Summary
Bacteria play a key role in the world's oceans, supporting nutrient remineratlisation and mediating carbon transfer. Most studies of marine bacteria in the Southern Ocean are restricted to the summer months. Thus, little is known about the effect of extreme seasonal changes in biological productivity on the concentration, production and metabolism of bacteria in Antarctic waters. Changes in nutritional status can alter the physiological state of bacteria (Gasol & del Giorgio 2000). We measured seasonal changes in physical chemical and biotic variables and used radiolabelled substrates and stains to estimate bacterial production and concentrations of total, intact and active bacteria. Here we examine the factors that limited the concentration, production and physiological state of marine bacteria at an Antarctic coastal site.