The distribution of macroinfauna along a Mediterranean submarine cave with sulphur springs

The distribution of macroinfauna and Total Organic Carbon (TOC) were investigated in the muddy substrates along a transect at 14 m depth in the Grotta Azzurra (Capo Palinuro, Tyrrhenian Sea, Italy), a submarine cave with warm (18-24degreesC) sulphur-water springs in its innermost, aphotic chamber. Due to thermal stratification, sulphidic compounds remain trapped above the cooler sea-water in the anoxic upper sulphidic layer supporting dense sulphur-oxidizing bacterial mats that detach and disperse when disturbed. The macroinfauna of Grotta Azzurra comprised 97 species. The assemblage bore similarities to those previously described from non-cave Mediterranean oligotrophic regions, and also indicated environmental instability. Unlike in other caves, where benthic zonation is prominent, no inward decrease of macroinfaunal abundance or diversity was observed. It is assumed that the chemosynthetic inputs in the inner region provide an additional source of food that has a positive effect on the colonization and survival of macroinfauna inside the resource limited cave environment.