Seasonal variations in the rates of calcification and productivity in the coral Acropora formosa on a high-latitude reef

Branches of Acropora formosa colonies from a high-latitude reef (Houtman Abrolhos Islands, Western Australia, 29' S latitude) were incubated with 45Ca and I4C in photosyntheticallysaturating light at ambient water temperatures.Seasonal changes in calcification rate (45Ca and 14C incorporation) and net 14C-productivity were determined.While calcification was depressed by winter temperatures (17.7 'C minimum), it did not cease.Net '4C-productivity was evaluated after fractionation of coral tissues.Carbon incorporation into the storage-structural tlssue fractlon was reduced by winter temperatures and apparently ceased at 17.7 "C.The winter temperature minimum is considered to be a primary determinant and light a secondary determinant for growth and survival of Acropora fomosa in this high-latitude reef.