Comparative investigation of microbial communities associated with hydrothermal activities in the okinawa trough

Abstract

In the Okinawa Trough, microbial communities in deep-sea hydrothermal vent chimneys have been extensively studied in the Iheya North (Iheya North Knoll) and the Yonaguni Knoll IV (Daiyon-Yonaguni Knoll) fields. In comparison of the microbial community patterns in geographically and geologically diverse deep-sea hydrothermal systems all the world, the Okinawa Trough deep-sea vent microbial communities have been known to be distinctive and to be associated with the unique hydrothermal fluid chemistry commonly observed in the Okinawa Trough systems. However, this implication is based only on the data from the above two hydrothermal systems. Here, we further show the microbial community patterns of Minami-Ensei (Minami-Ensei Knoll), Izena Hole Jade and Hakurei fields in the Okinawa Trough, using data by culture-dependent techniques. The comparison of the microbial community patterns determined in typical chimney habitats of representative Okinawa Trough hydrothermal systems including new data points that the diversity and abundance of cultivated microbial populations are significantly relevant with intra-field variation of hydrothermal fluid chemistry induced by the subseafloor phaseseparation and -partition processes rather than with inter-fields variability in the endmember fluid chemistry. Inter-fields variability in potential microbial community development in the Okinawa Trough hydrothermal systems may be caused by other possible bases in the microbial community development such as the physical mode of hydrothermal fluid discharges, the age of hydrothermal system and the hydrogeological complexity of subseafloor hydrothermal fluid flow structures. Nevertheless, the correlation between the H2 concentration in hydrothermal fluid and the culturable population size of H2-trophic methanogens is reinforced by the new results obtained from the Izena Hole Hakurei chimney habitat hosting the H2-enriched hydrothermal fluid. It seems very likely that the H2 concentration in the hydrothermal fluid is still a very important chemical factor to control the chemolithotrophic microbial community development essentially in the global deep-sea hydrothermal systems.