Geochemistry and biogeochemistry of deep-sea hydrothermal system

Deep-sea hydrothermal systems and associated biota have long attracted interest of many researchers (e.g., Humphris et al., 1995; Van Dover, 2000; Wilcock et al., 2004). In the past few decades, particular attention has been paid to chemolithoautotrophic microorganisms that sustain the hydrothermal vent-endemic animal communities as the primary producer. This type of microorganisms is often considered as an important modern analogue to the early ecosystems of the Earth as well as the extraterrestrial life in other planets and moons (e.g., Jannasch and Mottl, 1985; Nealson et al., 2005; Takai et al., 2006). 

The chemosynthetic ecosystems at deep-sea hydrothermal vents are sustained by chemical energy obtained from inorganic redox substances (e.g., H2S, CO2, H2, andCH4) in hydrothermal fluids. The chemical compositions of hydrothermal fluids are, in turn, controlled by subseafloor physical and chemical processes, including fluid–rock interactions, phase separation of fluids, and precipitation of minerals. Thus, it can be considered that specific physicochemical principles describe the linkages among the living ecosystems, hydrothermal fluids, and geological background in deep-sea hydrothermal systems.

In this presentation, geochemical characteristics of deep-sea hydrothermal fluids and their influence on the chemosynthetic ecosystems are presented. In addition, the potential biomass in seafloor and subseafloor chemosynthetic ecosystems sustained by high-temperature deep-sea hydrothermal activities is also estimated.