How does rising atmospheric CO2 affect marine organisms?

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Response of AM Fungal Spore Production to Elevated CO2
Reference
Wolf, J., Johnson, N.C., Rowland, D.L. and Reich, P.B.  2003.  Elevated CO2 and plant species richness impact arbuscular mycorrhizal fungal spore communities.  New Phytologist 157: 579-588.

What was done
As part of the long-term Bio-CON (Biodiversity, CO2 and N) FACE experiment being conducted at the Cedar Creek Natural History Area in east central Minnesota, USA (Reich et al., 2001a, 2001b), the authors evaluated the effects of atmospheric CO2 enrichment (from 368 to 560 ppm during the daylight hours of April to October 1998, April to November 1999 and April to October 2000) on arbuscular mycorrhizal (AM) fungal spore production within monocultures and polycultures of sixteen species of plants.

What was learned
"Under plant monocultures," in the words of the authors, "only Glomus clarum responded significantly to CO2 elevation out of 11 species present," but "this response was not detectable under plant polycultures," although "Glomus clarum was also significantly more abundant under plant polycultures."  In fact, they report that "abundances of this species were 2.5-4.5 times greater under elevated CO2 than under ambient."   The authors say "it is possible that other species responded, but were too rare to be detected statistically."

What it means
The authors suggest that "if we detect changes in what we can measure (spores), we may assume that the unmeasurable source of these changes (the collective thalli of the entire AM fungal community) is also undergoing change, possibly even greater change than what was detected in the subset of AM fungi that have sporulated."  They further note that "changes in AM fungal community structure may have complex feedbacks on C cycling, soil quality, and soil responses to rising atmospheric CO2."  Hence, they point out the potential for important new discoveries to be made along these lines in future experiments.

References
Reich, P.B., Knops, J., Tilman, D., Craine, J., Ellsworth, D., Tjoelker, M., Lee, T., Wedin, D., Naeem, S., Bahauddin, D., Hendrey, G., Jose, S., Wrage, K., Goth, J. and Bengtson, W.  2001a.  Plant diversity enhances ecosystem responses to elevated CO2 and nitrogen deposition.  Nature 410: 809-812.

Reich, P.B., Tilman, D., Craine, J., Ellsworth, D., Tjoelker, M.G., Knops, J., Wedin, D., Naeem, S., Bahauddin, D., Goth, J. Bengtson, W. and Lee, T.D.  2001b.  Do species and functional groups differ in acquisition and use of C, N and water under varying atmospheric CO2 and N availability regimes?  A field test with 16 grassland species.  New Phytologist 150: 435-448.


Reviewed 25 June 2003