Submarine hydrothermal vents of the Aeolian Islands: Relationship between microbial communities and thermal fluids

The relationship between fluid geochemistry and microbial communities was i nvestigated for shallow (<25 m) submarine hydrothermal vents in the Aeolian Islands (Southern Italy). Thermal waters, gases, and deposits of white fil amentous material were collected from 11 sites. The geochemical analyses sh owed a magmatic component was present in all sampled fluids. The total micr obial abundances, evaluated as direct counts of picoplanktonic cells (rangi ng from 0.2 to 2 mu m in diameter), were between 1.55 x 10(7) and 4.18 x 10 (8) cells per liter. Picophytoplankton (total autofluorescent cells) ranged from 9.6 x 10(5) to 7.88 x 10(6) cells per liter. Yellow-orange autofluore scent prokaryotes belonging to the cyanobacteria were more abundant than re d autofluorescent eukaryotic cells. Chemolithautotrophic sulfur-oxidizing, rod-shaped Bacteria were isolated from venting water samples and identified as Thiobacillus-like. Microscopic examination of the white mat deposits sh owed the presence of filamentous microorganisms.