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Harmful Algal Bloom in California: Pseudo-nitzschia Spread Along Coast Causing Massive Mortalities of Marine Life in Spring 2007

A massive harmful algal bloom along the California coast escalated in April 2007, resulting in record toxin levels and hundreds of seabird and marine mammal deaths. National Centers for Coastal Ocean Science-funded researchers and managers worked to predict and respond to the ongoing bloom, which impacted areas from San Luis Obispo south to Los Angeles. Harmful algae from the genus Pseudo-nitzschia produce a potent neurotoxin called domoic acid that can accumulate in shellfish and fish, such as sardines and anchovies, causing illness or death higher in the food chain. Humans that consume contaminated seafood can experience a syndrome called Amnesic Shellfish Poisoning (ASP).

Researchers monitored Pseudo-nitzschia abundance and analyzed water samples of water, shellfish, finfish, crab, and sick or dead animals to determine domoic acid levels. Managers with the Department of Health Services required shellfish growers in prior bloom hotspots to collect phytoplankton samples and screen harvest samples with quick tests, as a supplement to routine laboratory analysis, to provide early detection of toxicity. During late March 2007, researchers first detected an increase in Pseudo-nitzschia cells in San Luis Obispo, located north of Santa Barbara, California.

They alerted other researchers and resource managers in the region to the need for increased monitoring, which resulted in an earlier than normal quarantine of sport-harvested mussels and a warning against eating other sport-harvested shellfish, sardines, and anchovies and the organs of sport-harvested crab or lobster in some locations.

Bloom Reports

Southern California

Toxin in mussels sampled at the end of April indicated that the bloom had reached shore in some locations in the Los Angeles area. Sampling of Southern California coastal waters in April also revealed the highest concentrations of domoic acid ever reported in natural plankton samples. Analysis from field data collected in early May indicated that the bloom was subsiding and toxin concentrations had dropped by several orders of magnitude indicating this season’s algal bloom might potentially be subsiding.


A survey by the Center for Integrated Marine Technology (CIMT) shows toxin levels during this event (in red) compared to recent years at Santa Cruz Wharf. Figure courtesy of R. Kudela, UCSC

Central California

In early May, samples from the center of Monterey Bay indicated a patchy but intense bloom of Pseudo-nitzschia as far north as Santa Cruz with high levels of domoic acid measured in water in early May 8 (see plot provided by UCSC). However, the bloom did not appear to have touched shore to the same extent as in Southern California as evidenced by results from near shore cell and toxin monitoring. Water samples in early May also indicated cell and toxin concentrations were on the decline in the Monterey Bay region and to date Pseudo-nitzschia has disappeared from all samples. For more on sampling results, visit the Cal-PReEMPT webpage on the 2007 event.

Chain of Pseudo-nitzschia australis cells under light microscopy

Chain of Pseudo-nitzschia australis cells under light microscopy

CSCOR Collaborative Research on Pseudo-nitzschia in California is Working to Improve Management Capabilities

NOAA’s Monitoring and Event Response for Harmful Algal Blooms (MERHAB) program and EPA’s Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) program are funding collaborative projects in the Southern California Bight with the goal of understanding the relationship between toxic Pseudo-nitzschia blooms and the coastal oceanography of this highly urbanized region. The extensive data sets from these projects will be critical for determining relationships between toxic blooms and changing environmental conditions in Los Angeles coastal waters, where these blooms are a recurring problem. MERHAB will develop and demonstrate an innovative intensive HAB monitoring program that integrates in situ sensor networking technology, state-of-the-art remote sensing, and cutting-edge species identification and domoic acid quantification methods. Collaborators include University of Southern California, University of California Los Angeles, University of California Santa Cruz, California Institute of Technology, and the Southern California Coastal Water Research Project. This is a critical first step for developing predictive capabilities and other strategies to mitigate the impacts of HABs on regional coastal water quality, marine mammals, and harvestable shellfish.

Scanning electron micrograph of Pseudo-nitzschia australis, 1,000x and 10,000x (inset)

Scanning electron micrograph of Pseudo-nitzschia australis, 1,000x and 10,000x (inset)

MERHAB is funding another project focused in Central California (Cal-PReEMPT). Cal-PreEMPT aims to improve early toxin and cell detection, rapid response, and bloom tracking in order to minimize impacts on coastal communities with an ultimate goal of developing an economically sustainable monitoring plan for the California coastline. Core partners in this project include University of California Santa Cruz and the California Department of Health Services. Cal-PReEMPT is also affiliated with the Monterey Bay National Marine Sanctuary, the Center for Integrated Marine Technology and the Central and Northern California Ocean Observing System. All these projects are working together and with others in the region to advance the state of the knowledge and minimize impacts on humans and ecosystems.

NCCOS-sponsored HAB research in California is aimed at developing an automated system to warn coastal resource, health, and water quality managers of impending blooms and to bring new technologies for rapid toxin and species detection and tracking into existing state monitoring programs. NCCOS has invested $15 million since 1998 to support research on Pseudo-nitzschia on the West Coast. For a list of these and other agency projects, click here.

Information About CSCOR HAB Programs & Pseudo-nitzschia Research on the West Coast

Information About Pseudo-nitzschia and its Toxins

General Information About Harmful Algal Blooms

Key Legislative and Scientific Drivers Guiding NOAA Response to HABs

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