How does rising atmospheric CO2 affect marine organisms?

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Iron Released from the Melting of Antarctic Glaciers
Alderkamp, A.-C., Mills, M.M., van Dijken, G.L., Laan, P., Thuroczy, C.-E., Gerringa, L.J.A., de Baar, H.J.W., Payne, C.D., Visser, R.J.W., Buma, A.G.J. and Arrigo, K.R. 2012. Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity. Deep-Sea Research II 71-76: 32-48.

The authors write that Antarctic coastal polynyas "are local areas of reduced ice cover that generally form due to offshore katabatic winds and seasonal ice melt," and they say they are "some of the most biologically productive regions of the Southern Ocean." They also state that "phytoplankton primary productivity in polynyas is important for the support of biota who occupy higher trophic levels such as krill, penguins, and whales." In addition, they indicate that "polynyas play a disproportionally important role in sequestering anthropogenic CO2 because of their high rates of primary production, rapid organic matter sinking fluxes (DiTullio et al., 2000), and formation of dense bottom waters (Arrigo et al., 2008)."

What was done
Working under the aegis of the dynamic light and Fe (DynaLiFe) program - an international collaboration that was part of the International Polar Year - Alderkamp et al. determined how the phytoplankton community composition, together with the productivity of waters in the Amundsen Sea and surrounding sea ice zone, were impacted by iron (Fe) input from melting glaciers.

What was learned
The eleven-member research team found that "high Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted in dense phytoplankton blooms in surface waters of Pine Island Bay, Pine Island Polynya, and Amundsen Polynya," such that water column productivity in these regions was "approximately twice as high as in the sea ice zone."

What it means
In the words of the scientists who conducted the study, "the high phytoplankton productivity as a result of glacial input of dissolved Fe is the first evidence that melting glaciers have the potential to increase phytoplankton productivity and thereby CO2 uptake, resulting in a small negative feedback to anthropogenic CO2 emissions," which many believe would help to cool the planet.

Arrigo, K.R., Van Dijken, G.L. and Long, M.C. 2008. Coastal Southern Ocean: a strong anthropogenic CO2 sink. Geophysical Research Letters 35: 10.1029/2008GL035624.

DiTullio, G.R., Grebmeier, J.M., Arrigo, K.R., Lizotte, M.P., Robinson, D.H., Leventer, A., Barry, J.B., VanWoert, M.L. and Dunbar, R.B. 2000. Rapid and early export of Phaeocystis Antarctica blooms in the Ross Sea, Antarctica. Nature 404: 595-598.

Reviewed 9 January 2013