Annual growth rates of Montastraea annularis over the last 50+ years were determined for inshore, midshore, and offshore reef areas within the Key Largo Coral Reef Marine Sanctuary, Florida. In this study, 144 massive heads of M. annularis were sampled by coring and their
growth history examined, using X-radiography to facilitate accurate measurement of more than 7,000 individual annual growth increments. Key elements affecting growth and survival of M. annularis in the sanctuary appear to be water depth, turbidity, and temperature. Montastraea
annularis from offshore fore-reef areas grew most slowly, averaging only 6.3 mm of vertical growth per year from 1928 to 1978. Many cores at this location reveal a long history of environmental stress indicated by numerous healed-over “die-off” voids excavated by various boring
organisms, principally boring sponges. Abnormal density layers (stress bands) are common. Montastraea annularis from three reef areas nearest shore revealed a similar record of environmental stress, but grew slightly faster at an average rate of 8.2 mm per year. Stress banding and bioerosion
voids are common in all cores from this area as well. Growth rates of M. annularis were highest in midshore reef areas, averaging 11.2 mm per year at three of five sites. Stress banding was minimal in most cases, as were incidences of massive skeletal damage by bioerosion. Environmental
implications, though circumstantial, are provocative in that the recent decline in coral growth (1953 to 1968) at some midshore and inshore reefs coincides with increased dredge and fill operations in the Florida Keys area. A slight overall resurgence in coral growth on these same reefs (1973
to present) coincides with a ban on these operations.
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