Annual black bands in skeletons of reef corals (Scleractinia)

Abstract

Dark lscolorahons appear concentrated as black bands in the fresh skeletons of massive reef corals (Pontes), often restncted to the upper 7 5 cm of the coral skeleton The pattern of these bands runs parallel to that of the skeletal density bands the black bands occumng m the low density part of the p a r s of hgh/low denslty bands The black bands do not result from the inclus~on of foreign rnatenal by the coral but are characterized by high concentrahons of a dark fungus We suggest that the dark banding pattern correlates to an annual vanahon in the organic content of the skeleton Highest concentrahons of the dark myceha are reached where the frulting bodles are formed The frulting b o l e s occur in groups and open through small dead areas on the hvlng coral surface into the s u r r o u n h g seawater We found Infected colonles in 6 massive Pontes species but only at 2 locations Salayer and Take Bone Rate (Southwest Sulawesi) In the eastern Indonesian Archipelago At these locahons up to 33 % of the colonles showed the fungus discolorahons There appears to be no obvious effect on the strength of the coral skeletons the m a n ecological effect of the fungus IS that the formation of frulhng bodies interferes w t h the mtegnty mamtenance and growth of the llvlng coral surface This 1s the first example of a fungus belng involved in spahal compehtlon on coral reefs