Hydrogen Isotope Fingerprinting of Lipid Biomarkers in the Chinese Marginal Seas

Abstract The hydrogen isotope ratio (δ 2 H) of lipid biomarkers from phytoplankton and terrestrial plants were measured in surface sediments from Chinese marginal seas (CMS), in order to evaluate processes affecting their spatial distribution, and by extension, the controls on organic carbon cycling in these dynamic marginal seas. The dinoflagellate sterol dinosterol and the microalgal sterol brassicasterol had low δ 2 H values (<−300%) near the mouth of the Yangtze River. Near the mouth of the Yellow River, dinosterol again had low δ 2 H values but brassicasterol had intermediate (−292 to −281%) δ 2 H values. This discrepancy in the δ 2 H values of two phytoplankton sterols may be explained by the timing of dinoflagellate production relative to that of brassicasterol producers (e.g., diatoms). The δ 2 H values of C 16:0 fatty acid, synthesized by all organisms, had intermediate δ 2 H values (−199 to −178%) near the Yangtze River and lowest δ 2 H C 16:0 values (−216 to −206%) occurred near the old Yellow River delta. The lowest δ 2 H C 28:0 values (<−184%) occurred adjacent to rivers, suggesting that leaf‐wax lipids produced on the loess plateau, which are enriched in 2 H, may contribute less to the nearshore environment than the offshore regions. Higher δ 2 H C 28:0 values offshore may be explained by a larger contribution of leaf wax fatty acids from aerosols relative to river‐borne suspended particles. Lipid biomarker δ 2 H fingerprinting thus provides a new tool for deciphering the controls on organic carbon cycling and accumulation in the dynamic CMS.