Regression and correlation analyses were used to predict responses of phytoplankton biomass (chlorophyll) (microg L(-1)) to nitrate (NO(3)) (mg L(-1)), phosphate (PO(4)) (mg L(-1)) and ammonium (NH(4)) (mg L(-1)) dynamics in the shallow hypertrophic Lake Manyas, Turkey. Nutrient concentrations showed a descending gradient with distance, while chlorophyll concentrations showed an ascending gradient with the distance from the Siğirci Inlet to the Karadere Outlet. Higher nutrient concentrations did always not coincide with higher chlorophyll concentrations. The results showed that regression models developed using seasonal data were more accurate in predicting chlorophyll concentrations than those developed using the pooled data from whole year (based on R (2) and the difference between the measured and predicted values). The findings also revealed that within a single large shallow lake, chlorophyll-nutrient relationships might show significant variations spatially. The objective of this study was to determine the seasonal and spatial variations in the relationships between chlorophyll, nitrate, phosphate and ammonium in the shallow hypertrophic Lake Manyas, Turkey.