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 domoic acid (DA). Predicted suitable habitat for Pseudo-nitzschia spp. was spread around throughout coastal California in May, much like in previous months, with more widely distributed high probabilities for Pseudo-nitzschia blooms spread throughout the state. In general, the central coast from Monterey Bay to Pt. Conception and the SB Channel exhibited persistently high bloom probabilities. Bloom probabilities in the Southern California Bight were also high throughout the month, particularly in the nearshore zone. While COVID-19 sampling restrictions continue to hamper our ability to acquire HABMAP observations from piers, we do know that the more toxigenic Pseudo-nitzschia "seriata" size class reached abundances well above the bloom threshold at the Santa Cruz Wharf towards the end of May, consistent with the high C-HARM bloom probabilities for the Monterey Bay. Observed bloom levels of the less toxigenic Pseudo-nitzschia "delicatissima" size class at Cal Poly Pier were also consistent with the central CA peaks in bloom probability throughout May. The only southern California site where we have available observations in May is the Santa Monica Pier where there was no Pseudo-nitzschia activity despite high C-HARM probabilities in the LA county region during most of the month. The massive red tide of Lingulodinium polyedra that pervaded the region from northern Ventura County to Baja, starting at the end of March and peaking in mid-May, could account for elevated chlorophyll or high remote sensing reflectance in this area during April and May. These anomalous remote sensing retrievals could have created false positives in the Pseudo-nitzschia bloom model for the Southern California Bight. It should also be noted, however, that robotic microscope (IFCB) data presented from the Del Mar mooring about 3 nautical miles offshore of San Diego shows that Pseudo-nitzschia spp. was common in shelf waters even at the height of the bloom.

Moderate to high probabilities of particulate DA (pDA) were predicted for most of the California coast throughout May, with the Humboldt and Mendocino coast waxed and waned in terms of intensity, especially in offshore waters near the Oregon border where the risk of high pDA was predicted to be very low. Probabilities from Sonoma and Marin County to San Luis Obispo County were fairly consistently high for pDA for the first half to the month, consistent with the 16 California Sea Lion strandings reported by The Marine Mammal Center (TMMC) from mid to late May from Marin to San Luis Obispo Counties. The only available domoic acid measurement from HABMAP during May was collected at Santa Cruz Wharf and indicated no DA there at the end of May. Much of the elevated pDA probabilities extended very far offshore while the high cDA risk appeared to be contained in a fairly tight nearshore band for much of the coastline. The Southern California Bight saw elevated cDA probabilities that peaked in mid-May and occasionally grew intense in the Santa Barbara Channel, Los Angeles, and San Diego regions, consistent with one California Sea Lion stranding from suspected DA toxicosis reported from the Pacific Marine Mammal Center (PMMC) at the end of May. 

CDPH reported moderate to high percent composition for the Pseudo-nitzschia "seriata" size class near Tomales Bay (Marin County), Pacifica Pier (SF County), and Santa Cruz Wharf (SC County), consistent with C-HARM predictions along the central coast.

Alexandrium -  CDPH noted that Alexandrium spp. were in very low abundance or absent from all sites samples in California, consistent with the HABMAP sampling at Santa Cruz Wharf, Cal Poly Pier, and Santa Monica Pier. 

**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

Water samples were collected twice at Santa Cruz Wharf in the month of May. Molecular probes for toxigenic Pseudo-nitzschia in the "seriata" class are conducted for this site, and was detected above bloom levels on May 12th. Alexandrium spp. were detected below bloom levels on May 5th and May 12th. Domoic acid results are not yet available for May. Santa Cruz Wharf does not count for Pseudo-nitzschia delicatissima group.

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

Monterey Wharf

Water samples were not collected at Monterey Wharf in the month of April or May. 

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

Pseudo-nitzschia 'delicatissima' was detected above bloom levels on May 4th. Domoic acid results are not yet available for May.

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

Stearns Wharf

Water samples were not collected at Stearns Wharf in the month of April.

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

Santa Monica Pier

Water samples were not collected at Santa Monica Pier in the month of April or May.

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

Scripps Pier

Phytoplankton cell counts and domoic acid results are not yet available for Scripps Pier samples in April and May. 

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