Geomicrobiology of Deep-Sea Hydrothermal Vents

• Published in: Science (American Association for the Advancement of Science) Vol. 229; no. 4715; pp. 717 - 725
• Main Authors: Jannasch, Holger W., Mottl, Michael J.
• Format: Journal Article
• Language: English
• Published: Washington, DC The American Association for the Advancement of Science 23-08-1985; American Association for the Advancement of Science
• Subjects: Animal, plant and microbial ecology; Bacteria; Basalt; Biological and medical sciences; Carbon dioxide; Electrons; Fundamental and applied biological sciences. Psychology; Marine; Methane; Microbial ecology; Ocean floor; Oxidation; Sea water; Sulfur; Various environments (extraatmospheric space, air, water); Water temperature; Bathyal zone; Bacteria; Review; Biological activity; Seawater; Abyssal zone
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.229.4715.717

During the cycling of seawater through the earth's crust along the midocean ridge system, geothermal energy is transferred into chemical energy in the form of reduced inorganic compounds. These compounds are derived from the reaction of seawater with crustal rocks at high temperatures and are emitted from warm (≤25°C) and hot (∼ 350°C) submarine vents at depths of 2000 to 3000 meters. Chemolithotrophic bacteria use these reduced chemical species as sources of energy for the reduction of carbon dioxide (assimilation) to organic carbon. These bacteria form the base of the food chain, which permits copious populations of certain specifically adapted invertebrates to grow in the immediate vicinity of the vents. Such highly prolific, although narrowly localized, deep-sea communities are thus maintained primarily by terrestrial rather than by solar energy. Reduced sulfur compounds appear to represent the major electron donors for aerobic microbial metabolism, but methane-, hydrogen-, iron-, and manganese-oxidizing bacteria have also been found. Methanogenic, sulfur-respiring, and extremely thermophilic isolates carry out anaerobic chemosynthesis. Bacteria grow most abundantly in the shallow crust where upwelling hot, reducing hydrothermal fluid mixes with downwelling cold, oxygenated seawater. The predominant production of biomass, however, is the result of symbiotic associations between chemolithotrophic bacteria and certain invertebrates, which have also been found as fossils in Cretaceous sulfide ores of ophiolite deposits.