Effet du développement résidentiel sur la distribution et l’abondance des macrophytes submergés dans la région des Laurentides et de Lanaudière
We searched for empirical relationships between whole-lake submerged macrophyte abundance and residential development, lake properties and wetlands in 34 lakes from the Laurentides-Lanaudière region subjected to a wide range of residential development. Submerged macrophyte abundance was assessed by echosounding of the entire littoral zone. Human encroachment was measured at three spatial scales: Within 1- a 100 m-wide buffer strip circling the lake, 2- the fraction of the watershed that drains directly into the lake and 3- the entire watershed. Single and multiple regression were used to test the effect of residential development on macrophyte abundance in the entire littoral zone and within four optical growth zones defined by Secchi depth. The local effect of slope on local macrophyte abundance was also tested in individual lakes.   We found significant positive correlations between submerged macrophyte abundance and dwelling density present within the direct drainage area (r > 0.51).  In contrast, there was no significant relation between macrophyte abundance and human occupation of the 100 m-wide buffer circling lake and the entire watersheds.  Multiple regression analysis suggest that submerged macrophyte abundance is weakly correlated with lake area (+) and wetland importance within the entire watershed (-). Locally, macrophyte abundance is related to slope and depth which explained together 21% of the variance.  Maximum and optimum colonization depths of submerged macrophytes were positively correlated to residence time and Secchi depth and negatively to human occupation and to wetland importance.
Macrophyte Laurentides Human occupation Echosounding Eutrophication Residential development