noaa.gov

West Coast Harmful Algal Bloom

NOAA responds to unprecedented bloom that stretches from central California to the Alaska Peninsula.

people digging clams on the beach in Washington State

Clam diggers along the Washington state coast. So far this year, the presence of harmful algal bloom toxin in Washington state water's has resulted in fishery closures, which can have tremendous economic and ecological effects. In May, the razor clam fishery closed resulting in an estimated $9.2 million in lost income. The state's commercial crab fishery, worth roughly $84 million annually, has also been affected.

In the summer of 2015, a massive toxic bloom of the marine diatom Pseudo-nitzschia, stretching from central California to the Alaska Peninsula, resulted in significant impacts to coastal resources and marine life. NOAA worked closely with federal, state, tribal, academic, and other partners to respond to this unprecedented harmful algal bloom (HAB).

Blooms of Pseudo-nitzschia occur annually at "hot spots" along the U.S. West Coast and produce a potent neurotoxin, domoic acid, which can accumulate in shellfish, other invertebrates, and sometimes fish, leading to illness and death in a variety of seabirds and marine mammals. Human consumption of shellfish contaminated with domoic acid can result in Amnesic Shellfish Poisoning, which can be life threatening but is also rare. For finfish like salmon, tuna, and pollock, levels in edible portions of the animal are well below levels of concern for human consumption. Greatest human risk is from recreationally-harvested shellfish; commercial shellfish and finfish are closely monitored and safe to eat. Each state maintains public websites indicating where harvesting shellfish can be safely conducted.

This particular bloom was detected in early May 2015, when Washington closed its scheduled razor clam digs on coastal beaches. Scientists quickly recognized that the bloom extended from California's Channel Islands to as far north as Alaska. The bloom was the largest and longest-lasting in at least the past 15 years. Concentrations of domoic acid in seawater, some forage fish, and crab samples were among the highest ever reported for this region. By mid-May, domoic acid concentrations in Monterey Bay, California, were 10 to 30 times the level that would be considered high for a normal Pseudo-nitzschia bloom. Other HAB toxins were also detected on the West Coast. Shellfish closures in Puget Sound protected consumers from Paralytic Shellfish Poisoning and Diarrhetic Shellfish Poisoning.

Coastal Impacts

Impacts to coastal resources and marine life included shellfish and Dungeness crab harvesting closures in multiple states, anchovy and sardine fishery closures in some areas of California, and sea lion strandings in California and Washington. Other marine mammal and bird mortalities were reported in multiple states, but domoic acid was not confirmed as the cause. On August 20, 2015, NOAA declared an Unusual Mortality Event for large whales in the Western Gulf of Alaska. During the bloom, scientists recorded the mortality of 30 large whales. The HAB event was suspected of playing a role in the deaths of these whales given the noted warmer than usual ocean temperatures in the Gulf of Alaska and the algal bloom documented in neighboring areas (Kachemak Bay). However, there was no conclusive evidence at this date linking the whale deaths to HAB toxins.

Nearly one year since the start of the bloom, most shellfish and fish harvesting have reopened, but Dungeness crab and razor clam harvesting in some parts of northern California remain closed due to some persistent elevated domoic acid levels in the region.  The full economic impact of these closures is still being calculated.

While researchers are investigating the exact causes of the severity and early onset of the bloom, unusually warm surface water in the Pacific is considered a factor. First reported along the West Coast in the 1990s, Pseudo-nitzschia blooms have also been observed off the U.S. East Coast and in the Gulf of Mexico.

NOAA's Response

At the outset of this event, NOAA already had multiple HAB projects underway along the West Coast. NOAA responded quickly after the bloom was detected to determine its geographic extent and causes. Specific efforts by NOAA include:

  • NOS's National Centers for Coastal Ocean Science (NCCOS)  funded work to determine why there are Pseudo-nitzschia hot spots on the West Coast. The researchers were already conducting a field study in Monterey Bay and extended their sampling of Pseudo-nitzschia and domoic acid to waters off of Orange County, California, in order to determine the geographic extent of the bloom. They are trying to determine what combination of water movements and nutrients derived from either human activities (agriculture or sewage) or natural sources (upwelling), cause Pseudo-nitzschia hot spots.
  • With NASA funding, NOAA and its academic partners are collaborating to provide experimental forecasts of the probability of Pseudo-nitzschia blooms and elevated domoic acid levels along the California coast. Results are disseminated by the Central and Northern California Ocean Observing System, a regional component of the U.S. Integrated Ocean Observing System (U.S. IOOS®).
  • NOAA's Phytoplankton Monitoring Network and Northwest Fisheries Science Center helped establish the Southeast Alaska Tribal Toxins monitoring partnership and trained Alaska tribal natural resource specialists for improved HAB detection.
  • NCCOS' Kasitsna Bay Laboratory and the Phytoplankton Monitoring Network are monitoring HAB species and domoic acid levels in Kachemak Bay using field test kits developed from NOAA research.
  • The Olympic Region Harmful Algal Blooms partnership, established with NCCOS funding, is monitoring Pseudo-nitzschia and domoic acid along beaches on the Washington coast.
  • NOAA coordinated Pseudo-nitzschia and domoic acid sampling on NOAA Fisheries survey and ocean acidification cruises this summer from California to Alaska to identify Pseudo-nitzschia hotspots and assess the overall extent of the bloom.
  • The National Centers for Coastal Ocean Science and U.S. IOOS program office funded the Northwest Association of Networked Ocean Observing Systems (Pacific Northwest regional component of IOOS) to work with the Northwest Fisheries Science Center and University of Washington researchers to provide experimental HAB forecasts for coastal Washington this summer and fall, distribute domoic acid test kits to tribes, and develop understanding of the environmental causes of this large-scale event in order to improve future HAB forecasting efforts.
  • The Southern California Coastal Ocean Observing System (Pacific Southwest regional component of IOOS) maintains the Harmful Algae and Red Tide Regional Map, which disseminates HAB monitoring data from eight piers between Santa Cruz and San Diego, California.