|SS3.18 Habitat Coupling in Lakes|
|Date: Thursday, June 13, 2002|
|Location: Poster Session - VCC|
|Martin, C, , Université du Québec à Trois-Rivières, Trois-Rivières, Canada, Carl_Martin@uqtr.ca|
|Frenette, J, J, Université du Québec à Trois-Rivières, Trois-Rivières, Canada, Jean-Jacques_Frenette|
|BIO-OPTICAL IMPACT OF MACROPHYTES IN A LARGE FLUVIAL LAKE.|
|Large fluvial lakes are understudied with respect to their underwater light environment. These unique aquatic systems are challenging for photobiologists interested in the interactions between light climate, nutrients and microbial communities.
Recent studies on Lac St-Pierre, the largest fluvial lake along the St-Lawrence River, have shown significant bio-optical and chemical transversal differences between its distinct water masses. These are due to their watershed sources and the presence of extensive macrophyte beds within the lake, which increase the habitat complexity.
This study documents the small-scale (5km) spatial variability associated with the passage of water, originating from a near tributary, through a macrophyte bed. Significant changes in the optical and chemical environment have been observed along the upstream-downstream gradient. Due to their effect on hydrodynamics and residence time, macrophytes are responsible for a decrease in both particulate matter and DOM resulting in an increasing penetration depth of UVR and PAR. Three scenarios could explain the observed decrease in the CDOM/DOC ratio: a)photodegradation processes of CDOM due to the increased residence time, b)bacterial degradation of CDOM or c)increased utilization of CDOM.|