The Port of San Diego has renewed an emergency declaration in light of an invasive plant continuing to spread in the San Diego Bay.
The algae, Caulerpa prolifera, was discovered in the bay in September 2023. Additional patches have been found near the Coronado Cays.
The species is native to Florida and other subtropical and tropical locations, but it can take over non-native natural habitats, disrupting the ecosystem and displacing native plants and the animals who rely on them.
“Caulerpa can rapidly and aggressively expand from contact with vessels, fishing and even tidal exchanges,” says a statement from the Port. “To prevent unintentional spread of this invasive species, boaters, kayakers, swimmers, and divers are asked to avoid the areas, if possible, or to gently transit the channel at high tide.”
The statement also asks the public not to dump the contents of saltwater aquariums directly into bays, streams, ponds, or storm drains, as Caulerpa is a popular and common plant used in them.
It is illegal in California to possess, sell, or transport any Caulerpa seaweed. Fines can range from $500 to $10,000 for each violation.
“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,” said Chairman Frank Urtasun of the San Diego Board of Port Commissioners.
“Caulerpa is also a potential threat to local jobs and businesses,” he added. “In the 1980s, a Caulerpa outbreak in the Mediterranean Sea caused millions of dollars in losses to tourism and fishing industries because it was not contained. We will not let that happen in San Diego Bay.”
In San Diego Bay, Caulerpa threatens state and federally protected eelgrass habitats. Eelgrass is used by native green sea turtle population — a threatened species — and at least 70 different fish species rest within and feed on eelgrass.
The bay has nearly 2,600 acres of eelgrass.
In California, worker have conducted routine monitoring of Caulerpa since the early 2000s.
Last September, divers found a small patch of the plant while conducting an in-water, pre-construction dive survey as a permit condition for a dock replacement project. Additional patches were discovered nearby during follow-up surveys.
In mid-April, divers found small Caulerpa patches in the San Diego Bay National Wildlife Refuge adjacent to the Cays. To date, nearly 11,200 square feet of the seaweed have been discovered. Trained divers have covered all the patches with a sealed barrier to kill the algae by blocking it from light, oxygen, and tidal circulation.
Caulerpa is not harmful to humans.
City News Service contributed to this report.