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 March, much like in previous months, although everywhere the probability tended to hover around 50% in the most nearshore zone and was often even lower in the Southern California Bight, except for the Santa Barbara Channel. Beyond the nearshore local minimum zone, a robust crop of Pseudo-nitzschia biomass was predicted for a coastal swath from Santa Barbara to Eureka, often only out to 100 or 200 hundred kilometers offshore. Most of the activity for particulate DA (pDA) was predicted for the regions north of Monterey Bay, where probabilities of a pDA event were high (well above 70%) throughout most of the month. Interestingly, local minima persisted with some temporal variability for central CA south of Monterey Bay, although the region around Pt. Conception and in the more offshore zone of the Southern California Bight was predicted to have higher pDA probabilities from the middle of the March onward. In contrast, C-HARM really highlighted the entire coast north of San Francisco as a high probability (typically above 70%) region for high cellular DA (cDA) levels with a broad offshore extent, similar to February, although with much less activity projected for the central coast. Unlike February, cDA probabilities were generally low (50% or lower) for the entire Southern California Bight in March. A few patches of high cDA probability blipped on and off far offshore within the SCB, perhaps indicative of offshore eddy activity.

As a possible validation of where offshore DA is high, we like to look at marine mammal strandings. The only two potential DA toxicosis cases recorded during this time of highly reduced beach activity and monitoring were in Mendocino County and Los Angeles County. This is consistent with high pDA and cDA probabilities throughout Feb and March for waters offshore Mendocino and is consistent with the periodically high pDA probabilities noted for the LA area. While cDA probabilities were mostly low for the LA area in March, they were high in February. Given that the animal stranded March 1, February conditions are more relevant.

In comparison with the Harmful Algal Bloom Monitoring and Alert Program (HABMAP) measurements where we have March data currently available, the only sites with bloom levels of Pseudo-nitzscha (i.e. 10,000 cells/L or more) were in the Southern California Bight (Scripps Pier). The larger, more toxigenic "seriata" size class of Pseudo-nitzschia hit bloom levels in late February at Stearns Wharf (Santa Barbara) and for late Feb and early March at Newport Beach Pier (Orange County). Note that samples were not collected and/or reported for Stearns Wharf and Newport Beach Pier in March due to Covid-19 restrictions which limited comparisons of these sites to the March CHARM outputs. Sampling activities were able to continue, to varying extents, at Scripps Pier and Santa Monica Pier in March. The less toxigenic "deli" size class hit bloom levels at Scripps Pier in early March, while the larger size class only approached bloom levels at Scripps Pier and at Santa Monica Pier. This is consistent with C-HARM in that these piers lie within zones of high Pseudo-nitzschia bloom and pDA event probability. Piers within other regions highlighted by C-HARM as more consistent hot spots, however, did not experience bloom-level Pseudo-nitzschia spp. abundances, such as Monterey Bay/Santa Cruz or Cal Poly. No DA data are yet available from March given restrictions put on labs during the COVID-19 closures.

CDPH recorded Pseudo-nitzschia "seriata" at most of the sites they sampled. Their highest relative abundance of Pseudo-nitzschia "seriata" was found near Pacifica Pier (San Mateo County) on March 15th. The closest HABMAP sampling to this site would be Santa Cruz Wharf observed at the last sampling event on March 11^th prior to suspending sampling activities to comply with shelter in place orders.

Alexandrium -  HABMAP sampling noted a small uptick in Alexandrium spp. presence at Santa Cruz Wharf, while CDPH also noted the presence at nine sites, all at very low percent composition (less than 2% composition).

**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 at Santa Cruz Wharf two times in the month of March. Molecular probes for toxigenic Pseudo-nitzschia in the "seriata" class are conducted for this site, but was not detected in the samples. Alexandrium spp. were detected on March 4th and 11th. Domoic acid results are not yet available for March. 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 collected at Monterey Wharf two times in the month of March. Pseudo-nitzschia seriata and delicatissima group were detected below bloom levels on March 4th and 11th and Alexandrium spp. were detected at low levels on March 4th. Domoic acid results are not yet available for March. 

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 three times in the month of March. Pseudo-nitzschia delicatissima group was detected below bloom levels on March 15th and Alexandrium spp. were not detected in any of the samples. Domoic acid results are not yet available for March.

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 March. 

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

Santa Monica Pier

Water samples were collected at Santa Monica Pier three times in the month of March. Pseudo-nitzschia seriata was detected below bloom levels on March 2nd and 9th. Pseudo-nitzschia delicatissima group and Alexandrium spp. were not detected in any of the samples and domoic acid results are not yet available for March.   

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

Scripps Pier

Water samples were collected four times at Scripps Pier in the month of March. On March 2nd Pseudo-nitzschia delicatissima group was detected above bloom levels and Pseudo-nitzschia seriata group was detected below bloom levels. Alexandrium spp. were not detected in any of the water samples and domoic acid results are not yet available for March.

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