August 2021 Marine Biotoxin Monitoring Monthly Report
California Department of Public Health
Introduction
This report contains results from the California Department of Public Health (CDPH) monitoring programs for shellfish toxins and associated toxin-producing phytoplankton. Toxin concentration ranges are provided for the paralytic shellfish poisoning (PSP) toxins and for domoic acid, the latter associated with the syndrome called Amnesic Shellfish Poisoning. Estimates are provided for the distribution and relative abundance of Alexandrium, the dinoflagellate that produces PSP toxins, and Pseudo-nitzschia, the diatom that produces domoic acid. This report also contains summary information for any quarantine or health advisory in effect during the reporting period. Finally, lists of participating agencies and volunteers for each monitoring effort are provided.
Map Notations
Please note the following conventions for the phytoplankton and shellfish biotoxin distribution maps:
(i) All estimates for phytoplankton relative abundance are qualitative, based on sampling effort and percent composition;
(ii) Only known toxin-producing species (e.g., seriata complex for Pseudo-nitzschia) are represented on the maps;
(iii) The relative abundance of Alexandrium and Pseudo-nitzschia are represented by icons that increase in size with increasing relative abundance as shown in the phytoplankton map key to the right.
(i) All toxin data are for mussel samples, unless otherwise noted;
(ii) All shellfish samples are assayed for PSP toxins; DA analyses are performed as needed (e.g., on the basis of detected blooms of the diatoms that produce DA or as part of a continuing surveillance effort);
(iii) Weekly PSP data are represented by four color-coded boxes as shown in the shellfish biotoxin map key to the right;
(iv) Domoic acid data is represented as four weekly color-coded circles overlayed on the PSP boxes.
Northern California Summary
Alexandrium sp. from outer Morro Bay sample (photo courtesy of Skip Rotstein).
Paralytic Shellfish Poisoning
Alexandrium distribution and relative abundance increased in August, with observations of this dinoflagellate in samples from all seven counties between Mendocino and Monterey (Figure 1). Alexandrium was observed in 21 of 51 northern California phytoplankton samples. The percent composition of Alexandrium remained elevated in samples from Pacifica Pier (7% on August 8 and 15) and increased at the following locations: Schoolhouse Beach (2%, August 12), the Bodega Harbor sentinel station (1%, August 12), the Drakes Bay sentinel station (8%, August 25), Bolinas Lagoon (2%, August 17), Stinson Beach (2%, August 11), and the San Francisco Presidio Pier (1% and 4% on August 19 and 26, respectively); the cell mass was noticeably elevated in the two Marin County samples. Low numbers of this dinoflagellate were also observed in samples from Noyo Harbor (Mendocino County) on August 16, 23, and 31.
PSP toxicity was detected in several shellfish samples in August (Figure 2). Low toxin concentrations were detected in mussel samples from numerous sites in Mendocino, Sonoma, Marin and San Mateo counties. The low PSP concentration detected at the Drakes Bay sentinel station on August 10 (43 µg/100 g) increased above the alert level by August 25 (131 µg/100 g). Also of note was the detection of low toxin concentrations in sentinel mussels (August 23 and 30) and oysters (August 23, 25, and 30) from outer Tomales Bay and in oysters from the mid bay (August 25); the latter declined below the detection limit by August 30.
Domoic Acid
Pseudo-nitzschia distribution declined in August, occurring in 19 of 51 northern California samples (Figure 1). Despite this decline, Pseudo-nitzschia remained common in samples from Hunter Rock in Del Norte County (15%, August 31) and Trinidad Pier in Humboldt County (10% and 25% on August 7 and 28, respectively). The cell mass was elevated at both locations. Pseudo-nitzschia was also common at the Pacifica Pier (20%, August 22), although the cell mass was low.
Domoic acid was not detected in mussel or oyster samples collected in August. Three razor clam samples were collected at Crescent Beach (Del Norte County) by CDPH volunteer Ken Graves on August 23: one sample contained 3.7 ppm of domoic acid and the other two were below the detection limit. The California Department of Fish and Wildlife (CDFW) collected six razor clam samples at Clam Beach (Humboldt County) on August 8: all six clams contained domoic acid concentrations below the alert level (18.0, 10.0, 9.0, 6.4, 5.1, and 4.1 ppm).
Non-Toxic Species
While the diatoms Chaetoceros and Skeletonema were common at sites between Del Norte and Mendocino counties, a variety of dinoflagellates were more numerous along the remainder of the northern California coast. Ceratium furca and C. divaricatum were common to abundant at several sites throughout this range. Cochlodinium was abundant in samples from the Santa Cruz Wharf, Seacliff Pier, and the Monterey Commercial Wharf. Akashiwo sanguineum was common at the Santa Cruz Wharf and frequently observed in lower numbers at other sites, occurring in 20 of 51 samples. In a rather rare occurrence, Lingulodinium polyedrum was common at the Richmond Marina Bay Harbor inside San Francisco Bay. Noctiluca scintillans was less numerous but notable for occurring in samples from eight different counties ranging from Humboldt (Trinidad Pier) to San Diego (Scripps Pier).
Southern California Summary
Paralytic Shellfish Poisoning
Alexandrium was observed at an increased number of sites between San Luis Obispo and San Diego counties in August, occurring in 22 of the 61 phytoplankton samples collected in this region (Figure 3). This dinoflagellate remained common in mid Morro Bay with an elevated cell mass (10%, August 9). The relative abundance of Alexandrium declined to 8% of the phytoplankton assemblage at this site by August 16, however the cell mass increased noticeably from the previous observation. Alexandrium was observed throughout the month at this location. The relative abundance of Alexandrium remained elevated offshore of Diablo Cove (6% and 1% on August 9 and 27, respectively) and increased at the following sites: San Simeon Pier (4% and 2% on August 18 and 26, respectively) and the Cal Poly Pier (1%, August 24), both in San Luis Obispo County; and at Mohawk Reef offshore of Santa Barbara (1%, August 13).
Low concentrations of PSP toxins were detected in oysters from inner Morro Bay the latter three weeks of the month, as well as in mussel samples from Morro Strand, Montana de Oro State Park, the Cal Poly Pier, and Brown’s Beach in northern Santa Barbara County. The Morro Strand sample contained the highest concentration of PSP toxins detected in August (64 µg/100 g).
Domoic Acid
Pseudo-nitzschia was observed in 30 of the 61 southern California samples from multiple sampling sites in all southern California counties in August (Figure 3). This diatom was common in samples from Mohawk Reef (10%, August 13) and Scripps Pier in San Diego County (13%, August 2). The cell mass was low in all samples.
Domoic acid was not detected in any mussel or oyster samples in August (Figure 4).
Non-Toxic Species:
Dinoflagellates were most numerous along the southern California coast, although species diversity was similar between this group of phytoplankton and diatoms. Akashiwo sanguineum was common to abundant at most sampling sites in San Luis Obispo County. Lingulodinium polyedrum was common to abundant at sampling stations between Ventura and Orange counties, occurring in 53 of 61 southern California samples. Ceratium furca and C. fusus were common in samples from Imperial Beach Pier in southern San Diego County, with the former being the most commonly observed dinoflagellate, occurring in 57 of 61 samples. The diatom Chaetoceros was common in offshore samples from Santa Barbara and Los Angeles counties, as well as in the Back Bay region of Newport Bay and at Scripps Pier. Rarer species observed in August samples (and featured in this month’s photographs) include the diatom Planktoniella sol, which was observed in only two samples, and the dinoflagellate C. macroceros, which was rare to present in 16 samples.
Sampling Effort
The Marine Biotoxin Monitoring and Control Program, managed by the California Department of Public Health, is a state-wide effort involving a consortium of participating organizations, agencies, and volunteer samplers.
The phytoplankton sampling and observation element of the biotoxin monitoring program is a state-wide effort designed to detect toxin producing species of phytoplankton in ocean waters before they impact shellfish resources. The phytoplankton monitoring and observation effort can provide an advanced warning of a potential toxic bloom, allowing us to focus sampling efforts in the affected area before California's valuable shellfish resources or the public’s health is threatened.
Historically, the majority of shellfish toxicity episodes in California have originated along the open coast, occasionally moving into bays and estuaries. The shellfish sampling element of the program provides an early warning of shellfish toxicity by routinely assessing coastal resources for the presence of paralytic shellfish poisoning (PSP) toxins and domoic acid. Routine shellfish sampling is essential for protecting the public from these dangerous toxins.
For Information on Volunteering: Email redtide@cdph.ca.gov or call 510-412-4635
Phytoplankton Samplers
A volunteer collecting a phytoplankton sample.
Phytoplankton samples are primarily collected from coastal piers, although sampling can also be conducted from boat docks and offshore via vessel (kayak, boat). Samples are collected with a plankton net following our standard protocol. The sample bottle and sample collection form are placed in a shipping canister and sent to the CDPH laboratory in Richmond where program staff examine samples with light microscopy. CDPH provides all equipment and prepaid shipping containers.
Shellfish Samplers
Sea mussels along the northern California coast.
Mussel samples are routinely collected at one or more representative sampling stations in each coastal county following our standardized protocol. Samplers collect 15-20 individuals and place the shellfish tissue in a sample bottle, which is immediately refrigerated, then frozen overnight. Samples are shipped in an insulated container via 24-hour courier to the department’s laboratory in Richmond for toxin analysis. All materials and shipping are provided by CDPH.
Quarantines, Health Advisories
List of recent Health Advisories and Quarantines for bivalve shellfish prior to September 1, 2021.
● On August 27 CDPH warned consumers not to eat sports-harvested mussels, clams, or scallops from Marin County due to elevated levels of the PSP toxins.
● On August 11 CDPH lifted the August 2015 warning related to dangerous levels of domoic acid in sport-harvested razor clams in Humboldt County. Domoic acid, also referred to as Amnesic Shellfish Poisoning, can cause illness or death in humans. Razor clams are known to retain domoic acid in their meat and tissues much longer than other species of bivalve shellfish. Recent testing confirmed that concentrations of domoic acid are now at safe or undetectable levels in razor clams as well as other species of bivalve shellfish.
● On May 3 CDPH lifted the August 2015 warning related to dangerous levels of domoic acid in sport-harvested razor clams in Del Norte County.
● On April 30 CDPH announced the annual quarantine of sport-harvested mussels gathered along the California coast. The quarantine began on May 1 and applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. The quarantine will extend through midnight October 31, although it can be extended if dangerous PSP toxin levels persist in shellfish. Historically the majority of human cases of PSP illnesses occur between spring and fall. In California, PSP is extremely rare due to the efforts put forth by CDPH to protect the public against poisoning. There have been no reported human cases of domoic acid poisoning in California.
Paralytic Shellfish Poisoning Information:
Consumers of Washington clams, also known as butter clams (Saxidomus nuttalli), are cautioned to eat only the white meat. Washington clams can concentrate the PSP toxins in the viscera and in the dark parts of the siphon and can remain toxic for a long period of time. Persons taking scallops or clams, with the exception of razor clams, are advised to remove and discard the dark parts (i.e., the digestive organs or viscera). Razor clams (Siliqua patula) are an exception to this general guidance due to their ability to concentrate and retain domoic acid in the edible white meat as well as in the viscera.
PSP toxins can produce a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms can be followed by disturbed balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.
Domoic Acid Poisoning Information:
Symptoms of domoic acid poisoning can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, symptoms of exposure to this nerve toxin may include vomiting, diarrhea, abdominal cramps, headache and dizziness.
These symptoms disappear completely within several days. In severe cases, the victim may experience excessive bronchial secretions, difficulty breathing, confusion, disorientation, cardiovascular instability, seizures, permanent loss of short-term memory, coma and death.
Sport-harvester Information:
Any person experiencing any of these symptoms should seek immediate medical care. Consumers are also advised that neither cooking or freezing eliminates domoic acid or the PSP toxins from the shellfish tissue. These toxins may also accumulate in seafood species such as crab, lobster, and small finfish like sardines and anchovies.
Sportharvesters should only collect shellfish from areas that are not affected by a current health advisory or quarantine.
Contact the “Biotoxin Information Line” at 1-800-553-4133 or view the recreational bivalve shellfish advisory interactive map for a current update on marine biotoxin activity prior to gathering and consuming shellfish.
