Organic Carbon Export and Loss Rates in the Red Sea

Type Article
Date 2020-10
Language English
Author(s) Kheireddine Malika1, Dall'Olmo Giorgio2, 3, Ouhssain Mustapha1, Krokos George4, Claustre Hervé5, Schmechtig Catherine6, Poteau Antoine5, Zhan Peng4, Hoteit Ibrahim4, Jones Burton H.1
Affiliation(s) 1 : Red Sea Research Center (RSRC), Biological and Environmental Sciences and Engineering Division (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal ,Saudi Arabia
2 : Plymouth Marine Laboratory Plymouth, UK
3 : National Centre for Earth Observation Plymouth, UK
4 : Faculty of Earth Science and Engineering King Abdullah University of Science and Technology (KAUST) Thuwal ,Saudi Arabia
5 : Laboratoire d'Océanographie de Villefranche Sorbonne Université, CNRS UMR 7093 Villefranche‐sur‐mer ,France
6 : OSU Ecce‐Terra Sorbonne Université, CNRS, UMS 3455 Paris, France
Source Global Biogeochemical Cycles (0886-6236) (American Geophysical Union (AGU)), 2020-10 , Vol. 34 , N. 10 , P. e2020GB006650 (20p.)
DOI 10.1029/2020GB006650
Keyword(s) carbon export, carbon loss rates, mesopelagic zone, temperature, oxygen, tropical ecosystem
Abstract

The export and fate of organic carbon in the mesopelagic zone are still poorly understood and quantified due to lack of observations. We exploited data from a biogeochemical‐Argo float that was deployed in the Red Sea to study how a warm and hypoxic environment can affect the fate of the organic carbon in the ocean's interior. We observed that only 10% of the particulate organic carbon (POC) exported survived at depth due to remineralization processes in the upper mesopelagic zone. We also found that POC exported was rapidly degraded in a first stage and slowly in a second one, which may be dependent on the palatability of the organic matter. We observed that apparent oxygen utilization (AOU)‐based loss rates (a proxy of the remineralization of total organic matter) were significantly higher than the POC‐based loss rates, likely because changes in AOU are mainly attributed to changes in dissolved organic carbon. Finally, we showed that POC‐ and AOU‐based loss rates could be expressed as a function of temperature and oxygen concentration. These findings advance our understanding of the biological carbon pump and mesopelagic ecosystem.

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Kheireddine Malika, Dall'Olmo Giorgio, Ouhssain Mustapha, Krokos George, Claustre Hervé, Schmechtig Catherine, Poteau Antoine, Zhan Peng, Hoteit Ibrahim, Jones Burton H. (2020). Organic Carbon Export and Loss Rates in the Red Sea. Global Biogeochemical Cycles, 34(10), e2020GB006650 (20p.). Publisher's official version : https://doi.org/10.1029/2020GB006650 , Open Access version : https://archimer.ifremer.fr/doc/00655/76730/