Despite Record Levels, Domoic Acid Poisoning a No-Show So Far
A Threat in the Water
Despite hitting its highest historical level on the California coast in April, the marine neurotoxin domoic acid has so far been implicated in this area only as a suspect in the deaths of a gray whale that washed ashore in Santa Barbara and a minke whale that rolled onto a Ventura beach in the past month. The healthy condition of Santa Barbara sealife contrasts with reports of dead seabirds presently littering the coast in San Pedro and elsewhere in Southern California due to domoic acid poisoning. The current situation also differs from a 2002 outbreak that left 299 marine mammals dead on Santa Barbara beaches by the time the algae that produces the acid had stopped blooming, according to Peter Howarth, director of the Santa Barbara Marine Mammal Center.
Most marine birds and mammals are poisoned by eating sardines and other small, filter-feeding fin fish. Santa Barbara has escaped this year, Howarth speculated, because the fish on which seabirds feed may be absent from the area. “Maybe the concentrations of schools of fish are elsewhere now,” Howarth said. “If they move into our waters, we’re in deep trouble.” Symptoms in afflicted sea mammals include head-weaving, bulging eyes, mucus from the mouth, disorientation, drunken movements, and seizures-all of which may impair their ability to swim, so they often come to the beach to rest.
Domoic acid poisoning among humans is rare. There has never been a single reported case in California. Nonetheless, domoic acid poisoning was first identified following an outbreak among humans in 1987 on Prince Edward Island in Canada. Three people died, and about a hundred became ill. Among the effects: permanent brain damage, notably short-term memory loss. The small number of documented cases in humans may stem from the fact that people do not eat sardines and similar fish in the same quantity that sea mammals and birds do, said Rick Merrifield, environmental health director for Santa Barbara County. Furthermore, it is not on the list of diseases reported to the federal Centers for Disease Control for the purpose of tracking. However, many scientists believe that domaic acid, produced seasonally by several species of pseudonitzschia, is on the rise due to increased algae blooms, fed by nutrients washing into the ocean.
To avoid another human outbreak, the California Department of Health Services (DHS) issued three warnings and inaugurated an early quarantine on non-commercially harvested shellfish when it found the unprecedented levels-610 parts per million-during routine tests on shellfish on April 24 in the waters off of Santa Barbara. By contrast, in the 2002 outbreak, the highest spike measured was 380 ppm. The average level this season is under 450 parts per million, a level that can cause brain damage or death, according to DHS spokesperson Lea Brooks. What are termed “mild” symptoms including cramps, diarrhea, and vomiting are associated with levels above 27 ppm. Headaches and disorientation are associated with levels above 40 parts per million. Based on inferences from the Canadian outbreak, these figures are tentative. Warnings are normally issued at 20 ppm.
Bernard Friedman-owner of Santa Barbara Mariculture, a shellfish farm about a mile off Hope Ranch-is required to test weekly for domoic acid and other toxins. He first found high levels on April 11 and stopped harvesting, in accordance with DHS requirements.
The precautions that apply to Friedman’s business do not apply, however, to commercially caught crabs, crayfish, and lobsters, whose internal organs may harbor the toxin. There is no testing required of commercially harvested crustaceans. A local registered commercial crab fisher who sells a variety of rock crabs and spider crabs to numerous local restaurants, said he has never received so much as an advisory from the state on the matter of domoic acid. He noted that many crab fanciers eat the viscera, commonly known as “butter.” The viscera and the roe of female crabs are also a popular ingredient in Asian cuisines. The Santa Barbara Shellfish Company at the end of Stearns Wharf does not sell locally harvested shellfish, whose annual quarantine makes it simpler to import shellfish from Alaska year ’round, said manager Evan Rothman. However, like many Santa Barbara restaurants, it does serve locally caught crustaceans.