Influence of sedimentary organic matter sources on the distribution characteristics and preservation status of organic carbon, nitrogen, phosphorus, and biogenic silica in the Daya Bay, northern South China Sea

Solomon Felix Dan; Shengyong Li; Bin Yang; Dongyang Cui; Zhiming Ning; Haifang Huang; Jiaodi Zhou; Jian Yang

doi:10.1016/j.scitotenv.2021.146899

Influence of sedimentary organic matter sources on the distribution characteristics and preservation status of organic carbon, nitrogen, phosphorus, and biogenic silica in the Daya Bay, northern South China Sea

Sci Total Environ. 2021 Aug 20:783:146899. doi: 10.1016/j.scitotenv.2021.146899. Epub 2021 Apr 5.

Authors

Solomon Felix Dan¹, Shengyong Li², Bin Yang³, Dongyang Cui⁴, Zhiming Ning⁵, Haifang Huang¹, Jiaodi Zhou¹, Jian Yang⁶

Affiliations

¹ Guangxi Key Laboratory of Marine Disaster in the Beibu Gulf, Beibu Gulf University, Qinzhou 535011, China.
² South China Sea Environmental Monitoring Center, State Oceanic Administration, Guangzhou 510300, China.
³ Guangxi Key Laboratory of Marine Disaster in the Beibu Gulf, Beibu Gulf University, Qinzhou 535011, China. Electronic address: binyang@bbgu.edu.cn.
⁴ Key Laboratory of Urban Land Resources Monitoring and Simulation, Ministry of Natural Resources, Shenzhen 518000, China.
⁵ Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China.
⁶ Research Center for Coastal Environment Engineering Technology of Shandong Province, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China.

PMID: 33865127
DOI: 10.1016/j.scitotenv.2021.146899

Abstract

Surface sediment samples were collected from Daya Bay in October 2018, and analyzed for total organic carbon (OC), total nitrogen (TN) and their stable isotopes (δ¹³C and δ¹⁵N), total phosphorus (TP), biogenic silica (BSi), sediment textures and specific surface area (SSA). The primary objective was to evaluate the influence of mariculture/aquaculture on the distribution characteristics of organic matter (OM), and preservation status of OC, TN, TP, and BSi in sediments. The average δ¹³C and δ¹⁵N values, and OC/TN ratios were -21.27‰, 6.74‰, and 8.90, respectively. Monte Carlo simulation results revealed that mariculture/aquaculture biodeposits accounted for >40% of the buried OM at sites where the breeding rafts and cages are located, whereas marine OM increased gradually to the open sea. Terrestrial OM was generally low accounting for 17% by average. The contents and distribution characteristics of biogenic elements were more influenced by mariculture/aquaculture and primary productivity than sediment textures. Lower OC/SSA (0.3-1.2 mg OC/m²), TN/SSA (~0.05-0.18 mg TN/m²), and TP/SSA (0.02-0.04 mg TP/m²) loadings indicated that increased sequestration of labile OM in a coastal bay could contribute to significant degradation of recalcitrant OM in sediments with significant loss of P relative to OC. Nitrogen contamination in surface sediments was due to increased injection of aquaculture biodeposits, and may pose a detrimental effect on the ecological sustainability of the bay. Higher BSi/SSA loadings (0.9-1.7 mg BSi/m²) revealed that BSi was more preserved, and that BSi-based proxy could be used for paleo-productivity studies. However, such preservation may induce adverse dissolved silicate limitation in a bay perturbed by eutrophication. Fine-grained sediments (clay and silt) accounted for >77% of the sediment texture types with higher SSA, and while controlling the contents of biogenic elements under given depositional conditions were not the main determining factors of OC, TN, TP, and BSi preservation.

Keywords: Biogenic elements; Daya Bay; Influencing factors; Preservation status; Sedimentary organic matter.