Preprints
https://doi.org/10.5194/bg-2021-232
https://doi.org/10.5194/bg-2021-232

  03 Sep 2021

03 Sep 2021

Review status: this preprint is currently under review for the journal BG.

Intact polar lipids in the hadal seabed of the Atacama Trench point to lateral sediment transport and in situ production as key sources of labile organic matter

Edgart Flores1,2,3, Sebastian I. Cantarero4, Paula Ruiz-Fernández1,2,3, Nadia Dildar4, Matthias Zabel5, Osvaldo Ulloa2,3, and Julio Sepúlveda3,4 Edgart Flores et al.
  • 1Programa de Postgrado en Oceanografía, Departamento de Oceanografía, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile
  • 2Departamento de Oceanografía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
  • 3Millennium Institute of Oceanography, Universidad de Concepción, Concepción, Chile
  • 4Department of Geological Sciences and Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO 80309, USA
  • 5MARUM – Center for Marine Environmental Sciences & Department of Geosciences, Univ. of Bremen, D-28334, Bremen, Germany

Abstract. Elevated concentrations of organic matter are found in sediments of hadal trenches relative to those found in the abyssal seabed, but the origin of such biological material remains elusive. Here, we report the composition and distribution of cell membrane intact polar lipids (IPLs) in surface sediments around the deepest points of the Atacama Trench and adjacent bathyal depths to assess and constrain the sources of labile organic matter in the hadal seabed. Multiscale bootstrap resampling of IPLs’ structural diversity and abundance indicates distinct lipid signatures in the sediments of the Atacama Trench that are more closely related to those found in bathyal sediments than to those previously reported for the upper ocean water column in the region. While the overall number of unique IPL structures in hadal sediments is limited and they contribute a small fraction of the total IPL pool, they include a high contribution of phospholipids with mono- and di-unsaturated fatty acids that are not associated with photoautotrophic sources. The diversity of labile IPLs in hadal sediments of the Atacama Trench suggests the presence of in situ microbial production and biomass that resembles traits of physiological adaptation to high pressure and low temperature, and/or the transport of labile organic matter from shallower sediment. We argue that the export of the most labile lipid component of the organic matter pool from the euphotic zone and the overlying oxygen minimum zone into the hadal sediments is neglectable. Our results contribute to the understanding of the mechanisms that control the delivery of labile organic matter to this extreme deep-sea ecosystem, whereas they provide insights into some potential physiological adaptation of the in situ microbial community to high pressure and low temperature through lipid remodeling.

Edgart Flores et al.

Status: open (until 18 Oct 2021)

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Edgart Flores et al.

Edgart Flores et al.

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Short summary
In this study, we investigate the chemical diversity and abundance of microbial lipids as markers of organic matter sources in the deepest points of the Atacama Trench sediments, and compare them to similar lipids stocks in shallower surface sediments and in the overlying water column. We evaluate possible organic matter provenance and some potential chemical adaptations of the in situ microbial community to the extreme conditions of high hydrostatic pressure in hadal realm.
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