Diel dynamics of dissolved organic matter and heterotrophic prokaryotes reveal enhanced growth at the ocean's mesopelagic fish layer during daytime
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ArticleAuthors
Moran, Xose Anxelu G.
García, Francisca C.
Røstad, Anders

Silva, Luis
Al-Otaibi, Najwa
Irigoien, Xabier
Calleja, Maria L.
KAUST Department
Biological and Environmental Science and Engineering (BESE) DivisionKing Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Science & Engineering Division, 23955-6900 Thuwal, Saudi Arabia.
Marine Science Program
Microbial oceanography Research Group
Red Sea Research Center (RSRC)
Date
2021-09-04Online Publication Date
2021-09Print Publication Date
2022-01Submitted Date
2021-05-28Permanent link to this record
http://hdl.handle.net/10754/670973
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Contrary to epipelagic waters, where biogeochemical processes closely follow the light and dark periods, little is known about diel cycles in the ocean's mesopelagic realm. Here, we monitored the dynamics of dissolved organic matter (DOM) and planktonic heterotrophic prokaryotes every 2 h for one day at 0 and 550 m (a depth occupied by vertically migrating fishes during light hours) in oligotrophic waters of the central Red Sea. We additionally performed predator-free seawater incubations of samples collected from the same site both at midnight and at noon. Comparable in situ variability in microbial biomass and dissolved organic carbon concentration suggests a diel supply of fresh DOM in both layers. The presence of fishes in the mesopelagic zone during daytime likely promoted a sustained, longer growth of larger prokaryotic cells. The specific growth rates were consistently higher in the noon experiments from both depths (surface: 0.34 vs. 0.18 d-1, mesopelagic: 0.16 vs. 0.09 d-1). Heterotrophic prokaryotes in the mesopelagic layer were also more efficient at converting extant DOM into new biomass. These results suggest that the ocean's twilight zone receives a consistent diurnal supply of labile DOM from diel vertical migrating fishes, enabling an unexpectedly active community of heterotrophic prokaryotes.Citation
Morán, X. A. G., García, F. C., Røstad, A., Silva, L., Al-Otaibi, N., Irigoien, X., & Calleja, M. L. (2021). Diel dynamics of dissolved organic matter and heterotrophic prokaryotes reveal enhanced growth at the ocean’s mesopelagic fish layer during daytime. Science of The Total Environment, 150098. doi:10.1016/j.scitotenv.2021.150098Publisher
Elsevier BVJournal
Science of The Total EnvironmentAdditional Links
https://linkinghub.elsevier.com/retrieve/pii/S0048969721051731ae974a485f413a2113503eed53cd6c53
10.1016/j.scitotenv.2021.150098
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