A Nutrient-Phytoplankton-Zooplankton Model for Classifying Estuaries Based in Susceptibility to Nitrogen Loads

Abstract

Estuarine responses to nutrient loads can be remarkably different. Many driving variables including light, water residence time, physical stratification, and temperature are responsible for the diversity of the response. To classify estuaries based on their susceptibility to nutrient loads, a nutrient- phytoplankton- zooplankton (NPZ) model was developed and applied to river-dominated, well-mixed estuaries. Estuaries are classified as having low, medium, high and hyper eutrophic conditions by the model. The result of the model suggests that water residence time is an important controlling variable in the process of achieving a steady-state response to nutrient loads. Although phytoplankton responses to residence time vary under different loads, they have the same positive trend. Phytoplankton responses are almost linear with water residence time initially, then decrease, and eventually plateau.