Evaluating light and nutrient limitation in the Tagus estuary using a process-oriented ecological model

Abstract

Over the past decades, the Tagus estuary (Lisbon, Portugal) has been the focus of several experimental and numerical studies. Field observations suggest that light plays the major role in the control of phytoplankton production in the system, with nutrient limitation only in some confined areas. Light limitation has also been inferred by some modelling studies, but it has been an assumption in most model applications to the estuary. In this study, a process-oriented ecological model for the water column, coupled with a 2-D hydrodynamic model, has been applied to the Tagus estuary to assess the influence of light and nutrients on phytoplankton production. The preliminary results obtained using the model suggests that the system is mostly controlled by light. Nevertheless, nutrients may also control production to some extent but only in lower estuarine areas and in summer. This numerical study seems to agree with the general information on the system, supporting the idea that light control has a major role in the Tagus estuary