An exploration for hydrothermal plume evolution using the AUV "URASHIMA" with fluid sampling system at southern Mariana Trough

Hydrothermal fluids contain high concentration of anoxic chemical species, i.e. methane and hydrogen sulfide, helium-3, and heavy metals derived from the rock-water interaction. During the hydothermal plume spreading, it is known that several chemical species are oxidized which include available energy source for microorganism, however, few results have been reported on the spatial variation of both of chemical and microbiological concentration and species. In the southern Mariana Trough, some site surveys have been conducted with CTD hydrocasts, the manned submersible, and ROVs since 2003. In this field, three hydrothermal vent sites were discovered within the small area, where the chemistry of each hydrothermal fluid was different from each other. These differences of chemistry are prospected to affect the individual plume evolution. In order to discuss the each hydrothermal plume evolution, we conducted high-resolution plume mapping by the AUV "URASHIMA" with some chemical sensors. Additionally, we loaded 24 bottles of water sampler for the geochemical and microbial analysis. During this cruise, we detected hydrothermal plume anomalies derived from each hydrothermal site with the highly precise topographic results. Based on the results, we will discuss the relationships between the spreading of hydrothermal plume (geochemical evolution) and the ecology of plume microbes.