Aquatic Sciences Meeting, Albuquerque 2001

SS21 Ultraviolet Radiation and the Aquatic Biota (Disciplinary Connections)

Date: Wednesday, February 14, 2001, Time: 9:45:00 AM

Location: Galisteo

Belzile, C, , Universite Laval, Sainte-Foy, Canada, claude.belzile@bio.ulaval.ca

Vincent, W, F, Universite Laval, Sainte-Foy, Canada, warwick.vincent@bio.ulaval.ca

IRRADIANCE ABSORPTION BY POM AND CDOM IN THE THICK ICE COVER OF HIGH ARCTIC AQUATIC ECOSYSTEMS

We measured spectral absorption in the >2 m-thick ice cover of three contrasting aquatic ecosystems in the Canadian High Arctic: an oligotrophic lake with water of low conductivity (Char Lake), a meromictic lake with brackish surface waters (Lake Romulus), and the Arctic Ocean (Resolute Passage). Salt freeze-out was observed in all cases. CDOM was also rejected during ice formation; this process was more effective in Lake Romulus and Resolute Passage where the water showed relatively high CDOM absorption. However, at the bottom of the sea ice, CDOM produced by a dense layer of ice algae increased aCDOM by a factor of three relative to the underlying waters. Absorption due to particulate organic matter, aPOM, was much less in the ice than in the water, except at the bottom of the sea ice where ice algae increased aPOM 17 times relative to the water column. Measurements of the diffuse attenuation coefficient (Kd) of Lake Romulus ice showed that despite the elevated scattering of the brackish ice, CDOM exclusion was sufficient to produce Kd(UV) values that were lower than in the underlying water.

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Aquatic Sciences Meeting, Albuquerque 2001

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