Catherine Rusoff
The Port of San Diego renewed an emergency declaration intended to help the city combat an invasive algae that has proliferated in its bay.
The algae species, scientifically known as Caulerpa prolifera, was first spotted in San Diego Bay in September, according to a report. port press release. The algae grows and reproduces quickly, “choking out native algae and seagrass,” according to the port, and causing habitat loss for marine life.
In the bay, the species most at risk are the eel, a type of plant that many oceanic species use as a habitat, and the fish, birds and green sea turtles that use this eel as a source of food and shelter. In addition to its role as a habitat and nursery, the eel is a natural water filter that helps maintain good air and water quality.
About 2,600 acres of eel grow in the bay, according to the port.
So far, about 11,200 square feet of Caulerpa have been found in San Diego Bay, including near Coronado Cays and the San Diego Bay National Wildlife Refuge. Authorities have not confirmed the source of the infestation, but said in the press release that it was likely caused by someone emptying a saltwater aquarium in the bay, as seaweed is a “popular and common plant in saltwater aquariums.”
Port of San Diego
Possessing Caulerpa in California is illegal, as is selling and transporting it. Officials said anyone who owns or sells saltwater aquariums should not use Caulerpa or dump aquariums into state waters. Aquariums should also not be emptied into streets or storm drains, as these systems often discharge into the ocean.
Once in a waterway, seaweed can “expand rapidly and aggressively from contact with ships, fishing and even tidal changes,” officials said. Regular visitors have been asked to avoid infested areas to prevent the spread of the invasive plant. The seaweed poses no risk to humans, but boaters, divers and fishermen visiting the bay should keep an eye out for Caulerpa, inspect their equipment and supplies for the plant, and report sightings to the California Department of Fish and Wildlife.
Trained divers have responded to the infestation in San Diego Bay by covering known areas with a “sealed barrier designed to kill the algae by blocking it from light, oxygen and tidal circulation,” officials said. More than $900,000 has been committed to cover the costs of searching for the plant and eradicating it from the bay, officials said, with an additional $2.2 million in funding pending from state and federal sources. The emergency declaration is intended to help authorities secure additional funding for surveillance, control and monitoring measures.
Port of San Diego
Frank Urtasun, chairman of the Board of Port Commissioners for the Port of San Diego, issued a warning about a seaweed outbreak in the Mediterranean Sea in the 1980s. He said the Caulerpa infestation “caused millions of dollars in losses to tourism and fishing industries because it was not contained” and said that limiting the infestation in San Diego Bay was of paramount importance.
“It is absolutely critical that we find and remove or cover every little piece of Caulerpa as quickly as possible to preserve our bay’s strong and healthy ecosystem,” Urtasun said in the release.
While this is the first discovery of Caulerpa in San Diego Bay, it is far from the first time the algae has been seen in California. The state has been monitoring the plant since the early 2000s, officials said. A species of Caulerpa infested part of Huntington Harbor and the state’s Aqua Hedionda lagoon in Carlsbad at that time. Newport Bay has been battling an infestation of the plant since 2021, officials said.
