Warm Waters In Pacific Ocean Stoke Algal Bloom, Which Releases Neurotoxin, Delaying Dungeness Crab Fishing Season
California’s Dungeness crab fishing season has been delayed due to high levels of a dangerous neurotoxin, and scientists believe increasingly warm water in the Pacific Ocean is to blame.
In November, when boats should be fishing off the coast just north of Santa Barbara, they’re waiting on the shores instead, with anxious fishermen who rely on catching crabs to make a living. A large algal bloom, however, has made the crab living off the coast unsafe for consumption, as the algae release a toxin into the water that could possibly affect other seafood while they work their way up the food chain. The fishing season has therefore been delayed until the bloom dissipates, putting a $60 million commercial and recreational fishing industry on hold.
“This bloom has been unprecedented in its extent and its persistence,” Clarissa Anderson, a research scientists at the Institute of Marine Sciences at the University of California, Santa Cruz, told NPR News. “It started in May and continued on to September. And while we were expecting such a bloom in the spring and even into the summer, as has happened in years past, we did not really expect to see this continue into September.”
The bloom is created by an organism called Pseudo-nitzchia, which accumulates on the surface of the coastal waters. Algae blooms thrive in the warm summer waters; because climate change has increased temperatures in the Pacific Ocean, the bloom has been able to survive longer. One-third of all blooms produce potentially harmful toxins, which build up in the flesh of marine life. This particular neurotoxin is called domoic acid.
Anderson said that although it stops producing the toxin after the peak bloom season, sediment gets left behind where it continues to be consumed by all kinds of bottom feeders, like crustaceans and shrimp. “This is usually the time of year when we expect an algae bloom to dissipate, because typically the water is cooling off,” said Michael Milstein, a public affairs officer at the National Oceanic and Atmospheric Administration (NOAA). “But in this case it doesn’t seem to be tapering off as we would have expected, and that’s in large part because the ocean is still quite warm.”
The warmer temperatures also force fish to seek out colder waters for survival, which leaves sea lions — normally living on the coast — without their main food source. The combination of the persistent algae bloom and the migratory fish caused the NOAA to deem the situation “unusual mortality event.”
The warm water’s domino effect is largely unpredictable to scientists, but as the toxins have worked their way up the food chain, the consequences have become more apparent. In early September, for example, the Marine Mammal Center rescued 180 sea lions, 75 percent of which were suffering from the effects of the neurotoxin.
Ingesting the domoic acid can lead to severe illness in humans and other animals. Becoming sick from the neurotoxin, called “domoic acid poisoning” has been responsible for several deaths, permanent illnesses, and toxic symptoms. Some of these symptoms include loss of short term memory, seizures, lethargy, disorientation, vomiting, and diarrhea, according to NOAA’s Northwest Fisheries Science Center.
Sick and dying seabirds typically indicate the presence of such a neurotoxin in the water because they consume the crabs and other crustaceans. With sickness and danger lurking in the water, fishermen must remain wary as they’re responsible for keeping crabs out of the mouths of consumers.
"This is out of the fishermen's hands. We have to wait until the product is safe," commercial fishermen Frank Sousa told CBS News. "I have kids and I wouldn't want to bring that product home to them, so I can't bring it home to anybody else."
The crab season was supposed to begin on Nov. 15; however, it’ll remain delayed until the crabs have been tested and proven safe for consumption, according to the California Department of Fish and Wildlife. Scientists will determine safety by testing individual crab flesh for the dangerous toxins. The season will begin again when they’ve determined enough crabs contain levels of the toxin low enough for human consumption.
Still, that won’t mean crabbers are out of “warm” water. Scientists predict sea levels could rise up to one meter by the year 2100, creating “conditions that are perfect for the growth of algae.”