How does rising atmospheric CO2 affect marine organisms?

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Antarctica (Biology) - Summary
There are but two species that make up the totality of Antarctica's vascular plants: Colobanthus quitensis (a cushion-forming member of the Caryophyllaceae) and Deschampsia antarctica (a prostrate tussock grass), both of which are found on the Antarctic Peninsula, where it has warmed substantially over the last several decades.  Xiong et al. (2000) note that coincident with this warming, there have been increases in both the size and number of populations of these plants.  Hence, in an attempt to better understand what has been occurring, they collected several specimens and transported them in chilled boxes to Arizona State University, where they grew them under appropriately controlled conditions for 14 months, after which they propagated new plants from seeds (Colobanthus) and tillers (Deschampsia).  The new plants were then grown for 90 days at day/night temperatures of either 7C/7C, 12C/7C or 20C/7C, after which they were harvested and various growth responses determined.

The responses of the plants to increased warmth were dramatic.  In the words of the scientists who conducted the work, "plants of both species grown at a daytime temperature of 20C had greater relative growth rates and produced 2.2 - 3.3 times as much total biomass as plants grown at daytime temperatures of 12 or 7C."  In addition, they noted that the plants grown at 20C produced 2.0 - 4.1 times as many leaves and 3.4 - 5.5 times as much total leaf area.  Consequently, it was pretty much of a no-brainer for the researchers to conclude that "continued warming along the Peninsula will lead to improved vegetative growth of these species."

Going back somewhat in time - in a study of historical observations and paleoecological records from the western Antarctic Peninsula - Smith et al. (1999) observed a succession of 200- to 300-year cycles in both climate and organic matter preservation, the latter of which they attributed to increased plant productivity during periods of warming, which is right in line with what would be expected on the basis of the study of Xiong et al.  In addition, Smith et al. determined that Adelie penguins have continuously inhabited the region around Palmer Station for at least the past 500 years, and that in response to the warming of the past several decades, chinstrap penguins, followed by gentoo penguins, have begun to take up residence there as well.  Finally, in a study of sediment cores obtained from a lake on the Ardley Peninsula, Sun et al. (2000) determined that the penguin population there was "lowest at 1,800 - 2,300 years BP, a period of low temperature," after which "the population increased, peaking between 1,400 and 1,800 years BP" at a time that "corresponds almost exactly to a period of high precipitation."

In assessing these findings, it is clear that what is typically predicted for the future by today's state-of-the-art climate models, i.e., a warmer and wetter world, is exactly what is needed to enhance both the biological prowess and diversity of Antarctica.  Perhaps we should thus hope that such comes to pass, as indeed it likely will; for the world appears to be on the threshold of what could be called a Modern Warm Period, as the millennial-scale climatic oscillation that brought us the Medieval Warm Period and Little Ice Age appears to be heading back to just such Medieval Warm Period conditions, i.e., warmer and wetter.  With more precipitation, in fact, it is possible that enhanced snowfall over the continent would balance the mass loss of water from ice discharge and melting along the coast, thereby allowing life to proliferate in regions such as the Antarctic Peninsula without inducing a significant rise in global sea level.

References
Xiong, F.S., Meuller, E.C. and Day, T.A.  2000.  Photosynthetic and respiratory acclimation and growth response of Antarctic vascular plants to contrasting temperature regimes.  American Journal of Botany 87: 700-710.

Smith, R.C., Ainley, D., Baker, K., Domack, E., Emslie, S., Fraser, B., Kennett, J., Leventer, A., Mosley-Thompson, E., Stammerjohn, S. and Vernet, M.  1999.  Marine ecosystem sensitivity to climate change.  BioScience 49: 393-404.

Sun, L., Xie, Z. ande Zhao, J.  2000.  A 3,000-year record of penguin populations.  Nature 407: 858.