How does rising atmospheric CO2 affect marine organisms?

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CO2 Enrichment at Sea
Wu, H.-Y., Zou, D.-H. and Gao, K.-S. 2008. Impacts of increased atmospheric CO2 concentration on photosynthesis and growth of micro- and macro-algae. Science in China Series C: Life Sciences 51: 1144-1150.

What was done
The authors review what is known about the effects of a CO2-enriched atmosphere on micro- and macro-algae living in the world's oceans.

What was learned
Wu et al. write that "enriched CO2 up to several times the present atmospheric level [our italics] has been shown to enhance photosynthesis and growth of both phytoplanktonic and macro-species that have less capacity of CCMs [CO2-concentrating mechanisms]," adding that "even for species that operate active CCMs and those whose photosynthesis is not limited by CO2 in seawater, increased CO2 levels can down-regulate their CCMs and therefore enhance their growth under light-limiting conditions," because "at higher CO2 levels, less light energy is required to drive CCM." In addition, they report that enhanced CO2 levels have been found to enhance the activity of nitrogen reductase in several marine plants, and that this phenomenon "would support enhanced growth rate by providing adequate nitrogen required for the metabolism under the high CO2 level." Last of all, they say that "altered physiological performances under high-CO2 conditions may cause genetic alteration in view of adaptation over long time scales," and that "marine algae may adapt to a high CO2 oceanic environment so that evolved communities in [the] future are likely to be genetically different from contemporary communities."

What it means
The findings described by the three researchers represent good news for the biosphere, since "marine phytoplankton contribute to about half of the global primary productivity," and this phenomenon, in their words, "promotes the absorption of CO2 from the atmosphere." Consequently, both the micro- and macro-algae of the world's oceans should be able to do an even better job of performing these vital functions in the brave new (and CO2-enriched) world of the future.

Reviewed 1 July 2009