Invasive Algae – Caulerpa prolifera

Report Sightings of Caulerpa

Background

In September 2023, an invasive algae species was discovered in San Diego Bay, California in a small area off the Coronado Cays. The algae, which is native to Florida and other subtropical and tropical locales, is scientifically known as Caulerpa prolifera. It can grow quickly, choking out native seaweeds and potentially harming marine life through lost habitat.

Federal, state, and local agencies immediately joined forces to identify the extent of the algae's infestation. The Southern California Caulerpa Action Team (SCCAT), which includes partners from the Regional Water Quality Control Board, State Water Resources Control Board, California Coastal Commission, NOAA’s National Marine Fisheries Service, U.S. Fish and Wildlife Service, and the City and Port of San Diego, has been reactivated to lead efforts to address the new infestation.

In March 2021, a similar invasion was discovered in Newport Bay, California, centered within China Cove. In Newport Bay, the significant eradication effort appears to be working. Recent surveys have found no new growth and the hope is that all the algae has been removed. Only long-term survey efforts will be able to confirm if eradication has been successful (see Eradication Plan below).

Why is Caulerpa Bad?

The invasive algae can grow quickly, and rapidly out-compete native species including native eelgrass. Caulerpa prolifera may be inedible to native marine herbivorous fish and invertebrates. The species has invaded seagrass and soft‐bottom habitats in the Suez Canal, the Canary Islands, and Portugal, dramatically displacing native algae, plants, and animals.

Based on environmental impacts of other Caulerpa species, Caulerpa prolifera is potentially a serious invasive species. Other species of Caulerpa are well‐documented as having aggressively displaced native habitats when introduced in California, Australia, and the Mediterranean. Allowing any species of Caulerpa to become established and spread within California is likely to result in considerable economic, recreational, and biological impacts.

In 2000, a close relative of Caulerpa prolifera, called Caulerpa taxifolia, was found in two southern California lagoons. The seriousness and acknowledged threat of the situation prompted an effective, highly successful eradication project. This eradication took six years at a cost of more than seven million dollars. Although lengthy and expensive, the successful eradication led to the recovery of critically important eelgrass habitat and helped to protect California’s coastal ecosystems. Risk modeling for Caulerpa conducted in 2006 placed China Cove in the highest risk category for an introduction.

San Diego Bay Caulerpa Eradication Plan

The SCCAT has prepared a Rapid Response Eradication Plan (PDF) to address the immediate need to remove this invasive species. It is critical that the response be swift and sustained to prevent additional spread and to minimize the cost of the response effort while the infestation site is still small. Eradication efforts, which began in October 2023, include the following components:

• Control of Infestation Site - To prevent disturbance by boat anchors and boat wakes, the affected area will be controlled through coordination with local landowners. Additional visual exclusion markers will be deployed if necessary.
• Localized Eradication Level Survey - An intensive diver survey is being conducted within the affected area. Divers locate, record, and map any Caulerpa found.
• Treatment - The Caulerpa prolifera is being covered by trained divers with a sealed barrier that will kill the algae by exclusion from light, oxygen, and circulation. This method has been successfully used in the past at three other Caulerpa infestation sites.
• Post Removal Surveys - Diver surveys will be conducted both immediately following treatment and over a longer timeframe to help ensure the species is completely removed and does not repopulate the area.
• Broad Area Surveys - Diver surveys will occur in areas surrounding San Diego Bay to determine if other areas have been invaded.

Newport Bay Caulerpa Eradication Plan

Based on diver surveys, the infestation appears to be presently contained within a small area of Newport Harbor at China Cove. The scientific consensus is that it is critical to take immediate action to eradicate the species. Due to the high level of recreational activities in the area, and Caulerpa’s ability to spread through fragmentation, initial removal efforts began as soon as possible. CDFW and partners on the SCCAT created the Newport Bay Rapid Response Eradication Plan (PDF)(opens in new tab), to address the immediate need to remove the invasive algae Caulerpa prolifera from China Cove. This plan includes the following components:

• Initial Containment - To help prevent disturbance by boat anchors, boat wakes, divers, or swimmers, the identified infestation area was isolated by the City of Newport Beach through placement of floating buoys and lines surrounding the area.
• Localized Eradication Level Survey - Prior to removal, an intensive diver survey was conducted within the China Cove infestation area. Divers located, identified, and marked the Caulerpa they found.
• Localized Removal - Diver-assisted suction removal was used to completely remove Caulerpa prolifera, including sub-surface portions. The removed material was pumped to the beach for separation of algae and solids from the water. The discharge was handled with great caution to prevent re‐introduction to the nearshore environment.
• Post Removal Surveys - Diver surveys were conducted both immediately following removal and over a longer time frame to help ensure the species has been completely removed and does not repopulate the area.
• Broad Area Surveys - Diver surveys in surrounding areas have been conducted, both inside and outside Newport Harbor, to ensure other areas have not been invaded.

Species Identification

Caulerpa prolifera is a species of green algae in the family Caulerpaceae. The algae is bright green and consists of a number of blades linked by underground runners (stolons), which attach to the substrate with small root-like structures (rhizoids). Below are photos of Caulerpa prolifera found in Newport Bay.

What Should You Do?

Although there is significant concern that Caulerpa prolifera could potentially be harmful to native species, there is no danger to humans. However, it is imperative that the public avoid contact with the algae due to its extreme ease of recolonizing from just tiny fragments. If you believe you have seen this invasive algae, please use the form below to submit a notification to CDFW.