The Port of San Diego is continuing its emergency response to an invasive algae, known as Caulerpa (Caulerpa prolifera), found in San Diego Bay. The Board of Port Commissioners has extended the local emergency declaration through March 15, 2026, marking the 18th continuance since the initial declaration on November 14, 2023.
A Threat to Marine Ecosystems
Caulerpa is a fast-growing alga that spreads through fragmentation, aided by tidal movement, vessel traffic, and fishing activity. While not harmful to humans, it poses a significant threat to the bay’s native marine life by potentially choking out native seaweeds and eelgrass.
Protecting eelgrass is a key priority, as it forms the base of the food chain, providing shelter and food for numerous species, including over 70 types of fish and more than 100 endangered green sea turtles. Eelgrass also contributes to water quality and carbon storage.
Current Eradication Efforts
The first discovery of Caulerpa in San Diego Bay occurred in September 2023 during a routine dive survey in the Coronado Cays. Since then, approximately 11,300 square feet of the algae has been identified, with over 300 square feet within the Port’s jurisdiction. Divers have been applying sealed benthic barriers to known patches, a method that has proven successful in other Southern California locations like Huntington Harbor and Agua Hedionda Lagoon.
The Port is collaborating with the Southern California Caulerpa Action Team, a coalition of agencies working to prevent further spread. Complete eradication requires two years of monitoring with no new discoveries.
Currently, divers are surveying approximately 3,000 acres in South San Diego Bay. To date, over $3.1 million has been allocated to survey and eradication efforts, including $200,000 recently awarded from the Pacific States Marine Fisheries Commission’s Aquatic Invasive Species Rapid Response Fund.
Preventing Further Spread
Authorities believe the initial infestation likely originated from the release of aquarium contents into the bay. As a result, it is illegal in California to possess, sell, or transport Caulerpa, with violations carrying fines between $500 and $10,000.
Individuals with saltwater aquariums are advised to avoid dumping aquarium contents into California waters, to bleach aquarium water before disposal, and to refrain from purchasing or using Caulerpa. Suspected Caulerpa should be frozen for at least 48 hours before disposal.
Boaters, kayakers, swimmers, and divers are asked to avoid infested areas when possible and to report any suspected sightings to the California Department of Fish and Wildlife at wildlife.ca.gov/Conservation/Invasives/Species/Caulerpa.
Frequently Asked Questions
When was Caulerpa first discovered in San Diego Bay?
Caulerpa was first discovered in San Diego Bay in September 2023 during a routine dive survey in the Coronado Cays.
What method is being used to eradicate Caulerpa?
Trained divers are covering known patches of Caulerpa with sealed benthic barriers, which cut off light, oxygen, and water circulation, effectively killing the algae.
How long will it take to declare Caulerpa fully eradicated?
As part of the eradication process, two years of monitoring with no new discoveries are required before the alga can be declared fully eradicated.
Given the ongoing efforts and the potential for further spread, what steps do you think are most crucial to protect San Diego Bay’s delicate marine ecosystem?
