Alteration processes of alkenones and related lipids in water columns and sediments

Abstract

[1] Alkenones produced by the haptophyte algae are currently being used as indices of sea surface temperature in recent and past ocean environments, but limited information is available concerning the impact of biotic and abiotic processes on the integrity of these long chain lipids. This synthesis provides selected background information on major alteration processes that must be considered before such indices can be used with confidence. A number of processes in the water column and surface sediments have the potential to impact the structural integrity of alkenones and compromise their ability as temperature markers. Processes discussed include the alteration of alkenone structure during early diagenesis, direct biotic and abiotic impacts, and the effect of digestive processes by grazers. Current literature suggests that despite substantial changes in concentration from biological processing, the temperature signal is preserved. For each of these processes, information on the integrity of the alkenone isotopic signature is also needed and limited information available is reviewed. In addition to the alkenones, related lipids including the long chain alkadienes and akyl alkenoates that might serve as ancillary markers are discussed.