The rate of oxygen consumption and ammonia excretion by Mytilus edulis after various periods of exposure to air

Abstract

1. 1. The rates of oxygen consumption and nitrogen excretion in water before and after various periods of exposure to air have been recorded continuously in large groups of sea-mussels. Within 2 hr after re-immersion, the rates of oxygen consumption and nitrogen excretion reached values similar to those obtained before exposure to air, but between periods, both rates were higher. 2. 2. When the extra oxygen uptake in water following exposure to air (the oxygen debt) is plotted against exposure time, a non-linear relationship is obtained (Fig. 1). Depending on the size and location of the mussels, the curves representing this relationship show an optimum (large, littoral mussels) or reach a maximum (small littoral mussels and sub-littoral mussels). 3. 3. There is no direct correlation between the size of the oxygen debt and the amount of organic end-products present. A possible relation between the oxygen debt and the energy charge is discussed. 4. 4. Sea-mussels also show an ammonia debt which, in contrast to the oxygen debt, is proportional to the time of air exposure (Fig. 2).