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People flock to New Hampshire’s more than 1,000 lakes and ponds each summer to swim, boat, fish, and enjoy time on the water. But as the water warms, potentially harmful microbial inhabitants such as cyanobacteria, also known as blue-green algae, become more numerous. Researchers with the (NHAES) at the �鶹�� are studying what happens when cyanobacteria populations explode in what are known as blooms, which can lead to dangerous levels of environmental toxins that threaten animal and human health in ways that are still not fully understood. 

A multi-disciplinary team led by Anyin Li, Amanda McQuaid, and Anna O’Brien is working to develop new research methods to learn more about the toxins and where they go during and after blooms. Supported by the NHAES’s Collaborative Research Enhancement and Team Exploration (CREATE) program, the result of their work will be better, more precise detection methods to monitor and track the toxins throughout pond and lake environments. 

“In New Hampshire, the public warning threshold is 70,000 cyanobacteria cells per milliliter, which is a generic yes/no measurement,” says McQuaid, associate Extension state specialist in the �鶹�� College of Life Sciences and Agriculture, who also directs the . “We still don’t know the details about the presence of toxins in the water, sediment, and nearby ecosystems, or what the risks and health implications are in different situations.”

Not all cyanobacteria blooms result in toxicity, but they are unsightly and can curtail recreation on and in any affected lakes or ponds. This is key for New Hampshire, where lakes and ponds contribute $1.1 to $1.5 billion in annual total sales from recreational activities and public water supply, supporting an estimated 9,000–17,600 jobs. 

Duckweed is an effective green manure, but does it carry any risks of bringing microcystins with it?

For those exposed to toxin blooms, an upset stomach is the most common symptom, but they have also been associated with other health problems, including neurodegenerative disorders and damage to the liver. The uncertainty concerning potential harm is even captured by the New Hampshire Department of Environmental Services’ warning advice: “When in doubt, stay out!” 

The most prevalent toxins produced in blooms are called microcystins, which have more than 200 variants. A commonly used detection method, known as the enzyme-linked immunosorbent assay (ELISA), is able to detect the potential total amount of microcystins present, not which variants they are. ELISA is helpful for toxin screening — it is used by the (a New Hampshire collaborative for lake research)— but to get a better picture of what is happening in the environment and in turn better understand any present risks, more information about toxin variants is needed.  

Li, an associate professor of chemistry in the �鶹�� College of Engineering and Physical Sciences (CEPS), is working on mass spectrometry-based analysis methods that provide a clearer profile of the microcystin variants. They will also be able to track the toxin degradants, many of which have unknown toxicities.

“ELISA analysis detects microcystins by binding to one specific part of the molecule, but in real life they change and degrade, and the toxicity and behavior can be totally different,” says Li. “If we are able to detect the different states of the molecules, we can assess many more of the effects of microcystins in the system.” 

For O’Brien, assistant professor in the �鶹�� College of Life Sciences and Agriculture (COLSA), cyanobacteria toxins are a concern beyond the lakes. Part of her research focuses on whether duckweed — an aquatic plant that commonly grows in farm ponds and may remove phosphorous from pond water and recapture runoff nutrients — could be harvested and used as a “green manure” to improve plant growth while minimizing reliance on synthetic fertilizer products. O’Brien is concerned, however, about duckweed potentially carrying cyanobacteria and toxins with it into the fields and, potentially, into the food supply. 

Accurately assessing this risk depends on new detection and analysis methods that can reveal where the microcystins are located in and on the duckweed as well as in the water, what variants are present, whether it persists or degrades when used as green manure, and whether there is any danger of them being taken up by growing crops. 

“We need to be able to measure microcystin variants in different contexts with much more precision and accuracy,” says O’Brien. “The different variants and their degradants as they break down will have different biological consequences, and they can also change from season to season. If we gain a better understanding of what happens with them in the pond, on the plants, and in the field, we’ll be better able to assess their effects in the broader environment.” 

As summer approaches and people head to their favorite lakes and ponds, concerns about cyanobacteria blooms are sure to blossom as well. And until more about the blooms and their toxins is known, those concerns are well founded.

“If you can see microbes with no microscope needed, there is a problem!” says McQuaid. “We coexist with them all the time, but we need a better understanding of how toxic the cyanobacteria really are, and the risks associated with them. And that’s the goal of our work.”