Annual Banding in Corals: Climatological Implications
Geological Society of America Annual Meeting, Denver, CO
Coral Reefs, Bermuda
At selected stations in Bermuda, chronologies of annual band widths from coral skeletons were obtained up to 73 years in length. Correlation between individual growth patterns was present. By combining band width patterns from all individuals from a single area into master or summary chronologies, common variability was enhanced and random individual variation reduced. Masters were compared with similar time series of relevant (and available) environmental variables and, after smoothing to emphasize long term trends, negative correlation between band widths and temperature was found. This is probably a positive response to food since in Bermuda, surface water nutrient supply is directly related to the extent of winter breakup of the summer warm water thermocline and mixing with underlying cold (180 C), nutrient rich water. Thus over the long term, colder annual temperatures mean greater nutrient availability and apparently higher coral growth. Superimposed on this major effect, a smaller but positive response of coral growth directly to temperature is apparent. These results have climatological value in extrapolation of known relationships for analysis of Holocene climate shifts. In additional paleoclimate analysis from a study of recent and fossil coral banding in Barbados, our preliminary results indicate that weather conditions sensed by the growth of M. annularis today are the same as during previous high sea stands at approx. 82,000 and 125,000 yrs. B.P. Compared to the recent, banding in corals from the 105,000 yrs. B.P. stand shows a 50% decrease in variability and a 12% decrease in mean growth rate, possibly indicating corresponding differences in the climate of that period.
Dodge, Richard E. and Vaisnys, J. Rimas, "Annual Banding in Corals: Climatological Implications" (1976). Oceanography Faculty Proceedings, Presentations, Speeches, Lectures. 51.