HYPERTHERMOPHILIC ARCHAEBACTERIA WITHIN THE CRATER AND OPEN-SEA PLUME OF ERUPTING MACDONALD SEAMOUNT

HYPERTHERMOPHILIC archaebacteria, found in terrestrial and submarine hydrothermal areas1-6, thrive at temperatures between 80 and 110°C and are unable to grow below 60°C. They represent life at the known upper temperature limit. On the continent, their biotopes are solfataric fields and hot springs. Within the marine environment, hyperthermophilic archaebacteria have been found in shallow-water hydrothermal fields as well as in deep hot sediments and vents1,2,4-6. They include strictly anaerobic sul-phidogenic and methanogenic chemolithoautotrophs as well as fermentative and sulphidogenic heterotrophs, and are important as primary producers and consumers of organic matter within high-temperature ecosystems. Their distribution and possible modes of dissemination are at present unknown. Here, we report for the first time on a community of hyperthermophilic archaebacteria within the active zone of an erupting submarine volcano7, and on its spread through the ensuing cooled-down open-ocean plume. Most of the organisms are close relatives of species previously known only from a submarine solfataric field in Italy, whereas others are new. By their conversion of volcanic gases and sulphur at high temperatures, archaebacterial communities living in seamounts may be important participants in marine ecological, geochemical and volcanic processes. © 1990 Nature Publishing Group.