Effect of seawater turbulence on formation of coral primary polyp skeletons

Though seawater movement is among the important factors that maintain healthy conditions on coral reefs, little is known about the effects of seawater turbulence on the growth of coral primary polyps. We cultured aposymbiotic primary polyps of Acropora digitifera with and without seawater turbulence and investigated how seawater turbulence affected the physical characteristics of the polyp skeleton. Results showed that seawater turbulence increased the amount of skeletal carbonate and directly influenced calcification of coral hosts. Three-dimensional morphological measurements by X-ray micro-computed tomography revealed that seawater turbulence increased the thickness of the skeletal branches of polyps. Greater thickness of the skeletal branches and increased horizontal growth may significantly enhance survival of primary coral polyps during early life stages before the establishment of algal symbioses.