The study proposed herein will explore the evolution of the symbiotic association between endosymbiotic algae (zooxanthellae) and Mesozoic scleractinian corals. The aragonitic corals which will form the basis of this study include the oldest known sleractinians still composed of aragonite. The presence of the symbiotic association can be documented in diagenetically unalltered fossil corals by examining the statistical relationships between stable carbon and oxygen isotopes. We will systematically establish the geochemical, mineralogical, and petrographic integrity of our samples by (i) staining, (ii) x-ray, (iii) electron microscope analysis, (iv) catholuminescent studies, (v) scanning electron microscopy, and (vi) optical petrographic methods. Stable isotopic analysis will be performed only on diagenetically unaltered samples. The results will be compared to other, often controversial methods of establishing the presence of zooxanthellae and is expected to provide insight into the early evolution of Mesozoic corals.
