San Diego Bay Faces Crisis from Invasive Caulerpa Algae

The Port of San Diego has declared a local emergency in response to the alarming spread of an invasive algae species known as Caulerpa prolifera in the southern bay. First identified in September 2023, this fast-growing algae poses a significant threat to the local marine ecosystem, particularly to eelgrass, a vital habitat for various marine species, including fish, birds, and green sea turtles.

Caulerpa prolifera, a tropical algae native to regions like Florida, can rapidly reproduce and expand, effectively choking out native seaweeds and seagrasses. The Port of San Diego has reported that approximately 11,200 square feet of this invasive species have been located, particularly near the Coronado Cays and the San Diego Bay National Wildlife Refuge. The bay is home to about 2,600 acres of eelgrass, with 1,900 acres situated in the southern zone, making it crucial for the survival of local marine life.

The emergency declaration aims to facilitate swift action against the algae's spread, which is believed to have originated from someone improperly disposing of a saltwater aquarium. Despite being a popular decorative plant in aquariums, Caulerpa is illegal to possess, sell, or transport in California, with fines ranging from $500 to $10,000 for violations. Officials have urged aquarium owners to refrain from dumping their tanks into state waters or storm drains, as these actions can inadvertently introduce harmful species into the ecosystem.

Frank Urtasun, the chairman of the Port of San Diego Board of Port Commissioners, emphasized the urgency of the situation, stating, “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.” He drew parallels to a similar outbreak in the Mediterranean Sea during the 1980s, which resulted in millions of dollars in losses to the fishing and tourism industries due to the failure to contain the invasive algae.

To combat the infestation, trained divers have been deployed to cover known patches of Caulerpa with sealed barriers designed to block light, oxygen, and tidal circulation, effectively suffocating the algae. The Port has committed over $900,000 to the eradication efforts, with an additional $2.2 million in funding anticipated from state and federal sources. The emergency declaration is also intended to secure further grant funding for ongoing surveillance and control measures.

While the invasive algae does not pose a direct threat to human health, it can have devastating effects on the local economy and environment. Eelgrass serves not only as a habitat but also as a natural water filter, contributing to the overall health of the bay's ecosystem. The loss of eelgrass could disrupt the delicate balance of marine life, affecting species that rely on it for food and shelter.

Historically, California has been vigilant in monitoring for Caulerpa since the early 2000s, following previous infestations in locations such as Huntington Harbour and Newport Bay. The current situation in San Diego Bay marks a critical juncture in the ongoing battle against invasive species, highlighting the importance of public awareness and responsible aquarium practices to protect the state's natural resources.

As the Port of San Diego and its partners work to contain this invasive threat, the community is urged to remain vigilant and report any sightings of Caulerpa. The collaborative efforts of local, state, and federal agencies aim to safeguard the bay's ecosystem and the livelihoods that depend on its health, ensuring that history does not repeat itself in this coastal region.