No harmful algal blooms detected yet, but researchers stay vigilant

By Megan Gannon
Around this time last year, a colorless but toxic bloom of harmful algae was detected in the Bering Sea, prompting warnings about consuming some marine resources. This summer, no such warnings have been issued, but researchers are still monitoring the water to look for a potential bloom.
Last week Evie Fachon, a doctoral student the Woods Hole Oceanographic Institute, or WHOI, in Massachusetts, gave a Strait Science presentation to discuss her research on harmful algae.
Fachon, who works with WHOI scientist Don Anderson, was aboard the Norseman II last year as it cruised through the Bering Strait to study the algae Alexandrium cantenella, which can produce toxins that can cause paralytic shellfish poisoning, or PSP, when consumed in high concentrations. It just so happened that the researchers aboard that cruise detected a bloom in real time.
This year, there is no dedicated research cruise looking for algal blooms in the Bering Sea. Instead, the research vessel Sikuliaq is carrying an Imaging Flow CytoBot, or IFCB, which analyzes water samples for tiny particles like the single-celled Alexandrium. Fachon and her WHOI colleagues have a remote connection to the instrument and can look for a high concentrations of the cells from afar.
“One huge caveat to all of this is that we’re really limited by where and when the ship travels,” Fachon said. “We can see whatever’s in the water where the ship is, but we really don’t know anything about places or times beyond that limited sampling coverage.”
The researchers are also still poring over the data that they collected last year to better understand the threat of blooms. One big lingering question they have from the 2022 event: Where did that bloom come from?
The Bering Strait represents a confluence of many different water masses. The bloom was first spotted to the west of St. Lawrence Island, so the WHOI researchers at least know that the algae didn’t come from Alaska coastal waters. It may have originated in Bering Sea water or Gulf of Anadyr water, Fachon explained.
She said the team has now finished analyzing their sediment data from the 2022 cruise. Cysts of Alexandrium can lie dormant on the seafloor for decades, and the scientists’ work revealed a very significant accumulation of cysts in the southeastern Bering Sea near St. Paul.
“This southern cyst accumulation could serve as a source for blooms in the Bering Sea, but it’s unclear at this time whether something that starts down here would be able to make it all the way up to the Bering Strait by the end of July,” Fachon said. “We clearly have a lot more work that we need to do to understand the connectivity of this whole system, not to mention, we need a lot more data about what’s going on further to the west.”
Harmful algal blooms are an emerging threat in the Bering Strait and Arctic waters, but they’ve been a more regular summertime feature further in the Gulf of Alaska. This month the Knik Tribe has found several samples of mussels that have PSP toxins well above the FDA limit for consumption.


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