Ban on Caulerpa Algae

Back in July 2023 a state-wide ban came into effect across California banning several genus of the popular macroalgae Caulerpa. As of the 1st January 2024, a new law was passed that bans every species. The law enforces that you must not sell, possess or transport any of the Caulerpa species. This is in response to the macroalgae, native to Florida and the Caribbean, being not only discovered, but found to be thriving in the warm waters around California. In these numbers, it has been able to outcompete plant life native to the area. As well as growing at an increased rate to its native neighbours,  Caulerpa also contains toxins which can cause an undesirable affect to its environment as well as protecting them from being grazed upon.

It is believed that the algae first entered the shores of the West Coast state, by an aquarist emptying the contents of their tank into the surface water drainage system which flowed into the lagoon where the invasive species was first discovered.

Some of the reasons environmentalists are so worried about an outbreak is the adaptability of the algae. It has become resilient to lower temperatures, particularly the aquarium strains. It can grow up to half an inch (1.27cm) per day. It can displace native plants and vegetation quite easily due to its invasive growth rate as well as being able to be spread via fragmentation. Finally, particularly in non-native areas, it has no natural predator. All the more, if something did decide to try it, it contains toxins which provides an unpleasant taste.

The scale of the potential problem is highlighted in the Mediterranean where the algae has taken over hectares of seabed with one of the main issues being that fisheries here have reported that there are lower numbers of the fish that they traditionally catch in areas that are plagued by Caulerpa. 

Back in California, one of the biggest worries is that the Caulerpa could outcompete the native Eelgrass beds which forms a crucial part of the local food chain. This would have a detrimental effect on the species of fish higher up the chain, which are then caught by the local fisheries.

It is understood that the Californian government spent millions of dollars eradicating the first, reasonably small population, where they utilised weighed down tarpaulins and injected chlorine under them to kill the algae, an interesting approach to say the least, particularly as this had an affect on other wildlife, however, this was deemed necessary collateral damage to contain the problem. During this eradication, the Southern Califorinia Caulerpa Action Team or SCAAT was formed. Comprising local fisheries and scientists, as well as members of governmental departments. The team set out to educate locals in the identification of the algae and asked them to report any findings they may discover. They were explicit in requesting that the algae is not disturbed, including collecting any samples of it, as it is known to reproduce from very small segments. Current eradication methods include sending a diver down with a specially formed sealed barrier which starves the algae of light, water flow and oxygen which has been used on several findings now as is deemed a lot more environmentally friendly.

Aquarists worldwide are now being urged to get rid of their excess Caulerpa by placing it in a plastic bag and placing it in a freezer for 24 hours before disposing of it in their usual household waste. Aquarium water, from water changes for example, should only be disposed of down a sink or toilet to ensure if goes to a treatment works via the foul system. Surface water/storm systems can be bypassed and end up in local waterways which is what is believed led to this outbreak in the first place. With these measures in place, as well as educating people to be able to both identify and understand the risks, it is hoped that Caulerpa can be prevented from infesting any other non-native areas and wreaking havoc on their respective waters.

About author

Picture of Chris Nixon

Chris Nixon

When I was growing up, I always dreamed about being a Marine Biologist, but job opportunities and other factors led me down a very different path in Structural Engineering. I have therefore had to enjoy the marine world as a hobbyist instead and have passionately being involved in the reefing world for the last 10 years.
Whilst at University, I worked part time at a Garden Centre which had its own tropical fish section, this occupied me for a few years before wanting to make the move to the salty side. This appears to be the natural progression that most in the hobby go through.
My latest successes have been able to fill a 75l nano, and then a 250l system to the point where I was itching to upgrade. I struggle to choose a favourite type of coral and have therefore always opted for the challenges that come with having a mixed reef. I have recently upgraded to a 5ft, 500 litre system which is big as I can go without structurally modifying my home! I hope to keep this one for many years to come and turn it into a thriving mixed reef, but maybe I’ll try my luck with more SPS this time!
I love watching the tank first thing on a morning with a hot coffee as the lights ramp up and you see everything come to life, fish come from out of their hideouts and the polyps on the corals open up.
Hopefully you enjoy the pieces I write and learn plenty from Reefpedia on the whole.