Distributional variations in marine crenarchaeotal membrane lipids: a new tool for reconstructing ancient sea water temperatures?

It has recently been shown that membrane lipids of marine crenarchaeota, a ubiquitous and abundant component of plankton, occur in relatively high concentrations in recent and ancient sediments. In this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments. We especially focussed on temperature, as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature. Indeed, a significant linear correlation (r2=0.92) is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures. This suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives. In turn, archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments.