The sources and composition of organic matter in sediments of the Jiaozhou Bay: implications for environmental changes o
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The sources and composition of organic matter in sediments of the Jiaozhou Bay: implications for environmental changes on a centennial time scale KANG Xuming1, 2, SONG Jinming1, 2, 3*, YUAN Huamao1, 2, 3, LI Xuegang1, 2, 3, LI Ning1, 2, 3, DUAN Liqin1, 2, 3 1 Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of
Sciences, Qingdao 266071, China 2 Laboratory for Marine Ecology and Environmental Sciences, Qingdao National Laboratory for Marine Science and
Technology, Qingdao 266237, China 3 University of Chinese Academy of Sciences, Beijing 100049, China
Received 12 January 2017; accepted 8 February 2017 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2017
Abstract
The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon (TOC), total nitrogen (TN), the stable carbon (δ13C) and nitrogen (δ15N) isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale. Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920s in the inner bay and the 2000s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input. Considering TOC/TN ratio, δ13C and δ15N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member (terrigenous and marine) mixing model using δ13C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities (e.g., extensive use of fertilizers, and discharge of sewage) and climate changes (e.g., rainfall). Key words: organic matter, sources, anthropogenic activities, environmental changes, sediments, Jiaozhou Bay Citation: Kang Xuming, Song Jinming, Yuan Huamao, Li Xuegang, Li Ning, Duan Liqin. 2017. The sources and composition of organic matter in sediments of the Jiaozhou Bay: implications for environmental changes on a centennial time scale. Acta Oceanologica Sinica, 36(11): 68–78, doi: 10.1007/s13131-017-1076-1
1 Introduction The burial of organic matter in coastal and shelf sediments plays a key role in regulating the global carbon cycle, and up to 80% of organic matter is buried in shallow marine ecosystems (Berner, 1982). The coastal margins, especially those under significant river influence, are characterized by complex biogeochemical patterns of sedimentary organic matter due to significant land-sea exchange of materials along with anthropogenic impact (Gao et al., 2012; Wang et al., 2013). Knowledge
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