COMPARATIVE GROWTH RATES OF THE EXTINCT CORAL MONTASTRAEA NANCYI: A DOMINANT FRAMEWORK BUILDER IN THE PLEISTOCENE (MIS 5e) REEFS OF CURAÇAO, NETHERLANDS ANTILLES

The extinct organ-pipe coral Montastraea nancyi Pandolfi was a major framework building coral in reefs of the Pleistocene interglacial highstand (MIS 5e, ~125 kya) in Curaçao as well as many other islands in the Caribbean. In Curaçao we sampled well-preserved columns of this species from two exposures on the windward side of the island and two exposures on the leeward side including both seaward and backreef settings. Columns were slabbed and x-rayed to reveal well-preserved, regularly spaced density bands marking annual growth increments. Measurement of these growth increments provided the first growth rate data for this species from Curaçao, which can be compared to Pleistocene reefs elsewhere in the Caribbean. The mean growth rate (11.9 mm, annual linear extension) for both windward localities was significantly greater than mean growth rate for both leeward sites (9.1 mm). The two windward sites did not differ significantly, nor did the two leeward sites, indicating that seaward vs. backreef settings do not differ. The growth rates in Curaçao fall within the range (8.6 – 16.5 mm/yr, mean 12.6) reported for M. nancyi by Holcomb et al. (2004) in Barbados, confirming its ability to achieve high extension rates. Colony sizes for M. nancyi in Curaçao are truly spectacular, up to 6 m high on both windward and leeward coasts, extending the full height of the lowest reef terrace formed during the 5e highstand. Considering that this highstand spanned approximately 13 kyr, it is remarkable that the entire reef terrace may have built up in less than 1000 yr. Co-occurring with M. nancyi in the Curaçao fossil reefs are colonies of M. annularis, M. faveolata, and an unnamed columnar Montastraea morphotype similar to that found in Barbados. Well preserved density banding in samples of these taxa of the Montastraea species complex will provide further comparisons with the dominant M. nancyi in Curaçao and with other Pleistocene Caribbean reefs as well as with extant Montastraea species.