PHYSIOLOGICAL MEASUREMENTS ON ESTUARINE BIVALVE MOLLUSCS IN THE FIELD

Abstract

Techniques for measuring the rates of feeding and of oxygen consumption by bivalve molluscs have been tested and applied under various conditions in the field, including working from a research vessel and from a small mobile laboratory on the shore. The animals are held in flowing water pumped from their natural environment, and conditions of temperature, salinity and ration are kept at ambient values. Rates of feeding are determined either by particle counts (by Coulter Counter) on water samples taken before and after the water has passed over the animal, or by passing the water through a fluorimeter for the continuous estimation of living particulate plant material. Rates of oxygen consumption are determined by recording the decline in oxygen tension in respirometer vessels which are isolated for brief periods of time from the flowing seawater. These techniques are described in more detail, and their uses in the field illustrated with data on two aspects of the environmental physiology of bivalves. 1: Rates of oxygen consumption by the mussel, Mytilus edulis over two annual cycles, to illustrate seasonal changes in metabolic rate under ambient conditions. 2: Feeding rates by Mytilus and by the cockle, Cardium edule, at various concentrations of suspended particulate matter, including a discussion of particle-size selection.