UToledo Ecologist Explores Effect of Algal Toxins on Photosynthesis

UToledo Ecologist Explores Effect of Algal Toxins on Photosynthesis

Northwest Ohioans know to keep their thirsty pets away when the pea-green expanse of a harmful algal bloom creeps into the western basin of Lake Erie.

But what about their thirsty crops?

"Cyanobacterial harmful algal blooms are increasing in frequency and severity in freshwater systems worldwide, including in the Great Lakes," said Dr. Scott Heckathorn, a professor in the Department of Environmental Sciences at The University of Toledo. "When crops are irrigated with water from such blooms, as is common, plants can potentially accumulate algal toxins to levels that are harmful to plants and people."

The specific impacts of algal toxins on plants are not well understood, however.

Furthering past studies that have suggested that some algal toxins decrease photosynthesis in plants and algae, Heckathorn and a team of student researchers recently completed what he describes as the most rigorous examination to date of the effects of cyanobacterial toxins on this energy-conversion process.

Their recent research is published in the peer-reviewed journal Plants.

"We examined effects of four common cyanobacterial toxins and found that all four decreased photosynthesis," Heckathorn said. "Interestingly, but not surprisingly, we found that different aspects of photosynthesis were affected depending on the type of toxin and the method of exposure."

These results have relevance to both agriculture and ecology. Photosynthesis is the process by which plants and algae use sunlight to convert both water and carbon dioxide into both oxygen and the chemical energy needed to grow.

The researchers' work builds on an extensive body of research on harmful algal blooms out of UToledo, whose students, faculty and staff found themselves among the half-million people in the region affected by a bloom-induced drinking water crisis in August 2014.

In the immediate wake of the crisis, UToledo brought together a team of faculty ecologists, engineers, chemists, doctors and public health experts who lent their expertise to efforts to return potable water to taps and establish safeguards against another crisis.

More than 10 years later, UToledo's Water Task Force remains at the forefront of efforts to more effectively monitor water quality and accurately predict blooms, efficiently remove toxins from water, thoroughly understand health effects of exposure and prevent harmful algal blooms from forming altogether through policy and land management.

Heckathorn brings his expertise as a plant environmental physiologist to the study of harmful algal blooms, whose effects on agriculture have been investigated in earlier research that he cites in his article in Plants. Exposure to algal toxins via toxin-contaminated water or algae-based fertilizer can cause crop contamination and decreased crop productivity.

In his recent research funded by the U.S. Department of Agriculture, Heckathorn opted to zero in on the effects of toxin exposure on the multistep cellular process of photosynthesis. He led a team of researchers, including three graduates at UToledo and three students attending nearby Ottawa Hills High School and Sylvania Southview High School, in conducting a series of experiments that looked at the short- and long-term effects of cyanobacterial live cultures, cell extracts and individual toxins in both intact plants and leaf fragments of corn and lettuce.

Their findings related to carbon fixation, chlorophyll concentration, electron transport and other metrics are expected to inform ongoing research at and beyond UToledo.

This includes ongoing work in Heckathorn's lab investigating the effects of toxins on other aspects of plant metabolism, determining the pathway for toxin uptake in roots and genetically engineering plants to produce toxin-degrading enzymes.

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