Dunton, K. H.. University of Texas at Austin, email@example.com
Neale, P. H.. Smithsonian Environmental Research Center, firstname.lastname@example.org
Miller, H. L.. University of Texas at Austin, email@example.com
Banaszak, A. T.. Smithsonian Environmental Research Center, firstname.lastname@example.org
Major, K. M.. University of Texas at Austin,
THE EFFECT OF UV RADIATION ON IN SITU PHOTOSYNTHETIC CARBON FIXATION IN HIGH ARCTIC KELPS USING 13C
Differences in the photosynthetic response to ultraviolet radiation of two arctic kelps, Laminaria solidungula and L. saccharina, were determined under field conditions in the Canadian High Arctic (75 deg N). Both species were incubated in 13C enriched seawater in UV transparent (UVT) and UV opaque (UVO) chambers deployed in situ at five depths on three consecutive days in August 1997. In situ exposure to photosynthetically active radiation (PAR) and UV was estimated from records of incident spectral UV, PAR and spectral attenuation coefficients measured during the 8-h incubations. Measurements of variable fluorescence (Fv:Fm) were also made at the start and end of the experiments to assess differences in photosynthetic potential among incubated plants at the five depths.
Our results clearly show that both species are sensitive to in situ UV exposure. Significant photoinhibition of photosynthesis was observed in both species to depths of 2 m, where cumulative (unweighted) UV-B (290-320 nm) exposure ranged from 1.6 to 2.7 kJ/m2 and instantaneous dosage rates exceeded 0.16 W/m2 for sustained (>2 h) periods. Exposure to UV appeared to have the greatest effects on L. saccharina as reflected by lower rates of carbon fixation and lower levels of variable fluorescence between UVO and UVT exposed plants.
Day: Wednesday, Feb. 3
Location: Sweeney Center