Three stages of injuries regeneration on scleractinian corals

Regeneration of artificial injuries on scleractinian corals of massive colonies Porites lutea and branching Porites cylindrica and algal/coral competition on newly formed substrate are the subject of investigation. It was shown that the injured coral areas recovered at three stages (1) coral tissue recovery with the formation of a border between the regenerating live tissue and dead area, (2) growth and expansion of the live tissue on the substrate, and (3) new polyps development on the healed area. At the first stage of the regeneration, the rate of lesion healing was highest; it varied in respect to injury type and averaged 0.2-0.05 and 0.1-0.02mm day-1 for P. lutea and P. cylindrica, respectively. The regeneration rate mostly depended on morphology of corals and injury type. Coral entombed spores and thalli fragments of algae settled onto partially damaged live tissue and skeleton. At the second stage, the rate of lesion healing sharply decreased and varied from 0.1 to 0.03mm day-1 for P. lutea and from 0.05 to 0.02mm day-1 for P. cylindrica. Position of the injuries within the colony, light intensity, as well as the composition and abundance of algae and animals settled onto the damaged areas had a significant effect on the rate and duration of the recovery process. The algae growing on dead areas of the injuries acted as a physical and in rare cases as a chemical impediment for expansion of live tissue on the available substrate. At the second stage of healing, the live tissue overgrew twenty two algal species settled onto the lesions at winter and spring seasons. At the third stage of the regeneration, the recovery depended on external and internal conditions promoting the growth of coral polyps.