J School of Chemistry, University of Bath, Bath BA2 7A Y (UK.) ] Department of Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (U.S.A.) 3 United States Geological Survey, Reston, VA 2209 (US.A.) 4 Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, (US.A.) 5 Department of Physics, California Polytechnic State Universi...