THE EFFECTS OF HEBP, AN INHIBITOR OF MINERAL DEPOSITION, UPON PHOTOSYNTHESIS AND CALCIFICATION IN THE SCLERACTINIAN CORAL, STYLOPHORA-PISTILLATA

In reef-building corals, photosynthesis by endosymbiotic algae enhance s calcification; this rate of calcification is reduced by shading and by inhibitors of photosynthesis. Calcification can also be reduced by compounds which prevent mineral deposition rather than affecting the m etabolic processes. The effects of such compounds upon the photosynthe sis of endosymbiotic algae has not yet been tested. In the present stu dy, photosynthesis and calcification in branches of Stylophora pistill ata were measured in the presence of 1-hydroxyethylidene-1, 1-bisphosp honic acid (HEBP), a specific inhibitor of mineral deposition. HEBP st rongly inhibited calcification of the coral with 36% inhibition at 0.0 1 mM, 90% at 0.1 mM and 99% at more than 0.5 mM. However, the level of photosynthetically fixed organic carbon was almost constant in concen trations of HEBP up to 2 mM. Rate of photosynthesis was not affected w hen calcification was inhibited using 0.5 mM HEBP. It is suggested tha t coral calcification does not enhance algal photosynthesis.