Fritz, J. J.. Smithsonian Environmental Research Center, fritz@serc.si.edu
Neale, P. J.. Smithsonian Environmental Research Center, neale@serc.si.edu
Davis, R. F.. Dalhousie University, richard.davis@dal.ca

 
SPECTRAL AND TEMPORAL DEPENDENCE OF ULTRAVIOLET (UV)-INDUCED INHIBITION OF PHOTOSYNTHESIS IN COASTAL ANTARCTIC PHYTOPLANKTON
 
Sensitivity of photosynthesis to UV (280-400nm) was examined in coastal Antarctic phytoplankton assemblages from October to December, 1997. Biological weighting functions (BWFs) for UV inhibition of photosynthesis were determined in surface water samples collected near Palmer Station, Antarctica (64 deg S, 64 deg W). The ratio between UVB (280-320nm) and UVA (320-400nm) weights is similar to previous Antarctic BWFs (ca. 10 for 300nm:360nm). Weights (reciprocal mW/m2) at 300 nm were approximately one order of magnitude greater than for natural cultures at McMurdo Station and varied by more than three-fold during the three month period. BWFs with lower sensitivity to UV may be due to acclimation to higher light at the end of the austral spring and to the presence of mycosporine-like amino acids. Time-course incubations under solar exposure were also conducted in enclosures which transmitted UV (UVT) or blocked UV (UVO). Cumulative uptake of carbon by cells in UVT tanks was reduced at the end of 12-hr incubations by up to 49% compared to cells in UVO tanks, and rates of photosynthesis in UVO cells always exceeded rates of those exposed to UV. Additionally, after shifting to PAR-only conditions, these assemblages were capable of partial recovery from UV exposure.
 
Day: Wednesday, Feb. 3
Time: 11:15 - 11:30am
Location: Sweeney Center
 
Code: CS65WE1115S