December 2024 - February 2025

Summary written by Dr. Clarissa Anderson, 30 March

- SUMMARY: The big story of this La Niña winter and early spring is the intense domoic acid (DA) and marine mammal mortality event that seems to have begun in southern California and Baja in December, leading to reports of many sick animals in Mexican waters, followed by a late winter/early spring resurgence from Santa Barbara to San Diego, spreading into central California in early March (wait for next bulletin). Impacts were mostly seen in marine mammal populations, however, that began to shift in March (seabirds and shellfish). Localized impacts from fire-related ash deposition in the Los Angeles area are possible for that region. We report here in this bulletin on the earlier stages of the ongoing event and promise to flesh out the full story in the March and April bulletin. Reminder: this is the fourth year in a row of a DA event associated with a major marine mammal mortality event. Those were in summer (some unusally late in the year); this one in winter and early spring. All have been associated with some level of upwelling and even anomalous upwelling at times.
- C-HARM model predictions for Pseudo-nitzschia blooms and domoic acid events indicate areas of high DA potential in northern California in early December, waning significantly by mid-December, which coincides with the lifting of several shellfish and Dungeness crab advisories in that region. Potential hot spots were predicted in central and southern California in December, consistent with measurements of high DA at southern California pier sties at that time. C-HARM predicted increasing probabilities in central and southern California as the winter progressed into spring, although regions such as coastal northern California around Humboldt and central CA around San Francisco Bay were experiencing many days where the prediction was for a very high likelihood of toxic blooms in early January 2025 without much in the way of documented impacts. This was not the case for cellular domoic acid event predictions, which were elevated in central and southern California throughout January and increased in probabilities into February for the Santa Barbara Channel and areas southeast of the channel, into the Bight. Animal strandings due to DA toxicosis started as early as February 20th in the Santa Barbara and Los Angeles areas, although reports of a marine mammal mortality event in December in Baja California have been communicated to us by our partners at CICESE in Ensenada (not yet part of the HABMAP/HAB Early Warning Network).
- Weekly HABMAP sampling of phytoplankton and toxins at nearshore pier stations reveals interesting dynamics starting as early as December. The larger and more toxigenic Pseudo-nitzschia “seriata” size class well exceeded the bloom threshold of 10,000 cells/L at Scripps Pier in La Jolla, San Diego on December 23rd (171,470 cells/L) when few people were paying attention to coastal processes, with the holidays in full swing. A week later, cell abundance measurements at Scripps Pier were slightly lower but still at very high and worrisome levels (86,986 cells/L), followed by measurements of bloom levels of the P. “seriata” size class at Santa Monica Pier on January 13th (over 34,000 cells/L). Newport Beach Pier followed suit with 46,778 cells/L on February 4th. At Stearns Wharf in Santa Barbara, there were 8,400 cells/L of P. “seriata” on Dec 17 and another peak of 4,200 cells/L on Feb 3rd. This sort of progression north or south as ocean conditions slowly become favorable for an algae bloom over a wider geographic range is not unusual. In this case, the onset of favorable conditions in southern California and Baja seems to coincide with early-onset upwelling associated with La Niña conditions, something that has been seen during previous transitions from La Niña to El Niño in the winter and spring. While Pseudo-nitzschia blooms and DA events are not necesssarily a predetermined outcome of La Niña events, they were seen in conjunction with the transition in both 1997/1998 and 2010/2011 (and perhaps other years). DA measurements at those same piers track the development of the Pseudo-nitzschia bloom, with very high levels at Scripps Pier on December 23, 2024 (2,400 ng/L) followed by high levels (640 ng/L) at Newport Beach Pier on January 21, 2025. Keep in mind that 500 ng/L is our operational threshold for a potential DA “event.” DA levels were also detectable at Santa Monica Pier by January 21st. Cal Poly Pier also reported bloom levels of the P. “seriata group on January 19th (no detectable DA), but that localized bloom appeared to be short-lived. DA was detectable at Santa Cruz Wharf on February 12th but below the operational “event” threshold, with no reports of Pseudo-nitzschia or DA north of Santa Cruz Wharf in Dec 2024 through Feb 2025.
- The southern California DA detections and C-HARM predictions are consistent with the rapid increase in reports of stranded CA Sea Lions and long-beaked common dolphins beginning in late February but do not explain the lack of such reported wildlife cases in December 2024 and January 2025. Interestingly, with many animals reported early on in the Santa Barbara Channel region by CIMWI, we would have expected to see high abundances of Pseudo-nitzschia and high levels of DA at Stearns Wharf in late January or early to mid February, but that was not the case in the weekly HABMAP sampling. The bulk of the strandings by late February were being taken in by CIMWI, CWC, MMCC-LA, and PMMC from Santa Barbara to Orange County. The next bulletin will report on the extension of this major event into March as Sea World in San Diego and TMMC in Sausalito began taking in more animals in San Diego and central California, respectively.
- The Imaging Flow Cytobots (IFCBs) – robotic microscopes recording hourly observations – at the same piers and on some moorings out on the shelf tell a more nuanced story regarding Pseudo-nitzschia growth. IFCBs at Scripps Pier and Del Mar mooring in San Diego indicate that Pseudo-nitzschia spp. began dominating the phytoplankton community in early January with some waning towards the end of January, followed by a resurgence in mid-February. Unfortunately, the Newport Beach Pier IFCB was out of the water for maintenance during this time period, with storms and wave action preventing re-deployment. The Stearns Wharf IFCB was also pulled out for a period of February, but what is shown by the data we do have is that Pseudo-nitzschia was moving towards outcompeting other phytoplankton groups as early as late January in the nearshore Santa Barabara environment. It should be stressed that the IFCBs did not indicate particularly high abundance of Pseudo-nitzschia in January and February but did demonstrate the relationship between this group and other phytoplankton taxa. This may indicate high abundances and high DA offshore and in subsurface environments where large marine mammals are foraging and where we do not routinely monitor. Further north at Santa Cruz Wharf and Bodega Bay Marine Lab, Pseudo-nitzschia was not detected in the IFCBs in January and February 2025.
- California Department of Public Health conducts its own ad hoc phytoplankton sampling for recreational shellfish harvest regulation. They report “Common” levels of the P. “seriata” size class in San Diego County from Jan 27th to Feb 18th, in Orange County on Feb 7th and on Feb 14th, and in Los Angeles County on Feb 18th, 23rd (Catalina Island), and 24th. CDPH recorded the relative abundance of this group as “Abundant” only in San Diego County on Feb 17th. This nexus of Pseudo-nitzschia detection in the San Diego to Los Angeles areas is consistent with both HABMAP and IFCB sampling. Recreational shellfish harvest advisories for DA (Amnesic Shellfish Poisoning, ASP) are still in effect for razor clams in Del Norte County and Humboldt County since Nov 2023 and May 2024, respectively, although advisories were lifted for other types of bivalve shellfish in early December. Dungeness crab advisories for northern California near the Oregon border were lifted in mid December. The ASP outlook does change in March, and we are currently under an ASP advisory for shellfish in Santa Barbara and Los Angeles Counties.
- The harmful algae that causes Paralytic Shellfish Poisoning (PSP) is also heavily monitored along the U.S. West Coast. Alexandrium spp. (a dinoflagellate) were detected by HABMAP at worrisome levels on at Newport Beach Pier on Dec 17, 2024, Scripps Pier on Dec 30, 2024, and again at Scripps Pier on Jan 13 and Feb 24, 2025, and at both Scripps Pier and Stearns Wharf (Santa Barbara) on Feb 18, 2025. Similar levels were detected in central California at Monterey Wharf throughout January and again on February 26th, but not at other central California sites or in northern California. While no shellfish advisories were reported for the early part of 2025, these levels are a harbinger of things to come in the March CA HAB Bulletin, with Santa Barbara County now under a PSP shellfish advisory in addition to an ASP advisory.

Particulate Domoic Acid

Particulate domoic acid (pDA) is the measurement of total domoic acid toxin that is potentially extant in a given area. This forecast provides a probability for where that concentration of toxin is predicted to exceed the threshold that classifies a Harmful Algal Bloom (> 500 nanograms per liter).

The C-HARM v4 model generates nowcast and forecasts of the probability of Pseudo-nitzschia concentrations of in excess of 10,000 cells/L, the probability of particulate domoic acid > 500 nanograms/L, and the probability of cellular domoic acid > 10 picograms/cell in California and Southern Oregon coastal waters. Inputs for the model include near real-time satellite observations, gap-filled chlorophyll a, 486nm reflectance, and 551nm reflectance fields from the S-NPP NOAA VIIRS sensor plus nowcast and forecast data of surface salinity, sea surface temperature, and surface currents from WCOFS ROMS.

Cellular Domoic Acid

Cellular domoic acid (cDA) is the measure of total domoic acid toxin calculated per cell of Pseudo-nitzschia. This forecast provides a probability for where those cells are expected to be producing toxin at high levels (> 10 picograms per cell).

The C-HARM v4 model generates nowcast and forecasts of the probability of Pseudo-nitzschia concentrations of in excess of 10,000 cells/L, the probability of particulate domoic acid > 500 nanograms/L, and the probability of cellular domoic acid > 10 picograms/cell in California and Southern Oregon coastal waters. Inputs for the model include near real-time satellite observations, gap-filled chlorophyll a, 486nm reflectance, and 551nm reflectance fields from the S-NPP NOAA VIIRS sensor plus nowcast and forecast data of surface salinity, sea surface temperature, and surface currents from WCOFS ROMS.

Pseudo-nitzschia

Pseudo-nitzschia is a neurotoxin producing diatom that is observed along the California Coast. Blooms of this phytoplankton can be detrimental to surrounding marine ecosystems. This forecast provides a probability for where the concentration of cells in the water exceed the threshold of a Harmful Algal Bloom ( > 10,000 cells/L).

The C-HARM v4 model generates nowcast and forecasts of the probability of Pseudo-nitzschia concentrations of in excess of 10,000 cells/L, the probability of particulate domoic acid > 500 nanograms/L, and the probability of cellular domoic acid > 10 picograms/cell in California and Southern Oregon coastal waters. Inputs for the model include near real-time satellite observations, gap-filled chlorophyll a, 486nm reflectance, and 551nm reflectance fields from the S-NPP NOAA VIIRS sensor plus nowcast and forecast data of surface salinity, sea surface temperature, and surface currents from WCOFS ROMS.

California Harmful Algal Bloom Monitoring & Alert Program

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.

Data for some stations are not shown as they are not yet recorded in the public HABMAP archive.

These time series focus on data collected through the scope of this bulletin and the 12 month period that precedes it. Explore the variables and regions that make up the CalHABMAP collective dataset using the plot controls.

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

A network of Imaging FlowCytobots (IFCBs) continuously photographs particles, such as plankton, in the water. Using machine learning, plankton species can be automatically identified. This will help improve the ability to detect and respond to Harmful Algal Blooms, including the ability to assess conditions that may lead to toxin production or blooms of toxin-producing algae.

These data, coupled with the image classification algorithms developed in collaboration with SCCOOS and CeNCOOS, allow for estimates of species composition over time. The time series below depict sampling outcomes across several California sites. Support provided by NOAA IOOS and CA OPC.

Additional images and data are available on the IFCB dashboard.

Each month, water samples are collected by volunteers and sent to the California Department of Public Health (CDPH) for analysis.

Pseudo-nitzschia ‘seriata’

Alexandrium spp.

The relative abundance of DA-producing Pseudo-nitzschia ‘seriata’ size class (left) and PSP toxin-producing Alexandrium spp. (right) are catalogued from sample locations within each county. Each bar represents a sample outcome.

December 5

Del Norte
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CDPH lifts their warning about consuming certain types of sport-harvested bivalve shellfish from Del Norte County. The county advisory for razor clams remains in effect for Del Norte & Humboldt.

December 13

Northern California Coast
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CDPH reduces “Do Not Consume Whole Crab” of sport-harvested Dungeness crab caught between Oregon border and Reading Rock State Marine Reserve to "Do Not Consume the Internal Organs (Viscera)".

December 16

Northern California Coast
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CDPH lifts their consumption warning for sport-harvested Dungeness crab caught between Oregon border and Reading Rock State Marine Reserve.

Water Sample Detailed Data

Date_Sampled	County	Sample_Site	PN_Percent_Comp	PN_Density	AL_Percent_Comp	AL_Density
2025-02-17	San Diego	Oceanside Harbor	70	ABUNDANT	0	ABSENT
2025-02-13	San Diego	San Diego Bay, U.S. Navy Pier	45	COMMON	0	ABSENT
2025-02-18	San Diego	La Jolla, Scripps Pier	45	COMMON	0	ABSENT
2025-02-24	Los Angeles	Manhattan Beach Pier	45	COMMON	0	ABSENT
2025-02-14	Orange	Dana Pt. Harbor	30	COMMON	0	ABSENT
2025-02-07	Orange	Bolsa Chica	25	COMMON	0	ABSENT
2025-02-23	Los Angeles	Catalina Island, OFFSHORE	25	COMMON	0	ABSENT
2025-02-18	Los Angeles	Palos Verdes Rocky Pt Offshore	10	COMMON	0	ABSENT
2025-01-27	San Diego	La Jolla, Scripps Pier	10	COMMON	0	ABSENT
2025-02-05	San Diego	Imperial Beach Pier	10	COMMON	0	ABSENT
2025-02-19	San Diego	San Diego Harbor, Pier 159	9	PRESENT	0	ABSENT
2025-01-31	Orange	Bolsa Chica	8	PRESENT	0	ABSENT
2025-02-10	Marin	Tomales Bay, Lease #M430-15	5	PRESENT	0	ABSENT
2025-02-03	San Diego	La Jolla, Scripps Pier	5	PRESENT	1	PRESENT
2025-02-15	Los Angeles	Catalina Island, Avalon Bay	5	PRESENT	0	ABSENT
2025-02-21	Santa Barbara	Santa Barbara Ch., Naples Pt	5	PRESENT	6	PRESENT
2025-02-11	Santa Barbara	Goleta Pier	4	PRESENT	0	ABSENT
2025-02-10	Mendocino	Mendocino, Noyo Harbor	3	PRESENT	0	ABSENT
2025-02-26	San Diego	Imperial Beach Pier	3	PRESENT	0	ABSENT
2025-01-27	Ventura	Ventura, Port Hueneme Pier	2	PRESENT	0	ABSENT
2025-02-05	Orange	San Clemente Pier	2	PRESENT	0	ABSENT
2025-02-26	Orange	San Clemente Pier	2	PRESENT	0	ABSENT
2025-01-29	San Diego	San Diego Bay, U.S. Navy Pier	1.5	PRESENT	0.5	RARE
2025-01-29	San Luis Obispo	San Luis Obispo, Cal Poly Pier	1	PRESENT	0	ABSENT
2025-02-28	San Diego	San Diego Bay, U.S. Navy Pier	1	PRESENT	0.5	RARE
2025-02-03	San Luis Obispo	Morro Bay, Boat Launch	0.5	RARE	0	ABSENT
2025-02-03	Marin	Tomales Bay, Lease #M430-15	0.5	RARE	0	ABSENT
2025-01-29	Santa Barbara	Goleta Pier	0.5	RARE	0.5	RARE
2025-02-10	San Luis Obispo	Morro Bay, Boat Launch	0.5	RARE	0	ABSENT
2025-02-17	San Luis Obispo	Morro Bay, Boat Launch	0.5	RARE	0	ABSENT
2025-02-10	San Diego	La Jolla, Scripps Pier	0.5	RARE	0	ABSENT
2025-02-24	Marin	Tomales Bay, Lease #M430-15	0.5	RARE	0	ABSENT
2025-02-14	Orange	Bolsa Chica	0.5	RARE	0	ABSENT
2025-01-27	Marin	Tomales Bay, Lease #M430-15	0	ABSENT	0	ABSENT
2025-01-27	San Luis Obispo	Morro Bay, Boat Launch	0	ABSENT	0	ABSENT
2025-01-27	Humboldt	Humboldt Bay, Indian Is. Ch.	0	ABSENT	0	ABSENT
2025-01-29	Santa Barbara	Santa Barbara, Stearns Wharf	0	ABSENT	0	ABSENT
2025-01-29	Santa Cruz	Santa Cruz Wharf	0	ABSENT	0	ABSENT
2025-02-03	Humboldt	Humboldt Bay, Indian Is. Ch.	0	ABSENT	0	ABSENT
2025-01-27	Del Norte	Hunter Rock, north	0	ABSENT	0	ABSENT
2025-02-10	Humboldt	Humboldt Bay, Indian Is. Ch.	0	ABSENT	0	ABSENT
2025-02-12	Humboldt	Trinidad Pier	0	ABSENT	0	ABSENT
2025-02-12	Santa Cruz	Santa Cruz Wharf	0	ABSENT	0	ABSENT
2025-02-18	Humboldt	Humboldt Bay, Indian Is. Ch.	0	ABSENT	0	ABSENT
2025-02-17	Marin	Tomales Bay, Lease #M430-15	0	ABSENT	0	ABSENT
2025-01-30	Orange	Newport Bay, Back Bay	0	ABSENT	0	ABSENT
2025-01-28	Del Norte	Wilson Creek	0	ABSENT	0	ABSENT
2025-01-30	Mendocino	Mendocino, Noyo Harbor	0	ABSENT	0	ABSENT
2025-01-30	Mendocino	Mendocino, Noyo OFFSHORE	0	ABSENT	0	ABSENT
2025-02-06	Del Norte	Wilson Creek	0	ABSENT	0	ABSENT
2025-02-10	Mendocino	Point Arena Pier	0	ABSENT	0	ABSENT
2025-02-11	Del Norte	Wilson Creek	0	ABSENT	0	ABSENT
2025-02-04	Orange	Newport Bay, Back Bay	0	ABSENT	0	ABSENT
2025-02-28	Marin	Richmond, Marina Bay Harbor	0	ABSENT	0	ABSENT
2025-02-05	Santa Cruz	Santa Cruz Wharf	0	ABSENT	0	ABSENT
2025-02-24	Humboldt	Humboldt Bay, Indian Is. Ch.	0	ABSENT	0	ABSENT
2025-02-24	San Luis Obispo	Morro Bay, Boat Launch	0	ABSENT	0	ABSENT
2025-02-04	Los Angeles	Santa Monica Bay, 3901	0	ABSENT	0	ABSENT
2025-02-03	Orange	Crystal Cove SB, OFFSHORE	0	ABSENT	0	ABSENT
2025-02-26	Marin	Drakes Bay, Chimney Rock LBS	0	ABSENT	0	ABSENT
2025-02-18	Orange	Newport Bay, Back Bay	0	ABSENT	0	ABSENT
2025-02-25	San Mateo	Bean Hollow State Beach	0	ABSENT	0	ABSENT
2025-02-25	San Mateo	Pillar Point Harbor	0	ABSENT	0	ABSENT
2025-02-27	Del Norte	Hunter Rock, north	0	ABSENT	0	ABSENT
2025-02-24	San Diego	La Jolla, Scripps Pier	0	ABSENT	0	ABSENT
2025-02-24	Sonoma	Shell Beach, Sea Ranch	0	ABSENT	0	ABSENT
2025-02-26	Santa Barbara	Goleta Pier	0	ABSENT	1	PRESENT
2025-02-28	San Mateo	Pillar Point Harbor	0	ABSENT	0	ABSENT
2025-02-17	Mendocino	Mendocino, Noyo Harbor	0	ABSENT	0	ABSENT
2025-02-11	Orange	Newport Bay, Back Bay	0	ABSENT	0	ABSENT
2025-02-24	Sonoma	Kashia Coastal Reserve	0	ABSENT	0	ABSENT
2025-02-27	Del Norte	Wilson Creek	0	ABSENT	0	ABSENT
2025-02-21	Orange	Bolsa Chica	0	ABSENT	0.5	RARE

Percent composition categories help us look at phytoplankton trends across an entire region to evaluate risk of biotoxin presence. Many other factors contribute to our evaluation of risk in an area. These samples are posted for informational purposes only. They are not intended to inform the public of the presence or lack of risk. For the latest health advisory information, see the CDPH Health Advisory Map below.

Suspect DA Strandings, starting Feb. 21st

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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), Pacific Marine Mammal Center (PMMC), SeaWorld, and Southwest Fisheries Science Center (SWFSC) act like an emergency room by working to rescue and rehabilitate sick and injured marine mammals, seabirds, and sea turtles.

An overview of this active event and current forecast for domoic acid risk can be explored below.

California's Marine Mammal Stranding Network Map

This public acknowledgment serves to honor and respect Indigenous peoples and their land on which our organization resides. UC San Diego was built upon the territory of the Kumeyaay Nation. From time immemorial, the Kumeyaay people have been a part of this land, coast, and sea. Today, the Kumeyaay people continue to maintain their political sovereignty and cultural traditions as vital members of the San Diego community.
The nature and extent of observation that the Southern California Coastal Ocean Observing System directly supports is entirely within the historic purview of many distinct Indigenous nations & cultures, who subsisted on and shaped these coasts. With deep admiration & acknowledgement to these Indigenous peoples past and present, we hope to contribute our services to the shared vision of coastal stewardship and connection which they have created.

California HAB Bulletin

All data and reports have been synthesized by SCCOOS for the California Harmful Algal Bloom Monthly Bulletin.

Data Access & Resources:

C-HARM, NOAA CoastWatch ERDDAP
Toxic Phytoplankton Observations, CDPH
Imaging FlowCytoBot Dashboard
CalHABMAP Datasets, SCCOOS ERDDAP

California HAB Bulletin: December ’24 – February ’25