Smith, R. EH. University of Waterloo,
Allen, C. EH. University of Waterloo,
Wilhelm, S. W. University of Tennessee,

Realistic estimates of the column-integrated impact of ultraviolet radiation (UVR) on bacterial production require models to describe the kinetics and spectral dependence of UVR effects. We conducted two experiments at a mid-lake station in L. Erie to determine the spectral response of nucleic acid (by thymidine assimilation) and protein (by leucine assimilation) synthesis, and surveyed the impact of UVR on nucleic acid synthesis at additional stations elsewhere in the lake. Epilimnetic plankton samples were exposed for 1.5-4 h near mid-day at 50% of total incident radiation, then assayed for thymidine and/or leucine assimilation for 1 h in darkness. Assimilation of both tracers was the same, or higher, in samples previously-exposed to visible light (PAR) only compared to pre-exposure or dark control samples. Assimilation rates were 30-60% lower after full spectrum exposure compared to samples exposed to PAR only, with more inhibition in longer exposures. The spectral response of inhibition was variable but indicated an important role for UVA (>320 nm), including a major effect of long UVA (>340 nm) in the longer incubations. Biological weighting functions derived from the spectral response data will be presented as a basis for modeling column-integrated UVR effects on bacterial production.
Day: Wednesday, Feb. 3
Time: 09:45 - 10:00am
Location: Sweeney Center
Code: CS65WE0945S