Australia: The Land Where Time Began

A biography of the Australian continent 

Oxygen and Aerobic communities from the Sea Floor to Basement in Deep Sea Sediments

The depth to which oxygen penetrates into marine sediments differs considerably between locations (Emerson et al., 1985; Jahnke et al., 1982). Oxygen penetrates only millimetres to centimetres into the sediment in areas of high microbial respiration rates (Revsbech, Jøgensen & Blackburn, 1980), though communities of active anaerobic microbes are present down hundreds of metres or more in the oceanic sediment (Parkes et al., 1994; D'Hondt et al., 2004; Inagaki et al., 2006; Lomstein et al., 2012). Oxygen penetrates much deeper where there are low rates of sedimentary respiration (Murray & Grundmanis, 1980; D’Hondt et al., 2009; Røy et al., 2012; D’Hondt, et al., Inagaki & Alvarez Zarikan, 2011; Orcutt et al., 2013), though the depth to which microbial communities persist was previously not known (D’Hondt et al., 2009; Røy et al., 2012; Morita & Zobell., 1955). Extremely low rates of aerial respiration occur in the sediments beneath the South Pacific Gyre (D’Hondt et al., 2009). In this paper D’Hont et al. show that in this region microbial cells and aerobic respiration persist through the entire sediment sequence to depths of at least 75 m below the seafloor.  D’Hont et al. suggest that net aerobic respiration in these sediments is coupled to marine organic matter oxidation, based on the Redfield stoichiometry of dissolved oxygen and nitrate. They identify a relationship of the depth of penetration of oxygen to rate of sedimentation and the thickness of the sediment. When this relationship was extrapolated they suggest that oxygen and aerobic communities may be present throughout the entire sediment sequence in 15-40 % of the Pacific and 9-37 % in the global sea floor. When the sediments and basalt from these regions are subducted it becomes a source of oxidised material in the mantle.

Sources & Further reading

1. D'Hondt, S., F. Inagaki, C. A. Zarikian, L. J. Abrams, N. Dubois, T. Engelhardt, H. Evans, T. Ferdelman, B. Gribsholt, R. N. Harris, B. W. Hoppie, J.-H. Hyun, J. Kallmeyer, J. Kim, J. E. Lynch, C. C. McKinley, S. Mitsunobu, Y. Morono, R. W. Murray, R. Pockalny, J. Sauvage, T. Shimono, F. Shiraishi, D. C. Smith, C. E. Smith-Duque, A. J. Spivack, B. O. Steinsbu, Y. Suzuki, M. Szpak, L. Toffin, G. Uramoto, Y. T. Yamaguchi, G.-l. Zhang, X.-H. Zhang and W. Ziebis (2015). "Presence of oxygen and aerobic communities from sea floor to basement in deep-sea sediments." Nature Geosci 8(4): 299-304.