How does rising atmospheric CO2 affect marine organisms?

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The Effect of Atmospheric CO2 Enrichment on Ocean Carbon Uptake
Pasquer, B., Laruelle, G., Becquevort, S., Schoemann, V., Goosse, H. and Lancelot, C.  2005.  Linking ocean biogeochemical cycles and ecosystem structure and function: results of the complex SWAMCO-4 model.  Journal of Sea Research 53: 93-108.

What was done
The authors employed a complex model of growth regulation of diatoms, pico/nano phytoplankton, coccolithophorids and Phaeocystis spp. by light, temperature and nutrients (based on a comprehensive analysis of literature reviews on these taxonomic groups) to calculate changes in the ocean uptake of carbon in response to a sustained increase in atmospheric CO2 concentration of 1.2 ppm per year for three marine ecosystems where biogeochemical time-series of the data required for model initialization and comparison of results were readily available.  These systems were (1) the ice-free Southern Ocean Time Series station KERFIX (5040'S, 68E) for the period 1993-1994 (diatom-dominated), (2) the sea-ice associated Ross Sea domain (Station S; 76S, 180W) of the Antarctic Environment and Southern Ocean Process Study AESOPS in 1996-1997 (Phaeocystis-dominated), and (3) the North Atlantic Bloom Experiment NABE (60N, 20W) in 1991 (coccolithophorids).

What was learned
Pasquer et al. say their results "show that at all tested latitudes the prescribed increase of atmospheric CO2 enhances the carbon uptake by the ocean."  Indeed, we calculate from their graphical presentations that (1) at the NABE site a sustained atmospheric CO2 increase of 1.2 ppm per year over a period of eleven years increases the air-sea CO2 flux in the last year of that period by approximately 17%, (2) at the AESOPS site the same protocol applied over a period of six years increases the air-sea CO2 flux by about 45%, and (3) at the KERFIX site it increases the air-sea CO2 flux after nine years by about 78%.

What it means
The results of this interesting study based on the complex SWAMCO model of Lancelot et al. (2000), as modified by Hannon et al. (2001), seem overly large.  At the very least, however, they highlight the likelihood that the ongoing rise in the air's CO2 content may be having a significant positive impact on ocean productivity and the magnitude of the ocean carbon sink.

Hannon, E., Boyd, P.W., Silvoso, M. and Lancelot, C.  2001.  Modelling the bloom evolution and carbon flows during SOIREE: implications for future in situ iron-experiments in the Southern Ocean.  Deep-Sea Research II 48: 2745-2773

Lancelot, C., Hannon, E., Becquevort, S., Veth, C. and De Baar, H.J.W.  2000.  Modelling phytoplankton blooms and carbon export in the Southern Ocean: dominant controls by light and iron in the Atlantic sector in austral spring 1992.  Deep Sea Research I 47: 1621-1662.

Reviewed 4 May 2005