Bacterial and eukaryotic intact polar lipids point to in situ production as a key source of labile organic matter in hadal surface sediment of the Atacama Trench

Abstract. Elevated organic matter (OM) concentrations are found in hadal surface sediments relative to the surrounding abyssal seabed. However, origin of this biological material remains elusive. Here, we report on composition and distribution cellular membrane intact polar lipids (IPLs) extracted from around deepest points Atacama Trench adjacent bathyal margin assess constrain sources labile OM Multiscale bootstrap resampling IPLs' structural diversity abundance indicates distinct lipid signatures that more closely related those than previously reported for upper ocean water column region. Whereas overall number unique IPL structures contributes a small fraction total pool, also high contribution phospholipids with mono- di-unsaturated fatty acids not associated photoautotrophic resemble traits physiological adaptation pressure low temperature. Our results indicate IPLs predominantly derive situ microbial production biomass, whereas export most component pool euphotic zone overlying oxygen minimum is neglectable. While other such as downslope and/or lateral transport cannot be ruled out remain studied, they likely less important view lability ester-bond IPLs. contribute understanding mechanisms control delivery extreme deep-sea ecosystem. Furthermore, provide insights into some potential community temperature through remodeling.