SCIENCE ADVANCES | RESEARCH ARTICLE MARINE ECOLOGY Hypoxia causes preservation of labile organic matter and changes seafloor microbial community composition (Black Sea) Gerdhard L Jessen,1,2* Anna Lichtschlag,1,2† Alban Ramette,1,2‡ Silvio Pantoja,3 Pamela E Rossel,1,2,4 Carsten J Schubert,5 Ulrich Struck,6 Antje Boetius1,2* 2017 © The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC) INTRODUCTION Marine sediments preserve only