SETTLING OF PARTICLES IN A HYDROTHERMAL VENT FIELD (EAST PACIFIC RISE 13-DEGREES-N) MEASURED WITH SEDIMENT TRAPS

Samples from nine sediment traps moored in the vicinity of an active hydrothermal vent on a segment of the East Pacific Rise (EPR), near 13-degrees-N, were collected in 1987 during the Hydronaut cruise. The results show variability in the distribution and composition of the particle flux to the area immediately surrounding the sea-floor vents. The settling of material measured at three distances from the "Totem" vent field demonstrates a sharp decrease in total flux with increasing distance from the source. The amount of particles collected with sediment traps at the vent field is 5.6 times greater than the pelagic flux measured on this site. Comparison of elemental fluxes determined in the near- and far-field experiments reveals the spatial distribution of vent effluent. The sulphur particle flux decreases by a factor of 300 between the near-field station and the seamount station 15 km southeast of the vent. In contrast, the pelagic carbonate flux appears equally distributed throughout the studied area. Few organic particles produced by the vent ecosystem are reaching the seafloor only 80 m away. Organic output from vent sites to their surroundings in the central graben, or the ridge crest, via large settling particles appear negligible compared to the pelagic flux from surface waters. The production of organic matter by the hydrothermal ecosystem does not have a noticeable effect on the food supply of the deep-sea benthos near the vent because this organic flux is too diluted by the mineral fraction rich in sulphur.