Ozone Depletion and UV Inhibition of Photosynthesis in Arctic Kelps: Spectral and Temporal Dependence

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Depletion of stratospheric ozone, particularly in the polar regions, is causing increased concern over the effects of harmful UV radiation (mainly UVB, 280-320 nm). UVB is damaging to many biological processes, and in plants, specifically targets photosynthesis. Large increases in the penetration of solar UVB in the Southern Ocean during the austral spring from ozone depletion is known to have significant effects on phytoplankton productivity. The phenomenon is less severe in the Arctic, but ozone related increases in incident UVB have accelerated over the last three years. This proposal addresses the question of the effects of increased UVB on large benthic marine macroalgae (kelp) and the levels of UVB that penetrates into the coastal water of the Arctic. Little is known about the sensitivity of kelp photosynthesis to UVB. Assessment of UV effects (280-400 nm) in an environmental context can be made by weighting the spectrum of UV irradiance with a biological weighting function (BWF; similar to an action spectrum). The investigators will measure detailed BWF's and the kinetics of UV effects n photosynthesis of macroalgae in High Arctic, emphasizing the kelps, Laminaria saccharina and L. solidungula, which are distributed throughout the circumpolar Arctic. Both laboratory cultured plants and sporophytes collected during two spring and one summer field season in the Canadian High Arctic (Resolute, 79o30' N; 95oW) will be measured. Plants exposed to different natural light environments during the nine-month ice covered period will be examined for difference in their sensitivity to UV radiation; the importance of the nitrogen status of the plants in recovery processes that counteract UV-induced damage will also be investigated. The results will enable the first quantification of potential UV exposure in kelp habitats and the biological effects of such exposure in terms of kelp productivity in arctic coastal systems.