Three-dimensional ecological-eutrophication model for Singapore

A 3D multilevel eutrophication model has been developed and applied to the tropical coastal waters of Singapore. The model considers the nitrogen, pho sphor-us, and carbon cycles; phytoplankton and zooplankton dynamics; and di ssolved oxygen balance in the water column coupled to benthic processes and is driven by a 3D multilevel hydrodynamic model. The eutrophication model was calibrated with field data obtained from the Southwest Monsoon in Augus t 1998 and subsequently validated using data from the Northeast Monsoon in December 1998. Predictions of nutrient and phytoplankton concentrations fro m the model simulation agreed well with the observed data. The model result s show that the coastal waters of Singapore are relatively well-mixed and d ifferences in concentration with depth for all state variables are generall y < 20%. In the Singapore Strait, horizontal spatial differences for all th e variables are generally < 40%. In the Southwest Monsoon, slightly larger values for phytoplankton and dissolved oxygen but smaller nutrient values a re found in the eastern region of Singapore, compared to the west. The reve rse trend is found in the Northeast Monsoon.