SEASONAL-VARIATIONS IN THE RATES OF CALCIFICATION AND PRODUCTIVITY IN THE CORAL ACROPORA-FORMOSA ON A HIGH-LATITUDE REEF

Branches of A. formosa colonies from a high-latitude reef (Houtman Abrolhos Islands, Western Australia, 29.degree. S latitude) were incubated with 45C and 14C in photosynthetically-saturating light at ambient water temperatures. Seasonal changes in calcification rate (45C and 14C incorporation) and net 14C-productivity were determined. Although calcification was depressed by winter temperatures (17.7.degree. C minimum), it did not cease. Net 14C-productivity was evaluated after fractionation of coral tissues. C incorporation into the storage-structural tissue fraction was reduced by winter temperatures and apparently ceased at 17.7.degree. C. The winter temperature minimum is considered to be a primary determinant and light a secondary determinant for growth and survival of A. formosa in this high-latitude reef.