October 2023 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
Paralytic Shellfish Poisoning
Alexandrium sp.
Alexandrium was observed in four of the 43 northern California phytoplankton samples collected in October, a sharp decline from previous months (Figure 1). The elevated percent composition of this dinoflagellate observed in September at the Drakes Bay sentinel mussel station persisted into the beginning of October (3%, October 2).
The low levels of PSP toxicity detected in shellfish samples in September continued into October (Figure 2). Positive samples occurred at sites representing most coastal counties between Del Norte and Monterey.
Domoic Acid
Pseudo-nitzschia sp..
Pseudo-nitzschia was observed in 17 of 43 phytoplankton samples collected in October (Figure 1). This diatom was only observed at five sampling sites scattered between Del Norte and Santa Cruz counties. The percent composition of Pseudo-nitzschia remained elevated inside Humboldt Bay (15%, October 2 and 9).
Sentinel mussels from outer Humboldt Bay contained an elevated concentration of domoic acid, just below the alert level (19 ppm, October 9) (Figure 2).
Phytoplankton Observations
The dinoflagellate Prorocentrum micans was common to abundant at sites between Humboldt and Monterey counties. P. micans was abundant in samples from the Santa Cruz Pier (52% and 70%, October 14 and 28, respectively). The dinoflagellate Akashiwo sanguineum was common at several sites and abundant at the Monterey Commercial Wharf (83%, October 17). The diatom Chaetoceros was common inside Noyo Harbor and the Marina Bay Harbor inside San Francisco Bay.
This month’s photos include the dinoflagellate Ceratium fusus, observed in Tomales Bay and Monterey Bay (Santa Cruz Wharf and Monterey Commercial Wharf), and the diatom Rhizosolenia sp., which was observed at six sites between Humboldt and Monterey counties.
Southern California Summary
Paralytic Shellfish Poisoning
Alexandrium sp.
Alexandrium was observed in five of 55 phytoplankton samples collected in October (Figure 3). This dinoflagellate continued to be observed offshore of Diablo Cove (San Luis Obispo County), as well as at sites in Los Angeles, Orange, and San Diego counties. The cell mass was low in all samples.
PSP toxicity continued to be detected in shellfish samples from San Luis Obispo County in October (Figure 4). Low levels of toxin were detected in mussels from Montaña de Oro and the Cal Poly Pier.
Domoic Acid
Pseudo-nitzschia sp.
Pseudo-nitzschia was observed in 18 of the 55 October samples (Figure 3). While the frequency of occurrence increased relative to the previous month, the percent composition and cell mass were low in all samples.
Domoic acid was not detected in any mussel or oyster samples in October (Figure 4).
Phytoplankton Observations:
Dinoflagellates continued to dominate the phytoplankton assemblage along the southern California coast. Lingulodinium polyedrum was common to abundant in samples from most sampling sites between San Luis Obispo and San Diego counties. Akashiwo sanguineum continued to be common in mid Morro Bay and was also observed at the Cayucos Pier.
This month’s photos highlight the diatom Ditylum sp., observed at only three sites (Morro Bay, Pt. Dume, Bolsa Chica), and the dinoflagellate Ceratium azoricum, which was only observed offshore of Diablo Cove.
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
A Sonoma County mussel bed.
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
The following is a list of recent Health Advisories and Quarantines for bivalve shellfish prior to October 1, 2023. For access to current advisories, please refer to the end of this report.
● The annual mussel quarantine on sport-harvested mussels began on May 1. The quarantine applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. During the quarantine, mussels may only be harvested for use as bait. The quarantine is in place to protect the public against poisoning that can lead to serious illness, including coma and death.
● On October 27 CDPH announced that the annual mussel quarantine would end at midnight, October 31 for all counties except San Mateo and San Luis Obispo. CDPH also lifted the PSP shellfish advisory related to sport-harvested mussels, scallops, and clams in Mendocino County
● On September 7 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from Mendocino County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.
● On August 3 CDPH lifted the domoic acid shellfish advisory related to related to sport-harvested razor clams in Humboldt County.
● On August 1 CDPH lifted the domoic acid shellfish advisory related to related to sport-harvested mussels, scallops, and clams in Santa Barbara County.
● On July 28 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from San Mateo County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.
● On July 14 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from San Luis Obispo County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.
● On July 6 CDPH lifted the shellfish advisory related to sport-harvested razor clams in Del Norte County. The safety notification was issued on November 3, 2022 due to dangerous levels of naturally occurring domoic acid, also referred to as Amnesic Shellfish Poisoning. Razor clams have been continually tested and have now met the criteria for lifting the safety notification in Del Norte County. An advisory for razor clams in Humboldt County remains in effect.
On June 16 CDPH advised consumers not to eat sport-harvested mussels, clams, or scallops from Santa Barbara County due to the presence of dangerous levels of domoic acid in shellfish samples.
● On June 16 CDPH advised consumers not to eat sport-harvested mussels, clams, or scallops from Santa Barbara County due to the presence of dangerous levels of domoic acid in shellfish samples.
● On May 1 CDPH initiated the annual quarantine of sport-harvested mussels gathered along the California coast. The quarantine normally extends from May 1 through October 31, although elevated toxin levels can extend the quarantine period. This annual quarantine applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. The quarantine is in place to protect the public from poisoning that can lead to serious illness, including coma and death.
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.
