ROLE OF SYMBIOTIC ALGAE (ZOOXANTHELLAE) IN CORAL CALCIFICATION

1. In branches of the coral Acropora cervicornis, the abundance of symbiotic algae (zooxanthellae) increases from tip to base, while active calcification decreases. Light enhancement of calcification rates is, paradoxically, greatest in the algae-poor tips of branches.2. Calcium-45 experiments on intact and isolated tips of the coral branches suggest that light enhancement of calcification in the algae-poor tip results from photosynthesis by zooxanthellae farther down in the branch.3. Carbon-14 experiments indicate that organic products of algal photosynthesis are translocated to the coral tip. The main carbon-14 labeled products in the tip are lipids, glycerol and glucose.4. Our data are consistent with the hypothesis that translocated algal products enhance coral calcification rates.