Correlating pumping behavior and oxygen gradients in the tissue of Dysidea avara and Haliclona xena (Porifera: Demospongiae)

A Clark-type microelectrode was used to measure oxygen gradients near and inside the tissue of live Dysidea avara and Haliclona xena sponges held in a flow chamber. Oxygen measurements were carried out concurrently with measurements of flow rate exiting an osculum by applying the particle tracking velocimetry (PTV) technique. This is a novel manner of combining two methods for correlating pumping behavior and its effect on oxygen levels withina live sponge. The results showed that if the sponge was pumping, the oxygen concentration in the tissue was only marginally lower than that of the ambient water. However, if the sponge stopped pumping, the oxygen profiles were typically of the diffusive type, with a clear boundary layer. The combination of these two techniques allows us to calculate fine-scale oxygen fluxes in-and-out of active sponges, even at low pumping rates. These combined methods may have applications to ascertain the physiological state of sponges held in ex situ aquaculture tanks.