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 April, much like in previous months. There were periods of contraction towards the coast mid-month, flanked by offshore probabilities that were very high and often followed what appear to be eddy contours. Bloom probabilities in the Southern California Bight started off low but increased throughout the month, particularly in the nearshore zone. While we do not have much in the way of HABMAP cell counts in April due to COVID-19 sampling restrictions, we do know that the Pseudo-nitzschia "delicatissima" size class bloomed in early April at Cal Poly Pier.  We also know that a massive red tide pervaded the region from the Santa Barbara Channel to Baja from March to May and could account for elevated chlorophyll or high remote sensing reflectance in this area during April, perhaps leading to false positives in the Pseudo-nitzschia bloom model. It should also be noted, however, that robotic microscope (IFCB) data presented in the Red Tide Bulletin showed fairly elevated abundance of Pseuodo-nitzschia spp. in shelf waters as the bloom was starting.

Most of the activity for particulate DA (pDA) was predicted for central and northern California, with the Humboldt and Mendocino coasts waxing and waning in terms of intensity throughout the month of April. Probabilities off the coast of the San Francisco/Bay Area and the Monterey Bay were fairly consistently high for pDA where three California Sea Lions and one Guadalupe Fur Seal were reported stranded due to suspected DA toxicosis by The Marine Mammal Center (TMMC). The Southern California Bight saw elevated pDA probabilities that mostly remained offshore but occasionally grew intense in the Santa Barbara Channel, Los Angeles, and San Diego regions, consistent with two possible DA toxicosis cases from the Pacific Marine Mammal Center (PMMC) and one possible DA toxicosis case from the Marine Mammal Care Center Los Angeles (MMCC-LA). C-HARM predicted high cDA probabilities for the central and northern coasts, Pt. Conception to Humboldt, for high cellular DA (cDA) levels with a broad offshore extent, similar to March.  probabilities for cDA were even lower in the Southern California Bight than in March, and in contrast to the pDA predictions. This may suggest that there was not a lot of active DA production in the Bight (south of the SBC) overall during April.

CDPH recorded that Pseudo-nitzschia "seriata" was common near Drakes Bay and Tomales Bay (Marin County) and Diablo Cove (central coast, SLO County) and present at many other sites from San Diego to Humboldt counties, consistent with C-HARM.

Alexandrium -  CDPH noted that Alexandrium spp. were present but a low abundance in Agua Hedionda Lagoon in Carlsbad (San Diego County) and in Humboldt Bay.

**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 not collected at Santa Cruz Wharf in the month of April. 

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. 

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

Water samples at Cal Poly Pier were collected four times in the month of April. Pseudo-nitzschia 'delicatissima' and 'seriata' were detected above bloom levels on April 6th. Domoic acid results are not yet available for April.

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.

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

Scripps Pier

Water samples were collected X times at Scripps Pier in the month of April. 

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