The exact function of the alkenones remains under debate although they may be storage lipids.
Coccolithophoroids, for instance Emiliania huxleyi, respond to changes in water temperature by altering the production of long-chain unsaturated alkenones in the structure of their cell. At higher temperatures, more of the di-unsaturated molecules are produced than tri-unsaturated  The molecules are resistant to diagenesis, and can be recovered from sediments up to old.
The ambient water temperature in which the organisms dwelt can be estimated from ratio of their unsaturated alkenones (C37-C39) that are preserved in marine sediments. The modified Unsaturation Index of “di” versus “tri” unsaturated C37 alkenone is calculated according to the following relationship from, which is modified after the original Unsaturation Index from  that included the tetra-unsaturated alkenone:
- 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 [°C] = (UK′37 - 0.039)/0.034
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