Algal Blooms

This page includes recent information or images on active algal blooms or factors that may cause them in central and northern California. Blooms are composed of one or more species of phytoplankton. Some blooms can become 'red tides', that appear brown to red in color and can be harmful or harmless to people or wildlife depending on the species forming the bloom. Other blooms are not visible but can still cause health problems. Learn more about algal blooms at the CeNCOOS algal bloom education page.

*Current Bloom Alert: Beginning in May 2010, researchers in Monterey Bay (Monterey and Santa Cruz) reported a bloom of the plankton species: Pseudo-nitzschia. No toxins have been detected yet in association with the bloom. See links below for up-to-date info on this event:

Real-time Satellite Sea Surface Temperature and Chlorophyll maps  

Real-time Santa Cruz Ocean Observing Platform (SCOOP)


Real-time CeNCOOS Shore Stations (including chlorophyll data)

Trinidad | Humboldt Bay | Tiburon | Morro Bay





CalPReMPT Santa Cruz Wharf Plankton Weekly Updates


BOG Bits - The Blog of the Bodega Oceanography Group


California Public Health Dept - Marine Biotoxin Monthly Reports


Report Ongoing Blooms!

Past bloom reports from the CeNCOOS region:

(Left image) A bloom of Ceratium in Monterey Bay on Oct 6th, 2009 contributed by John Ryan of MBARI using imaging spectrometry onboard a Airship Ventures, Inc. airship project run by Steve Dunagan of NASA/AMES.

- October 17th: A bloom was reported off Stinson Beach (Marin County north of SF) by a helpful observer in our region. Pseudo-nitzschia was more abundant in the blooms at this time, this species can be harmful to wildlife and humans through shellfish poisoning etc.

- September 27th: A bloom was also reported 5-7 miles W/SW of the Golden Gate by a concerned citizen. This bloom was likely dominated by Ceratium, which is non-harmful.





(Left image) Photo by Lana Ellis. Late-August 2009: Half Moon Bay Review reported an intense bloom at Surfer's Beach in Half Moon Bay, CA.






We attempt to post information on current algal blooms in the CeNCOOS region on this page. If you have any information on a potential algal bloom in central or northern California, please contact Tom Wadsworth (twadsworth@mbari.org) with CeNCOOS. In your email message, please provide as specific information as possible on the location, date and nature of the bloom you observed as well as your contact information. Thanks for you help!

Sources of further information:

  • During October 2008, the Monterey Bay Aquarium Research Institute (MBARI) and other US, European, and Japanese partners institutions conducted oceanographic surveys as part of the "Monterey Bay 2008 Experiment". View results from this project.
  • A significant harmful algal bloom (red tide) event occured during November 2007 in Monterey Bay (view the CeNCOOS report). 2007 Red tide event linked to large scale seabird strandings (pdf publication)
  • View CeNCOOS report on 2007 algal bloom here
  • View the CIMT Fact Sheet on harmful algal blooms (HABs) here

  • View results and discussions from MB08 project hereMBARI


For more information contact Tom Wadsworth (twadsworth@mbari.org) or Heather Kerkering (heather@mbari.org).