FIG. 1.

Reef structure sampled in this study. (A) Complete reef structure (total height, approximately 150 cm). The dashed line indicates the approximate height at which the structure was cut down. The image consists of two single images which were assembled to show the complete structure. (B) Reef structure after it was cut down. The inner gray core consists of porous carbonates, through which gas bubbles were rising. The carbonated core is covered by a voluminous microbial mat with a thick pink inner layer and a thin black outer layer. (C) Close-up of the carbonated core and the microbial mat. (D) Reef sample, from which subsamples were obtained for this study, grabbed by the submersible arm. (E) Diagram of the mat and carbonate zones in the reef and the area of where subsamples were obtained. The images were obtained from a video sequence filmed by the JAGO Team and were made available through the courtesy of W. Michaelis, GHOSTDABS Project.