Short-term fate of photosynthetic products in a hermatypic coral

The short-term fate of photosynthetic products within the tissues of the branching coral Stylophora pistillata (Esper) was studied at Eilat, Red Sea. Colonies of S. pistillata were labelled in situ with NaH¹⁴CO₃ for 24 h and were periodically sampled after 4, 24, 48 h and 1 month. Amounts of ¹⁴C products were measured in the upper parts of the branches (up to 2.5 cm below the tips). Branches were divided into different fragments: branch-tips, mid-branches, and bases. All fragments below a branch-tip contain significantly more ¹⁴C products than the tip (the upper 0.5 cm), while no significant differences were recorded between all the other fragments. The rate of decrease in ¹⁴C materials was followed in 11 colonies. No significant loss was recorded in the first 24 h after incubation. After 48 h, a significant reduction was found only in one colony. After one month all experimental colonies showed a significant reduction in ¹⁴C materials. The retention rate in ¹⁴C materials in tips and bases within the same colony is approximately equal. This and the result that no gradual increase of ¹⁴C products in the tissue of the tips is recorded, exclude the possibility of significant translocation of ¹⁴C materials from bases to tips during the first month after incubation. It is suggested that the marked loss of photosynthetic products (up to 80%) is the result of a combination of several processes such as production of mucus, larval release, tissue growth, and metabolic requirements.