Tagus estuary, Portugal

Case study area

This estuary is one of the largest in Europe, with a broad shallow bay covering an area of about 320 km2. It is mesotidal with semi-diurnal tides. The Tagus river is the main source of freshwater to the estuary.

An in situ monitoring program with monthly sampling at four sites has been running since 1999.  This measures chlorophyll a and other photosynthetic pigments by HPLC, total suspended matter, in water radiation, Secchi disk, nutrients content, and in some years, phytoplankton cell counts. The estuary demonstrates a maximum chlorophyll concentration in the spring/summer and minimum in the winter.