FY 2000

Microbial biomass in the hydrothermal plumes associated with the 1998 Axial Volcano eruption

Cowen, J.P., R. Shackelford, D. McGee, E.T. Baker, P. Lam, and E.J. Olson

Geophys. Res. Lett., 26(24), 3637–3640 (1999)

The Axial Response Team (ART-1) documented greatly intensified chronic-style hydrothermal plumes at Axial Volcano following a 1998 eruptive event. Significantly higher numbers of bacteria were found in the plume versus background stations and depths, due largely to five samples with high numbers (to 1.8 × 10 /ml) in far-field stations. Highest ratios (0.20) of metal depositing capsuled bacteria to total bacteria were found in the near-field (over caldera) plume. An unusual capsule form (FeCap), that dominated the near field plume capsule populations, was present in all plume samples, but were absent in background samples. Multi-cell filaments, metal-encrusted sheathed clusters and matrix-enmeshed colonies, all uncommon in the water column, were also present in plume samples.