Researchers Develop Convenient Approach to Track Harmful Algae

Microscopic algae can have an outsized impact on working waterfronts. While many benefit their ecosystems, some species can grow out of control or produce toxins that can cause devastating economic and ecological effects.

Sydney Greenlee, a University of Maine Ph.D. candidate based at Bigelow Laboratory for Ocean Sciences, has worked with Bigelow Laboratory researchers Robin Sleith and Peter Countway, to develop a faster, more accurate way using environmental DNA to detect a toxic species of algae, Pseudo-nitzschia australis.

Their approach, recently published in the journal Harmful Algae, offers a way to proactively detect this species at a much lower abundance than is possible with traditional microscopy techniques. The study also includes Damian Brady, an associate professor of marine science at the UMaine Darling Marine Center.

Approximately half of Pseudo-nitzschia species are toxic, with P. australis producing the highest levels of the potent neurotoxin domoic acid. People and animals that eat shellfish contaminated with domoic acid can develop amnesic shellfish poisoning, which is deadly to humans and causes aggressive behavior in marine mammals. (A separate Bigelow Laboratory research team recently showed how domoic acid can also cause physiological and behavioral changes in keystone species like sea stars).

Harmful blooms of algae like P. australis are becoming more frequent throughout the world due to changing ocean conditions, and in 2016 P. australis unexpectedly bloomed along the East Coast for the first time. While a major event like the 2016 bloom has not occurred in the Gulf of Maine since, P. australis continues to threaten hatcheries and Maine’s working waterfront. The risk makes it critical for resource managers to have convenient methods to regularly monitor the presence of the algae and potentially link it to particular environmental conditions.

To that end, the research team developed a test that uses a quantitative version of the Polymerase Chain Reaction method, similar to a Covid test, to detect P. australis in environmental DNA samples. The test builds on Pseudo-nitzschia research conducted over the past decade in Countway’s lab, where Greenlee is based, and offers a more accurate approach to monitoring these toxic algae — giving the shellfish industry and resource managers tools to better track and respond to harmful algal blooms.

"This new approach finally gives us the opportunity to study the ecology of Pseudo-nitzschia australis against the backdrop of many other types of Pseudo-nitzschia that are found in the Gulf of Maine, and will hopefully lead to some explanations for the drivers of its bloom dynamics,” Countway said. “A goal for our ongoing work is to implement this and similar detection methods along the coast of Maine so this species never surprises us again.”

Currently, researchers use light microscopy to monitor samples of seawater, a method that can be costly and time intensive. When the number of Pseudo-nitzschia cells reaches a certain level in the water, precautionary measures are taken to avoid harvesting contaminated products. But not all Pseudo-nitzschia species produce toxins like P. australis, and it is nearly impossible to differentiate toxic and non-toxic species visually.

In contrast, the new eDNA test is able to quickly identify P. australis by detecting its unique genetic markers. The test can be run in as little as a liter of water and allows for more precise, species-level identification than is possible with microscopy.

With a faster and more accurate detection method, water can be tested more often and with a quicker turnaround time for results. Greenlee and Sleith, a research scientist at Bigelow Laboratory, recently trained scientists at the Maine Department of Marine Resources on the procedure, which will allow resource managers to better identify threats and target interventions to reduce potential damage.

As the Gulf of Maine continues to warm, Greenlee hopes to see this new eDNA tool eventually integrated into existing processes for monitoring Pseudo-nitzschia levels to help protect coastal industries and ecosystems in Maine and beyond.

“I hope this gives a little more visibility to how we could apply eDNA tools to research questions that are really important for coastal communities,” Greenlee said. “Whether those research questions involve harmful algal blooms, or other species expanding into the Gulf of Maine, the research demonstrates eDNA’s potential to be part of the solution.”

This work was made possible with support from the NSF EPSCoR Research Infrastructure Improvement Track-1 Maine-eDNA grant, a NOAA National Centers for Coastal Ocean Sciences Monitoring and Event Response for Harmful Algal Blooms award, and a NOAA Northeastern Regional Association of Coastal Ocean Observing Systems award.

A version of this story originally appeared on UMaine News.

Photo 1: Light microscopy of Pseudo-nitzschia australis cells collected off the coast of Maine during the 2016 bloom, the first time that P. australis was detected in the Gulf of Maine (Credit: Peter Countway).

Photo 2: An oyster farmer washes oysters in southern Maine in 2024 (Photo courtesy of the University of Maine).