FY 1999

Hydrothermal activity along the southwest Indian Ridge

German, C.R., E.T. Baker, C. Mevel, K. Tamaki, and FUJI Scientific Team

Nature, 395(6701), 490–493 (1998)

Twenty years after the discovery of sea-floor hot springs, vast stretches of the global mid-ocean-ridge system remain unexplored for hydrothermal venting. The southwest Indian ridge is a particularly intriguing region, as it is both the slowest-spreading of the main ridges and the sole modern migration pathway between the diverse vent fauna of the Atlantic and Pacific oceans. A recent model postulates that a linear relation exists between vent frequency and spreading rate and predicts vent fields to be scarcest along the slowest-spreading ridge sections, thus impeding migration and enhancing faunal diversity. Here, however, we report evidence of hydrothermal plumes at six locations within two 200-km-long sections of the southwest Indian ridge indicating a higher frequency of venting than expected. These results suggest that fluxes of heat and chemicals from slow-spreading ridges may be greater than previously thought and that faunal migration along the southwest Indian ridge may serve as an important corridor for gene-flow between Pacific and Atlantic hydrothermal fields.