HOW VULNERABLE IS ACROPORA CERVICORNIS CORAL TO CLIMATE CHANGE? LESSONS FROM THE MID-HOLOCENE

Acropora cervicornis is an important component of modern coral reef frameworks in the wider Caribbean, but populations of this branching coral suffered a dramatic decline in the last decades of the 20th century. Elevated sea surface temperatures, white-band disease, and storm activity have all been cited as potential causes for this decline. It also has been suggested that A. cervicornis is particularly vulnerable to human activity, with its decline serving as a warning of greater coral reef devastation to come.

An extensive three-dimensional exposure of mid-Holocene A. cervicornis located in the Enriquillo Valley, Dominican Republic, provides a high-resolution and temporally broad window to paleoenvironmental conditions ideal for growth of this species. Data from this outcrop may shed light on the root cause(s) of current A. cervicornis decline. Over 50 radiocarbon and 3 ²³⁴U/²³⁰Th dates from an 11 m vertical exposure of A. cervicornis reveal virtually continual accumulation of this species between ~9.5 to ~7.3 ka with only minor reversals thought to result from individual storm events. This period was marked by increasing regional sea surface temperature to a mid-Holocene thermal maximum, a time warmer than present.

Despite assumed repeated exposure to tropical storms and hurricanes, the A. cervicornis reef suffered no major breaks in growth as a result of storm activity. There is also no indication of A. cervicornis decline as a result of warmer than present conditions. Evidence from stable carbon and oxygen isotope data from A. cervicornis specimens and associated bivalves show potentially large changes in precipitation during reef formation with no resulting change in coral accumulation. Despite evidence of high sedimentation rates, A. cervicornis thrived in potentially turbid water. Taphonomy data show changes in rate of bioerosion or physical breakage of this coral, yet the species did not suffer as a result of change in physical or biological environment.

If looking only at this outcrop, A. cervicornis could be considered a relatively hardy survivor during the Holocene. It is therefore unlikely that projected global warming alone is the cause for A. cervicornis decline.