Thirty nine oceanographic stations were conducted off Rio de Janeiro and northern São Paulo, encompassing Cabo Frio, Guanabara Bay, Sepetiba Bay and Ubatuba in the winter of 2010. Dissolved inorganic nutrients (ammonium, nitrite, nitrate, phosphate and silicate) and chlorophyll-a data were used to investigate biogeochemical and physical processes occurring on the continental shelf. Four major sources of nutrients were identified: local estuarine plumes; remote origins coastal waters; intrusion of South Atlantic Central Water over the continental shelf; and bottom sediments ressuspension and remineralization processes.