How scientists discovered toxic algae blooms are increasing in the Arctic

Yahoo

10-07-2025

Harmful algae blooms have been rapidly producing in a place previously too cold to host the toxin: the Arctic.
And climate change over the last several decades is to blame, according to new research.
Scientists have found a link between rising ocean temperatures and an increasing amount of toxins from algae blooms entering the marine food chain by analyzing the feces of bowhead whales in the Arctic, according to a paper published Wednesday in Nature.
MORE: Toxin detected in Lake Erie weeks earlier than ever before, NOAA says
Collaborations with native tribal communities in the Arctic helped researchers in their findings, said Kathi Lefebvre, a research biologist for NOAA fisheries at the Northwest Fisheries Science Center in Seattle and lead of the Wildlife Algal Toxins Research & Response Network (WARRN-West).
Researchers at WARRN-West have received fecal samples from 205 bowhead whales from the indigenous groups that were collected by either subsistence harvesting or found stranded in an unusual mortality event in the Beaufort Sea over the past 19 years, which put them in a unique position to monitor the progression of harmful algal blooms on the West Coast of North America, Lefebvre, lead author of the study, told ABC News.
By studying the samples, the biologists could look at algal toxin concentrations in the food web, Lefebvre. The krill and copepods that ingest the toxins are then eaten by the bowhead whales, which are filter feeders.
Over the past century, sea surface temperatures in the region have been rising, causing the amount of sea ice to shrink significantly. The warmer waters combined with more open water is leading to the higher concentrations of at least two algal toxins: Alexandrium, which are dinoflagellates that produce saxitoxin -- a neurotoxin that can cause Paralytic Shellfish Poisoning; as well as domoic acid, which is produced by Pseudo-nitzschia, a needle-like group of single-celled algae, and causes amnesic shellfish poisoning, according to the study.
"We know from laboratory studies that these algae grow faster in warmer conditions," Lefebvre said. "There's more light because the open water is there and the ice is not reflecting the light."
MORE: How humpback whales are playfully communicating with humans, according to scientists
The cells have always been present in low concentrations in the Arctic, but the potential blooms are now larger, longer lasting and more toxic, Lefebvre said. Alexandrium drops cyst-like seeds that lay dormant in the sediments until conditions are right to produce.
"So seeds have been dropping from these Alexandrian cells for hundreds, maybe thousands of years, and these seeds need a certain temperature to be able to germinate," she said.
MORE: What to know about the toxic algae bloom killing marine life in Southern California
In the past, the bottom waters of the Arctic have been too cold for the cysts to germinate, but as the ocean warms, conditions are becoming ripe for reproduction.
This is the first study of its kind to quantitatively show a direct link between climate change, sea ice loss and harmful algal bloom concentrations in the food web, Lefebvre said.
The Arctic tribal communities that collected the samples are still fully reliant on marine resources for subsistence, Lefebvre said.
"Marine resources are utilized for survival, for cultural practices, for economic well being, etc.," she said. "They've been doing this for thousands of years."
In most places around the world, there are protections in place to test for these toxins for commercial seafood. But in the "vast remote" regions of the Arctic, such testing would be difficult to conduct on a regular basis, Lefebvre said.
The communities harvest everything from clams, crabs, sea birds and anemones.
"We're finding these toxins in all of these species," Lefebvre said.
MORE: 'Demonic' sea lion reports spark concerns about toxic algae on California coast
It is unclear how many whales in the Arctic have died as a result of harmful algae blooms, but walrus populations in the region, which feed on clams found at the bottom of the ocean, have been likely dying off as a result, Lefebvre said.
Lefebvre has been studying harmful algae blooms for her entire career and was involved in the first-ever study in 1998 that found domoic acid was impacting marine mammals in Central California.
Ever since, dozens to hundreds of marine animals have been documented to suffer from domoic acid poisoning every year, Lefebvre said.
Southern California is currently recovering from its worst harmful algal bloom event, which impacted more than 1,000 marine animals overall since it began earlier this year, according to the Marine Stranding Network.