Benthic foraminifera from a recent, shallow-water hydrothermal environment in the Aeolian Arc (Tyrrhenian Sea)

Benthic foraminiferal assemblages from sediments around active or recently active hydrothermal vents in the Aeolian Arc have been investigated in four areas with different hydrothermal mineralization and seafloor exhalative activity at depths between ~60 and ~300 m. Active hydrothermal spots were distinguished from the surrounding sediments by direct observations by a Remotely Operated Vehicle (ROV) and subsequent seafloor sampling. Samples were taken at different water depths and are characterized by a number of mineralogies reflecting the changing temperature of the hydrothermal fluids. Overall, benthic foraminifera are absent from sites with high-temperature hydrothermal emissions, and their distribution at sites of low-temperature emissions is very patchy, depending on the physical and/or chemical conditions reflecting differences in temperature and composition of the emitted fluids. In the Secca del Capo area, which is free from recent emission activity, the benthic foraminiferal population is indicative of a normal marine environment, with Globocassidulina subglobosa, Cassidulina crassa, and Gavelinopsis lobatulus. In the Basiluzzo, Secca dei Pesci, and Panarea areas, which are characterized by different degrees of hydrothermal activity, three distinct assemblages have been recognized. The first assemblage is dominated by Ammodiscus catinus, Glomospira charoides, and Glomospira gordialis and indicates hydrothermal influence. The second assemblage, with Lobatula lobatula, Asterigerinata mamilla, Rosalina globularis, and Quinqueloculina spp. as main constituents, indicates a seagrass environment influenced by diffuse emissions. The third assemblage with abundant A. catinus, Ammoglobigerina globigeriniformis, G. gordialis and Haplophragmoides canariensis suggests low pH conditions resulting from acidic hydrothermal emissions, leading to the dissolution of calcium carbonate tests.