Risk analysis of dissolved organic matter-mediated ultraviolet B exposure in Canadian inland waters

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Molot, L A, Keller, W, Leavitt, P R, Robarts, R D, Waiser, M J, Arts, M T, Clair, T A, Pienitz, R, Yan, N D, McNicol, D K, Prairie, Y T, Dillon, P J, Macrae, M, Bello, R, Nordin, R N, Curtis, P J, Smol, J P, Douglas, M SV
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2004
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Canada; Arctic Cordillera; Climate change; Zooplankton
• Online Access: http://dx.doi.org/10.1139/f04-165; http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-165

With depleted ozone levels and the possibility that climate change might lower dissolved organic matter (DOM) concentrations, the risk of exposure of fresh waters in Canada to ultraviolet B (UV-B) was evaluated. First, the distribution of a UV-B-sensitive zooplankton genus, Daphnia, was examined as a function of DOM concentration and maximum depth (Z max ) in 258 systems. Distribution was not restricted by UV-B, although very clear, shallow systems are underrepresented. Secondly, the depth at which 1% of surface radiance at 320 nm occurs (Z 320,1% ) was compared with Z max in over 1000 aquatic systems in 15 ecozones to determine the proportions of optically clear systems (Z max ≤ Z 320,1% ) and systems that may become clear (i.e., are "at risk") should DOM decrease by 50%. South of the treeline, <6% of systems were clear, with the exception of two ecozones with 10%–20%. The proportion of systems at risk was 0% in most regions, with 5%–9% in four regions. DOM levels appear adequate to prevent extirpation of sensitive taxa like Daphnia through direct exposure to UV-B in most regions south of the treeline. However, optically clear and at-risk ponds were much more common in the three Artic ecozones, especially the Northern Arctic and Arctic Cordillera.