Different controls on sedimentary organic carbon in the Bohai Sea: River mouth relocation, turbidity and eutrophication

• Published in: Journal of marine systems Vol. 180; pp. 1 - 8
• Main Authors: Xu, Yunping, Zhou, Shangzhe, Hu, Limin, Wang, Yinghui, Xiao, Wenjie
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2018
• Subjects: Biomarker; Bohai Sea; Eutrophication; Organic carbon; River mouth relocation; Yellow River; Organic carbon; Biomarker; River mouth relocation; Bohai Sea; Yellow River; Eutrophication
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/j.jmarsys.2017.12.004

The extractable lipids and bulk organic geochemical parameters in three sediment cores (M-1, M-3 and M-7) from southern, central and northern Bohai Sea were analyzed in order to reconstruct environmental changes since 1900. The C/N ratio and multiple biomarkers (e.g., C27+C29+C31n-alkanes, C24+C26+C28n-alkanols, branched versus isoprenoid tetraether index) suggest more terrigenous organic carbon (OC) inputs in southern Bohai Sea. The abrupt changes of biomarker indicators in core M-1 are generally synchronous with the Yellow River mouth relocation events (e.g., 1964, 1976 and 1996), suggesting the distance to the river mouth being an important factor for sedimentary OC dispersal in the southern Bohai Sea. However, in cores M-3 and M-7, terrigenous biomarkers (i.e., BIT) show a long-term declining trend, consistent with a continuous reduction of the Yellow River sediment load, whereas marine biomarkers such as cholesterol, brassicasterol and dinosterol dramatically increased post-1980, apparently related to human-induced eutrophication in the Bohai Sea. Our study suggests different controlling factors on sedimentary OC distribution in the southern (high turbidity) and other parts (less turbidity) of the Bohai Sea, which should be considered for interpretation of paleoenvironments and biogeochemical processes in the river dominated margins that are hotspots of the global carbon cycling. •Different controls on OC distributions in southern Bohai Sea and other areas•Rapid response of biomarkers in southern Bohai Sea to Yellow River mouth relocations•No obvious response in central and northern Bohai Sea to Yellow River mouth relocations•Rapid increase of marine biomarkers in central and northern areas caused by eutrophication