Effects of temperature elevation and entrainment on heterotrophic uptake of [U-C]glutamic acid

The effect of temperature elevation and station passage on the heterotrophic uptake of glutamate in condenser cooling water was investigated at three Ontario Hydro generating stations. Glutamate uptake increased approx. 1.9 times with a 10°C rise in lakewater temperature providing the total (discharge) temperature did not exceed 30°C. Above 30°C inhibition of bacterioplankton activity was observed. Mechanical stress encountered during station passage resulted in a reduction of heterotrophic activity of approx. 57%. Temperature elevation and mechanical stress experienced during the once-through cooling process could be expected to result in a net increase in heterotrophic productivity, largely in peripheral areas of the effluent thermal plume and contiguous waters.