When warmer weather arrives on Lake Erie each year, it means harmful algal bloom season is around the corner. Cyanobacteria, fueled by an excess of nutrients in the water, will grow rapidly, often producing toxins that are a threat to the environment and human health in the region.

But for Dr. Justin Chaffin, Stone Laboratory’s research coordinator, these warmer months also mean it’s time to track blooms and their resultant toxins. The goal is to keep water clean and safe on Lake Erie’s coastline.

“Everyone drinks water,” said Chaffin. “We don’t want toxins in our water if they’re from algae or other sources. We don’t want to drink it, swim in it, or boat in it. So anything that we can do to help minimize people’s exposure to it or to ultimately prevent pollutants in the first place is important.”

Since joining Stone Lab in 2012, Chaffin has led research to better understand what drives cyanobacterial blooms and the production of different cyanotoxins on Lake Erie. Recent studies — in which Chaffin played a key role, often utilizing Stone Lab’s facilities — have yielded significant findings about these topics.

Forecasting Toxins on Lake Erie

One such study, published in 2023, helped advance the ability of researchers to forecast algal bloom toxins on Lake Erie, focusing on microcystin concentrations. Currently, cyanobacteria models in use on the lake can only predict the occurrence and location of blooms, not the toxins they produce.

“Models can predict the presence of biomass and how thick it is, but there’s really no correlation between how thick the bloom is and microcystin concentration,” Chaffin explained.

To help remedy this, a team of researchers from Ohio State, Michigan Technological University, LimnoTech, and the Argonne National Laboratory developed models to simulate microcystin transport on Lake Erie, thanks to funding from NOAA’s National Centers for Coastal Ocean Science. Models were built on an extensive dataset of toxin concentrations from 2018 and 2019 compiled from multiple sources, including university researchers, federal and state agencies, water treatment plant intakes, and volunteer scientists.

“The best thing about Stone Lab is our location. Our boat docks are right at the lab, and our lab’s right at the lake. So we can take advantage of easily collecting samples.”
Dr. Justin Chaffin

Through the project, Chaffin and other researchers compared the models’ predictions to actual data recorded in those years. Notably, they found that models that considered microcystin production rates were 10% more accurate than those without. Those models also successfully predicted microcystin concentrations in a “large bloom” year. The findings are essential to creating a Lake Erie microcystin forecast that will help minimize exposure to toxins and improve management recommendations, whether for drinking water treatment plant operators or beach managers.

“That will basically give water treatment plant operators an early warning so they can prepare to deal with the toxins,” Chaffin said. “When microcystin does get to the plant, they’re ready for it. And then if it’s being forecasted that toxins are going to decrease over the next week, they can be more efficient and not waste their supplies.”

Researchers stress that accurate, high-quality data — sampled frequently across a large area on the lake — will improve the development of more models in the future.

“We want to develop a toxin forecast for obvious reasons, but we’re also investigating what factors trigger cyanobacteria toxin production,” Chaffin said. “Understanding those fundamental questions not only applies to Lake Erie but any other lake that’s dealing with the same type of cyanobacteria.”

Going Beyond Microcystin

While microcystin remains the most well-known and well-researched algal toxin on Lake Erie, other toxins are present on the lake, previous research has showed. Chaffin, alongside other researchers from Ohio State and Bowling Green State University, investigated the distribution of cyanobacteria that can produce saxitoxins, a potent neurotoxin that can pose health risks.

“It’s important to get past the mindset that microcystins are the only toxins that cyanobacteria can make,” Chaffin said. “Microcystins are probably one of the most common ones, and it’s also one of the easier toxins to measure. It’s out there, and we know a lot about what triggers its production.”

“Other cyanotoxins, like saxitoxins, we know a lot less about because they’re harder to measure and we don’t know what triggers cyanobacteria to produce them,” he continued.

For this particular study, researchers focused on the stxA gene, which encodes the production of saxitoxins in cyanobacteria. The team collected water samples and conducted water column experiments off South Bass Island at Stone Lab and in Maumee Bay at The University of Toledo’s Lake Erie Center.

While the study did detect saxitoxins and stxA in varying amounts in the lake’s western basin, their levels don’t seem to be concerning so far, Chaffin said. Researchers concluded that continued monitoring is needed to determine saxitoxin drivers, and future research should not solely focus on microcystins.

Chaffin’s lab is also tracking anabaenopeptins. While toxicological studies on anabaenopeptins are sparse, they appear to be less toxic than most microcystins. Further, these toxins can appear in much higher concentrations than microcystins and could be an overlooked stressor on aquatic organisms, Chaffin said.

“It’s something to keep our eye on, if things change in the lake and the blooms go from producing microcystins to producing saxitoxins,” he said. “On the applied side, if I have a beach and I only do a microcystin test, it might not be a microcystin-producing bloom. It’s not accurate to equate all toxins to microcystin.”

Using Stone Lab’s Island Advantages

Chaffin’s research is based out of Stone Lab, which offers numerous benefits for studying harmful algal bloom, or HABs. In warmer months, researchers go out on boats to predetermined locations each week to collect water samples and analyze them for environmental parameters, such as nutrients, temperature, or pH, Chaffin said. They’ll also look for what types of algae and toxins are present to begin looking for correlations and trends over time.

“The best thing about Stone Lab is our location,” he said. “Our boat docks are right at the lab, and our lab’s right at the lake. So we can take advantage of easily collecting samples.”

In an ongoing study, led by Ohio State and The University of Toledo and funded by the Great Lakes Restoration Initiative, Chaffin and other researchers are continuing work to improve forecasting of microcystin concentrations on Lake Erie by quantifying production rate throughout the bloom season. The project is similarly taking advantage of Stone Lab’s facilities, using incubated lake water to conduct experiments on toxin production.

To study blooms at Stone Lab, Chaffin and his team will conduct bioassays, in which they take bloom water from Lake Erie and see how the bloom responds to different conditions, such as the presence or absence of phosphorus and nitrogen. Samples are often kept in containers suspended from piers adjacent to Stone Lab.

“They’re incubated at the same temperature and at the same light levels that the algae in the lake are, so it has advantages over a controlled incubator on a college campus,” Chaffin said.

One recent study that Chaffin contributed to, alongside Dr. Hans Paerl of the University of North Carolina at Chapel Hill, used such on-site bioassays to determine the importance of nitrogen and phosphorus in mitigating blooms in Lake Erie. The team found that year-round reductions in both nitrogen and phosphorus by 40% would be more beneficial than a phosphorus-only approach for long-term control of eutrophication and blooms in Lake Erie.

“We’ve known for decades that phosphorus is important for bloom biomass,” Chaffin said. “But we now know that nitrogen is equally if not more important that phosphorus for bloom toxicity, at least for microcystin. If blooms don’t have nitrogen, they can’t make microcystin.”

Other recent studies are using Stone Lab’s new Mesocosm Facility, which allows researchers to conduct larger-scale experiments in outdoor, circular, 600-gallon tanks, offering advantages over laboratory work. For example, Chaffin worked with Heather Raymond, director of the Water Quality Initiative within the College of Food, Agricultural, and Environmental Sciences (CFAES), others at Ohio State, researchers from the University of Florida, and Greenwater Services to study the effectiveness of ozone “nanobubbles” to treat harmful algal blooms. The team ran experiments using Stone Lab’s mesocosms to control blooms with tiny bubbles of ozone — technology that required more space than a laboratory could provide.

“We were looking at these ozone generators, and these instruments are fairly large. You can’t do beaker or bottle experiments with them,” Chaffin said. “You need large incubation vessels to actually use the technology. From that study, we learned that bloom biomass, ambient water quality, and how thick the bloom is are all important factors.”

“We and our colleagues are doing important research on HABs that can inform not only bloom management on Lake Erie but any lake that experiences HABs around the world,” he added.

For more information about this research, contact Chaffin at chaffin.46@osu.edu or watch his Freshwater Science webinar.

Ohio Sea Grant is supported by The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) School of Environment and Natural Resources, Ohio State University Extension, and NOAA Sea Grant, a network of 34 Sea Grant programs nation-wide dedicated to the protection and sustainable use of marine and Great Lakes resources. Stone Laboratory is Ohio State’s island campus on Lake Erie and is the research, education, and outreach facility of Ohio Sea Grant and part of CFAES School of Environment and Natural Resources.