Abiotic degradation of free phytol in the water column: A new pathway for the production of acyclic isoprenoids in the marine environment

The acyclic isoprenoid aldehydes—E and Z 3,7,11,15-tetramethylhexadec-2-enal (phytenals) and 2,6,10,14-tetramethylpentadecanal (pristanal), themselves previously shown to be products of the photosensitized oxidation of phytol in seawater—were stirred in the dark in synthetic seawater. Examination of the products showed that the phytenals were partially transformed to the corresponding unsaturated acids and the ketone 6,10,14-trimethylpentadecan-2-one, whereas pristanal was converted solely to the corresponding acid. A new pathway for abiotic production of acyclic isoprenoids in the water column is postulated. This theory is supported by the identification of several of the compounds in particulate matter and sediments from the Gulf of Lyon (Mediterranean Sea).