Study finds concerning levels of toxins in water near farm fields
COLUMBUS, Ohio – Harmful algae isn’t just a problem for high-profile bodies of water – it poses serious, toxic threats in small ponds and lakes as well, new research has found.
A team of researchers from The Ohio State University examined water samples from two dozen ponds and small lakes in rural Ohio and found plenty of cause for concern, with particularly high levels of toxins at one lake.
Toxins from algae can cause skin rashes, intestinal problems and damage to the liver and nervous system. Fertilizers common to agriculture – including nitrogen and phosphorous – create an environment in which harmful algae can flourish.
The researchers said that the way farmers manage runoff could play a significant role in creating water bodies that are ripe for harmful algal blooms. A primary concern is tile drainage, a widely used agricultural approach to removing excess water from the soil below the surface. That water – and the nutrients found in it – are rerouted, often toward ponds on farm property, said study co-author Seungjun Lee, a postdoctoral researcher in environmental health sciences at Ohio State.
“A lot of people and government agencies are paying attention to larger lakes, including Lake Erie, but these smaller bodies of water are also used for recreation, fishing and irrigation,” he said.
The study was published recently in the journal Environmental Science & Technology.
The research team, led by Ohio State’s Jiyoung Lee, analyzed samples from the 24 bodies of water over a three-month period in late summer 2015.
Ten of the sites had detectable levels of microcystins, toxins produced by freshwater cyanobacteria during algal blooms.
One site had repeated instances of microcystin concentrations above recreational guidelines set by the Ohio Environmental Protection Agency, and so the research team paid particular attention to the samples from that site.
“Samples from this lake in early July were particularly concerning, as they contained four times the recommended amount of microcystin for recreational use and more than 800 times the recommended level for drinking,” Seungjun Lee said.
A pond or lake with high toxin levels presents a risk to people, pets, farm animals, wildlife (including fish) and crops and could benefit from routine monitoring and work to lower the risk of algal blooms, he said. The researchers did not name the lake in question, because it is privately owned.
Jiyoung Lee said the impact of tile drainage may be elevated in small lakes and ponds, compared to larger lakes.
“Highly concentrated nutrients are being introduced into a smaller volume of water, making small lakes and ponds more sensitive to this influx of phosphorous, nitrogen and other nutrients,” she said.
Nitrate and phosphorous are linked to the primary type of toxic microcystin found in the water. Judicious use of fertilizers could help control the algal blooms, as could measures to reduce animal waste contamination of ponds and lakes, Seungjun Lee said.
Though the study concentrated on Ohio agricultural areas, its findings likely apply to many areas throughout the U.S. and the world where agriculture and small lakes and ponds coexist, the researchers said.
Researchers from Kenyon College also contributed to the study, which was partially funded by the Ohio Water Development Authority.
Algae a threat to walleye vision, study finds
Increase in algal blooms could pose problems for freshwater fish
Walleye and the fish they eat struggle to see in water clouded by algae, and that could potentially jeopardize the species’ future if harmful algal blooms persist, according to a new study.
The research, led by Suzanne Gray of The Ohio State University, found that algae posed more of a threat to adequate vision than an equal amount of sediment – another common cause of murky waters in the western basin of Lake Erie.
The researchers found a decrease of more than 40 percent in the fishes’ ability to see in water clouded by simulated algae as opposed to water equally clouded by sediment. The study appears in the journal Conservation Physiology.
For many fish, vision is the primary tool for survival, leading them to food and away from predators that want to eat them.
“This is concerning for these important fish populations. If we can’t get a handle on algal blooms, this could threaten their well-being,” said Gray, an assistant professor of aquatic physiological ecology at Ohio State.
The researchers placed individual fish – six juvenile walleye and 17 emerald shiner – in round tanks of water surrounded by a rotating screen with alternating black and white stripes. The screen moved around slowly and, in clear water, the fish would naturally identify the pattern and swim circles in time with the rotating stripes.
“It’s an innate response for the fish to identify the difference between black and white and follow the screen,” Gray said.
The researchers added increasing amounts of either sediment taken from Lake Erie or spinach (to mimic algae) to the tank. Emulsified spinach was used in this and a previous study because of its similarity in color, size and light-scattering properties to common algal bloom species.
After adding sediment or spinach, the researchers observed the behavior of the fish. When the fish stop following the moving stripes, they presumably can no longer see them, Gray said.
Though the amount of turbidity – a term scientists use to describe cloudiness in water – was equal with both substances, the fishes’ response was not.
They were far better equipped to see in water made murky with sediment than in the green, cloudy water created with the addition of spinach.
“The difference was way more profound than I expected. You could make the water really muddy and they would keep on swimming round and round, but you only had to add a little ‘algae’ and they would just sit there,” Gray said.
Increasing threats of harmful algal blooms in Lake Erie and in freshwater lakes and streams elsewhere are cause for widespread ecological concern, and it’s important to understand how they could be impacting fish populations, Gray said.
“This isn’t just an Ohio problem, it’s a problem all around the world,” she said.
The difference the researchers saw in this study may be because the fish have adapted to low-light vision (walleye hunt at dusk and dawn) in the intermittently muddy waters of the relatively shallow western basin of Lake Erie, she said.
“But algae is different. It’s green and it changes the light. It could be that both the reduction in light and the change in color inhibits vision differently than sediment,” Gray said.
Gray, who has studied fish around the world, became interested in walleye and the emerald shiner on which they feed not long after relocating to Ohio State.
It was 2014, and Toledo had just warned against drinking its water due to a major harmful algal bloom in Lake Erie that had found its way into the public water system.
“I saw an editorial cartoon showing an angler trying to fish in murky green water and saying something like ‘Can the fish even see the bait on my hook?’ and I thought that I could probably help answer that question,” Gray said.
Ohio State doctoral student Chelsey Nieman and undergraduate students Andrew Oppliger and Caroline McElwain also worked on the study.
Ohio Sea Grant supported the research.
Written by Misti Crane.