The fauna of Grotta del Bel Torrente, Golfo di Orosei, Sardegna, Italy

Oertel, A. (1), R.A. Patzner (2)

(1) Dept. of Cell Biology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria (2) Dept. of Organismic Biology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria

Correspondence
Anke Oertel
E-mail: Anke.Oertel@gmx.at

Abstract

Cave diving expeditions took place in the Golfo di Orosei in July 2003 and August 2004. The main site of the exploration is located 500m north of Cala Sisine. The anchihaline cave system of Grotta del Bel Torrente is one of the biggest in Sardegna. Until now more than 2.5 km dry and water filled passages are surveyed in total. A map of the cave was generated as a basis for further investigations. The focus of the biological work concentrates on diversity of species and their distribution throughout the cave until 800 m from entrance. Depending on salinity, water temperature, room structure and room content several different habitats can be distinguished along the passages. Until 350 m from entrance a clearly visible halocline is developed between the upper layer (20° C, salinity about 22) and the underlying water column (22° C, salinity about 33). A zone of intermediate water salinity and temperature without halocline follows on a distance of 100 m. In more than 450 m from entrance the salinity drops to 1 and temperature amounts 15° C. Surprisingly deep inside the cave marine molluscs, crustaceans (decapods and isopods) and ascidians were observed. Some fish like the golden grey mullet (Liza aurata) and juvenile conger eels (Conger conger) migrate between fresh and salt water column. Common soles (Solea solea) appear on sandy ground about 300 m from entrance in salty water. The typical “cave fish” of the Mediterranean Sea, the brotula (Gramonus ater) was not found in Grotta del Bel Torrente until now.