California HAB Bulletin: March 2021

Be sure to also read the special Red Tide Bulletin: Spring 2020 

Pseudo-nitzschia - C-HARM tells us where conditions are suitable for species of the diatom Pseudo-nitzschia spp. (all size classes) to grow well and where they might be more likely to produce the deadly neurotoxin, domoic acid (DA). The predicted suitable habitat for Pseudo-nitzschia spp. in March 2021 suggested widespread suitability throughout the state for Pseudo-nitzschia to grow and reach bloom levels, although the centers of highest likelihood shifted up and down the state throughout the month. The focal point was central California to the Santa Barbara Channel and into the nearshore zones of the Southern California Bight. Generally, though, C-HARM is still predicting positive habitat suitability for the genus Pseudo-nitzschia in most parts of coastal California much of the time, something that is corroborated by the frequent presence of Pseudo-nitzschia species in water samples at nearshore sites in most months. Given ongoing COVID-19 sampling restrictions and delays that continue to hamper our ability to acquire timely HABMAP observations from piers, not all piers are currently providing data, but we do know that the more toxigenic size class of Pseudo-nitzschia was observed at or above the bloom threshold at Santa Cruz Wharf, Cal Poly Pier, Santa Monica Pier, and Newport Beach Pier (where the less toxigenic "delicatissima" size class also bloomed in February and March). This is consistent with the fluctuating loci of high Pseudo-nitzschia probability that were skewed towards central to southern California. The Relative Abundance Index (RAI) for the Pseudo-nitzschia "seriata" size class recorded by the CDPH reached moderate levels (9-15%) in and around San Francisco and Tomales Bays, Santa Cruz Wharf, San Luis Obispo, similar to February. The difference was that sites in the Santa Barbara area and throughout Los Angeles and Orange Counties exhibited lower RAI for Pseudo-nitzschia "seriata" than they did in February, in contrast to the bloom levels seen at southern California pier sites sampled via HABMAP.

Moderate to very high C-HARM probabilities (50-100%) for particulate domoic acid (pDA) were predicted at different times for several sections of the California coastline in March with a focus on the central coast and southern California, similar to the pattern in February. As the month progressed, zones of high pDA likelihood, or "hotspots," intensified and moved more offshore along the central coast near the Santa Barbara Channel, San Luis Obispo, Monterey Bay, around San Francisco Bay, and throughout much of the Southern California Bight to San Diego (mid to late March). HABMAP particulate domoic acid data are not yet available for March. Similar patterns were predicted for cellular DA (cDA) risk as those for pDA, although often with more intensity and further offshore, particularly in San Luis Obispo and Monterey Counties. Unlike in February, both pDA and cDA probabilities were high much of March in a narrow band along the North Coast, suggesting a return to seasonal domoic acid problems in that region. However, a razor clam health advisory is still in effect for Humboldt and Del Norte Counties due to domoic acid. The only California Sea Lion stranding from suspected DA toxicosis in March was reported by The Marine Mammal Center (TMMC) on March 10th in Monterey County, a region that was a potential hot spot according to C-HARM and HABMAP sampling; no other regions reported suspected DA toxicosis cases in March.

Alexandrium - CDPH did not observe any Alexandrium spp. at sites sampled in March, consistent with HABMAP sampling, and there are no recreational shellfish advisories related to PSP at this time.

*Please note that HABMAP sampling, CDPH sampling, and marine mammal rescues have been greatly reduced in response to COVID-19 safety measures.

C-HARM Model

Probability of Pseudo-nitzschia Bloom for March 2021

Probability of Particulate DA for March 2021

Probability of Cellular DA for March 2021

Harmful Algal Bloom Monitoring & Alert Program (HABMAP) 

**HABMAP sampling resumed after being suspended in March 2020 in accordance with the Governor's stay at home order. However, COVID-19 safety protocols and sampling restrictions may continue to affect operations and delay results.**

Note that data for some stations are not shown because they are not yet recorded in the public HABMAP archive.

Differentiating Pseudo-nitzschia species by light microscopy is difficult. For this reason, Pseudo-nitzschia "seriata" does not refer to an actual species but rather the larger size class of Pseudo-nitzschia, which is generally a more toxigenic group of species. Alternatively, Pseudo-nitzschia "delicatissima" refers to the smaller size class that is generally non-toxigenic. The dashed line on the plots demarcates the 10,000 cells/L "bloom" threshold designated here for Pseudo-nitzschia populations only.

More information and data visualizations on the statewide HAB network and forecasting system can be found on the California HABMAP website and on the SCCOOS Harmful Algal Bloom page.  

Santa Cruz Wharf

Four water samples were collected at Santa Cruz Wharf in March. Molecular probes for toxigenic Pseudo-nitzschia in the "seriata" class are conducted for this site, and was detected twice: once on March 3 (above the bloom threshold level) and on March 17 (below the threshold). Alexandrium spp. were not detected. Domoic acid results are not yet available.

The Santa Cruz Wharf shore station is supported by CeNCOOS PI Raphael Kudela at UCSC.

Monterey Wharf

Water sampling has been suspended at Monterey Wharf since March 2020 in response to COVID-19 safety measures. 

Monterey Wharf shore station is supported by CeNCOOS PI's Raphael Kudela at USCS and Jason Smith and Moss Landing Marine Labs.

Cal Poly Pier

Five water samples were collected at Cal Poly Pier in March. Pseudo-nitzschia "delicatissima" was detected on three occasions (March 1, 22, 29) as was Pseudo-nitzschia "seriata" (March 1, 8, 29). All detections were below the bloom threshold value except for Pseudo-nitzschia "seriata" on March 1. Alexandrium spp. were detected once on March 22 (below the threshold). Domoic acid results are not yet available. 

Cal Poly Pier shore station is supported by SCCOOS PI Ryan Walter and Ally Pasulka at Cal Poly. 

Stearns Wharf

No samples were collected at Stearns Wharf in March.

Stearns Wharf is supported by SCCOOS PI Mark Brzezinski and Libe Washburn at UCSB. 

Santa Monica Pier

Four water samples were collected at Santa Monica Pier in March. Pseudo-nitzschia "delicatissima" was detected on each occasion (March 8, 15, 22, 29). All detections were below the bloom threshold value except on March 22. Pseudo-nitzschia "seriata" was also detected on each occasion, with March 22, 29 values being above the threshold. Alexandrium spp. were not detected and domoic acid results are not yet available. 

Santa Monica Pier shore station is supported by SCCOOS PI Rebecca Shipe at UCLA.

Newport Pier

Four water samples were collected at Newport Beach Pier in March. Pseudo-nitzschia "delicatissima" was detected on three occasions (March 1, 8, 29), with the first two samples being above the bloom threshold value. Pseudo-nitzschia "seriata" was also detected on three occasions (March 1, 8, 29), with the last two detections being above the threshold value. Neither "delicatissima" nor "seriata" were detected on March 15. Alexandrium spp. were not detected and domoic acid results are not yet available.

Newport Beach Pier is supported by SCCOOS PI David Caron at USC.

Scripps Pier

Scripps Pier water samples are not available for April 2020 through March 2021.

Scripps Pier is supported by SCCOOS and PIs Melissa Carter and Clarissa Anderson at UCSD.

CDPH observations for Pseudo-nitzschia "seriata". and Alexandrium spp.

Please note, starting in July 2019, CDPH moved to only reporting Pseudo-nitzschia of the seriata complex and not all Pseudo-nitzschia spp. as previously provided. 

From 1-31 March 2021, water samples were collected by volunteers and sent to the California Department of Public Health (CDPH) for analysis. Pseudo-nitzschia "seriata" group was detected in 44 of the 66 samples. Pseudo-nitzschia "seriata" was detected at "Common" density levels (using CDPH relative abundance index) on 2 occasions: March 1 (Capitola Pier in Santa Cruz, 15% composition) and March 6 (Presidio Pier in San Francisco, 12% composition). Alexandrium spp. were detected in 2 of the 66 samples. Of the 2 samples, one was at the "Rare" density level (Marina Bay Harbor in Richmond, 0.5% composition) and the other at the "Present" level (at Goleta Pier, 1% composition). 

You can view an interactive map and data table of CDPH data from January 2019 to present developed by SCCOOS below or you can also view CDPH Toxic Phytoplankton Observations Map with layers of Pseudo-nitzschia and Alexandrium spp. as well as other phytoplankton species observations (in the pop-up windows).

Data are provided by the California Department of Public Health, Environmental Management Branch.

Please email CDPH at for any potential marine HAB-related illness in humans.

CDPH and OEHHA Health Advisories

February 8. The California Department of Public Health (CDPH) has lifted the December 31, 2020 shellfish safety notification today related to sport-harvested mussels, scallops, and clams in Marin County.

January 12. The California Department of Public Health (CDPH) has lifted the November 18, 2020 shellfish safety notification today related to sport-harvested mussels, whole scallops, and clams in Mendocino County.

December 31. California Department of Public Health (CDPH) is advising consumers not to eat sports-harvested mussels, clams, or scallops from Marin County due to dangerous levels of paralytic shellfish poisoning (PSP) toxins being detected.

For the latest closures and updates, please visit the CDPH Health Advisories page as a central location of information related to CDPH health advisories. Also available is a map showing the current CDPH Recreational Bivalve Shellfish Advisories (see below).

NEWS: The HAB-related illness workgroup has developed a new webpage for marine HAB-related illness tracking work ( 

California Marine Mammal and Seabird Strandings from Suspected DA Toxicosis

Domoic acid (DA) is a potent neurotoxin produced by some diatom species of the genus Pseudo-nitzschia. Species exposed to DA can result in seizures, epilepsy, cardiomyopathy, and death depending upon the ingested dose. DA toxicosis commonly occurs in California Sea Lions (Zalophus californianus), presumably due to a combination of foraging behavior and seasonal movements. The Marine Mammal Center (TMMC), Channel Islands Marine Wildlife Institute (CIMWI), California Wildlife Center (CWC), Marine Mammal Care Center Los Angeles (MMCC-LA), Marine Animal Rescue (MAR), the Pacific Marine Mammal Center (PMMC), and SeaWorld act like an emergency room by working to rescue and rehabilitate sick and injured marine mammals, seabirds, and sea turtles. 

Among the seven rehabilitation centers we received data for in the month of March, 1 marine mammal stranding presented with symptoms of domoic acid toxicosis. 

The CIMWI, PMMC, MMCCLA and CWC, did not record any strandings due to suspected domoic acid in March 2021.   

March strandings due to suspected DA toxicosis occurred in the following counties:

  • Monterey (TMMC)
    • March 10 - subadult, male, California Sea Lion 

At this time we do not have data from the North Coast Marine Mammal Center.  

Contacts if you find a LIVE stranded animal

Contacts if you find a DEAD stranded animal

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