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Island Ecology

by José P Ribas

Caulerpa Taxifolia
More About Seaweed, Heaven And Hell


Ibiza Ecology

There's a dark side of the seabed, too. Last week I told you of the seaweed from Heaven and this week I'm writing of the other kind… from Hell.

This algae is new to the Mediterranean and comes with a reputation as dangerous as a voodoo curse.

"Caulerpa Taxifolia" was studied at the "Monaco's Oceanographic Institute, Jacques Cousteau" in the early 1980s.

The plant seems to be a sign of the times we go through. It is a "Winner"; it was created to conquer, especially when circumstances are ideal (with the right politics and moving in the darkness) and when it is not expected.

Its nature is stronger, more adaptable and poisonous than its rivals. It only takes, never gives.

Originally from the Caribbean Sea, it possesses certain unique characteristics, such as resistance to the cold, gigantism, vigour of development, density and ecological dominance. Nothing like it has ever before been observed in tropical populations of this kind or in other seaweed introduced in the Mediterranean.

In 1984, just like proper witchcraft, it got out of human control and appeared for the first time in the Mediterranean Sea, right by the Institute cliff (most probably through the laboratory drains).

And now it is threatening the Balearic seabed.

It even has its own unofficial Website - "Caulerpa Taxifolia" from the European Government (Life). I am grateful to them for the following:

How to recognise it

It is beautiful, fluorescent green seaweed with a characteristic creeping stem, called the stolon. The name "Caulerpa" refers to this feature. In Latin, "Caulos" means axis and "erpa" comes from a verb meaning to creep. This stolon can measure over 1 m in length and is fixed to the bottom by the roots or rhizoids. The stolon bears leaves or fronds, covered in needles or pinnules. These long fronds, often exhibiting extensive ramifications, are 5 cm to 65 cm in length and resemble those of certain conifers such as the Yew (Latin, yew = Taxus and leaf = folia, whence the name taxifolia given to seaweed).

Can I handle it? Should I pull up?

You can touch the seaweed without risk to yourself, but there are laws and guidelines (adopted by France and Spain and by the International organisations) banning or recommending against the harvesting, sale or transportation of "Caulerpa Taxifolia". The harvesting and uprooting of the plant are delicate operations that should only be undertaken with proper authorisation (because any handling increases the risk of dissemination and makes policing the contaminated area more difficult).

Take care; do not help "Caulerpa Taxifolia" to spread! Do not contaminate new areas! A fragment of the seaweed can survive for more than a week out of water in a warm, damp place (anchor well off a boat, rolled up fishing net, scuba diving bag or equipment). Once released in the sea, it will again start to develop.

Unless we are all extremely vigilant, no site is safe from contamination! It is all too easy to transport this seaweed unwittingly from already colonised sites to other areas. This explains how "Caulerpa" has managed to spread by leaps and bounds sometimes jumping a distance of several hundred km., and why it is that it is generally found at anchorages, in ports or in fishing areas.

Recommendations for yachtsmen: Take care to inspect your anchors and chains when leaving an anchorage.

Fishermen: Check your nets and trawls.

Divers: Check your bag and equipment each dive.

If you have accidentally picked up fragments of this seaweed, do not throw it into the sea. Put it in a bag and put it in a dustbin when you go to shore.

To date, more of 90% of known "Caulerpa" locations have been reported by divers, yachtsmen or fishermen. If we are to monitor the progression of this seaweed and thus be in a position to devise effective strategies to control and combat its spread, we need your assistance.

Since its introduction into the Mediterranean in 1984, the surface area colonised by "Caulerpa" has increased constantly. The rate of increase at each location is similar to that recorded at the first site (at Monaco, the first hectare was covered in 5 years). The most extensive areas thus correspond to the oldest colonies. At the end of 1996, these stretched for 10 km on either side of the site where first sighting was made, and 99% of the total colonised surface area was to be found within 100 of it, between Toulon (France) and Alassio (Italy).

All the stable substrates (rock, sand, stilt, and Posidonia meadows) can be colonised. All types of bottom, especially from 3 m to 40 m, can be invaded. "Caulerpa" has even been found in summer, alive and well established, as deep as 99 m. It is to be found both in good quality water and in polluted harbours, on rocky headlands exposed to waves and in sheltered bays.

It can survive for a few days at 7° C and for 3 month at 10° C. It starts growing again when the water rises above 15° C. No winter, however rigorous, will make it disappear all together.

A devastating impact

The spread of this permanent vegetal meadow continues from year to year, until it has covered all the available bottom area. Little by little, it dominates or eliminates the other seaweed and affects the Posidonia meadows. The Fauna too undergoes profound changes, especially the fixed species (Gorgonia, sponges, etc.) and small mobile fauna, sea urchins, crustaceans, molluscs, etc. This new dominant plant is little or not at all consumed by fish or marine invertebrates and thus is not replacement food, which makes its ecological impact even more severe.

In areas that have been invaded most densely and for the longest time, a decline in the abundance of some fish has been observed. Repercussions on the economy and human activities have also begun to make themselves felt, with offshore fishing and diving beginning be affected in some areas.

Overall, there has been a decline in biodiversity. Gradually, richly coloured and varied Mediterranean populations are being replaced by the uniform fluorescent green landscape of the "Caulerpa Taxifolia" meadows.

It is major risk for the Mediterranean shallow water ecosystems. Research on the progression of this seaweed and its impact has confirmed the fears of scientists, who, as long as 1990, alerted the authorities to the major risk that the invasion of this introduced species might represent for the biodiversity, ecological balance and commercial resources of all the shallow water areas in the Mediterranean.


Although it was called for back in 1991, when it would still have been possible, the total eradication of "Caulerpa" was not undertaken.

Since the end of 1992, the surface area covered by the seaweed has become too extensive and it is now known that it will not be possible to eliminate it altogether by chemical or physical means (manual extraction, aspiration salt, copper, etc.). Some of these techniques are still being tested. They could be used to eliminate small isolated patches that are far enough away from the large colonised areas and this has already been done successfully in some places. There have also been some promising results from biological studies (involving the use of slugs -molluscs- that feed exclusively on "Caulerpa").

In short, while little can be done to save areas that have already been invaded by "Caulerpa", at least measures can be taken to slow its spread.

In the first colonised areas at Monaco, a vast, monotonous fluorescent green blanket has gradually replaced richly coloured and variant underwater landscapes.

Since 1990, more then 30 Spanish, French, Italian and Croatian organisations and more then 200 research scientists have taken part in monitoring the spread of "Caulerpa Taxifolia" or have been published in about 300 scientific Journals or publications for the general public.

As we can see, the problem is well-known by now, yet at the end of the 1990s, the plant was detected in the Adriatic Sea and in the West coast of Mallorca, and still remains today. Other suspicious areas are the anchorage sites of Ibiza-Formentera, where it has been detected on boats.

The Heavenly, delicate and generous "Posidonia", has no chance. Those days have gone and its time has passed. How can anybody be generous nowadays? Live and let live is not enough for today, not enough to survive, like our ancestral culture that is vanishing away, pushed out by a Devil-like "Territorial Caulerpa" also poisonous and green, Dollar green, that shines even brighter then proper "Caulerpa", invading our Islands and society, stealing (or buying) our hearts and feelings, turning us greedy, selfish, rich and vulgar.

Goodbye century, goodbye Posidonia, goodbye to a sensible style of life.

Goodbye love, I think I'm going to cry.


If you know of or find any news of areas that "Caulerpa Taxifolia" has already reached, it is vital to warn us as quickly as possible at these numbers:

Turkey: Prof. Dr Sukran Cirik Telephone +90 232 278 52 72 / 278 55 65.
Institute of Marine Science and Technology Izmir

France: Prof. A Meinesz. Telephone 04 92 07 68 46 & Fax 04 92 07 68 49.
Laboratoire Environnemant Marin Littoral. Nice

Italy: Prof. Francesco Cinelli Telephone 050 23054/500018 & Fax 050 49694
Universita di Pisa

Liguria (Italy): Prof. Dott Giorgio Matricardi Telephone 010 3538053
Universita di Genova

Sicily (Italy): Dott. Carla Frada Orestano Telephone 091 6161493
Universita degli studi di Palermo

Spain: Dr E Ballesteros Telephone 972 33 61 01 & Fax 972 33 78 06
Centro de estudios avanzados de Blanes (CSIC)

Croatia: Dr N Zavodnik or A Jaklin Telephone 052 811 544 - Dr B Antolic Telephone 021 358 688
Institute of Oceanography and Fisheries. Split.

Caulerpa Taxifolia invading a Posidonia Oceanica meadow
Caulerpa Taxifolia: The Bad Guy

José P Ribas