Pseudo-nitzschia and Domoic Acid Predictions - C-HARM tells us where conditions are suitable for Pseudo-nitzschia spp. (all size classes) to grow well and where they might be more likely to produce Domoic acid (DA). In August, suitable habitat for Pseudo-nitzschia spp. was even more evenly spread throughout coastal California than in July, again with more patchy and slightly lower probabilities in the Southern California Bight and higher probabilities in offshore regions of Sonoma and Humboldt Counties as the month progressed. C-HARM predicted high but very patchy particulate DA (pDA) throughout most of the state, with the greatest probabilities of high DA along sections of the Humboldt and Sonoma coastlines, Half Moon Bay, Monterey Bay, and the Southern California Bight (including the Santa Barbara Channel and the transition region around Pt Conception). Notably, nearshore probabilities of pDA were low for the San Luis Obispo coast but high in offshore eddy-like patches, as was the case in July. C-HARM also indicates very high probabilities in cellular DA (cDA) distributed in patches. These patches intensify over the course of the month along the Humboldt coastline. In Sonoma and Monterey counties, cDA probabilities remained high throughout the month of August, extending offshore around 50-70 km and with a local minimum in probabilities just outside SF Bay. Patches of high cDA probability around Pt. Conception and San Miguel Island were not seen in the nearshore San Luis Obispo zone to the north, nor in the SB Channel proper, aside from some moderate blips throughout the month.

In comparison with the HABMAP measurements where we have the August data already available, bloom levels of both P. "seriata" and "delicatissima" size classes occurred at various times throughout the month in the Southern California Bight at Santa Monica Pier (Los Angeles Co.), Newport Beach Pier (Orange Co.) and Scripps Pier (San Diego Co.), but interestingly, not at Stearns Wharf in Santa Barbara. Blooms levels of the "seriata" (i.e., more toxigenic) size class were seen at Newport Beach Pier from late July to mid-August. Bloom levels of the "delicatissima" size class were also recorded at Cal Poly Pier (San Luis Obispo Co.) throughout most of August, but no Pseudo-nitzschia were seen at the Santa Cruz Wharf this month. DA data were not yet available for any of the HABMAP sites. Animal strandings potentially related to DA were concentrated in central California throughout August, consistent with the high C-HARM cDA and pDA probabilities in this region but inconsistent with the very low abundances of Pseudo-nitzschia spp. recorded at the Santa Cruz Wharf. Notably, northern fur seals are stranding in record numbers at The Marine Mammal Center (TMMC) in central CA, consistent with the bolus of high cDA probabilities in Sonoma County waters fairly far offshore. Tenaya Norris at TMMC says that "this species primarily breeds on islands in Alaska and Russia, and <2% of the population breeds on San Miguel and Farallon Islands. We don’t know too much about where these animals feed off of California, but they typically are at or just beyond the shelf break and are pretty shallow divers compared with sea lions (but they feed on similar prey items). Females nurse their pups June-November. Based on the stranding location of these animals, my guess would be they were exposed [to DA] off San Mateo-Sonoma Counties."

CDPH recorded their highest relative abundances of Pseudo-nitzschia spp. along the North Coast near Humboldt Co. and in the southern Monterey Bay. Moderate levels of Pseudo-nitzschia were measured along the San Luis Obispo coastline and near Santa Barbara. Unlike in July, Pseudo-nitzschia was no longer observed as a large proportion of the phytoplankton community in the Southern California Bight, although this is inconsistent with the high abundance values observed at Santa Monica Pier, Newport Beach Pier, and Scripps Pier via the HABMAP pier sampling program, highlighting the patchy nature of phytoplankton species composition from day to day and site to site.

Alexandrium - HABMAP records for Alexandrium spp. at pier sites. Only Cal Poly Pier (SLO Co.) and Santa Cruz Wharf showed any concerning rise in Alexandrium spp. abundance in August. This is somewhat consistent with CDPH sampling, which showed elevated relative abundance on the SLO coast and even higher composition rates outside San Francisco Bay, enough to lead to an early September alert from CDPH on the risk of paralytic shellfish (PSP) toxins in mussels from Sonoma Co.  CDPH lifted a PSP advisory in SLO Co. on August 13th, just preceding the small peak in abundance of Alexandrium spp. recorded at Cal Poly Pier at the very end of August.

Santa Cruz Wharf

Water samples were collected at Santa Cruz Wharf four times in the month of August. Pseudo-nitzschia seriata group and domoic acid were not detected in any of the samples. Alexandrium were detected below bloom levels on all four sampling dates. Santa Cruz Wharf does not count for Pseudo-nitzschia delicatissima group.  

Monterey Wharf

Water samples were collected at Monterey Wharf four times in the month of August. Pseudo-nitzschia delicatissima group and Pseudo-nitzschia seriata group was detected above bloom levels on August 14th. Alexandrium spp. were not detected above bloom levels. Domoic Acid results are not yet available for the month of August.

Cal Poly Pier

Water samples were collected at Cal Poly Pier four times in the month of August. Pseudo-nitzschia delicatissima group was detected above bloom levels on August 11th and 17th. Pseudo-nitzschia seriata group and Alexandrium spp. were not detected above bloom levels in any of the samples. Domoic Acid results are not yet available for the month of August.  

Stearns Wharf

Water samples were collected four times at Stearns Wharf in the month of August. Alexandrium spp. were not detected in any of the samples. Pseudo-nitzschia delicatissima group was detected above blooms levels on August 12th, 19th, and 26th. Pseudo-nitzschia seriata group was detected below bloom levels on all sample dates. Domoic Acid results are not yet available for the month of August.

Santa Monica Pier

Water samples were collected at Santa Monica Pier four times in the month of August. Pseudo-nitzschia delicatissima group was detected below bloom levels in all the samples. Pseudo-nitzschia seriata group and Alexandrium spp. were not detected in any of the August water samples. Domoic Acid results are not yet available for the month of August.  

Scripps Pier

Water samples were collected at Scripps Pier four times in the month of August. Pseudo-nitzschia delicatissima group was detected below bloom levels in all the samples. Pseudo-nitzschia seriata group was detected below bloom levels in all the samples and Alexandrium spp. were not detected in any of the August water samples. Domoic Acid results are not yet available for the month of August.