You are here:
A SIMPLE MODEL OF THE EFFECTS OF NITROGEN LOADING, FRESHWATER RESIDENCE TIME, AND INTERNAL LOSSES ON THE NITROGEN CONCENTRATIONS AND EXPORT IN ESTUARIES
Citation:
Dettmann, E H. A SIMPLE MODEL OF THE EFFECTS OF NITROGEN LOADING, FRESHWATER RESIDENCE TIME, AND INTERNAL LOSSES ON THE NITROGEN CONCENTRATIONS AND EXPORT IN ESTUARIES. Presented at Chesapeake Bay Program Monitoring Subcommittee Meeting, Forte Meade, MD, September 13, 2000.
Description:
This simple model uses the annual loading rate of total nitrogen (TN) and the water residence time to calculate average annual TN concentration and internal loss rates (e.g. denitrification and incorporation in sediments) in an estuary, and rate of nitrogen export across the seaward boundary. The model, which is based on an annual mass balance, is adapted from the approach used by Vollenweider to calculate phosphorus concentrations in lakes. The model has been applied and calibrated to field data for 11 North American and European estuaries having a broad range of characteristics. Results show strong relationships between freshwater residence time and the fractions of nitrogen that are exported, denitrified, and permanently incorporated into sediments. The calibrated model has also been applied to calculate TN concentrations in 18 small side-embayments of Buzzards Bay, Massachusetts. While developed for TN, the model also appears to predict well the concentrations of dissolved inorganic nitrogen [DIN] in mesocosms and a group of 12 North American estuaries. The relatively small data requirements of the model may suit it particularly to management applications in small estuaries. This presentation describes some preliminary tests of model application, including analysis of interannual response to changes in nutrient loading and water residence time, and the value of model-calculated TN concentrations as predictors of other indicators of trophic state, such as peak chlorophyll a concentration and peak macroalgal abundance.