COMPARATIVE ANALYSIS OF MODERN AND FOSSIL CORAL COMMUNITY STRUCTURES AT LITTLE CAYMAN, CENTRAL CARIBBEAN

Little Cayman’s pristine living coral reef systems have attracted marine scientists and tourists from all around the world. However, the value of Little Cayman’s fossilized coral platforms have been systemically overlooked. The Ironshore Formation, a poorly consolidated reef limestone unit along the shorelines of all three Cayman Islands, has been dated back to Marine Isotope Stage 5e (125,000 years B.P.). This time slice is known for having temperatures 1° C to 2° C and sea levels 4-6 meters higher than present day. Thus, the Ironshore Formation can be utilized as an analog to understand how modern Caribbean corals will adapt to rising sea surface temperatures and sea levels in the near future.

We aim to understand Caribbean corals adaptation by conducting two different studies: 1) Comparing the extension rates of an in-situ fossil Montastraea sp. in the Ironshore Formation and an X-radiograph of a modern Montastraea sp. from the fore reef 2) Comparing fossil and modern coral assemblages within 20 x 10 meter belt transects. The first study displays that fossil Montastraea sp. had higher extension rates (on average 7.7 mm/year) than the modern Montastraea sp. (on average 5.79 mm/year). Our second study exhibits evidence that Montastraea nancyi, an extinct organ pipe Montastraea species, Montastraea annularis, and Acropora cervicornis dominated the fossil coral transects, while the modern coral transects are dominated by Montastraea annularis and Diploria sp. Utilizing fossil corals from the Pleistocene growing under climactic boundary conditions will help to better understand how modern coral reef assemblages may respond to predicted global warming scenarios.