Microbial Ecology of Mid-Ocean Ridges and Back-Arc Basins

Over the past two decades, microbiologists have gained significant insights into the diversity and physiology of microbial communities associated with deep-sea hydrothermal systems. Much of the initial research focused on mid-ocean ridge (MOR) systems; however, because of the greater heterogeneity of vent fluid chemistry and sulfide structures from back-arc basin (BAB) systems, recent studies have begun to explore the linkages between geochemistry and microbial diversity in these systems. The impact of microbes on local fluid chemistry and mineralogy has been recognized, and local fluid physical-geochemical states and mineralogical properties have significant impacts on the formation and composition of local microbial communities. Data are being accumulated that enable microbiologists not only to link phylogenetic and physiological diversity of microbial communities to geological and geochemical settings within a hydrothermal field, but also to review microbial ecosystems in global deep-sea hydrothermal systems with comparison of representative MOR and BAB systems. In this review, we briefly outline methods in microbial ecology and microbial ecophysiology at vents and discuss the patterns of diversity (phylogenetic and physiological) emerging from studies in the global hydrothermal systems. As this volume is dedicated to BABs, we highlight several case studies on hydrothermal vent microbial communities in BAB systems that are comparable to the communities in MOR systems.