In Marine Ecosystems

Abstract

The working group explored the potential of marine ecosystems for carbon sequestration. Carbon is naturally sequestered by two processes: deep-water formation in the North Atlantic and around the Antarctic continent, and primary production. There is a close coupling between turn-over and biomass produced per unit nutrient input and carbon pumps and sinks on a regional and global scale. High production will in general involve both increased grazing and increased losses through sedimentation. It has been claimed that sedimentation of particulate organic carbon is the only net transport process of carbon from the atmosphere to deep water and to stable marine sediments (Longhurst, 1991). In suitable environments and situations increased carbon net sedimentation may reduce anthropogenic CO₂ from the atmosphere. The ongoing carbon sequestration is about 2 Gt yr^-1 and mainly physico-chemically. In order to play a role on a global scale stimulated sequestration needs to be greater then 0.1 Gt yr^-1 and the carbon must be removed from contact with the atmosphere for periods greater than 10² to 10³ years. Simple back-of-envelope evaluations imply that stimulated sequestration requires considerable spatial scales. Supposing an increase of carbon sequestration of 10 g C m^-2 y^-1, 10⁶ km² of ocean surface would be required to achieve 0.1 Gt C yr^-1.