Downstream nutrient changes through the Mackenzie River Delta and Estuary, western Canadian Arctic

The effect of the large lake-rich delta and freshwater-saltwater transition zone (FSTZ) on nutrients from the Mackenzie River was investigated during open water of 2003-2004. Water volume storage in the Mackenzie Delta at peak levels was estimated by quantitatively partitioning the landscape (via GIs analysis) into discrete floodplain lake, wetland and channel environments. A river and lake mixing model and biogeochemical sampling of upstream and downstream delta channels were used to estimate average nutrient composition of water outflow from the delta. Results showed that the delta was a sink for particulates and dissolved inorganic nutrients while dissolved organic matter was enhanced. The composition of river water across the FSTZ was investigated during a mid summer cruise in 2004. Results showed particulate, dissolved inorganic nutrient and dissolved organic carbon patterns typical of most estuaries while dissolved organic nitrogen and phosphorus increased across the FSTZ, atypical of most estuaries.