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Spatial heterogeneity in trophic status of shallow lakes on the Boreal Plain: Influence of hydrologic setting
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- Author(s) / Creator(s)
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[1] We used metrics of surface water and groundwater connectivity as explanatory variables in nonparametric regression models to explain the spatial heterogeneity in trophic status of shallow lakes. The concentration of chlorophyll a (Chl a) was used as an indicator of trophic status and was estimated from 17 Landsat images acquired during the end of summer (August) over a 20-year period from 1984 to 2003. A long-term median of Chl a was computed for each of 40 lakes on the basis of the 17-year data set. Hydrologic metrics explained 72% of the spatial variation in Chl a. The regression tree showed that lakes with a higher concentration of calcium plus magnesium (Ca + Mg) exhibited higher Chl a than lakes with a lower Ca + Mg. We hypothesized that this trend was a result of either higher internal nutrient loading in high Ca + Mg lakes due to groundwater discharge or differences in surficial geology. Among high Ca + Mg lakes, lakes with no inflowing streams had lower Chl a, while connected lakes had higher Chl a, possibly reflecting enhanced nutrient delivery to lakes connected to the stream network. Among low Ca + Mg lakes, lakes with larger wetland cover in their drainage basins had lower Chl a, while lakes with smaller wetland cover in their drainage basins had higher Chl a, possibly reflecting differential water loading rates between small and large wetlands that lead to either Chl a concentration or dilution. These results suggest that relatively simple hydrologic metrics can be used to predict the trophic status of lakes in this area of the boreal forest.
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- Date created
- 2008
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- Type of Item
- Article (Published)
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- License
- Copyright 2008 by the American Geophysical Union