Kinetics of Dark Oxygen Uptake of Pocillopora damicornis

Abstract

Colonies of Pocillopora damicornis were placed in a sealed aquarium in the dark. Water velocity was altered and measured in 10 different experiments. During each experiment, seawater in the aquarium was supersaturated with oxygen (02 ) and then O2 concentration was measured through time until the concentration in the aquarium decreased to 0.3 mg O2 1-1 . Resulting O2 uptake curves were interpreted as a function of water velocity. Rate of O2 uptake fit a hyperbolic equation (d02 /dt = Vm02 /Ks + O2 ) . Maximum uptake rate (Vm ) varied between 0.12 and 0.27 mg O2 1- 1 min " (mean = 0. 18), and the half-saturation constant (Ks ) varied between 0.86 and 2.52 mg O2 1-1. Both Vm and K, did not vary with water velocity, indicating that in these experiments, water motion had little influence on either diffusive boundary layers near the coral tissue or the metabolic rate of O2 uptake. Even supersaturated concentrations of O2 did not completely saturate the uptake capacity of this enzyme system.