Moeller, R. E.. Lehigh University, rem3@lehigh.edu
, . E.. ,

 
INHIBITION OF FRESHWATER PHYTOPLANKTON PRODUCTIVITY BY ULTRAVIOLET RADIATION: SEASONAL PATTERNS AND EXPERIMENTAL EVIDENCE FOR ACCLIMATION TO UV-A
 
Ultraviolet radiation (UVR) inhibits primary productivity in 14C bottle incubations to a depth of 2-4 m in a UV-transparent lake in NE Pennsylvania (30-90% inhibition at the surface). Inhibition is least in early summer, when exposure to irradiance is greatest. Experiments with a cultured alga isolated from the summer epilimnion suggest that the residual inhibition of productivity in July, mostly assignable to UV-A wavelengths, possibly overestimates the impact of summer UVR on algal growth rates. Sphaerocystis schroeteri grew at the same rate under ambient lake-surface irradiance and under UVR-filtered irradiance, although both treatments showed apparent sensitivity to UV-A during productivity assays under manipulated irradiance (PAR, PAR+UVA, PAR+UVA+UVB). Adaptation over several days enabled equal growth rates (as well as productivity rates per unit biovolume) in the presence or absence of ambient UVR, but productivity still shifted misleadingly in response to irradiance manipulation during short-term (<1 day) 14C productivity incubations. In contrast, laboratory experiments with artificial UV-B irradiance showed a lack of adaptation to damaging levels of UV-B in a different isolate of the same chlorophyte.
 
Day: Wednesday, Feb. 3
Time: Poster
Location: Sweeney Center
 
Code: CS65WE1107S