Animal evolution, bioturbation, and the sulfate concentration of the oceans
- aNordic Center for Earth Evolution, and Institute of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark; and
- bEarth System Science Interdisciplinary Center and Department of Geology, University of Maryland, College Park, MD 20742
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Contributed by Donald E. Canfield, March 3, 2009 (received for review December 17, 2008)
Abstract
As recognized already by Charles Darwin, animals are geobiological agents. Darwin observed that worms aerate and mix soils on a massive scale, aiding in the decomposition of soil organic matter. A similar statement can be made about marine benthic animals. This mixing, also known as bioturbation, not only aides in the decomposition of sedimentary organic material, but as contended here, it has also significantly influenced the chemistry of seawater. In particular, it is proposed that sediment mixing by bioturbating organisms resulted in a severalfold increase in seawater sulfate concentration. For this reason, the evolution of bioturbation is linked to the significant deposition of sulfate evaporate minerals, which is largely a phenomena of the Phanerozoic, the last 542 million years and the time over which animals rose to prominence.
Footnotes
- 1To whom correspondence should be addressed. E-mail: dec{at}biology.sdu.dk
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Author contributions: D.E.C. designed research; D.E.C. and J.F. performed research; D.E.C. and J.F. analyzed data; and D.E.C. and J.F. wrote the paper.
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The authors declare no conflict of interest.
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See Commentary on page 8081.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0902037106/DCSupplemental.
