Port of San Diego declares emergency over invasive seaweed in southern bay

The Port of San Diego has declared a local emergency due to the spread of an invasive algae species in South San Diego Bay.

The algae, called Caulerpa prolifera, was first discovered in the bay in September 2023, with additional patches popping up within and adjacent to the Coronado Cays, a press release from the port stated.

This kind of tropical algae “grows and reproduces extremely quickly, choking out native seaweeds and seagrasses, potentially harming marine life through loss of habitat,” the press release noted.

In the San Diego Bay, the invader poses a threat to eelgrass, a type of plant that the local fish, birds and green sea turtles rely upon for food and shelter. While the entire bay has about 2,600 acres of eelgrass, 1,900 of those acres are in the southern zone, according to the port.

“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,” Frank Urtasun, chair of the Port of San Diego Board of Port Commissioners, said in a statement. “Caulerpa is also a potential threat to local jobs and businesses.”

This infestation was likely the result of a release from a saltwater aquarium into the bay, as Caulerpa is a popular type of decorative plant — despite its prohibition in California, per the port.

Any person caught in possession of, selling or transporting this type of seaweed in the state is subject to fines ranging from $500 to $10,000 for each violation, port officials noted.

Stressing the environmental risks associated with this type of invasive algae, Urtasun noted that in the 1980s, an outbreak in the Mediterranean Sea brought millions of dollars of losses to the fishing and tourism industries of the region.

“We will not let that happen in San Diego Bay,” he said. “With our many local, state, and federal partners, we are being swift and prudent to protect both our environment and our economic interests.”