Depth and turbidity affect in situ pumping activity of the Mediterranean sponge Chondrosia reniformis (Nardo, 1847)
Effects of depth and turbidity on the in situ pumping activity of the Mediterranean sponge Chondrosia reniformis (Nardo, 1847) were characterized by measuring osculum diameter, oscular outflow velocity, osculum density per sponge and sponge surface area at different locations around the Bodrum peninsula (Turkey). Outflow velocity was measured using a new method based on video analysis of neutrally buoyant particles moving in the exhalant stream of sponge oscula, which yielded results that were in good comparison to other studies. Using the new method, it was shown that for C. reniformis, oscular outflow had a location-dependent, in most cases positive relationship with oscular size: bigger oscules process more water per cm2 of osculum surface. Turbidity and depth both affected sponge pumping in a negative way, but for the locations tested, the effect of depth was more profound than the effect of turbidity. Depth affected all parameters investigated except sponge size, whereas turbidity only affected specific pumping rates normalized to sponge surface area. Deep water sponges had clearly smaller oscula than shallow water sponges, but partially compensated for this lower pumping potential by showing a higher osculum density. Both increasing turbidity and increasing depth considerably decreased volumetric pumping rates of C. reniformis. These findings have important implications for selecting sites for mariculture of this species.