Riebesell, U. Alfred Wegener Inst. for Polar & Marine Research,

 
CARBON ISOTOPE FRACTIONATION IN MARINE MICROALGAE: EFFECT OF LIGHT- VS. NUTRIENT-LIMITED GROWTH
 
The large spatial and temporal variability in carbon isotope fractionation of marine phytoplankton is thought to reflect differences in environmental conditions. While numerous factors have been suggested to potentially influence fractionation, recent theoretical and experimental evidence has emphasized the primary role of algal growth rate and CO2 concentration, [CO2]. Whereas in previous experimental studies growth rates were generally controlled by nutrient supply, light intensity is an equally important factor determining phytoplankton growth rates under natural conditions. In the present study we have therefore examined isotope fractionation in relation to [CO2] and light-dependent growth rate in various marine microalgal species. Our results show that light intensity affects isotope fractionation independent of its effect on growth rate. Light-dependent responses in fractionation, which differ between species, may be related to energetic demands for active transport of inorganic carbon. Direct comparison of carbon isotope fractionation measured in light- and nutrient-limited cultures reveals large differences in the relationship of fractionation with growth rate and [CO2] depending on the growth rate limiting resource. Thus, correct interpretation of phytoplankton carbon isotope measurements may require knowledge of the factor(s) controlling algal growth rate.
 
Day: Monday, Feb. 1
Time: 02:30 - 02:45pm
Location: Eldorado Hotel
 
Code: SS32MO0230E