Over the past 20 years, the composition of Caribbean coral reef communities has changed drastically. The ecology of modern reefs, however, has only been studied since the late 1950s (with the advent of SCUBA). Thus, only a thirty-year data set on changes in coral community composition exists with which to compare the current faunal transition. This limited temporal scale is a source of frustration to marine ecologists, and the need for longer-term data has been realized as essential for determining whether the current transition is part of a long-term cycle or itself is an unprecedented phenomenon in geologic history.
On Telephone Pole reef, San Salvador, Bahamas, a transition from Acropora dominance to that of Porites has been observed in recent years. Acropora specimens found at this locality display high levels of taphonomic alteration, which may serve as a marker for prior transitions of this type in other reefs. It is not known, however, if a transition of this nature occurred in the past.
The fossil record provides precisely the database required for answering this question. A detailed examination of the fossil reef at Cockburn Town, San Salvador, Bahamas, has been performed in order to evaluate the presence of community transitions analogous to those occurring today preserved in the fossil record. Specimens of fossil corals were collected from six vertical transects through the fossil reef. These samples have been identified and a variety of taphonomic data, such as percent cover by encrusting organisms, has been gathered. These data indicate that different styles of taphonomic preservation characterize specific horizons in the fossil reef. However, evidence does not exist for a Pleistocene precedent for the transition currently observed offshore.
Thomas Rothfus, ’99 Arlington Heights, IL
Sponsor: Benjamin Greenstein