Apparent timing of Siderastrea siderea density banding in relation to colony growth and physiology

Undergraduates: Brooke Benson, JP Rippe, Colleen Bove

Faculty Advisor: Karl Castillo
Department: Environmental Studies

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Massive reef-building corals are increasingly used as valuable proxies for environmental records due to semiannual density growth bands deposited within their skeletons. The bands, arising from seasonal patterns in light and temperature, reflect both short-term variability and long-term trends in environmental conditions. Conflicting reports about the apparent timing of semiannual high- and low-density coral growth bands has led to uncertainty about the physiological and environmental factors driving their formation. Consequently, this uncertainty may confound the ability to interpret the source and timing of environmental signals reflected in a coral¿¿¿s growth history. Here, we analyzed 16 cores extracted from Siderastrea siderea colonies on the Florida Reef Tract to investigate how the timing of band deposition may be influenced by several factors that have previously been shown to play a role, including colony extension rate and size, tissue thickness, and gender. Growth records and the timing of density band deposition were obtained from the cores via computed tomography. Tissue thickness was measured at the top of the cores, and gender was determined using histological techniques. Preliminary results suggest that the current understanding of banding timing and the factors influencing it may be insufficient to resolve the observed discrepancies in our S. siderea cores.