Denitrification rates in the sediments of Lake Memphremagog, Canada-USA.

Denitrification is the most important mechanism of nitrogen retention in aquatic systems. Research into the spatial variability of sediment denitrification has been relatively rare. Here, we use the N2 flux technique to measure sediment denitrification rates at 19 littoral and 1 profundal site in Lake Memphremagog. Littoral denitrification rates were highly variable with an average rate of 111 mumol N m-2 h-1. Littoral denitrification rates were positively related to temperature (r2 = 0.66, p < 0.01), % organic matter (r2 = 0.31, p < 0.05) and macrophyte biomass density and negatively related to depth. These results in combination with an analysis of the literature and a predictive model created from literature data relating site depth and denitrification rates show that the littoral zone dominates whole lake denitrification.