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Alkenones are highly resistant organic compounds (ketones) produced by phytoplankton of the class Prymnesiophyceae. Specifically, coccolithophoroid Emiliania huxleyi respond to changes in water temperature by altering the production of long-chain unsaturated alkenones in the structure of their cell. It has been established experimentally that the temperature of the ambient water in which the organisms form their cell can be estimated from measuring the ratio of their unsaturated alkenones (C37-C39) that are preserved in marine sediments. The Unsaturation Index of “di” versus “tri” unsaturated C37 alkenone is calculated according to the following relationship:

UK′37=[C37:2]/[C37:2+ C37:3]

The Unsaturation Index can then be used to estimate the water temperature according to the following experimental relationship:

T (οC) = (UK′37 - 0.039) / 0.034


Bradley, S R. (1999) Paleoclimatology: Reconstructing Climates of the Quaternary. Second edition. Academic Press

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