Skeletal Extension Rates of Cenozoic Caribbean Reef Corals

Abstract

There has been significant biological and environmental change in Caribbean coral reefs during the past 30 million years, including two periods of accelerated turnover of species in the zooxanthellate coral biota that may have been correlated with changes in regional sea-surface productivity during the Early Miocene and the Early Pleistocene. Skeletal extension rates measured on x-radiographs of 11 massive genera of fossil corals collected from Late Oligocene to Pleistocene units from across the Caribbean were analyzed to determine whether average coral growth responded to these regional environmental changes. The observed patterns were evaluated by comparisons with records of Recent coral growth rates taken from published literature. These analyses suggest that there is significant variation in average growth rate among corals living in the Recent Indo-west Pacific, eastern Pacific, and Caribbean, even when broad ranges of taxa and habitats are intermingled. When applied to fossils, a similar analysis suggests that rates of growth do not change overall through time. One exception is during the Late Miocene, when rates of growth were significantly lower than from other fossil units or for Recent colonies from the Caribbean. However, the Late Miocene colonies sampled for this study lived in relatively deep, turbid habitats, so the observed reduced growth rates may have resulted from local low availability of light. Similar facies were not sampled in other stratigraphic intervals, so there is no strong evidence for reduced regional average growth rates for Caribbean corals during the past 30 million years.