A salinity-related occurrence of a novel alkenone and alkenoate in Late Pleistocene sediments from the Japan Sea

The novel alkenoate, ethyl tetratriacontadienoate (C34:2EE), has been found in late Quaternary sediments of the Japan Sea by using gas chromatography-mass spectrometry (GC-MS). It accompanied hexatriacontadien-3-one (C36:2EK) previously found in Black Sea sediments. A linear relationship between C36:2EK and C34:2EE concentrations points to both compounds being derived from the same source, most likely a specific haptophyte. The relative abundance of C34:2EE in total alkenones and alkenoates was significantly higher during the Last Glacial Maximum when the δ18O in planktonic foraminifera was anomalously light, strongly suggesting that C34:2EE is associated with low salinity environments. As samples with abundant C34:2EE also possessed anomalously high U37K′ values, low salinity may have an ecological or physiological influence on both the unsaturation and carbon chain length of alkenones and alkenoates.