Environmental Climate Change : The role of marine and aquatic photosynthetic organisms in the global carbon cycle
Franklin, Linda A. .
Interactions of UV Radiation and Carbon on Marine Photosynthesis.
Of the three basic requirements of photosynthesis, both carbonate chemistry and the solar spectrum in marine ecosystems have been changing on a global level. Yet, the effects of these changes on cellular physiology are most frequently studied separately. While responses vary among organisms, single factor experiments suggest that increased CO2 concentration and UV radiation will act antagonistically. The higher proportion of UV radiation at the surface and at depth has been shown to damage photosynthetic reactions and to alter carbon and nitrogen allocation in phytoplankton. Allocation of fixed carbon to macromolecular storage products (carbohydrates and lipids) is more inhibited by UVA relative to more “critical” molecules like proteins, which in turn is more inhibited by UVB. In contrast, elevated CO2 may increase carbon fixation and growth rates by down-regulating carbon concentrating mechanisms and improving resource use efficiency. A polychromatic spectral approach combined with growth at various CO2 concentrations allows us to assess the interaction between carbon concentration and UV exposure with respect to photosynthetic processes. In the model phytoplankter Thalassiosira pseudonana, synthesis of carbohydrates and proteins was greater at higher than ambient levels of CO2, but the addition of UV, especially UVB, to the exposure spectrum had a greater inhibitive effect on carbohydrate synthesis than on any other macromolecular compound. In this talk, we will summarize the current state and future projections of UV exposure, especially with respect to the effect of high atmospheric CO2 levels, and our current understanding of the photosynthetic and ecosystem level implications of these changes.
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1 - Smithsonian Environmental Research Center,, PO Box 28, Edgewater, MD, 21037, USA
increased carbon dioxide
synergistic effect UV and CO2.
Presentation Type: Symposium or Colloquium Presentation
Location: Cottonwood B/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 10:30 AM