The submarine hydrothermal system of Panarea (Southern Italy): biogeochemical processes at the thermal fluids - sea bottom interface

Abstract

Among the submarine hydrothermal systems located offshore the volcanic archipelago of the Aeolian Islands (Southern Italy), the most active is located off the coasts of Panarea island. Thermal waters, gases and sulfur deposits coexist at the sea bottom where hydrothermal fluids are released from both shallow and deep vents. The chemical and isotopic composition of the fluid phase shows the presence of a significant magmatic component and the physico-chemical conditions of the geothermal reservoir allow the release of reduced chemical species that are microbially mediated towards the production of organic carbon as a form of biochemical energy. Microorganisms inhabiting this environment possess nutritional requirements and overall metabolic pathways ideally suited to such ecosystem that represents a clear example of the close connection between geosphere and biosphere. Microscopic examination of the white mat attached to rock surfaces showed the presence of Thiothrix-like filamentous bacteria. Moderately thermophilic heterotrophic isolates were identified as strains of the genus Bacillus. Although the hydrothermal system of Panarea has to be considered a “shallow” system, it shows many characteristics that make it similar to the “deep” oceanic systems, giving a unique opportunity for improving our knowledge on such an unexplored world by working at this easily accessible site.