BUCK ISLAND REEF – A CITY OF TWO TALES
Core data from Buck Island reef, US Virgin Islands (avg. coral abundance=31%; Acropora palmata=53% of total coral) compare more favorably with survey data prior to the onset of coral disease (1976: avg. cover=52%; A. palmata=53% of live coral) than afterward (1988-93: avg. cover <15%; A. palmata <15% of coral). However, close examination of the cores reveals two gaps in the occurrence of A. palmata within the reef over the past 7,000 years (at ca. 6,000 and 3,000 CalBP). In each case, the absence of this primary Caribbean frame-builder lasted a millennium and corresponded temporally to losses of the species throughout the Caribbean and western Atlantic. These observations illustrate that spatial dominance of a particular coral or zonation pattern in core or outcrop need not reflect temporal persistence. The use of Quaternary reefs as a frame of reference for recent change will require characterizations that extend beyond traditional paleoenvironmental descriptions and utilize detailed chronological measurements capable of resolving change at the scale of the monitoring studies to which they are being compared. Until this is accomplished the usefulness of geologic data in separating natural from anthropogenic change will remain enigmatic.