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 N-2 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 mu mol N m(-2) h(-1) Littoral denitrification rates were positively related to temperature (r(2) = 0,66. p < 0.01). % organic matter (r(2) = 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. (C) 2001 Elsevier Science Ltd. All rights reserved.