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). The predicted suitable habitat for Pseudo-nitzschia spp. was spread around throughout coastal California in June, much like in previous months, with more widely distributed high probabilities for Pseudo-nitzschia blooms spread throughout the state. In general, the central and north coasts and the Santa Barbara Channel exhibited persistently high bloom probabilities. Bloom probabilities in the Southern California Bight were also high throughout the month, particularly in the nearshore zone, with some dips into very low probabilities skewed towards the end of the month. 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 exceeded the bloom threshold at the Santa Cruz Wharf in early June, consistent with the high C-HARM bloom probabilities for Monterey Bay. Observed abundance of both Pseudo-nitzschia "seriata" and the less toxigenic Pseudo-nitzschia "delicatissima" size class at Cal Poly Pier well exceeded bloom levels in mid-June, coinciding with the central CA peaks in bloom probability throughout June; abundances of the P. "seriata" class dipped just below the bloom threshold in late June. The only southern California site where we have observations for all of June is the Santa Monica Pier where the less toxigenic group Pseudo-nitzschia "delicatissima" well exceeded bloom levels (291,000 cells/L!!), consistent with high daily C-HARM probabilities in the LA county region during the month (caveat: the more toxigenic seriata group did not bloom at SM Pier). The toxigenic P. "seriata" size class exceeded bloom levels at Newport Beach Pier on the June 29th weekly sampling, consistent with elevated C-HARM probabilities that day. HABMAP samples were either not collected or data are not yet available for Monterey Wharf, Stearns Wharf, and Scripps Pier.

Moderate to high probabilities of particulate DA (pDA) were predicted for most of the California coast throughout June, with the Humboldt and Mendocino coast and offshore waters increasing in predicted intensity over the course of the month. Probabilities from Sonoma and Marin County to San Luis Obispo County exhibited local minima in pDA probabilities but never dropped below 60% probability of high pDA. The consistently high probabilities for pDA from Monterey Bay to San Francisco Bay and further north are consistent with the five California Sea Lion strandings reported by The Marine Mammal Center (TMMC) from Monterey to Marin Counties throughout June. The only available domoic acid measurements from HABMAP during June were collected at Santa Cruz Wharf and indicated no DA at that site, as has been the case for a year or more. This is inconsistent with C-HARM predictions for the Monterey Bay area. While much of the elevated pDA probabilities extended very far offshore, much like in May, predicted cellular DA (cDA) risk appeared to be contained in a fairly tight nearshore band for much of the coastline and was consistently high from northern San Luis Obispo County to the Oregon border. Measurements of DA are not yet readily available in that region for HABMAP, but the pDA and cDA predictions from C-HARM are consistent with the health advisories issued by the CDPH for domoic acid in razor clams in Del Norte and Humboldt Counties. The Southern California Bight exhibited much lower potential risk for cDA with high-probability patches appearing in and around the Santa Barbara Channel and the San Pedro Bay towards the end of the month. No marine mammal strandings were recorded for the Southern California Bight in June.

CDPH reported a high percent composition for the Pseudo-nitzschia "seriata" size class near Tomales Bay (Marin County).

Alexandrium -  CDPH noted that Alexandrium spp. were very abundant at Pacifica Pier in mid-June and Monterey Bay in late June, consistent with similarly high (and alarming) abundances observed by HABMAP at Santa Cruz Wharf throughout June and rising into early July. Subsequent evaluation of saxitoxin in shellfish led the CDPH to issue health advisories for mussels, clams, and whole scallops in San Mateo, San Francisco, Santa Cruz, and Monterey Counties due to the threat of Paralytic Shellfish Poisoning.

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