Seasonal Changes in Nitrogen Compartments of Lakes Under Different Loading Conditions

To develop a better conceptual picture for nitrogen dynamics in lake ecosystems, the seasonal changes in the concentrations of nitrate, ammonia, dissolved organic and particulate nitrogen were monitored in the water contained in three limnocorrals located in the Bay of Quinte, Ontario. Following the decline in summer particulate N, there was an increase in ammonia. This was followed by an increase in nitrate throughout the winter suggesting that nitrification was a significant process. To assess the potential contribution of the sediments, ammonia, nitrate, and dissolved organic N were measured for pore waters and total N, exchangeable ammonia, and nitrate in the solid fraction. The influence of nutrient addition was evaluated by comparing corral I, receiving no nutrient additions, with corral II to which phosphate was added (0.92 g P/m2 per yr) and corral III which received the same amount of phosphate plus nitrate at an N:P weight ratio of 13. Increases and decreases in phosphorus, nitrogen, and chlorop...