MOSS LANDING — Microscopic marine plants — or phytoplankton — are crucial to sea creatures, as well as life on Earth. Because of their photosynthesizing abilities, phytoplankton expire oxygen, which accounts for roughly 50% to 80% of our home planet’s total budget of the element.
“They’re essential, and yet some species of phytoplankton can cause harm,” explained John Ryan, a biological oceanographer with the Monterey Bay Aquarium Research Institute.
A naturally occurring chemical phytoplankton cultivates — domoic acid — is a neurotoxin. When ingested by marine creatures, and other vertebrate species, the toxin can cause food-poisoning like symptoms, seizures, and in severe cases, death.
State officials, academics and regional groups monitor domoic acid. Seafood is tested for it before it makes its way to consumer’s plates. But little is known about the molecular and environmental factors that trigger toxin-laced algal blooms, which have become increasingly common, and severe in recent years.
Ryan, and collaborators are investigating just that.
Using underwater robots, researchers with the Monterey Bay Aquarium Research Institute, UC San Diego’s Scripps Institution of Oceanography and UC Santa Cruz are tracking the toxin in the bay.
“This experiment is bringing new technology not only to the ocean, but also to the lab on land, to drill more deeply into the molecular underpinnings of how this species works — what causes it to turn on the production of toxin?” Ryan asked.
The number and severity of harmful algal blooms triggered by domoic acid have increased in recent years, Ryan said. In 2015, a bloom containing high levels of domoic acid, flourished, shortly after which “the blob” — a mass of unusually warm water, hugged West Coast waters.
During that bloom, the largest number of marine mammals “ever observed” were poisioned by domoic acid, according to Ryan. That outbreak also had devastating impacts on local fisheries, and commercial fishermen who depend on shellfish for their livelihood.
To understand what’s behind the blooms, the team is documenting, and decoding environmental and genetic clues in domoic-acid-producing phytoplankton.
Three different robots work in tandem, some of which provide real-time data to the scientists. The first, “sniffs around” for domoic acid and takes samples to determine if there’s toxin present, Ryan said. Robot No. 2 samples ocean temperature, saltiness and depth. It also measures light — or bioluminescence — some species of phytoplankton emit. The third, a remotely operated vehicle, swims at the surface, and transmits data from the underwater robots, back to scientists on ship, and land.
A Monterey Bay Aquarium Research Institute researcher transfers seawater samples to portable containers. Scientists will analyze these samples to uncover environmental and genetic factors associated with domoic acid. (Contribute photo – John Ryan © 2021 MBARI)Just like microscopic algae, the underwater robots are passenger to the ocean’s currents, tides, and eddies.
“It’s like a window into their lives — we’re moving with them as they experience changes in the ocean,” Ryan said.
In the next days, the robots will continue to drift and swim across Monterey Bay.
Ryan and other oceanographer-crew members, take their own water samples as well, to get a larger picture of the ocean conditions and chemistry, taking place near the robots’ swimming range.
The robot’s real-time sample data is transmitted back to scientists onshore, who can track a potential algal bloom from their laptops.
Scripps researchers are also investigating the chemicals linked to domoic acid.
“In a cup of ocean water, there’s millions if not billions of microorganisms, things like bacteria, viruses, phytoplankton — they are all talking to each other, but instead of using words they use chemicals,” Monica Thukral, a Scripps graduate student on the project, said.
Thurkal and collaborators decode those chemical signals in ocean water samples, to know if the robots are in a toxin hotspot, or not.
In the longer-term the researchers are also investigating the cellular and environmental factors that breed domoic acid production. MBARI scientists will deploy the robot fleet again next year, to gather more data.
In the lab, UC San Diego Scripps researcher Monica Thukral analyzes seawater samples. (Contributed photo – Monica Thukral)“Which species are producing the toxin and when? And is that correlated to certain genes they have?,” Thurkal asked.
There are about 60 species of phytoplankton, but only 30% produce the biotoxin according to Thurkal. Later on, researchers at Scripps will investigate the organisms’ genetics.
“Each organism has a DNA or RNA barcode that we can sequence, and determine who’s actually living in the water at that time,” Thurkal said.
Identifying those genes and the molecular pathways linked to domoic acid, is critical, according to Raphael Kudela, UC Santa Cruz ocean sciences professor.
Kudela’s lab is also on the collaborative project.
“Right now, we go down to the wharf every week and we’re measuring toxin both in the water and in the shellfish,” Kudela said. “But it would be so much better if we can look at the genes and know, these genes are being activated, therefore, a week from now there might actually be a bloom coming on — that would be a game-changer.”
Having a library of those toxin genes could help researchers, environmentalists and officials have an early warning system for domoic acid outbreaks.
Beyond that, Kudela, who’s a technical adviser on the research project, said the science may further uncover climatic factors behind toxin production.
“There’s lots of questions about what’s going on at a molecular level, and what does that tell us about how it might change in the future,” Kudea said. “It’s going to fill in a big piece of the puzzle that we’ve been waiting to figure out.”