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Harmful Algal Blooms (HABs)

Harmful algae do occur along the coast and estuaries of the Northwest. Some marine algae produce toxins (biotoxins) that can accumulate in shellfish that are feeding on the algae. Humans and other animals can be harmed if they eat shellfish harvested from such an area. In the Northwest, the diatom Pseudo-nitzschia, can produce the toxin domoic acid, which can cause amnesic shellfish poisoning (ASP). Paralytic Shellfish Poisoning (PSP), is caused by a toxin produced by a dinoflagellate marine algae, Alexandrium. Recently, the algae Dinophysis, which causes Diarrhetic Shellfish Poisoning (DSP) has also become a species of concern in the Pacific Northwest. Other algal toxins can kill aqua-cultured fish, such as produced by the algal species Heterosigma akashiwo.


HABs can lead to closures of recreational and commercial fisheries, which can cause serious economic impacts to coastal communities.

State agencies along the West Coast continually monitor shellfish for toxins and will close areas to shellfish harvest if toxins reach a certain minimum level.

State and local agencies along the West Coast continually monitor water quality and shellfish for toxins and will close areas to shellfish harvest if toxins reach a certain minimum level. In the Pacific Northwest, HAB events and the subsequent closing of beaches to shellfish harvest can have a major economic impact on communities which depend on shellfish aquaculture and tourism associated with recreational shellfish harvesting. Ongoing research and monitoring of HABs by NANOOS partners at the federal, tribal, state and local levels are working to:

  • Build our understanding of the causes of HAB events
  • Improve detection of HABs
  • Better identify health risk from HABs
  • Improve prediction of HAB events
  • Protect human health and support the recreational and commercial shellfish harvesting industry and the communities potentially affected by HABs

Amy Sprenger

Razor clamming along the Pacific Northwest coast is a popular recreational activity, bringing many visitors to coastal communities. When harmful algal blooms are detected along the coast, local health departments need to close the beaches to shellfish harvesting.

Is Shellfish Safe?

HABs Resources

Additional Resources

Detecting Harmful Algal Blooms in the Pacific Northwest

NANOOS Awarded Funds to Study 2015 West Coast Bloom

NOAA Funds HAB Forecasting System

Phytoplankton Bloom in Hood Canal 2016

NANOOS Ocean Technology Transfer Grant for 2014-2017

Overview of 2015 HAB Event

How are HABs Monitored?



HABs Research

Related NANOOS Products

Real-Time Data

The NANOOS Visualization System (NVS) provides easy access to forecast and observation data across a wide range of assets such as buoys, shore and land stations, high-frequency radar, and satellites.

Water Quality for Shellfish Growers

Access a wide range of water quality data tailored to the shellfish growing community.

Samish Bay Biosensor

The NWFSC Environmental Sample Processor (ESP) is an advanced biosensor for micro-organisms, including those responsible for harmful algal blooms.

Regional Coastal Observing Systems



Central and Northern California

Great Lakes

Gulf of Mexico

Pacific Islands


Atlantic - Northeast

Pacific Northwest

Southern California

Atlantic - Southeast