Palana Envrionnement

News

This experimental project was born out of the observation of the decline in the number of gorgonians (coral) in the Mediterranean. Faced with the main threats facing gorgonians – rising water temperatures, boat anchoring, fishing nets and wires, and finning by divers – Palana Environnement wanted to set up a transplant protocol for the 3 main species of gorgonian coral in the Mediterranean. The aim of this experiment was to find the most effective transplantation method for restoring the ecosystems to which these invertebrate animals belong.

The Palana team therefore established a 3-step protocol:

• Gathering of gorgonian sea fans during a dive at a site considered “favorable” for the presence of gorgonian sea fans;
• Preparation of the gorgonians (removal of necrotic branches, removal of large epiphytes if necessary);
• Planting by positioning the prepared gorgonian plants and securing them with epoxy glue.

This protocol was tested on two study sites: the Erevine drop-off (Côte Bleue) and the Mourres drop-off (La Ciotat).

Experimentation at the La Ciotat site

The first dive of the experiment at La Ciotat, in May 2021, enabled us to locate a colony of gorgonians that had been ripped out, and then, a week later, to transplant them at depths of 10 and 20 meters. Three months later, the first follow-up dive at the La Ciotat site revealed that all the red gorgonians and most of the replanted yellow gorgonians had disappeared.

This observation led to a revision of the protocol in several stages: revision of the preparation and quality of the glue used, the characteristics of the sites chosen and the marking methods used to find the transplants.

Experimentation on the Côte Bleue site

The first dive took place in May 2022, during which 10 colonies were recovered and transplanted to a depth of 30m, 5 of which were marked with identification collars. The second dive, two days later, showed 100% survival of the transplanted individuals. New gorgonians were transplanted again, this time to a depth of 20m, as the protocol seemed to work best in these conditions.

Two months later, the first follow-up dive took place, during which the divers noted 100% survival of the transplanted gorgonians at different depths.

The conclusions

From this experiment, the scientists from Palana Environnement drew several conclusions. Firstly, the time-consuming nature of the preparation and transplantation activities, coupled with the difficulty of using the glue within 30 minutes of its preparation on the surface.
Secondly, the need for underwater markers in order to find the experimental sites, which was lacking during the first dives at La Ciotat. This need is accompanied by another: that of marking the gorgonians themselves, in order to follow precisely the survival rate of the colonies in order to exploit the results later in a context of wanting to repopulate the colonies.

What happens next?

Palana environnement is continuing its experimental activity on other sites and on other scales, in partnership with the French Office for Biodiversity.
Its work over the past year has contributed to the success of this project and to the promising results obtained on the Côte Bleue site. The various characteristics of this study now need to be further developed in order to democratise the transplants methods used and make them a tool for preserving marine ecosystems.