R.Z. Poore
C. D. Reich
J. A. Flannery
Christopher R. Maupin
T. M. Quinn
K. L. DeLong
2010
<p><span>Paleoclimatologists have reconstructed century-long records of sea surface temperature (SST) in the Pacific using the Sr/Ca of massive corals, whereas similar reconstructions in the Atlantic have not proceeded at the same pace. Past research in the Florida Keys has focused on </span><i>Montastrea spp.</i><span>, an abundant and fast-growing massive coral, thus a good candidate for climate reconstructions. However, coral records from the Florida Keys are complicated by freshwater flux, which varies the Sr/Ca in seawater, thus confounding the Sr/Ca to SST signal. In this research, we compared the monthly Sr/Ca variations in three massive corals species (</span><i>Montastraea faveolata, Diploria strigosa, and Siderastrea siderea</i><span>) from the same reef in the nearly pristine Dry Tortugas National Park (24.70N, 82.80W) at the southwestern extent of the Florida Keys. This location is ideal for a calibration study as hourly water temperature records are available and the remote reef is far from mainland freshwater influence. These corals experienced the same environmental conditions (water depth, clarity, Sr/Ca of seawater, etc.) but differ in the mean annual growth rates (0.86 ±0.10 (1σ) cm/year </span><i>M. faveolata</i><span>; 0.67 ±0.04 (1σ) cm/year </span><i>D. strigosa</i><span>; 0.44 ±0.04 (1σ) cm/year </span><i>S. siderea</i><span>). The mean Sr/Ca values are not the same but decrease with mean annual growth rates (9.201 ±0.091 (1σ) mmol/mol </span><i>M. faveolata</i><span>; 9.177 ±0.081 (1σ) mmol/mol </span><i>D. strigosa</i><span>; 8.964 ±0.12 (1σ) mmol/mol </span><i>S. siderea</i><span>), thus supporting the “vital effect” or biological differences during calcification between coral species. The amplitude of the seasonal cycle in Sr/Ca varies with the slower growing </span><i>S. siderea</i><span>having the largest mean amplitude and </span><i>D. strigosa</i><span> the smallest (0.340 mmol/mol </span><i>S. siderea</i><span>; 0.284 mmol/mol </span><i>M. faveolata</i><span>; 0.238 mmol/mol </span><i>D. strigosa</i><span>). We confirmed our sampling methods by conducting several intracolony and intercolony coral Sr/Ca replication tests and found a high correlation in all tests (>0.95 </span><i>S. siderea</i><span>; >0.90 </span><i>D. strigosa</i><span>; >0.83 </span><i>M. faveolata; p</i><span> < 0.05). The weighted linear regression of monthly coral Sr/Ca to mean monthly SST revealed that </span><i>S. siderea</i><span>captured the seasonal and interannual variability in SST (</span><i>r</i><span> = -0.97, -0.61 monthly and monthly anomalies, respectively, </span><i>p</i><span> < 0.05). The other corals have reduced correlation with monthly anomalies and do not capture the seasonal variability with the same fidelity as </span><i>S. siderea</i><span>. All three corals were sampled along the thecal wall following the same procedures; however, each coral species has a different skeletal structure, density, and micro-scale growth patterns. We hypothesize the thecal wall of </span><i>S. siderea</i><span> calcifies at a continuous rate along the time-growth axis whereas the wall of </span><i>D. strigosa</i><span> and </span><i>M. faveolata</i><span> reflects a more complex signal. Of the three species, the slow growing </span><i>S. siderea</i><span> provides a robust reconstruction of mean monthly SST for the Dry Tortugas thus suitable for longer centennial-scale reconstructions.</span></p>
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American Geophysical Union
Do three massive coral species from the same reef record the same SST signal? A test from the Dry Tortugas, Florida Keys
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