THRIVING ACROPORA IN CAICOS – A CLIMATE CHANGE REFUGIA?

Acropora palmata and to a lesser extent Acropora cervicornis are thriving on reefs along the eastern margin of Caicos Platform in the southeast Bahamian archipelago. These occur both on sections of barrier reef just north of Ambergris Cay and northward on patch reefs a few kilometers inboard from the margin where a barrier reef is absent. Until 2008 these reefs were covered by a luxuriant and dense growth of A. palmata which built into the intertidal.

In August 2008, Hurricane Ike crossed these reefs as a Category 4 storm, decimating the reefs. In the seven years since, aggressive recovery has occurred – A. Palmata on the shallower portions and A. cervicornis in the deeper areas.

At a time when healthy Acropora reef growth is a scarcity in the south Florida/Bahamian/Caribbean region and not doing well in other portions of Caicos Platform, the setting of these healthy eastern margin reefs may be instructive as to critical refugia during this time of climate stress. Three features of the setting may be important. First, the area receives waters from the open Atlantic pushed onto the platform by Easterly Trade Winds. Second, these waters are essentially unaffected by local pollution. Third, Caicos Platform is situated downwind from platforms just to the East – Salt Cay and Grand Turk. Brisk easterly Trade Winds blowing across these platforms cause upwelling of cool waters. These upwelled waters drift westwards, bathing the eastern margin of Caicos Platform in cooler waters with characteristics that may be more conducive to coral growth and reefal maintenance than elsewhere.