Harmful Algal Bloom System. Public health programs in states, including North Carolina, report human and animal illness linked to algae exposure, as well as environmental conditions where the blooms occur.

The goal is to expand understanding and prevention of harmful blooms and illnesses associated with them.

Why now?

Scientists link evidence of increased incidences of toxic algal blooms to climate change. Because algae have been around for millions of years, they have adapted to live pretty much anywhere on this planet.

But they often thrive in warmer waters and as Earth’s surface temperatures rise, so does that water.

Thick green sludge floats on top of a waterway up until a bulkhead.
DEQ’s water sciences lab identified algae blooming in Edenton Bay off the Chown River last July as Dolichospermum planctonicum, a filamentous blue green algae that is capable of producing cyanotoxins. Source: NC DEQ

It doesn’t help that human activities feed algae. Nitrogen and phosphorous that wash into our waterways from lawn and crop fertilizers, livestock animal manure, and underperforming sewage treatment plants are nutrients that feed algae.

North Carolina is no stranger to these blooms. They appear here mostly in freshwater ponds and sometimes quite dramatically in rivers, including the Chowan River last summer, said Mark Vander Borgh, a DEQ senior environmental biologist.

Sometimes they surge in estuaries as well, he said.

But they occur unpredictably, which can make them hard to catch, never mind quantify. Even as DEQ receives more complaints than ever, agency staff can’t say conclusively that more are occurring, Vander Borgh said.

“We don’t have the data to say if they are more common,” he said.

Mina Shehee, of the North Carolina Division of Public Health, said after Backer’s talk she wonders if small farmers raising livestock are losing more animals than they realize to toxins produced by algal blooms.

She’s heard reports of animals dying for unknown reasons, she said, and wonders if ponds with algae might sometimes be to blame.

“We don’t know the extent of it. They are out there but we’re not capturing it,” said Shehee, who works in the Occupational and Environmental Epidemiology Branch the Division.

Microscopic photograph of chains of small organisms
When nutrients are plentiful and other conditions are right, microscopic algae, including Dolichospermum species, reproduce so profusely that they produce blooms that appear to coat ponds and other waters.

She and colleagues are considering partnering with North Carolina Cooperative Extension agents to collect more data on animal deaths coinciding with algal blooms to get a clearer picture, she said.

Linking human, animal and environment

Spreading the word on the rising risk from harmful algal blooms fits well with the goals of the One Health movement, which strives to increase awareness of ways that the health of people, animals and the environment overlap.

There is good evidence that pets have been sentinels to the presence of cyanotoxins.

While no human deaths have been linked to exposure to cyanobacteria in North Carolina, for instance, dogs have been made sick and may have perished from contact, according to state Department of Health and Human Services educational material on bloom threats.

“If water is stinky and green, people are not going to go into it. But a dog will,” Backer said.

Zach McKinney, a North Carolina State University graduate student in physiology attending the talk, said the general public is probably most in the dark about potential risks of harmful algae blooms.

While growing up in Pamlico County, he said, a member of the church his family attended had intense algae blooms strike ponds where he grew fish for profit. As the green slime spread, his fish were dying.

To help out, volunteers, including children, jumped into the water to scoop out the surviving fish to try to save them. That produced a lot of splashing and close contact with whatever the algae might have released into the air.

“No one considered the potential harm,” he said.

Editor’s note: Locations where state officials detected toxic microcystins in 2016 were added to this story on April 22.

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Catherine Clabby

Catherine Clabby (senior environmental reporter) is a writer and editor. A former senior editor at American Scientist magazine, Clabby won multiple awards reporting on science, medicine and higher education...