Regeneration of artificial injuries on scleractinian corals and coral/algal competition for newly formed substrate

Porites cylindrica and Porites lutea fragments of colonies were inflicted with five different injury types: chisel, file, Water Pik, osmotic and cement injuries. The fragments were maintained in outdoor aquaria for a period of 240 days under light intensities varying from 2-5% to 70-90% of incident surface photosynthetic active radiation (PAR₀). During the exposure, changes in weight of the fragments, the rates of regeneration of the injuries, abundance of algae and animals settled onto injured areas were monitored. The regeneration rate of the injuries depended on interspecific differences in corals, injury types, number and composition of algae and animals settled onto the lesions, and light and temperature conditions. Competitive interactions between polyps and settlers occurred after colonizers settled onto the damaged surface or the live tissue. It is noteworthy that recovered coral tissue generally overgrew about 100 algal species with or without inhibition of coral growth by algae. In the summer period, the cyanobacterium Lyngbya majuscula covered some lesions (osmotic and cement) by 100%, thus reducing dramatically the regeneration rate of the inflicted injuries and also caused coral bleaching when in direct contact.