Effect of Water Motion on Coral Photosynthesis and Calcification

Water motion effects on metabolism of a common reef-building coral, Acropora formosa Dana, were studied utilizing laboratory incubations. Net photosynthesis and respiration were significantly reduced (≈ 25% lower) in unstirred conditions compared with stirred conditions. Dark calcification was reduced by ≈60% in unstirred conditions. Light-enhanced calcification appeared to be reduced by ≈ 25% in unstirred conditions; however, this effect was not statistically significant. A possible diffusion limitation on exchange of dissolved gases was indicated by a lack of stirring effect on net photosynthesis when photosynthesis was near the light compensation point. A boundary layer of unstirred water adjacent to the surface of the animal could account for the observed metabolic responses to stirring regimes. Comparisons of water motion measured in the field with rates of water motion in the laboratory incubations indicate that coral growth and reef development are influenced by the metabolic responses of corals to water motion over and around coral reefs.

Keywords: