Site details

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5 stars - Fully protected as a national park or Natura 2000 site by national legislation
LTBR Focal Site

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3 PP cave, counting deep-sea hexactinellid sponge Oopsacas minuta. Photo: J Vacelet

Synoptic description of site:

Long cave in conglomerate layers below the cliff of Bec-de-l'Aigle Cape, exceptional for its thermal regime (cold homothermy) and a unique bathyal fauna in the littoral zone.

Extensive description of site:

The 3PP cave, near La Ciotat, is a 120 m long tunnel in a conglomerate layer, with a deep mud layer on the floor. Due to its descending profile, with the entrance 15 m deep and the end 24 m deep, the cave traps by density a cold water mass and has a thermal regime of cold homothermy similar to that of the deep Mediterranean.

Habitats present:
Seagrass beds 

Description of fauna and flora:

There are typical faunal assemblages from shadowed and dark caves. Most remarkable are bathyal organisms, such as hexactinellid and carnivorous sponges, that have colonized the cave from a nearby deep canyon.

Human impact:

There is no notable pollution. The cave is rarely visited by local divers.


Facilities are available from the Centre d’Océanologie de Marseille (COM) 25 km distant. There is easy boat access from La Ciotat harbour (1 km).

Available database and website:

A species inventory for several invertebrate groups (sponges, serpulid polychaetes, bryozoans, crustaceans) is available in the COM.

Commitment and ongoing research:

The cave has been intensively studied by the COM for 11 years: continuous temperature recordings, species inventories, biodiversity researches, studies on the physiology, taxonomy and phylogeny of deep-sea species found in this “bathyal island in a littoral environment”.

Additional Information:

Examples of references available: Boury-Esnault, N., J.G. Harmelin & J. Vacelet 1993. Les abysses méditerranéennes à 20 m de profondeur ? La Recherche 24(256 Les grands fonds sous-marins): 848-851. Harmelin, J.G. & J. Vacelet 1997. Clues to deep-sea biodiversity in a nearshore cave. Vie et Milieu 47: 351-354. Vacelet, J., N. Boury-Esnault & J.G. Harmelin 1994. Hexactinellid cave, a unique deep-sea habitat in the scuba zone. Deep-Sea Res., 1 41: 965-973. Vacelet, J. & N. Boury-Esnault 1995. Carnivorous sponges. Nature 373: 333-335