CORAL REEF ACCRETION AND CORAL COMMUNITY SUCCESSION PATTERNS IN LATE PLEISTOCENE CORAL REEFS EXPOSED ON CURACAO

Quaternary fossil coral reef assemblages preserve a very different picture of ecological stability or succession than the empirical work conducted on modern coral reefs over limited temporal scales. Coral species abundance patterns on modern reefs tend to be disturbance driven; community composition varies temporally and spatially. In contrast, Pleistocene fossil coral reefs show resounding consistencies in within habitat community structure over much larger spatial (10’s of km) and temporal (10⁴-10⁵ years) scales. We have examined coral community composition through the entire thickness of a single reef-building interval preserved in a marine terrace exposed on the island of Curaçao. We can thus elucidate patterns of succession over a time scale intermediate between the decadal-scale studies of modern reefs and the 10⁴-10⁵ year intervals encompassed by paleocommunity studies of Pleistocene assemblages.

We conducted systematic surveys of the fossil coral reefs exposed in the Hato Unit of the Lower Terrace Limestone. At four sites on the leeward coast of Curacao, 25 m-long transects were established at vertical intervals of 0.5 m from near the disconformity that marks the base of the unit, to the top of the terrace. We have integrated our paleoecological data with the most recent work on reef accretion rates, the timing and rate of sea level rise during the onset of the Last Interglacial, and radiometric ages obtained for distinct intervals within the Hato Unit to evaluate whether, and in what manner, succession of reef building corals occurred in a leeward reef crest environment during the last interglacial as accommodation space was created by a rise in sea level. Results reveal that intra-habitat changes among coral assemblages are greater than those occurring over the ~ 4000 years represented by the assemblage; suggesting that the Acropora palmata-dominated communities preserved on Curaçao “caught up” with a rising sea level with no significant changes in coral community composition.