Action D2. Surveillance and removal of Caulerpa taxifolia.
Partner: Direcció general de Pesca.


The eradication of Caulerpa taxifolia sprouts detected in the marine areas within the SCI areas included in this project. To strengthen the Network of Volunteer Scuba-divers encouraging participation in the same (Action E.4), in order to carry out regular inspections of the areas most susceptible to colonization, including main ports and anchoring areas in the Balearics.

Removal is to take place only when the size of the colony and the nature of the sea floor guarantee success.

Development and execution of the Action:

This action was not carried out as it had been previewed. After monitoring the evolution and expansion of Caulerpa taxifolia in all SCI areas round the Balearic Islands—in particular those already affected by its presence—it was confirmed that its growth and colonization was in frank recession due, perhaps, to natural causes. Therefore, the DGP (General Directorate of Fishing), decided not to carry out the action but to maintain the surveillance and continue monitoring in order to detect possible outbreaks which could be removed.

Constant monitoring of the possible sprouting areas of Portocolom, Es Pontàs, Portopetro and Cala d’or continues, as these were suffering a strong expansion in 2000. However, at present , they are in recession both in terms of extension occupied and in growth rate. In areas where Caulerpa taxifolia and Posidonia grow together, it has been observed that due to the length size of the Posidonia bushes, there occurs a considerable lessening of the light reaching the bottom and this, in turn, makes Cuaulerpa’s growth diminish or become lethargic while at the same time making it impossible for the plant to colonize larger areas. In substrates where the two compete, density of Caulerpa t. is very low and the plant is only able to colonize such areas as are not occupied by Posidonia. It has been observed that in areas colonized exclusively by Caulerpa t. there is diminishing density and reduced expansion of the same .In comparison with previous years, total areas colonized had diminished and such colonies as do exist are of low density and few and far between: there is a clear tendency towards recession.

Because of the aforementioned circumstances, the DGP decided that the eradication of Caulerpa t. situated in areas where recession has been observed would cause a negative and unnecessary impact on the environment. Therefore it was decided to limit action to the constant surveillance and monitoring without carrying out any further removal campaigns.

Action D.2 was therefore successfully completed in terms of the surveillance of the eastern coastline of Majorca and in terms of anchoring areas which are susceptible to being colonized by invasive algae.
In order to carry out Action D.2, the DGP organized a group of volunteer scuba-divers that work along the west coast of Majorca, exploring in order to detect new colonies. This group of volunteers are members of the “Red de monitorización de la praderas de Posidonia” ( Posidonia Field Monitoring Network) –Action E.4.
As will be seen further on, and thanks to this Action, the breadth of monitored coastal areas has increased considerably in the Balearics. The work of volunteer scuba-divers is an invaluable contribution towards the goal of detecting and controlling colonies of this and other invading algae.

The aim of this action is considered to have been fulfilled because although the action was not carried out as originally previewed, the work done has made it possible to monitor this species and prevent its expansion. The plant remains in a state of almost zero reproduction.