Ocean scientist Raphael Kudela, the Lynn Professor of Ocean Health at the University of California-Santa Cruz presented the latest research findings on the extraordinary duration and intensity of the 2015 domoic acid event that has occurred along the Pacific coast of North America at the American Geophysical Union (AGU) Fall Meeting in San Francisco on Friday.
Scientists conducted the investigation to document the spread of the algal toxin in the marine food chain. Domoic acid is a powerful neurotoxin produced by a particular type of microscopic algae called Pseudo-nitzschia. It is normally found in coastal waters of California, occurring for just a few weeks in the spring and fall.
This year, however, unusual oceanographic conditions led to the largest and longest-lasting algae bloom ever recorded. Researchers say the event was not related to El Nino, reports Science News on Line.
“The duration of the bloom and the intensity of the toxicity were unprecedented, and that led to record levels of the toxin in species such as anchovies, razor clams, and crabs,” Kudela said. “We also saw the toxin in organisms and parts of organisms where we thought it was not supposed to be, like the fillets of fish.”
The information in the report has already brought about some changes, including stepped up monitoring programs to ensure the safety of seafood for human consumption. Additionally, several west coast fisheries have been shut down and the opening of the Dungeness crab season has been delayed.
While the levels of domoic acid found this year in the fillets of salmon, rockfish, and ling cod were below regulatory limits, Kudela said that once the toxin gets into the muscle, it will stay in the fish and in the food chain longer than if it was just in the intestinal tract.
“Before this year, it was a big question whether it gets into the fillet at all,” he said. “We think what happened is the bloom lasted so long and was so toxic that the prolonged exposure allowed the toxin to perfuse into the muscle tissue, and it also worked its way into the food web to an extent that we hadn’t seen before.”
Kudela also explained the reason for the delay in the opening of the Dungeness crab season. Because of the large size of the algae bloom, the toxin has built up in the seafloor, and that explains why the crabs are still toxic. Domoic acid can stay toxic for months after the algae bloom is gone.
“The crabs are feeding on the seafloor, and all the things they would typically eat can hold the toxin for months,” he said. “It could be another month or longer before the toxin in crabs drops below the regulatory limit everywhere in California.”
Kudela blames the unusual toxic algae bloom this year on the two “warm blobs” that occurred, the first one appearing in the North Pacific west of Seattle in late 2013. In 2014, the second blob appeared off of southern California. In 2015, the two blobs merged. “We had two pools of warm water hitting the coast in the Pacific Northwest and southern California and merging, so all at once there were warm waters over the whole west coast,” Kudela said.
The warm water created perfect conditions for Pseudo-nitzschia. What few upwellings of cold water-rich nutrients there were always got pushed back down by the warm blob. All this created a record-breaking toxic algae bloom that started in April and lasted into early October. The bloom also spread from Santa Barbara clear up the North American coast to Alaska.
There is a worrisome question in all of this. What effect will the El Nino event have on a toxic algae bloom leading into 2016? El Nino brings warming waters. “The predictions are for this El Niño to be as strong as the one in 1997-98 when the warm water lasted through 1998. So we could be looking at a big bloom again next year,” Kudela said.
Articles on domoic acid and marine life off the North American coast that may be of interest:
Study: Stranded sea lions have brain damage from algal toxins
Deadly harvest: Toxic algae killing sea life at record levels
