Spatio-Temporal Reconstruction of insular and regional climatic oscillations in the E. Caribbean

FINAL REPORT Spatio-Temporal Reconstruction of insular and regional climatic oscillations in the E. Caribbean using fluorescent coral banding J. Morell, J. Corredor and A. Cabrera, Department of Marine Sciences U. of Puerto Rico, Mayaguez INTRODUCTION Credible evidence of climate change has slowly but unequivocally arisen from the observation and or reconstruction of current and past biological, chemical and physical processes. This evidence has prompted the scientific community to search for information regarding processes pertinent to the prediction of future climate changes (i.e. estimation of biochemical processes with inherent importance on global change). Furthermore, the community has recognized the need to reconstruct past climate oscillations as a mean to enhance our understanding of the processes modulating them. These needs indicate the urgency for reconstructing climate indicators, such as precipitation, across various time scales. Water-soluble humic acids, arising from the degradation of plant material in soil, are readily transported through river runoff to the coastal ocean. Given their fluorescent nature (Zepp and Schlotzhauser, 1981), dissolved humic materials (HM) have been used extensively as river plume tracers and characteristic fluorescent signatures can in fact be used to discriminate different water masses (De Zouza Sierra et al., 1994). Reef-building corals, long-lived organisms that constantly deposit calcium carbonate skeletons, have been analyzed by numerous researchers with the purpose of documenting recent environmental changes. The fluorescent banding along the growth axes of these organisms has been linked to their exposure to insular and continental runoff (Susic et al. 1991). Fluorescent fulvic and humic acids of terrestrial origin are argued to be sequestered in discreet bands in the skeletal material of massive corals (Isdale, 1984; Boto, and Isdale, 1985) and may thus provide a paleo-climatic record of terrestrial runoff. Freshwater flow to the coral reef might thus be reconstructed from fluorescent banding in corals subject to terrestrial runoff sources. Such reconstructions have been performed for the Florida Everglades as recorded in corals of Florida Bay (Smith III et al., 1989) and the Australian Great Barrier Reef (Susic and Isdale, 1989). More recent studies (Hendy et al. 2003) used yellow luminescent lines seen in multicentury Porites cores obtained from eight different locations on the central Great Barrier Reef, to developed "a 373-year chronology providing a good proxy for both nearby river runoff and Queensland summer rainfall”. The influence of fresh waters from the Orinoco and Amazon Rivers is apparent in the eastern Caribbean region extending as far north as the greater Antilles and as far west as 75o W in the central Caribbean Sea (Froelich et.al. 1978; Muller Karger et al., 1989;