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Abstract.In order to study geochemical and biogeochemical processes in estuaries, particularly in the turbidity maximum and at the plume water fronts, two cruises were carried out in the summer and winter of 1988 in the Changjiang Estuary region. The study permitted to identify two major sources of nutrients: firstly the Changjiang River carried abundant nutrients with 90-l 10 pmol/l of Si(OH),, 70-95 pmol/l of NO; and 0.5-0.8 pmol/l of PO:-. The annual average nutrient fluxes of the studied year were estimated as about 2.5 X 1012, 1.0 X lOI* and 1.9 X 1O'O g/yr for Si, N and P, respectively. However, NO; and NH: did not principally originate from the freshwater discharge. Their distribution was more affected by geochemical and biogeochemical processes. Secondly nutrient release in the turbidity maximum and from sediments outside the plume water fronts was observed. In the regions where vertical convection was strengthened due to the complex hydrographic features of the studied region, nutrients released from sediments dispersed upward to the surface waters providing a basis for an increase of primary productivity.In addition to seawater dilution, biological activities were another important factor for nutrient consumption, particularly outside the plume water fronts where biological consumption led to a noticeable removal of nutrients from surface waters.