Bacteriohopanepolyols signature in sediments of the East China Sea and its indications for hypoxia and organic matter sources

Abstract The bacterial biomarker group of bacteriohopanepolyols (BHPs) has shown a significant potential to track terrestrial inputs and to respond to environmental changes. A total of 12 BHPs were detected in surface sediments of the East China Sea (ECS), with the contents of 3.79–361 μg/g TOC. The spatial distribution patterns and correlation analyses of bacteriohopanetetrol (BHT) and soil marker BHPs in sediments of the ECS indicate that they were mainly derived from marine autochthonous and terrestrial sources, respectively. The Rsoil index presented an “offshore decrease” trend, with the contribution of terrestrial organic matter (OM) decreasing from 63% in the coastal waters to 0.81% in the outer seas. This suggests that sedimentary OM in the coastal waters is mainly from terrestrial sources while that in the outer seas is dominantly from marine sources. The spatial distribution patterns and correlation analyses suggest mainly marine sources for the BHT-isomer in the ECS. Thus, although the co-eluted BHT-x and BHT-34R cannot be distinguished, the BHT-isomer in the ECS may be mainly BHT-x derived from marine bacteria rather than BHT-34R derived from terrestrial bacteria. Zones with high value of BHT-isomer ratios in sediments were consistent with the seasonal hypoxic zones in the ECS; furthermore, these ratios were negatively correlated with dissolved oxygen concentrations in the bottom waters. These results indicate that hypoxic environments are beneficial to BHT-isomer production, further confirming that the BHT-isomer can be a biomarker for marine hypoxia. Aminotetrol and aminopentol were closely related to the aerobic methane-oxidation gene pmoA and dissolved CH4, suggesting their potential as markers for aerobic methane oxidation.