Monumental algal bloom
The effects on humans of the ingestion of domoic acid can lead to Amnesic Shellfish Poisoning (ASP), which usually displays the following symptoms:
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Low doses: gastric upset.
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Moderate doses: confusion, permanent loss of short-term memory.
- High doses: can be fatal (3 deaths were recorded in Eastern Canada in 1987).
There is no antidote available to neutralize this toxin, and there is currently no way to detoxify infected meat. There have already been records of the death of some marine mammals due to this year’s bloom - animals that have been feeding on infected shellfish. The bloom is said to occur from the Pacific shoreline to a distance of 50 – 100 km offshore. The immediate coastline is currently fairly cold, while offshore waters are unusually warm, and this leads to a strong episode of upwelling of nutrients, which provide food for the proliferation of these algae, which can also affect fish species that feed on microalgae like herring, sardines and anchovies and their predators.
As this news release, issued by the US National Oceanic and Atmospheric Administration (NOAA) earlier this week explains, fisheries have already been closed due to this phenomenon, which last occurred in 2002/03. The organization is mobilizing to gauge this unprecedented occurrence:
NOAA Fisheries’ Northwest Fisheries Science Center in Seattle has mobilized extra scientists to join a fisheries survey along the West Coast to chart an extensive harmful algal bloom that spans much of the West Coast and has triggered numerous closures of important shellfish fisheries in Washington, Oregon and California. The bloom stretches from the Central California Coast north to Washington and possibly Alaska, and involves some of the highest concentrations of the natural toxin domoic acid ever observed in Monterey Bay and off the Central Oregon Coast. In early June elevated toxin levels led shellfish managers to close the southern Washington Coast to Dungeness crab fishing, the largest-ever closure of Washington’s multi-million-dollar crab fishery. “We’re taking advantage of our active surveys to focus research on a serious concern for coastal communities and the seafood industry,” said Eileen Sobeck, assistant administrator for NOAA fisheries. “The better we understand what’s happening out on the water, the better we can address the impacts.”
While localized blooms of marine algae that naturally produce domoic acid are common in spring, the bloom that began earlier this year has grown into the largest and most severe in more than a decade. Sardines, anchovy and other fish that feed on the algae and other microorganisms known as plankton can accumulate the toxin, in turn poisoning birds and sea lions that feed on them. “This is unprecedented in terms of the extent and magnitude of this harmful algal bloom and the warm water conditions we’re seeing offshore,” said Vera Trainer, manager of the Marine Microbes and Toxins Program at the Northwest Fisheries Science Center (NWFSC) in Seattle. “Whether they’re related we can’t really say yet, but this survey gives us the opportunity to put these pieces together.”
State agencies monitor toxin levels closely and impose harvest closures where necessary to ensure that all commercial seafood remains safe to eat. NOAA Fisheries and others are also developing advanced robotic systems and models to better detect and forecast harmful algal blooms. See state agency websites linked d below for the latest details on closures in California, Oregon and Washington.
The NWFSC’s Marine Microbes and Toxins Program is working closely with the University of California Santa Cruz, University of Washington, Quileute Nation and Makah Tribe to add scientists to an already scheduled fisheries survey leaving today (June 15) from Newport, Ore., aboard the NOAA research ship Bell M. Shimada. The survey is a partnership between the NWFSC in Seattle and the Southwest Fisheries Science Center in La Jolla, Calif., to assess sardine and hake populations on the West Coast. The additional scientists will examine levels of marine toxins and the organisms that produce them.
The researchers will collect samples of water, the microscopic diatoms that produce domoic acid and another form of marine microorganism called dinoflagellates that produce another type of toxin called paralytic shellfish toxins (PSTs) that have also been detected in some shellfish. Domoic acid and PSTs are rarely found in shellfish at the same time, but they have been this year. The scientists will also sample plankton-feeding fish such as anchovies and sardines that concentrate the toxins and transfer them to other marine animals.
Research during previous harmful algal blooms found “hot spots” of toxin-producing organisms along the West Coast, Trainer said, and the survey will search for similar concentrations this year. The Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Research Program is completing a study of one such hot spot in California’s Monterey Bay and provides funding for UC Santa Cruz to analyze samples that will be collected during the survey. The results will help investigate connections between the current bloom and unusually warm ocean temperatures that have dominated the West Coast since last year, which may offer a preview of ocean conditions likely to become more common with climate change.
California officials have warned against consuming recreationally harvested mussels and clams, commercially or recreationally caught anchovy and sardines, or the internal organs of commercially or recreationally caught crab taken from Monterey and Santa Cruz counties. Officials in Oregon have halted all shellfish harvesting from the Columbia River south to Tillamook Head and closed the entire state coastline to razor clamming because of elevated levels of domoic acid. High levels of PSTs have led to the closure of mussel harvesting along the Oregon Coast north of Gold Beach. All coastal Washington beaches have also been closed to razor clamming, at an estimated loss of more than $9 million (~€8 million) in revenue for coastal communities in the last month alone.
