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). C-HARM now routinely predicts suitable habitat for Pseudo-nitzschia spp. throughout the state for, suggesting most places are routinely experiencing conditions conducive to growth and blooms throughout the year, with variability from month to month on where the centers of highest likelihood occur. In April, the focal point was central California to the Santa Barbara Channel and into the nearshore zones of the Southern California Bight, with probabilities waning dramatically in the southern most region around Orange and San Diego Counties as the month progressed. 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 at or well above the bloom threshold at Santa Monica Pier and Newport Beach Pier from mid to late April before dropping to zero by the end of the month; this is not entirely consistent with the very low probabilities in that area from mid to late April, however, some of the nearshore pixel probabilities remained high. HABMAP records for Santa Cruz Wharf show non-bloom levels of Pseudo-nitzschia in April even though bloom probabilities were periodically very high in the Monterey Bay area. The Relative Abundance Index (RAI) for the Pseudo-nitzschia "seriata" size class recorded by the California Department of Public Health (CDPH) reached moderate levels (20%) at Mohawk Reef in the Santa Barbara Channel nearshore zone but was generally low at all other sites sampled in the state. Note that HABMAP observations for Stearns Wharf in Santa Barbara were not yet available for April at the time of compiling this bulletin.

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 April with a focus on the central coast, Sonoma County and Mendocino County coastlines, and the northern parts of southern California. 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. That pattern reversed for southern California (Orange County and San Diego), and unlike in March, pDA probabilities were very low outside SF Bay. HABMAP pDA data are so far only available for Santa Cruz Wharf in April and show zero (or non-detectable) levels. Similar patterns were predicted for cellular domoic acid (cDA) risk as those for pDA, although often with more intensity, particularly for northern California (high probabilities, Mendocino County) and southern California (Orange County and San Diego). As in March, both pDA and cDA probabilities were high much of April in a narrow band along the North Coast, suggesting a possible return to more seasonal domoic acid problems in that region. However, a razor clam health advisory that has been in effect since 2015 for Del Norte County due to domoic acid was finally lifted, indicating that this population of organisms that holds onto (and accumulates) DA for long periods has finally started to purge toxins to a safe level for consumption. The only California Sea Lion stranding from suspected DA toxicosis in April was reported by The Marine Mammal Center (TMMC) in mid-April in Marin County (just north of San Francisco), a region that was a potential hot spot according to C-HARM and HABMAP sampling; no other regions reported suspected DA toxicosis cases in April.

Alexandrium - CDPH did not observe any Alexandrium spp. at sites sampled in April, 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.

Santa Cruz Wharf

Three water samples were collected at Santa Cruz Wharf in April. Molecular probes for toxigenic Pseudo-nitzschia in the "seriata" class are conducted for this site; Pseudo-nitzschia "seriata" was detected twice (April 14, 21) below the bloom threshold value. Alexandrium spp. and domoic acid were not detected. 

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

Cal Poly Pier

Four water samples were collected at Cal Poly Pier in April. Pseudo-nitzschia "delicatissima" was detected only once (April 12) and was above the bloom threshold value. Pseudo-nitzschia "seriata" was detected on each occasion (April 5, 12, 18, 26), with only April 12 being above the threshold value. Alexandrium spp. were not detected and 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 April.

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 April. Pseudo-nitzschia "delicatissima" was detected on three occasions (April 5, 17, 24), all below the bloom threshold. Pseudo-nitzschia "seriata" was also detected on the same three occasions (April 5, 17, 24), with April 5 being above the threshold. Alexandrium spp. were not detected. Domoic acid results are not yet available. 

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

Scripps Pier

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

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