A gradient diver for measurement of respiration in individual organisms from the micro- and meiofauna

A gradient diver method suitable for gasometric studies on aquatic organisms of 1.0 g–1.0 mg wet weight is described. The microgasometer consists of an open glass capillary (diver) which encloses the biological object and an air bubble. It floats in an aqueous density gradient with constant pressure above the gradient. In response to changes in the volume of the air bubble, caused by consumption or release of gas by the biological object, the diver migrates either downwards or upwards in the gradient. On the basis of the rate of migration the rate of gas exchanges is calculated. The method is adaptable to a wide range of laboratory conditions and should also be of use in field laboratories.