Fig. 3.

Effects of pulsation and ambient oxygen concentration on the rates of gross photosynthesis and respiration in H. fuscescens (n = 3). (A) Average rates (±SD) of gross photosynthesis and dark respiration under conditions of ambient (filled bars) and high (open bars) oxygen concentrations in pulsating and resting states. (B) Average rates (±SD) of gross photosynthesis normalized by the colony’s surface area exposed to downwelling light (see text). Note that the artificially elevated oxygen concentration in the chamber water practically eliminated the effect of pulsation on normalized photosynthesis (Mann–Whitney, P = 0.51, n = 3 colonies, testing for a difference in gross photosynthesis between pulsation under high oxygen and rest under normal oxygen). In both A and B, the difference in gross photosynthesis under pulsating state between ambient and high oxygen conditions was significant (Mann–Whitney, P < 0.05, n = 3).