Illustration by Nastasic, DigitalVision Vectors, Getty Images

“It is absolutely critical that we find and remove or cover every little piece of Caulerpa as quickly as possible”

Imagine a piece of paper. Now imagine shredding it into confetti and scattering it to the wind. Now imagine each piece of confetti growing into a new piece of paper. Now shred those new pieces and repeat. And on and on, more and more paper, until you’re drowning in it like some cartoon office drone — you and everybody around you.

Photograph by MTS/M&A

That’s Caulerpa, an invasive seaweed that grows incredibly fast — up to a centimeter a day — and which has been found in San Diego Bay since September of 2023. Various species of Caulerpa have been used in aquariums, both home and institutional, for some time. When it gets introduced into natural coastal environments via aquarium release or discharge, new colonies begin. And when those colonies are fragmented — by anchors, fishing line or diving gear — the fragments spread via ocean currents, tides or human transport. And just like our imaginary confetti, each of those fragments can grow into a new colony. If left alone, Caulerpa will outgrow whatever is around it. It will smother ocean floors, sandy sea beds, and coastal reefs. Native biodiversity — eelgrass beds, fish species, shellfish, and marine plants — gets displaced. Eliminated. Removed. Gone. Along with the benefits and habitat they provide.

If you could identify and remove that first piece of paper, or even the second or third, that would be a worthwhile victory. And that is what various governmental entities, resource agencies, and biological contractors are trying to do right now to address the Caulerpa invasion in San Diego Bay. But it can be tricky to get people to care about a problem they can’t see, and even trickier when the problem looks so very, very small. Unfortunately, it’s when the problem is still small that dealing with it remains possible, and it’s only when the problem is quite large that its surprisingly adverse effects become noticeable. That is the challenge of containing Caulerpa.

Caulerpa vs. San Diego Bay

Caulerpa prolifera was first detected in Coronado Cays boat slips in September 2023. The most likely introduction was via home salt-water aquarium release. It poses a very real threat to over 70 fish species, and to the 60-80 sea turtles residing in the South Bay. But it doesn’t stop there. Frank Urtasun, chairman of the board of port commissioners for the Port of San Diego, issued a press release on May 15, 2024 that stated, “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. Caulerpa is also a potential threat to local jobs and businesses. 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. With our many local, state, and federal partners, we are being swift and prudent to protect both our environment and our economic interests.”

Lessons from Carlsbad’s Caulerpa Conquest 

The Port of San Diego acts in conjunction with other regional, state and federal partner agencies, but it is the lead agency with jurisdictional oversight of tidelands around San Diego Bay. It knows what’s at stake and what needs to be done, partly because San Diego has been here before. From 2000 until 2006, Carlsbad’s Agua Hedionda Lagoon, along with a segment of the Huntington Harbour boat slips in Orange County, was the site of a surprisingly successful battle to eradicate another Caulerpa species (Caulerpa taxifolia). This was thanks to the the formation of the multi-agency Southern California Caulerpa Action Team and the participation of other stakeholders, including the lagoon foundation, the power plant, the local Homeowners’ Association, and the city of Carlsbad. Now, the current configuration of the action team is at work in San Diego Bay.

California team in New Zealand (left to right): Eric Muñoz, Dr. Robert Mooney, and Seth Jones.

Photograph by Eric Noel Muñoz

During that first battle, I was well into my career as a city staff planner with Carlsbad, putting my degree in geography from SDSU to good use. Tasked with environmental, habitat and coastal resource management projects, I became the city liaison with the team. I was glad for the opportunity, because I was frustrated and angry about the threat posed by this non-native seaweed — as with San Diego Bay, it was likely introduced via aquarium release — to both our local lagoon and beyond. We could only imagine what would happen if a small patch of the stuff escaped the lagoon to Tamarack reef and spread offshore up and down the coast. We saw both the losses and the missed opportunities to stop the Mediterranean Sea invasion. And we learned from them.

In his 1999 book Killer Algae, French marine biologist Dr. Alexandre Meinesz told the sad story of the inability of marine scientists and coastal managers to convince policy makers to give the Mediterranean invasion timely attention and funding. As a result, several countries have been unable to overcome their Caulerpa taxifolia problem, most recently Malta.

A big obstacle was the fact that famed marine biologist Jacques Cousteau was the aquarium manager of the Monaco Oceanographic Museum during the mid-1980s, and it was believed that the museum’s discharge pipe had released Caulerpa into the sea. A political and media campaign ensued, as people in power sought to protect Cousteau’s reputation instead of fighting the invasion with sound scientific policy and funding. Caulerpa was essentially deemed “fake news.” Meinesz was personally and professionally discredited even as he claimed that the biodiversity of Med Sea coastal regions was at stake.

From our dealing with Meinesz and his fellow scientists and coastal managers from Italy, Croatia, France, Monaco, Spain, Japan, and Australia, we learned two things: (1) you cannot really touch Caulerpa because one-centimeter fragments can break off, drift away and form new colonies of growth; and (2) the value of rapid response after detection. Based on this, a tarp-in-place containment method was devised for the lagoon. Biological contractors, skilled in containment and eradication efforts, were called in and deployed with the action team’s oversight: Keith Merkel and Rachel Woodfield with Merkel and Associates, and Marine Taxonomic Services, run by Seth Jones and Dr. Robert Mooney. They did the underwater survey work, and the actual eradication and monitoring. The tarp they laid cut off sunlight and the growth that results from photosynthesis. Further, chlorine was pumped under the tarps in areas of high biomass. Over time, the native eelgrass emerged and Caulerpa was removed.

After eradication, I served as two-time president of the Agua Hedionda Lagoon Foundation, co-produced an animated TED video titled Attack of the Killer Algae (2014) and authored Caulerpa Conquest, A Biological Eradication on the California Coast (2016). (While speaking with Alex Meinesz in Monaco during my research for that book, I learned that another source of aquarium release may be luxury mega yachts. Their role in the story of Caulerpa distribution may one day become clearer than it is now.) The lessons learned and victory secured by community and multi-agency support earned global attention. Closer to home, many of the players, the action team, and procedures from the Carlsbad experience are involved with the current response in San Diego Bay. That same tarp-in-place method is now being employed — thus far without the use of chlorine. In both cases, early detection and rapid response was crucial to the success of our efforts.

Caulerpa invading native San Diego Bay eelgrass.

Photograph by MTS/M&A

Another significant outcome of that Carlsbad victory was a new Caulerpa protocol: a policy mandate that requires in-water Coastal Development Permits — permits that themselves require federal and state agency approvals — for work in tidal areas of southern California (between Morro Bay and the Mexican border). Pre- and post-work surveys to assess the presence of native eelgrass beds, and specifically to confirm the absence of Caulerpa, are now mandatory. Projects such as a pier replacement, new pilings for boat docks, a dredging project, soil remediation, or bulkhead replacement of a ship repair yard — is subject to the Caulerpa protocol. In 2021, implementation of that protocol in Newport Bay resulted in the detection and action-team-directed response to contain an area of Caulerpa prolifera. The confluence of science, policy, and funding, along with early detection and rapid response, once again proved the best measures against the stunningly aggressive invasion of Caulerpa.

Current Status in SD Bay

The protocol was the reason behind the September 2023 Caulerpa discovery in the Coronado Cays, following a Coastal Development Permit application for dock work. Response action was initiated immediately after detection, and the Port put up approximately $92,000 for treatment of initially detected infestation areas and follow-up surveys in vulnerable areas. (So far, approximately $950,000 has been spent on containment and surveillance efforts, monies obtained through grants and other funding.) As of summer 2024, between 200 to 300 acres of Bay tidelands have been surveyed; approximately less than half an acre of combined areas hosting Caulerpa have been detected.

San Diego Bay has approximately 2600 acres of eelgrass habitat, of which approximately 1900 are in South Bay. Per Eileen Maher, the Port’s director of environmental conservation, outreach information has been distributed to all marinas and yacht clubs in San Diego Bay, and she noted the cooperation of the boating community. (However, no limitations are in place baywide for fishing, boating, or anchoring outside the infested areas.) Emergency declarations have been made and extended several times by the Port as well as the city of Coronado, which enables the flow of grant funds from various sources.

Closed off dock in Coronado Cays due to a Caulerpa discovery.

Photograph by Eric Noel Muñoz

She informed me that the action team is working with large online retailers like eBay and Amazon to prohibit the sale of aquarium Caulerpa to California consumers. All forms of possession, use or transport of Caulerpa in California are illegal, with fines varying from $500 to $10,000 per incident. Still, many home-based aquariums may have the now-illegal species of Caulerpa in them. If that’s you: the proper method for removal is to freeze it and throw it away with your landfill trash. Under no circumstance should there be aquarium release into ocean, coastal, harbor, or wetland waters, nor into any storm drains which connect to such waters. Anyone with Caulerpa should just purge it from their tanks right now: freeze it, kill it, and throw it away.

Rich Grunow, community development director with the city of Coronado, serves as a liaison between his community and the action team, similar to my role in Carlsbad. Coronado is doing outreach with target audiences: marinas, their yacht club, and the city citizenry. (One key message: if a boater or fisherman comes into contact with a piece of Caulerpa: do not throw it back into the Bay waters! Bag it, report it to Port staff, and freeze it. Kill it.) Like me, Grunow is pleased by the inter-agency cooperation, and by how effectively the action team has been operating. He says that everyone seems to be “rowing in the same direction.” Upon detection of Caulerpa, it is not business as usual. Time is ticking, and Caulerpa is growing. Instead of bureaucratic wrangling, there is coordinated cooperation among affected stakeholders, which serves as a foundation for success.

Containing Caulerpa Within SD Bay

In my book, I recounted a meeting two Navy officers who attended a city outreach workshop during the Carlsbad invasion. They said that if Caulerpa were allowed to escape Agua Hedionda Lagoon and disperse up and down the southern California coast, there could be a scenario where container ships, military vessels, and recreational boats in LA Harbor, Long Beach Harbor, Newport Bay, San Diego Bay, etc would need to be cleaned and waters treated. An unprecedented biological and economic shutdown could take place. As the U.S. Pacific Navy fleet is based in San Diego Bay, the current containment efforts are even more important: national security resources are at stake. It is therefore reassuring that the Navy is an active team stakeholder and is subject to the Caulerpa protocol for applicable projects.

The author standing with a Caulerpa outreach sign in New Zealand. The California team was collectively unable to make sense of the instructions to “Chuck It Straight Back.” The messaging was later changed to “Bag It and Bin it.”

Photograph by Eric Noel Muñoz

Besides the Navy fleet, there is growing cruise ship traffic, a commercial sportfishing fleet, and a host of recreational boats. Any of them could conceivably carry a piece of Caulerpa on an anchor, or on fishing or diving gear, to some new location, and start up a new invasion. And if that new invasion is not detected early, there may be little chance to stop it completely, resulting in biodiversity loss, reduced tourism, and displaced fisheries.

Caulerpa vs. New Zealand

Currently, coastal areas in the Mediterranean Sea, southeast Australia and most recently New Zealand (Aotearoa) are under the grip of colonization by Caulerpa. In April of 2002, during the midst of Carlsbad’s eradication effort, I made a presentation at the first joint conference of Australian and New Zealand city planners, explaining my role as a liaison between the community and the action team. Australia had already detected Caulerpa taxifolia on the east coast of New South Wales. Six months after the conference, it was detected in South Australia. Once again, manifestations were attributed to salt water aquarium releases. I hoped that New Zealand’s biosecurity vigilance and luck would prevent Caulerpa invasions there as well, but in late 2022, Paul Hansen — a New Zealander I met during a surfing trip to El Salvador during the civil war of 1988 — informed me that another strain of Caulerpa had been found on Great Barrier Island (Aotea) waters in mid-2021. I was stunned. Even more stunning were the reports of a delayed, tepid response from the central government.

Hansen works in a natural resource management role for Te Rarawa, an indigenous Māori tribe addressing environmental stewardship, community development, and education projects, based out of Kaitaia in Northland. He set up a Zoom meeting with central government’s Biosecurity staff, and brought me in as a voice representing the California Caulerpa conquest. I implored them to check and monitor boats for anchors with Caulerpa, to check mega yachts for aquariums, to conduct outreach to coastal communities, and to ban anchoring in impacted areas. They said “Thank you very much” but assured me they had different strains of Caulerpa than the California species, and that a ban on anchoring was going a bit too far. They said they had things under control, and asked if there was anything else I wanted to discuss.

Looking for (and finding) Caulerpa on Waiheke Island, New Zealand.

Photograph by Eric Noel Muñoz

They did not have things under control. The infestation on Aotea continued invading westward to the mainland coast of North Island. There are theories about whether anchor lines, boat transport, or swells carried the small Caulerpa fragments. I suspected a mega yacht. Regardless, the national situation with regards to expanding invasions was becoming gravely serious during 2023. Imagine if Caulerpa showed up on Catalina Island, and no real or effective agency response was undertaken. It would then spread to Palos Verdes, Malibu, Laguna, and La Jolla. The coastal geography of New Zealand is far more complex, but it’s a fair analogy. Furthermore, the Biosecurity position was that they had consulted with global “experts,” and due to the scale of the infestation, eradication was deemed infeasible. Wow, I thought, who are these unnamed experts and how did they determine that? Were the California experts consulted?

One thing about resource management in Aotearoa is that there is a voice from First Nation people at the table: the indigenous Māori tribes (iwi). The modern history of New Zealand is dominated by the story of colonization. And now Caulerpa is re-configuring the colonization story so that all New Zealanders regardless of race or culture are feeling the bite of being invaded. Prior ways of life are being disrupted as alterations to coastal food resources, loss of biodiversity, ecosystem health, access to waterways, recreational limitations, boating restrictions, and impacts to fish species emerge.

For the Māori, the relationship to all things in the environment is personal. There is a whakatoki (proverb) in Aotearoa which states, “Kō āu te awa, kō te awa kō āu” – “I am the river and the river is me”. The same relationship exists with mountains, water, the ocean, etc. Many Māori iwi and coastal communities rely heavily on the ocean as a food resource. Therefore, the impending impact — both culturally and on food resources — would be devastating.

Enter Nicola MacDonald, leader of a prominent coastal iwi (Ngati Manuhiri) with territory ranging from Auckland northward. A Māori leader with connections to other coastal iwi, government agencies, elected officials, academia, stakeholders, and media, she is a force of action and movement. In early 2023, she secured contact with Dr. Robert Mooney, visited him in Newport Beach, and implored him to come help. Soon after that, Robert, Rachel, Seth Jones, and I were working out logistics with Nicola’s team back in Auckland. Years back, we had learned from the Med Sea scientists and experts, and we had put our learning to good use. Now we were being called on to teach and on the global stage. We were there to provide input, context, technical support, and, unknowingly, hope. In August 2023 we arrived in Aotearoa. We were greeted with traditional Māori protocols and ceremonies and allowed into typically restricted-access areas for the non-Māori. A roadshow was planned out over the course of a week, called Te Wero Nui (The Big Challenge): Combatting Caulerpa. The overwhelming dynamic we encountered was coastal people, stakeholders, and Māori iwi at ground zero of an invasion, seeing their beloved reefs, fish species and coastal areas being adversely impacted. That and dissatisfaction with central government’s Biosecurity response. Time had been lost.

Tarp over Caulerpa next to native San Diego Bay eelgrass. The tarp cuts off sunlight and the growth that results from photosynthesis.

Photograph by MTS/M&A

Without making promises, we recited the tenets of our lessons learned: rapid response, outreach, education, action, aim to kill it, don’t overthink it and lose time, force a marriage of science, policy, and funding. Now. Because Caulerpa will laugh at your toolbox of outdated protocols, laws, mindsets, policies and procedures whether they be for permits, consensus, in-water operations, or spending. One example was a stunning bit of messaging from Biosecurity that urged boaters, upon finding a piece of Caulerpa on an anchor or fishing line, to “Chuck It Straight Back.” The California team was unable to make sense of this message, which was posted on six-foot tall vertical banners at the domestic airline terminal (where flights left daily for Caulerpa-infested Great Barrier Island), on websites, and on to ground-mounted billboards overlooking invaded waters. We urged agency staff to re-think this harmful message. It was fiercely defended during Q-and-A sessions during Roadshow presentations.

A positive development: months after our return, the messaging was changed to “Bag It and Bin It.” That change of posture from officials, agency staff, and outreach communications was the result of coastal iwi and stakeholder groups demanding accountability and a reversal of the “surrender” position. Agency staff tend to think in terms of their careers and date of retirement. Political officials think in terms of election and fiscal cycles. But the indigenous Māori think in terms of ‘forever’ and multiple generations, past and future. Their connection to ocean and terrestrial resources is spiritual and functional. Time was up to turn the corner and face down Caulerpa with combat.

This will be a decade-long war. There are hopeful and promising updates from various battlefield locations. There are new innovative containment and control techniques that were not available or developed during the time of our Caulerpa battle that typify “Kiwi ingenuity” — a new dredge device, biodegradable mats to cover Caulerpa, and remotely operated underwater drone surveys. If successful, these new techniques could be deployed nationally in New Zealand and then worldwide. And there are finally anchoring bans in certain areas, even though enforcement challenges loom — there are still some surprising disconnects among recreational and organized boating fraternities regarding the real threats from Caulerpa. Human nature will always represent a challenge to nature. Still, many have told us that the California team initiated a positive metamorphosis in Aotearoa. Our team met with then prime minister Chris Hipkins; we had a spot on national television on the Breakfast Show. We had media interviews and coverage, most of which were arranged by Nicola.

The national challenge to combat Caulerpa is now connecting various community and cross-cultural elements. The renowned Kelly Tarlton Sea Life Aquarium in Auckland is committed to new outreach campaigns. Coastal coalitions are forming partnerships and developing websites. Biosecurity is increasing accountability, action, and communications. Apathetic surrender is not being tolerated, and agency action is acutely monitored. But the situation is far from contained. Waiheke Island, just offshore of Auckland Harbour, is the equivalent of Catalina Island, connected to the mainland by regular commuter and tourist ferry service. Waiheke Island has Caulerpa, and the threat of invading Auckland Harbour is very real. At that point, Caulerpa gets exported throughout the South Pacific. On Aotea continued surveys are finding new infestations, and existing ones are growing. Government funding is a fraction of what is needed. Scallops and crayfish have disappeared from affected reefs. And besides Aotea, there are ongoing invasions at the Bay of Islands, Kawau Island, Iris Shoal, Mercury Islands, Waiheke Island, and the Coromandel Peninsula.

But we keep fighting, and we keep hoping. In March 2024, Nicola MacDonald was named New Zealand’s Environmental Hero of the Year. Specific reference was made to her efforts in hosting the California team and putting an overdue national spotlight on the Caulerpa invasions along the east coast and offshore islands of North Island. As the Caulerpa storyteller, I feel the need to communicate the intelligence, goodwill, and concern for coastal stewardship that I have seen first-hand. And to testify that in a world full of environmental problems, we need to be mindful that we do own a rare success story with our Caulerpa conquest. Our lessons learned remain relevant. We have a good toolbox. We are viewed positively within a global context. Connecting the dots from the Mediterranean Sea to the California coast to the southern hemisphere waters of New Zealand allows us to realize that saving the world means saving the oceans. And saving the oceans can start with one patch of water at a time.