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Marine Ecology Progress Series

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MEPS 728:1-14 (2024)  -  DOI:

Quantifying sedimentary oxygen consumption contribution to total oxygen depletion in shallow waters via the oxygen isotope approach

Zhi-Hao Zhang1, Zhuo-Yi Zhu1,2,*, Huan-Ting Hu2, Jun Zhou2, Zhong-Zhou Lin3, Cheng-Xu Zhou3

1State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, PR China
2School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, PR China
3College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo 315800, PR China
*Corresponding author:

ABSTRACT: To understand dissolved oxygen depletion in estuaries and coasts, it is essential to distinguish the contributions of diffusion-mediated sedimentary oxygen respiration (SOR) and water column respiration (WCR). For the present study, near-bottom waters were sampled in May, July, and October 2019 in Dinghai Bay, China, to reveal the oxygen depletion mechanism in shallow nearshore waters (3-20 m). Field observations of oxygen isotopes and endmember incubations were conducted. Dissolved oxygen concentration ([O2]) and δ18O ranged from 157 to 241 μM and -1.34 to 3.41‰, respectively. Except for one outlier value, -1.34‰ (site TT1), there was a strong negative relationship between [O2] and δ18O among all 3 seasons (r2 = 0.97, p < 0.001, n = 10), suggesting the prevalence of fractionation in the process of O2 consumption. Given the contrasting fractionation effect during SOR (fractionation factor, ε = -3.57‰) and WCR (ε = -18.58‰), the contributions of SOR and WCR to total oxygen depletion were quantified via a respiration-only model or photosynthesis-respiration model (TT1), respectively. The SOR% range was 18-96% (mean 73%), with the remaining contributed by WCR%. There was no clear relationship between SOR% and temperature or depth or [O2] in the near-bottom waters, but [O2] was the best indicator for SOR% when data was pooled with results from deeper waters (20-50 m) in the East China Sea. For shallow waters <20 m in Dinghai Bay, [O2] was an essential control of SOR% and hence should be considered in the water column oxygen budget in coastal ecosystem modeling and management.

KEY WORDS: Oxygen consumption · Water column respiration · Sedimentary oxygen respiration · δ18O · Fractionation

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Cite this article as: Zhang ZH, Zhu ZY, Hu HT, Zhou J, Lin ZZ, Zhou CX (2024) Quantifying sedimentary oxygen consumption contribution to total oxygen depletion in shallow waters via the oxygen isotope approach. Mar Ecol Prog Ser 728:1-14.

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