An Ocean (and Bacteria) Run Through It

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Science  28 Sep 2001:
Vol. 293, Issue 5539, pp. 2351
DOI: 10.1126/science.293.5539.2351b

Soon after new oceanic crust forms at mid-ocean ridges, it begins to be corroded by seawater. This alteration of the crust is important because it affects the chemistry of the oceans, and it also can affect the chemistry of Earth's mantle and even the formation of volcanoes when the hydrated crust is subducted. It has long been thought that alteration is primarily an inorganic reaction between seawater and fresh basalt glass, but recent work has found evidence for bacterial alteration.

Furnes et al. have surveyed and attempted to quantify the relative proportions of inorganic and biological alteration by examining drill cores from oceanic crust of various ages and tectonic settings. Their survey shows that microbes may be responsible for 20 to 90% of the alteration in the upper 300 meters of the crust and may account for as much as 10% of the alteration even at 500 meters. Microbial activity can alter both young and old crust, and it can generate microchannels and pits that may facilitate the inorganic reactions. — BH

Geochem. Geophys. Geosys.2, 2000GC000150 (2001).


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