Hydrogeochemical fluxes and their relationship to environmental factors were evaluated in three catchments of the Maricá-Guarapina fluvio-lagoonar system located on the coast of Rio de Janeiro State, Brazil. Sampling was performed biweekly from March to December 1993 at the outlets of three sub-basins with different land use distributions. Water discharge, physico-chemical parameters, major cations and anions, and dissolved inorganic N and P were analyzed. Despite an increase in contributions of weathering processes westward, the major constituent concentrations covaried temporally among catchments, indicating similarity of the involved biogeochemistry processes. Moreover, there is a spatial dissolved nutrient pattern, with concentrations increasing westward in association with urbanization and farming. Land use classes were arranged according to their potential impacts as follows: forest < small properties < farming < urbanization.