COLUMBUS, Ohio — By now people should know to avoid too much exposure to water contaminated by harmful algal blooms (HABs). But what about eating the vegetables that producers irrigated with HAB-contaminated water? Or fish that swim in that water?

 

Researchers at The Ohio State University are studying the effects of exposure to microcystin, one of the major toxins produced not just from contact with contaminated water, but also from food. Microcystin has been implicated in several health issues from skin rashes to liver and nervous system damage.

 

Drs. Jay Martin, Stu Ludsin and Jiyoung Lee are striving to answer questions about whether those fish and vegetables retain any of the algal toxins they are exposed to and, if they do, whether those toxin concentrations are high enough to be of concern. So far results have shown that in both cases there may be some  toxin accumulation, but there is no reason to avoid consumption completely.

 

Lee, an associate professor of environmental microbiology, is researching toxins and cyanobacteria in irrigation water used on fresh produce. She picked microcystin because it is one of the most prevalent cyanobacteria found in Ohio and the United States, as well as across the world. She studied its effect on lettuce, carrots and green beans using two irrigation methods: spraying and drip. Depending on the crop, 40-50 percent goes to the soil and the rest goes to the plant, Lee said. If the toxin goes a little higher the crop shows stress response.

 

“When we talk about the risk, we have to look at how often they eat these foods and how much they eat,” she said. “So we cannot say there is no risk as toxin accumulates.”

 

Lee’s role as a public health researcher is conservative, she said. Ongoing research will show if there is a health risk to eating these vegetables.

 

She suggests that agriculture find an alternative source of water for irrigation. Most large farms already use groundwater on their operations, while most smaller farms tend to use more surface water, which can lead to microcystin contamination during bloom season.

 

In those cases, regular water testing and switching to alternative water sources is essential to reduce or prevent exposure that can lead to microcystin contamination. If the toxin is found in the soil, rotating cropland gives it time to degrade before planting new crops.

 

“In both of these projects we’re trying to find ways to look at specific types of  microcystins, particularly the most toxic strain, and then another way is to quantify all the microcystins that might be out there,” said Ludsin, associate professor and co-director of the Aquatic Ecology Laboratory.

 

The researchers looked at toxin levels in fish in Lake Erie and Grand Lake St. Marys in 2015 and 2016; results are not complete for 2016, Ludsin said. In both those lakes, few of the fish had toxins and even the ones that did were very low-level in 2015.

 

That was encouraging because if people would follow the consumption guidelines for fish that contain mercury of no more than one fish meal eaten per week for species like walleye, for example, then there would be no risk for accumulating excessive levels of these toxins.

 

The state is interested in pondering these harmful algal blooms because cyanobacteria like microcystins are becoming more prominent, Ludsin said. Researchers think agriculture contributes some of the nutrients to HABs, but climate change also plays a role.

 

“With continued climate change the very intense storms, particularly in spring when the fields are fallow and vegetation isn’t fully on the fields, that  can lead to excessive nutrient runoff,” Ludsin said. “That’s where you get a lot of variability in the amount of nutrients that come off the landscape. “Predictions from the model that we’re working on show more intense runoff events that can lead to cyanobacteria in the next century.”