Climate controls on coral growth in the Caribbean

Thesis (Ph. D.)--Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 77-85).Accurate predictions of Caribbean coral reef responses to global climate change are currently limited by a lack of knowledge of the dominant environmental controls on coral growth. Corals exhibit significant responses to environmental variability occurring on multi-annual to decadal timescales, which are significantly longer than the duration of typical laboratory and field-based experiments. Skeletal growth records, which provide annually-resolved histories spanning several centuries, enable links to be established between coral growth and both long term trends and low-frequency oscillations in environmental conditions. We used 3-D CT scan and imaging techniques to quantify the growth of 3 massive corals (Siderastrea siderea) from the US Virgin Islands (USVI) over the period 1950-2009 and compared these growth rates to other records collected from the USVI, Puerto Rico, the Yucatan, Belize and the Bahamas. While coral growth rates were inversely correlated to sea surface temperature (SST) in the Western Caribbean basin (Yucatan, Belize, Bahamas), we found no significant relationship between SST and coral growth in the Eastern basin (USVI, Puerto Rico). Instead, we found a significant inverse relationship between coral growth in the Western Caribbean and changes in the Atlantic Multidecadal Oscillation and a significant positive relationship between coral growth in the Eastern Caribbean Region and shifts in the Pacific Decadal Oscillation. Using data from the Simple Ocean Data Assimilation (SODA) we compared the wind field anomalies during periods of positive coral growth in both regions with the wind field anomalies during phases of these climactic modes that are conducive to coral growth. We find that both the AMO and the PDO play a significant role in shifting the mean wind patters in these Caribbean regions, with the PDO primarily affecting wind patters in the Eastern Basin and the AMO affecting wind patterns in the Western basin. We suggest that the altered wind patterns associated with these modes may induce upwelling favorable conditions in their respective regions of influence, increasing the availability of nutrients for coral growth.by Sara A. Bosshart.Ph.D