Geochemical analysis for GR10, Altree 2 and 82/3, six monthly reports of inspection and sample removal

Abstract

The biomarkers indicate that the ecological community was bacterially dominated with a struggling, non-diverse eukaryotic community comprised of dinoflagellates (or their ancestors). There were also green sulfur bacteria, purple sulfur bacteria and methanotrophs present. If methanotrophy was present, likely so was methanogenesis, which suggests that sulfate was low. This is corroborated by the sulfur data. The iron speciation data suggest that the deep waters had a significant extent of euxinia. It is our hypothesis that the green and purple sulfur bacteria lived on shelves in mats with free sulfide present in shelf porewaters in a water column that was oxic at the surface and euxic at mid to possibly deep water depths.