Effects of seasonal deposition-erosion cycle on sedimentary organic carbon remineralization and oxygen consumption in a large-river delta-front estuary

Bin Zhao; Peng Yao; Qinsheng Wei; Thomas S Bianchi; Emily G Watts; Baodong Wang; Zhigang Yu

doi:10.1016/j.scitotenv.2024.170377

Effects of seasonal deposition-erosion cycle on sedimentary organic carbon remineralization and oxygen consumption in a large-river delta-front estuary

Sci Total Environ. 2024 Mar 15:916:170377. doi: 10.1016/j.scitotenv.2024.170377. Epub 2024 Jan 26.

Authors

Bin Zhao¹, Peng Yao², Qinsheng Wei³, Thomas S Bianchi⁴, Emily G Watts⁴, Baodong Wang³, Zhigang Yu⁵

Affiliations

¹ Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China; Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao 266237, China.
² Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao 266237, China. Electronic address: yaopeng@ouc.edu.cn.
³ Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China; Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao 266237, China.
⁴ Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA.
⁵ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Ecology and Environmental Science, Laoshan Laboratory, Qingdao 266237, China.

PMID: 38280579
DOI: 10.1016/j.scitotenv.2024.170377

Abstract

Seasonal sediment deposition-erosion events are dominant drivers of particle-solute dynamics in large-river delta-front estuaries (LDEs), but their influence on elemental cycles is not yet fully understood. To better constrain the role of deposition-erosion events on elemental cycling in LDEs, benthic fluxes of dissolved inorganic carbon (DIC), oxygen, and pore-water solute profiles were measured over different seasons in the Changjiang LDE. Benthic DIC efflux (23.4 ± 6.0 mmol C m^-2 d^-1) was greater than oxygen influx (7.5 ± 2.0 mmol O₂ m^-2 d^-1) in summer but less in winter (7.7 ± 1.2 mmol C m^-2 d^-1 and 10.1 ± 1.5 mmol O₂ m^-2 d^-1, respectively). The additional oxygen consumption in sediments in winter was likely due to the oxidation of inorganic diagenetic reductive products (IDRP) (e.g., NH₄⁺, Fe²⁺, and Mn²⁺) in deeper sediments exposed by erosion, which resulted in the development of an "oxygen debt". Sedimentary oxygen respiration accounted for at least 48 % of total oxygen consumption (oxygen consumption in both water column and sediment) in winter and was significantly greater than in summer (∼15 %); this highlighted the importance of winter sediment erosion in oxygen depletion. In addition to IDRP oxidation, the remineralization of resuspended sedimentary organic carbon in water column also contributed to the oxygen consumption. The global dataset on benthic DIC and oxygen fluxes provides evidence that the "oxygen debt" is likely to be widespread in LDEs, exerting a significant impact on global carbon and oxygen cycling.

Keywords: Benthic flux; Changjiang Estuary; Mobile muds; Oxygen debt; Pore-water.