Australia: The Land Where Time Began

A biography of the Australian continent 

Microbial Carbon Turnover - High Rates in Sediments in Deepest Oceanic Trench

The decomposition of organic matter in marine sediments is controlled by microbes, contributing to the organic nutrient regeneration and the preservation of organic carbon (Canfield, 1993). As water depth increases the rates of benthic decomposition generally decline, though because of the vast extent of the abyss, sediments of the deep sea are a quantitatively important component in the global carbon cycle (Glud, 2008; Burdige, Princeton University Press), though the deepest regions of the ocean still remain virtually unexplored (Jamieson, 2011). The authors¹ present here observations of microbial activity in sediments in the Challenger Deep in the Mariana Trench, central west Pacific Ocean, that reaches a depth of almost 11,000 m, the deepest oceanic site on Earth. An autonomous micro-profiling system was used to assess the benthic oxygen rates of consumption. Their results indicate that biological oxygen consumption rates are high, exceeding by a factor of 2 the rates of oxygen consumption at a nearby site that is 6,000 m deep, in spite of the restricted numbers of macrofauna at the Challenger Deep. Analyses of sediments from the 2 sites have consistently shown that the concentrations of microbial cells at the Challenger Deep are consistently higher than at the 6,000 m deep site, and ²¹⁰Pb sediment profiles have shown that there is relatively high sediment deposition in the Trench. The authors¹ concluded that the intensified microbial activity at the extreme pressures characteristic of the trench environment is maintained by elevated organic matter matter deposition.

Sources & Further reading

Glud, Ronnie N., Frank Wenzhofer, Mathias Middelboe, Kazumasa Oguri, Robert Turnewitsch, Donald E. Canfield, and Hiroshi Kitazato. "High Rates of Microbial Carbon Turnover in Sediments in the Deepest Oceanic Trench on Earth." Nature Geosci 6, no. 4 (04//print 2013): 284-88.