The aim of this study was to investigate the post-dam conditions of the loads and yields of dissolved inorganic
nitrogen (DIN), orthophosphate (DIP, silicate (DSi) and total phosphorous (TP) in the Lower São Francisco riverestuary
(NE-Brazil) after the river was regulated to a constant flow by the dams. Loads and yields of monthly
measurements performed from November 2000 to March 2002 at a gauging station downstream of the dams (80 km
from the coast) showed 4.1 x 103 t/yr and 0.006 t/km2/yr of DIN, 0.2 x 103 t/yr and 0.002 t/km2/yr of DIP, and 448 x
103 t/yr and 0.71 t/km2/yr of DSi, respectively. Over the last 15 years, DIN loads reduced by 94 % and DSi by 31%.
The river turned into an oligotrophic system with primary production limited by nitrogen and nutrient yields being
among the lowest of Brazilian coastal rivers.
