Abstract: Phytoplankton biomass and water column temperature dynamics of Lake James, NC were studied between 1997 and 1999. Continuous water temperature data showed that thermal stratification starts in late March and breakdowns in early November in Lake James. At 2 m phytoplankton biomass dynamics were mostly seasonal, being high in the fall and spring and low in the summer. The hypolimnetic biomass was the lowest and the least influenced by the temperature dynamics. The only layer in which the biomass responded to the oscillations of the water temperature was metalimnion. The biomass in this layer usually increased after periodic oscillations of the water temperature.