Science 15 August 2008:
Vol. 321. no. 5891, pp. 926 - 929
DOI: 10.1126/science.1156401

Review

Spreading Dead Zones and Consequences for Marine Ecosystems

Robert J. Diaz1* and Rutger Rosenberg2

Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

1 Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA.
2 Department of Marine Ecology, University of Gothenburg, Kristineberg 566, 450 34 Fiskebckskil, Sweden.

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Suffocating the Oceans

In many coastal regions of the world during the past 60 years, the concentration of dissolved oxygen has declined to levels anathema to life and the number and extent of listed hypoxic areas has increased from 46 in 1995 to more than 400. Loss of dissolved oxygen is linked to the release of nutrients when organic waste or fertilizer runs off into river outflows. Hypoxia poses a grave threat to the viability of coastal marine and estuarine ecosystems and can quickly lead to the elimination of the sea bed organisms and fish. Diaz and Rosenberg (p. 926) review how the issue of dissolved oxygen may become the most important factor controlling man's use of the sea