Introduced organisms inhabit areas outside of their habitat or local regions and are not native to the area. Introduced organisms in marine habitats are mostly found in the areas where anthropogenic facilities (harbors, aquaculture facilities, etc.) are present. Introduced organisms threaten biodiversity and in some areas, introduced species are higher in number than native species.

Introduced species may be introduced to areas outside their normal range either on purpose or unintentionally. Once they settle into their new habitat, they become a potential threat to their environment. They compete with the native species and can overtake them.

Introduced species can be transported from one place to another in various ways. They can be transported through natural phenomena such as winds and ocean currents but they can also attach themselves to marine plants and plastic containers. However, many introduced species are transported by anthropogenic activities. Shipping is the most important factor in the transportation of organisms from one place to the other. Larvae can stay alive in the ballast water for long periods and they are discharged to new areas alongside the ballast water. Adult animals can colonize the ships’ bottoms and leave their larvae during the travel. Aquaculture also introduces new species. Furthermore, new species are introduced to create stocks.


All around the world, for centuries, mankind affects the distribution of plants and animals either on purpose or accidentally. Prevention becomes more difficult and costly once introduced species settle down to the new areas.


• Keeping import of the aquaculture species under control

• Processing ballast waters and keeping the ballast water discharge under control

• Decreasing the amount of fouling organisms on ships’ hulls

• Ensuring appropriate use of aquarium species

• Cleaning diving and fishing equipment and tools

• Using native species in the restoration and rehabilitation programs


If you find any of these species;

•Record the region and date

•Take a sample or a photograph

•Contact us. TUDAV will definitely inform you about the species you have sent and you will have contributed to the database. HELP US understand the ecological changes in our seas.

Note: Caulerpa taxifolia (Caulerpa seaweed) shouldn’t be severed for sampling because pieces that are shredded or torn off have the ability to create new colonies.

Caulerpa taxifolia
For Protecting our seas

If you find this seaweed,
Do not help it spread,
But phone us at: +90 216 424 07 72

How to recognize it:

It is a 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 1m in length and is fixed to the bottom by the “roots”, or rhizoids. The stolon bears “leaves”, or fronds, covered in needless or pinnules. These long fronds, often exhibiting extensive ramifications, are 5 to 65 cm in length and resemble those of certain conifers such as the Yew (in Latin, yew = Taxus and leaf = folia, whence the name taxifolia given to the seaweed).

“Can I handle it? ” “Should I pull it up?”

You can touch the seaweed without risk to yourself, but there are laws and guidelines (that have been adopted by France and Spain and by international organizations) 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 authorization (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 of 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 colonized sites to other areas. This explains how Caulerpa taxifolia has managed to spread by leaps and bounds, sometimes jumping a distance of several hundred kms, and why it is that it is generally found at anchorages, in ports or in fishing areas.

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 ashore.

It is important to phone us and let us know:

To date, more than 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.

Known locations are indicated on the map in this brochure.

It would be particularly helpful if you can give research scientists the following information: exact location and depth of your observation, type of substrate (sand, rock, Posidonia meadows, etc.) and the approximate surface area occupied by the plant.

Since its introduction into the Mediterranean in 1984, the surface area colonized by Caulerpa taxifolia 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 the first sighting was made, and 99 % of the total colonized surface area was found within 100 km of it, between Toulon (France) and Alassio (25 km to the east of Imperia, Italy).

What is the purpose of this research program?

A seaweed unlike any other

Accidentally introduced to the sea in Monaco in 1984, the green tropical seaweed Caulerpa taxifolia spread rapidly along the Mediterranean coast. It possesses certain unique characteristics (resistance to cold, gigantism, vigor of development, density, ecological dominance, etc.) that have never before been observed in tropical populations of this kind or in other seaweeds introduced to the Mediterranean.

All the stable substrates (rock, sand, silt, Posidonia meadows) can be colonized. All types of bottom, especially from 3 to 40 m, can be invaded. Caulerpa has even been observed in summer, alive and well established, though in low density, as deep as -99 m.

It is found both in good quality water and in polluted harbors, on rocky headlands exposed to waves and in sheltered bays.

Although more discreet in winter, Caulerpa taxifolia never altogether disappears: it can survive for a few days at 7 degree Celsius and for 3 months at 10 degree Celsius. It starts growing again when the water rises above 15 degree Celsius. Its development and its survival in the Mediterranean thus have nothing to do with global warming or climate. And what is more, no winter, however rigorous, will make it disappear altogether.

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 seaweeds and affects the Posidonia meadows. The fauna too undergoes profound changes, especially the fixed species (Gorgonia, sponges, etc.) and small mobile fauna (e.g. sea urchins). This new dominant plant is little or not at all consumed by fishes or marine invertebrates, and thus does not constitute a 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 fishes has been observed. Repercussions in terms of the economy and human activities have also begun to make themselves felt, with offshore fishing and diving beginning be affected in some areas.

A 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 far back as 1990, alerted the authorities to the major risk that the invasion of this introduced species might represent for biodiversity, ecological balance and commercial resources of all 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 taxifolia 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 colonized 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).