Study: Lake Erie fish safe to eat, one meal a week
By John Hageman
Columbus — The Ohio State University Aquatic Ecology Lab’s Co-Director Stuart Ludsin was awarded grant money in 2015 to study the accumulation of the algae toxin microcystin in Lake Erie fish fillets. It was one of the Ohio Board of Regents (now known as the Ohio Department of Higher Education) Harmful Algal Bloom Research Initiative projects.
As indicated when the grant was awarded, the goals and benefits were to include:
• Developing new methods for isolating microcystin-LR from fish flesh.
• Determining levels found in the fillets.
• To see if the toxins are reduced or eliminated by cooking.
• Helping the Ohio Department of Health and the Ohio Environmental Protection Agency set fish consumption level advisories.
• Learning the effects of harmful algae/cyanobacteria blooms on the food web.
Ludsin partnered with investigators from the OSU College of Food, Agriculture, and Environmental Science’s School of Evolution Ecology and Organismal Biology who specialize in public health and food science and technology respectfully.
They studied the risks for people who consume fish from Lake Erie and Grand Lake St. Marys while blooms of the blue-green algae microcystis, properly categorized as cyanobacteria, were underway.
This species of cyanobacteria often produces the LR form (or congener) of microcystin, a well-known liver toxin that may pose human health dangers when exposed to it in the environment or by consuming contaminated foods.
For example, in a Brazilian study from 1996 to 1999, tilapia fish species were found to reach World Health Organization consumption threshold levels of microcystin.
Since this is a relatively new concern in North America with widespread blooms mainly occurring since 2000, there have been few studies here to check on the levels of microcystin-LR in local fish tissue.
In 2011, a laboratory experiment where yellow perch were given measured doses of one often-toxic congener, microcystin-LR determined that when exposed to the toxin, yellow perch absorbed it into their liver in 8-10 hours and into muscle tissue in 12-16 hours.
Microcystin-LR collected in the liver of the fish at rates reaching 10-100 times the amount in the flesh, but purged 99 percent of it within 24 hours. The researchers concluded that as long as the fish were not caught from within a cyanobacteria bloom, eating yellow perch not should lead to human exposure to microcystin-LR.
Where the cyanobacteria blooms typically occur, Western Basin yellow perch tend to avoid them, according to a number of charter boat captains who operate in the area.
The toxin has previously been found to be present in the lower food chain such as in mussels, snails, and in zooplankton. Earlier research suggests that by only harvesting larger perch, anglers may avoid those that may have been feeding upon high numbers of the water flea (zooplankton) bosmina, which were found to be the most contaminated.
According to a story published in the Winter/Spring 2017 issue of Ohio Sea Grant’s newsletter, Twine Line, some of the results of Ludsin’s study are now coming in.
They report that with the help of M.S. student David Witiszinski, Ludsin’s team ran a common microcystin in tissue test and found higher than expected levels of the toxin in walleye, yellow perch, and white perch samples. However, in past studies, the results of following this testing protocol have led to artificially high readings.
So, they tried to confirm the results using other algal toxin detection in tissue testing techniques. By doing so, they were able to learn how to reliably detect nine forms of algal toxins, a big help to water treatment operators, while fine-tuning their detection in fish tissue.
In Ludsin’s case, of the 73 fish analyzed so far from 2015 taken from Lake Erie, only six had detectable levels of microcystin. This is noteworthy, as Western Lake Erie experienced the worst harmful algae bloom on record, due to high nutrient loading during the month of June, when the Maumee River experienced heavy precipitation levels.
Luckily, microcystin levels tested lower in 2015 than in 2014 when the City of Toledo had to stop providing water to customers because of levels that climbed above WHO recommendations.
Ludsin also determined that since the fish can normally metabolize the algal toxins in the liver before they build up in the “meat,” anglers can avoid overexposure to the combined forms of microcystin by following the already-existing fish consumption warnings in place.
To be clear, walleyes and yellow perch from Lake Erie may be consumed safely at the rate of one meal per week, according to Ludsin. This restriction is due to the deposition of mercury from the atmosphere, primarily through the burning of coal.
Another aspect of the study looked at whether or not vegetables irrigated with water containing microcystin were affected or contaminated. Jiyoung Lee and his doctoral student, Seungjun Lee, raised green beans, carrots, and lettuce; green beans absorbed the most toxins.