2007/05/31 by R. John Parkes, Henrik Sass · 1 citation
Environmental Science · Earth and Planetary Sciences · #Methane Hydrates and Related Phenomena #Microbial Community Ecology and Physiology #Geology and Paleoclimatology Research
paper · doi:10.1017/cbo9780511541490.012
openalex publication_date 2007/05/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
GENERAL INTRODUCTION Approximately 70% of the Earth's environment is marine, which includes substantial sediment deposits, some of which can be greater than 10 km in depth (Fowler, 1990). Although these sediments contain the largest global organic carbon reservoir (∼15 000 × 10 18 g C, Hedges and Keil, 1995), apart from shallow margin sediments (to 200 m water depth), they have been considered to be relatively biogeochemically inactive. For example, Jørgensen (1983) calculated that margin sediments accounted for 83% of global marine sediment oxygen uptake whilst only representing 8.6% of global sediment area. In contrast, deeper sediments (200 to >4000 m water depths), despite being ∼91% of marine sediment area, accounted for only 17% of global oxygen uptake. The situation was considered even more extreme for rates of sulphate reduction, with this being responsible for, respectively, 50% and 0% of all organic matter being degraded in margin and deep water sediments (>4000 m water depths) (Jørgensen, 1983). This low activity was consistent with results demonstrating the limited depth distribution of prokaryotic populations in deep sediments. Morita and ZoBell (1955) concluded that the marine biosphere ended at 7.47 m deep, based on their inability to culture bacteria at this or greater depths. Reports of prokaryotes being isolated from deeper sediments were considered to be contaminants introduced during sampling, or dormant organisms being re-activated (ZoBell, 1938).