A 50 YEAR RECORD OF δ13C FLUCTUATIONS IN PORITIES LOBATA CORALS FROM MICRONESIA LINKED TO TURBIDITY

As corals grow they incorporate the isotopic ratios of the surrounding seawater into their aragonitic skeletons. These ratios are essential for determining past environmental conditions which in turn increases our understanding of modern climate change. Previous studies have shown that Carbon isotopes in the Atlantic coral species Montastraea annularis are strongly dependent on light intensity and display annularity with ¹³C enriched values during months of increased light intensity (Fairbanks and Dodge, 1979). However, there is little research into carbon isotopic annularity within Porites lobata, an Indo-Pacific coral. Development of a 50-year record of carbon isotopes within Porites lobata cores taken from the Chuuk Atoll In the Federated States of Micronesia allows us to determine whether the isotopes reveal any annularity and whether this annularity corresponds with changes in light intensity. Decreases in light intensity are often related to increased water turbidity and atmospheric cloud clover. An increase in sea surface temperatures within the Indo-Pacific warm pool occurs cyclically and corresponds with increased rain in Micronesia. Increased rain in Micronesia causes more atmospheric cloud cover and more terrestrial runoff, which increases ocean turbidity. This 50-year record tracks recent environmental changes and could reveal periods of higher rain and turbidity and even contribute to tracking of the Indo-Pacific warm pool. This record will develop a higher resolution climate proxy for Micronesia.