Algae toxin study: St. Lucie River, Indian River Lagoon fish safe to eat 'occasionally'

Fish in the St. Lucie River and Indian River Lagoon in Martin County contain the blue-green algae toxin microcystin, but in levels low enough they're safe to eat — occasionally and in moderate amounts.

That's the bottom line of a study by the Ocean Research & Conservation Association in Fort Pierce, which measured the toxin in 51 fish caught in the river and lagoon.

Long-term exposure to microcystin has been linked to liver disease; and ORCA researchers wanted to see how much of the toxin people would get by eating locally caught fish.

Examining fish

In the study funded by the Guardians of Martin County, ORCA researchers examined fish caught in the river and lagoon in Martin County from May 1 to Aug. 24.

More: Do St. Lucie River, Indian River Lagoon fish contain blue-green algae toxins?

The fish — which included mullet, mangrove snapper, croaker, snook, bluefish, Jack Crevalle and catfish — were donated by anglers and caught by ORCA staffers.

"We had hoped for a bigger sampling," said Beth Falls, an ORCA researcher and leader of the study, "but the time period was during the Lake Okeechobee discharges, and not as many people were fishing in the river."

Here's what the researchers found:

In the fish fillets:

• 21: No microcystin
• 15: Microcystin levels too low to count
• 15: Microcystin levels ranging from 0.8 to 39 parts per billion and averaging 7.4 parts per billion

In the fish livers (where the toxin tends to concentrate):

• 3: No microcystin
• 10: Microcystin levels too low to count
• 37: Microcystin levels ranging from 0.6 to 149 parts per billion and averaging 17.2 parts per billion
• Note: One liver could not be measured

What do all the numbers mean to a fish fan?

An 8-ounce fish fillet with an average level of microcystin found by ORCA would contain 1,776 billionths of a gram of microcystin.

That's less than the 2,800 billionths of a gram "provisional tolerable daily intake" of microcystin for a person who weighs 155 pounds, according to the World Health Organization.

In moderation

"This tells us that, at average levels, eating fish from the river and the lagoon occasionally and in moderate amounts is not considered a risk to health," Falls said. "But not all fish have average levels; and we're talking about healthy people here, not people with health issues or the young or the elderly."

Plus, a study by Florida Atlantic University's Harbor Branch Oceanographic Institute at Fort Pierce shows people who live and work around water with blue-green algae blooms also take in toxins from the air.

More:People living, working along St. Lucie River breathing toxins, study shows

And researchers at Florida Gulf Coast University found blue-green algae toxins, both microcystin and BMAA — which some scientists believe can trigger neurological diseases such as Alzheimer's, Parkinson's and amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig's Disease — may be in the air all the time, even away from algae blooms.

More: Blue-green algae toxins may be in the air all the time, researchers say

The ORCA study didn't measure other toxins such as BMAA.

"I would not eat any fish caught in this area right now," Larry Brand, a marine biology and ecology professor at the University of Miami working on the link between toxic algae and serious neurological diseases, told TCPalm in July.

More: Are fish in Florida's polluted waters safe to eat?

"Our study doesn't raise any red flags," Falls said, "but we need to better understand what the overall exposure — from the air, from physical contact and from consumption — does to people in our community."

Falls suggested bringing together all the researchers studying microcystin effects on people "to see what all we know and, more importantly, what we don't know but need to know."