OCEANOGRAPHY: Limits to Growth

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Science  05 Jul 2002:
Vol. 297, Issue 5578, pp. 15a
DOI: 10.1126/science.297.5578.15a

The realization that iron availability can limit phytoplankton growth has stimulated a wave of studies in which areas of the ocean that harbor low phytoplankton densities are fertilized with iron and productivity is measured. Moreover, it has been suggested that adding iron to the ocean could help to combat global warming by removing carbon dioxide from the atmosphere. As appealing as that might be, though, it is not clear what other effects might be produced by iron fertilization on the scale that would be needed to effect a reduction in atmospheric CO2.

Neufeld et al. present a mathematical model that combines the effects of stirring by ocean eddies and phytoplankton community growth. They find that plankton blooms exhibit characteristics of an excitable system—meaning that perturbations exceeding a certain threshold can induce a large and temporary deviation from the equilibrium state—and that a larger-than-expected, iron-induced bloom could occur through the development of a structure they call a “propagating bloom filament.” The authors caution that more analysis of ecosystem and geoengineering interventions is needed before we can be confident of the possible outcomes. — HJS

Geophys. Res. Lett. 29, 10.1029/2001GL013677 (2002).

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