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Calanque* de Podestat

Encorbellement à <i>Lithophyllum</i>.
Encorbellement à Lithophyllum.
Gorgone blanche, <i>Eunicella sticta</i>, proche de la surface.
Gorgone blanche, Eunicella sticta, proche de la surface.
Paroi constituée de gorgones <i>Eunicella cavolini</i>.
Paroi constituée de gorgones Eunicella cavolini.
Balise repère dans la calanque. <i>Toutes les photos ci-dessus ont été réalisées dans la calanque de Podestat.</i> (Ph. P. Lelong).
Balise repère dans la calanque. Toutes les photos ci-dessus ont été réalisées dans la calanque de Podestat. (Ph. P. Lelong).

CONTEXT – AIMS OF THE PROGRAMME
The Calanque de Podestat is situated right in the heart of the Calanques National Park, Marseille. Since 1930, it belongs to the French electricity company EDF which today wishes to use it as a laboratory for the observation and preservation of biodiversity.

For this purpose, E.D.F. entrusted the Paul Ricard Oceanography Institute with a research study aimed at drawing up an exhaustive inventory of the fauna and flora of this calanque*, which covers a surface area of 1.26 hectares with a maximum depth of 16 metres.

This inventory will be carried out over a period of three years, with, each year, two main field surveys, in spring and in autumn. Four complementary studies will be devoted to microbiological monitoring.

The realisation of this inventory and the mapping of the area will provide a basis for defining the initial state of the Calanque de Podestat and for assessing, during later surveys, changes in the populations, in response to :
- overall climate change in the Mediterranean,
- alterations in the water quality linked to the treatment of urban sewage and rainwater at the nearby sewage treatment plant,
- changes in the protection status resulting from the creation of the Calanques National Park.

Summary of results of the first inventories of the study :
a fairly satisfactory ecological state

The Paul Ricard Oceanography Institute carried out the first survey in spring 2012. This was devoted to the bathymetric cartography and to the mapping of the biocenoses of the calanque.

This spring survey was also the first stage of the biological monitoring : gorgonians, echinoderms, fishes and water quality.

Much of the calanque is occupied by bottoms consisting of sand of varying degrees of coarseness surrounded to the east and the west by a rocky border made up of large blocks, scree, rocky cliffs or fixed rocks with a large cave to the south-west.

The calanque ends in a pebble beach, which extends below the water. There is no Posidonia seagrass meadow, but the presence of roots of dead matte under a few centimetres of sediment shows that this ecosystem was previously implanted in this calanque. Its disappearance is probably related to the proximity of the sewage outfall at Cortiou, which discharged the sewage of the Marseille conurbation from 1896.

Despite the presence of species indicative of pollution, such as the green algae (ulva and enteromorpha) at the edge of the beach, and the richness of echinoderms, this first study would appear to indicate a fairly satisfactory ecological state. The most remarkable habitats of the site are situated in the south-western area : Lithophyllum rim, biocenosis of semi-dark caves and underwater caves.

* Calanque : a long, narrow sea inlet

PARTNERSHIPS
Scientific
Calanques National Park

Financial
Groupe EDF (French electricity company)

BIBLIOGRAPHY
Download the press release (in French) : (click here)
Listen to an interview with Patricia Ricard (in French) : www.neo-planete.com, 3 déc. 2012