New way to track toxic algae that threatens shellfish industries developed by researchers

Tiny organisms called algae can have an outsized impact on working waterfronts. While many benefit their ecosystems, others can cause devastating economic and ecological effects. 

University of Maine Ph.D. candidate Sydney Greenlee, alongside researchers Robin Sleith and Peter Countway from the Bigelow Laboratory for Ocean Sciences, have developed a faster, more accurate way to detect a toxic species of algae known as Pseudo-nitzschia australis (P. australis). 

In 2016, the algae bloomed along the East Coast for the first time, spreading a neurotoxin in its wake. The neurotoxin contaminates shellfish, causing amnesic shellfish poisoning in those who eat the affected seafood. It can be deadly to humans and cause aggressive behavior in marine mammals. Shellfish farms from the Bay of Fundy to Rhode Island halted harvesting for weeks and recalled products. While a major event like this has not occurred in the Gulf of Maine since, P. australis continues to threaten hatcheries and Maine’s working waterfront.

The team developed a test that uses a quantitative version of the Polymerase Chain Reaction (qPCR) to detect P. australis in environmental DNA (eDNA) 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. As a result, this test can help the shellfish industry better track and respond to harmful algae blooms. 

“Genetic tools like this are becoming an important tool in our monitoring efforts for the Marine Biotoxin Monitoring Program within the Department of Marine Resources’ Bureau of Public Health and Aquaculture,”said Tyler Spillane, a marine resource scientist with Maine’s Department of Marine Resources. “This assay will help us in better identifying toxin forming blooms of Pseudo-nitzschia phytoplankton, allowing us to refine our management practices to better protect public health and potentially minimize growing area closures that impact the shellfish industry in Maine.”

Approximately half of Pseudo-nitzschia species are toxic, with P. australis producing the highest levels of domoic acid, the neurotoxin that causes amnesic shellfish poisoning. Harmful algal blooms occur when a toxic species becomes more abundant than normal, sometimes taking over an ecosystem. While the bloom species is dominant, its toxins accumulate in shellfish, and when humans and other animals ingest those shellfish, it can lead to dangerous and even lethal consequences. The dangers of P. australis in Maine loomed after its unexpected arrival in 2016, especially as scientists did not have the tools to best monitor and understand the species. 

Currently, researchers use light microscopy to monitor samples of seawater for Pseudo-nitzschia. While not all Pseudo-nitzschia produce toxins like P. australis, it is nearly impossible to differentiate toxic and non-toxic species visually, even based on observations by a skilled technician. When Pseudo-nitzschia cells reach a certain abundance in the water, precautionary measures are taken within the shellfish industry to avoid selling contaminated products. 

These measures remain in place until resource managers determine whether shellfish meat contains domoic acid. Collectively, this makes the benefits of identification costly to resource managers and other stakeholders.

The team’s new eDNA assay is able to quickly identify P. australis by detecting a unique genetic marker in as little as a liter of water. This approach, which was published in the journal Harmful Algae, offers new species-level identification at a much lower cell density than is possible by microscopy. 

With a faster and more accurate method of detection, water can be tested more often and with a quicker turnaround time for results. This would allow resource managers to better identify threats to hatcheries and ecosystems, and target interventions to reduce potential damage. Greenlee and Sleith recently trained scientists at Maine’s Department of Marine Resources on this exact procedure.

“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,” said Countway. “A goal for our ongoing work is to implement this and similar detection methods along the coast of Maine so that this species never surprises us again, as was the case with the 2016 bloom event.”

Greenlee hopes to see this new eDNA tool integrated into existing processes that test Pseudo-nitzschia levels in seawater and demonstrate its potential to help protect Maine’s coastal economy and ecosystems globally.

“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,” said Greenlee. 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.

Greenlee is a Ph.D. candidate studying oceanography at UMaine’s School of Marine Sciences. She’s advised by Countway and Damian Brady, professor of marine sciences at UMaine’s Darling Marine Center. 

This project received support from an Infrastructure Improvement Track-1 Maine-eDNA grant from the National Science Foundation’s Established Program to Stimulate Competitive Research. It also received partial support from a National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Coastal Ocean Sciences Monitoring and Event Response for Harmful Algal Blooms award to Bigelow Laboratory, and from a NOAA Northeastern Regional Association of Coastal Ocean Observing Systems award to UMaine.

Story by: Emma Beauregard. research media intern

Contact: Daniel Timmermann, daniel.timmermann@maine.edu