The Rising Tide of Marine Mammal Strandings in California
From August to October of 2022, the California coast witnessed a troubling pattern: 300 marine mammal strandings occurred between Los Angeles and San Mateo counties. A year later, from May to July 2023, Southern California experienced an unprecedented mass stranding event, with nearly 1,000 marine mammals washing ashore. Now, in 2024, California is facing yet another surge of strandings, this time from Santa Barbara to Santa Monica Bay, with cases as south as Orange County. These consecutive years of mass strandings highlight an alarming trend tied to one culprit: domoic acid.
Domoic acid, a potent neurotoxin, is released by Pseudo-nitzschia, a common phytoplankton species found in coastal waters. This toxin accumulates in the bodies of fish and invertebrates, which in turn become food for marine mammals like sea lions. When sea lions consume large amounts of these contaminated prey, they are poisoned, often resulting in mass stranding events along the California coastline.
Marine mammals, particularly sea lions, suffer severe consequences from domoic acid exposure. The toxin attacks the central nervous system, leading to symptoms such as seizures, gastrointestinal distress, and even pregnancy loss in female sea lions. Other signs of poisoning include confusion, lethargy, excessive scratching, repetitive head movements, foaming at the mouth, and even unusual aggression. Tragically, many of these animals succumb to the effects, stranding themselves on beaches where they eventually die or require euthanasia.
While California sea lions are the most commonly affected species, domoic acid also poses a threat to dolphins, otters, seabirds, and other marine life. These events are a stark reminder of the growing impact harmful algal blooms (HABs) are having on marine ecosystems and wildlife along the coast.
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Addressing the Crisis: California’s Response to Harmful Algal Blooms
Harmful algal blooms (HABs), including those that produce domoic acid, have increased frequency and intensity along the California coast. HABs not only impact marine life but also lead to fisheries closures, posing significant challenges for local communities and the state’s economy. In response, numerous state agencies are actively monitoring HABs to mitigate risks to both public and environmental health.
The California Department of Public Health, California Department of Fish and Wildlife, and the Office of Environmental Health Hazard Assessment work together to monitor HABs and take necessary actions. The California Ocean Protection Council (OPC) also plays an important role in advancing the state’s capacity for HAB preparedness, monitoring, and response by enhancing early warning systems and increasing the effectiveness of real-time tracking of HABs across the coast.
Innovative Solutions: Real-Time Tracking and Early Warning
In 2019, OPC approved funding to support a cutting-edge project at the University of California, San Diego, aimed at creating an automated, real-time tracking and early warning system for HABs. This system uses a network of submersible, high-resolution underwater microscopes known as imaging-flow cytobots (IFCBs) to capture real-time images of phytoplankton and transmit data instantly to scientists. This real-time monitoring allows scientists to detect harmful phytoplankton blooms early, providing critical alerts to coastal managers and the public.
Data from the IFCB network feed into the Harmful Algal Bloom Data Assembly Center (HABDAC), a publicly available online resource. This platform offers up-to-date HAB monitoring data and daily alerts, ensuring that decision-makers and the public are informed of potential risks before they escalate. The California-Harmful Algae Risk Mapping (C-HARM) Model further supports HAB forecasts by generating near-term predictions of HAB conditions daily to provide a forecast of where HABs or domoic acid events may be encountered in the next 1-3 days. Such systems are essential in helping California address the growing threat of HABs and protect vulnerable marine wildlife.
For those interested in staying informed about HAB events, the California Harmful Algal Bloom Monitoring and Alert Program (Cal-HABMAP) provides valuable resources, including real-time updates and public alerts on harmful algal blooms across the state.
Moving Forward: A Shared Responsibility
At OPC, we are committed to working with our partners to enhance HAB monitoring and response efforts, while also supporting research and innovation to understand and address the causes of toxic HABs along California’s coasts.
Through continued collaboration and investment in cutting-edge technology, we hope to reduce the impact of HABs on California’s marine life and support the resilience of coastal communities. Together, we can safeguard the health of our oceans and all the creatures that call them home.
For more information about OPC’s work on HABs and marine pollution, visit our page on Harmful Algal Blooms.