Twenty-four hour in situ monitoring of oxygen production and respiration of the colonial zoanthid Palythoa

Abstract

The rates of oxygen production and respiration of the colonial zoanthid of the genus Palythoa were measured in situ at a depth of 3.4m (reef-edge) using an automated respirometer. The respirometer recorded changes in oxygen concentration of four samples of Palythoa enclosed in separate perspex chambers concurrently with light intensity (irradiance) readings every 20 seconds for 24 hours. Photosynthetic parameters (Pm((gross)) Rd and Ik) were estimated from photosynthesis-irradiance (PI) curves generated for each of the four samples. Average instantaneous maximum gross photosynthetic (Pm((gross))) and respiration (Rd) rates obtained for Palythoa were 12.50 μmo2lO cm-2h-1 and 4.24 μmolO2cm-2h-1, giving a Pm((gross))/(-Rd) ratio of 2.92. The net 24 hour production (Pn24) at 3.4m, estimated by integrating the photokinetic parameters over 7 days of light data, was negative, resulting in a daily gross photosynthesis to respiration [Pg24/(-Rd24)] ratio of 0.77, while estimated 24 hour productivity at 1.4 m gave a ratio of 1.13. This suggests that Palythoa would be able to sustain positive production at 1.4 m but not at 3.4 m.