ESTIMATION OF NUTRIENT LOADING TO AN EUTROPHIC LAGOON WATER BY MASSIVE OVERWINTERING OF WATERFOWL

Abstract

Waterfowl represent an important component of aquatic ecosystems. Conservation efforts for migratory waterfowls can serve as an important mechanism to promote the conservation of wetlands and other habitats. Nevertheless, the role of the migratory waterfowl in relation to nutrients loadings to eutrophic waters has been far less studied than what it should be. In this note, we estimate nutrients loadings by droppings of waterfowls in Sakata Lagoon, which has been registered as a “Ramsar Site” in 1996. The total phosphorus (TP) and nitrogen (TN) loadings associated with the massive overwintering waterfowls in the lagoon were estimated to be 800 gP/d and 3619 gN/d, respectively. Contributions for increases of TP and TN concentrations in the lagoong water by the waterfowls during the wintering period were accounted by 70% and 30%, respectively. Preliminary analysis suggested that the lagoon sediment might also have been eutrophicated by the waterfowl.