Heterotrophic utilization of glucose and glutamate in an estuary: effect of season and nutrient load.

Uptake of 14C-labeled glucose and glutamate was studied at several sites in Baltimore Harbor, Eastern Bay, and the Rhode River. Levels of uptake of 14C-labeled glutamate, measured over a period of 1 year during September, December, April, May, and June to estimate seasonal effects on heterotrophic utilization of selected nutrients, were highest in May and lowest in December. In a comparison of visibly polluted and unpolluted sites, the greatest amount of incorporation of glucose or glutamate and the highest Vmax values were observed at those sites where the microorganisms were exposed to varied and higher levels of pollutants, suggesting that Vmax may function as an indicator of relative pollution. Mineralization values ranged from 30 to 43%. A range of 0.44 to 2.32 mumol of C/liter per day was calculated for glutamate uptake.