Bacterial profiles in hydrothermally active deep sediment layers from Middle Valley (NE Pacific), Sites 857 and 858

Abstract

Average total organic carbon in the top 5 m was 0.56% at Site 857 and 0.48% at Site 858. However, due to the steep termal gradients encountered at Site 858 (1.7 to 11oC/m), bacteria even at shallow depths appear to be adapted to high temperatures and hence may be considered thermophilic. Depth profiles of bacterial populations at the vent sites are related to chlorinity changes, which reflect the influence of vent fluid. At the two "hot' holes (858B and 858D) which were influences by near-surface lateral fluid flow, there was a significant subsurface peak in the bacterial population associated with increases in chlorinity and a temperature increase to 169oC. -from Author