TIME-SERIES OF TEMPERATURE FROM 3 DEEP-SEA HYDROTHERMAL VENT SITES

Temperature time-series have been recorded with THYDRO, a new multi-probe temperature recorder, in three different hydrothermal vent sites: 13-degrees-N on the East Pacific Rise (EPR), the Lau Back-Arc Basin, and the North-Fiji Basin. The probes were placed on clumps of living animals (molluscs and polychaetes) for periods of up to 47 h, in zones where hydrothermal fluids mix with seawater. Spatial variability of temperature was often very important, thus demonstrating the necessity of a thorough study of the hydrothermal microenvironment. Temporal variability was analysed through standard spectral analysis methods. Several periodicities are superimposed, ranging from tens of seconds to tens of hours. The origin of these periods is discussed, and although the tidal cycle seems to be of greater importance in the driving forces of these variations, other periods exist that may be generated by the turbulent mixing occurring in this environment, and/or by variations in the hydrothermal fluid discharge. Aperiodic phenomena were also noted and, therefore, random processes should not be neglected. Consequences of the encountered variabilities on the vent fauna are also discussed, especially for Alvinella species that live in the studied zone and must have developed adaptive responses.