Geochemical Response of Pocillopora Damicornis Coral to Changes in Temperature, Salinity, and Oxygen Isotopic Composition of Modern Seawater.

The ratio of ¹⁸O to ¹⁶O (expressed as δ¹⁸O) in biogenic carbonates has been used as a paleothermometer since the 1940’s. Corals are very sensitive to environmental changes and their δ¹⁸O is widely used for studying recent and past climate variability. It has been shown that coral δ¹⁸O depends not only on temperature, but also on oxygen isotopic composition of water (δ¹⁸O _w), which has an empirical relationship with seawater salinity.

We intend to present geochemical data from Pocillopora Damicornis coral sample that experienced rapid change on its growth environment. The coral specimen was collected from Baja California, La Gaviota Island, Mexico, with an observed annual temperature range of 20-30°C. The specimen was then replanted to the running seawater aquarium on the coast of Caribbean Sea, Puerto Morelos, Mexico in July 2009, and kept there under constant temperature of 28ºC ± 0.5 ºC for 9 months.

Powdered coral samples will be obtained using the New Wave Micromill housed at the Department of Geosciences, MSU. Samples will be milled incrementally across accretionary growth following the organism’s ontogeny. δ¹⁸O will then be measured using Isotopic Ratio Mass Spectrometry. We will present the obtained shift of coral δ¹⁸O as a result of the change in habitat, and compare the results with δ¹⁸O data predicted from temperature and salinity differences between Baja California and Caribbean Sea.