[EN]The Cova des Coll (Felanitx) has a current survey length of 7,020 m, of which 5,529 m are subaquatic. The cave has two natural entrances and two artificial wells also connect with it. One of the natural entrances connects with the bay of Portocolom and the other is inland. Part of the cave lies below an urbanised area of Portocolom. The principal characteristic which highlights the geomorphology of the cave is the almost complete absence of speleothems due to the corrosive effects of the water and the large abundance of corrosion morphologies, which we have catalogued by form. It appears that the level of destruction of speleothems decreases moving inland and moving downward. The sediments of the Cova des Coll have two clearly definable units identifiable both by colour and by mineral content: an upper layer whose composition is mainly carbonate where calcite dominates and its colour is lighter and a lower one where silicic components are its principal characteristic along with its reddish tone. There are important differences moving through the cave, especially between the sections closer to the sea, which lack the upper layer, and those more inland, which are formed by more or less sandy mud with high levels of clays. In addition to these accumulations which can be considered as being earlier, red muddy accumulations have been seen on the walls in many places, which show signs of erosion and which represent earlier stages of in-filling during different environmental conditions to those now. The water-column profiles of salinity and temperature have four well-defined bands. The directness of communication with the bay determines the currents which distort the typical profile, except at greater depths. These depths are less effected by mass movements of water into and out of the cave as the bay level changes with barometric changes. An important flow of water in the interior chambers has been observed, where the water rises up the chamber walls owing to the different densities toward the surface of the water column. The faunal distribution, including salinity preferences, has been studied in the different sections of the cave. 15 species of non-arthropod invertebrates have been catalogued and their distribution is closely related to their distance inland from the sea. 7 sponges have been classified, three of which are not worthy for their first sighting along the Spanish coast. Amorphinopsis pallescens, if not a new species, is the second sighting of this species in the Mediterranean. The sponges have robust spicules, which indicate a high level of available silica. The studies carried out show evidence that the source of this is the sediment. Of the two polychaeta Found Bispira viola constitutes the first sighting of the species for the Iberian Peninsula and the Balearic Islands. Twenty-nine species of crustaceans are reported from the cave, 5 of them corresponing to harpacticoid copepods and 1 to an ostracod. The rest belong to diverse groups such as leptostracans, decapods, amphipods, isopods, mysids, thermosbaenaceans, and calanoid, misophrioid and cyclopoid copepods. 61% of the species are stygobionts (i.e., obligate groundwater dwellers); the rest correspond to littoral marine species characteristic of suprabenthic or crevicular marine habitats, preadapted in some way to live in caves, or are neritic species characteristic of the plankton of bays and harbours. Four of the stygobiont species are new to Science. 9 of the species found in the cave are Balearic endemics. Following the detailed study of this cave it has become apparent the urgent need to establish effective protective measures which will permit the conservation of this natural and culturally valuable patrimony.

Part de les prospeccions faunístiques realitzades s’inclouen dins el projecte REN2001-0580/GLO del Ministeri de Ciència i Tecnologia. Aquest treball s’integra al projecte de la Dirección General de Investigación del Ministerio de Ciencia y Tecnología, BTE 2002-04552-C03, “El modelat càrstic i l’evolució morfològica i sedimentària del litoral a les Balears, València i Sardenya”.

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