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Spectral gradients of downwelling light in a fluvial lake (Lake Saint-Pierre, St-Lawrence River)
Frenette, J.-J.; Arts, M.T.; Morin, J. (2003). Spectral gradients of downwelling light in a fluvial lake (Lake Saint-Pierre, St-Lawrence River). Aquat. Toxicol. 37(1): 77-85
In: Aquatic Toxicology. Elsevier Science: Tokyo; New York; London; Amsterdam. ISSN 0166-445X, more
Peer reviewed article  

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Keywords
    Climate; Fluvial deposits; Lake basins; Light attenuation; Spectra; Ultraviolet radiation; Canada, Quebec, St. Lawrence R. [Marine Regions]

Authors  Top 
  • Frenette, J.-J., correspondent
  • Arts, M.T.
  • Morin, J.

Abstract
    Large fluvial lakes are understudied with respect to their underwater light climates. Fluvial lakes pose unique challenges for photobiologists interested in the interactions amongst light climate, nutrients and microbial community structure and biodiversity. This is because fluvial lakes are typified by highly dynamic flow regimes often incorporating different inflows and discharges each characterized by their own unique physico-chemical composition. These compositional characteristics include the concentrations of chromophoric dissolved organic matter (CDOM), suspended solids, and pigments such as chlorophyll. Together these factors contribute to the distribution and composition of the water masses that make up fluvial lakes. These water masses, in turn, flow over lakebeds that are typically complex in their morphometry and feature extensive macrophyte beds, further enhancing the habitat heterogeneity of these ecosystems. We here report on the spectral attenuation of ultraviolet radiation (UVR = 280-400 nm) and photosynthetically active radiation (PAR = 400-700 nm) in the three main water masses of Lake Saint-Pierre and evaluate the relative contribution of CDOM, and particulate organic material to UVR attenuation. We demonstrate that UVR penetrates 18 to 30% of the water column (1% penetration depth) in the Lake Saint-Pierre ecosystem, and show how the underwater spectral UVR varies within the three water masses.

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