Litchman, E. Smithsonian Environmental Research Center, litchman@serc.si.edu
Neale, P. Smithsonian Environmental Research Center, neale@serc.si.edu

 
SENSITIVITY OF NITROGEN-LIMITED PHYTOPLANKTON TO UV: RESULTS FROM MONOCULTURE AND NATURAL ASSEMBLAGE EXPERIMENTS
 
Nitrogen limitation can potentially affect sensitivity of photosynthesis to UV by decreasing the amount of photoprotective compounds or repair enzymes. We investigated the effect of nitrogen limitation on the sensitivity to UV in experiments with monocultures and natural phytoplankton assemblages. Semicontinuous monocultures of dinoflagellates were grown under nutrient-replete and nitrogen-deficient conditions. N-replete cultures were less sensitive to UV in the region of 330-395 nm as determined by polychromatic exposure experiments. The lower sensitivity corresponded to a higher particulate absorbance of the N-replete cultures in this region. In outdoor tank experiments, nitrate enrichment of natural plankton assemblages from the Chesapeake Bay lead to a three-fold increase in Chl a compared to the ambient nitrate treatment (<5 uM) and a rapid change in the phytoplankton community composition --from dominance by dinoflagellates to dominance by green flagellates. In contrast to the monoculture experiments, however, N addition did not lead to a decreased sensitivity to UV. Community responses to changes in nutrient conditions might be important in determining the resulting susceptibility of phytoplankton to UV and caution should be used when extrapolating results of monoculture experiments to natural conditions.
 
Day: Wednesday, Feb. 3
Time: 11:30 - 11:45am
Location: Sweeney Center
 
Code: CS65WE1130S