Dissolved organic matter and heterotrophic prokaryotes diel patterns reveal enhanced growth at the mesopelagic fish layer during daytime
AuthorsMoran, Xose Anxelu G.
Garcia, Francisca C.
Al-otaibi, Najwa Aziz
Calleja, Maria L.
KAUST DepartmentBiological and Environmental Sciences and Engineering (BESE) Division
Marine Science Program
Red Sea Research Center (RSRC)
King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Science & Engineering Division, 23955-6900 Thuwal, Saudi Arabia
Permanent link to this recordhttp://hdl.handle.net/10754/656587
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AbstractContrary to epipelagic waters, where biogeochemical processes closely follow the light and dark periods, little is known about diel cycles in the mesopelagic realm. Here, we monitored the dynamics of dissolved organic matter (DOM) and planktonic heterotrophic prokaryotes every 2 h for one day at the surface and 550 m (a depth occupied by mesopelagic fish 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 at midnight and noon. Comparable variability in microbial biomass and dissolved organic carbon in situ suggests a diel supply of fresh DOM in both layers. The presence of mesopelagic fishes during daytime promoted a sustained, longer growth of larger prokaryotic cells, with specific growth rates consistently higher in both noon experiments (surface: 0.34 vs. 0.18 d-1, deep: 0.16 vs. 0.09 d-1). Heterotrophic prokaryotes in the mesopelagic fish layer were also more efficient at converting DOM into new biomass. These results suggest that the ocean’s twilight zone receives a continuous diurnal supply of labile DOM from diel vertical migrating fishes, enabling an unexpectedly active community of heterotrophic prokaryotes.
CitationMoran, X. A. G., Garcia, F. C., Rostad, A., Silva, L., Al-Otaibi, N., Irigoien, X., & Calleja, M. L. (2019). Dissolved organic matter and heterotrophic prokaryotes diel patterns reveal enhanced growth at the mesopelagic fish layer during daytime. doi:10.1101/712570
SponsorsWe are greatly indebted to the crew of RV Thuwal and the rest of the personnel from the Coastal and Marine Resources (CMOR) Core Lab at KAUST for their assistance during field work. Besides participating in the sample collection M. Viegas helped us with the rest of the work in the Red Sea Research Center (RSRC) lab. We are also grateful to past and current members of the Microbial Oceanography and Biogeochemistry lab at the RSRC. X.A.G.M. conceived the research, led the experiment design, data analysis and wrote the paper. F.C.G. modeled in situ growth rates. A.R. performed the acoustic research. L.S. and N. A-O. analyzed the heterotrophic prokaryotes. X.I. contributed to the interpretation of results. M.L.C. was responsible for DOC and FDOM measurements, contributed to experimental design and data analysis. F.C.G., A.R., X.I. and M.L.C. also contributed to writing.
PublisherCold Spring Harbor Laboratory
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