When I was studying marine algae in Florida many years ago, I used to collect several species belonging to the genus Caulerpa. We would bring our collecting gear and snorkels to many of the shallow waters in the Florida Keys. There were different species of Caulerpa, but most of them formed small mats in the substrate with erect, feather-like fronds. For the most part they were no longer than a few centimeters, though occasionally they were quite abundant.
Since the mid-1980ís however, a new form of this green alga has appeared in many parts of the world, particularly the Mediterranean Sea, and it is far from a welcoming sight. This species is called Caulerpa taxifolia, and it is one of the most invasive marine species on earth. It was once widely used in home saltwater aquariums, and was probably accidently released into the marine environment. Like so many other nuisance organisms, this species can reproduce quickly. In fact, it can grow a couple of inches a day. It also has the ability to reproduce asexually, and small broken sections of the fronds can grow into entire plants.
Early warnings were expressed by marine biologist Alexandre Meinesz, but he was largely ignored until the algae had spread over thousands of acres on the ocean floor. Caulerpa taxifolia prevents the growth of other, more beneficial, plants by blocking sunlight in the area. It is also quite unpalatable by marine animals to the point where starvation is preferable. Once this alga gets established in an area, it becomes an unstoppable monoculture, and completely decimates the diversity normally seen.
Preventing its spread is not easy. It has already appeared in California, and severe methods for its control were implemented. So far it has not been observed on Cape Cod. The waters here may be too cold for its colonization. Still, the lesson to be learned regarding invasive species is that caution should be exercised when dealing with an organism such as Caulerpa taxifolia. It is now banned as an aquarium plant, and monitoring its distribution is underway.
When I first heard of this problem I though back to my early days of seaweed studies and remember that I thought Caulerpa was a harmless, even fragile plant. But with names like killer algae, I now realize that the most delicate organism can become dangerous if grown in waters where it does not belong.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.