Prokaryotic Respiration and Production in the Meso- and Bathypelagic Realm of the Eastern and Western North Atlantic Basin

• Published in: Limnology and oceanography 2006-05, Vol.51 (3), p.1262-1273
• Main Authors: Reinthaler, Thomas, van Aken, Hendrik, Veth, Cornelis, Arístegui, Javier, Robinson, Carol, Peter J. le B. Williams, Lebaron, Philippe, Herndl, Gerhard J.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Average linear density; Bacteria; Basins; Biological and medical sciences; Deep water; Fundamental and applied biological sciences. Psychology; Marine; Oceans; Oxygen; Prokaryotic cells; Respiration; Sea water; Sea water ecosystems; Seas; Synecology
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.2006.51.3.1262

We measured prokaryotic production and respiration in the major water masses of the North Atlantic down to a depth of ~4,000 m by following the progression of the two branches of North Atlantic Deep Water (NADW) in the oceanic conveyor belt. Prokaryotic abundance decreased exponentially with depth from $3 to 0.4 \times 10^5 cells mL^{-1}$ in the eastern basin and from $3.6 to 0.3 \times 10^5 cells mL^{-1}$ in the western basin. Prokaryotic production measured via 3H-leucine incorporation showed a similar pattern to that of prokaryotic abundance and decreased with depth from $9.2 to 1.1 \mu mol C m^{-3} d^{-1}$ in the eastern and from $20.6 to 1.2 \mu mol C m^{-3} d^{-1}$ in the western basin. Prokaryotic respiration, measured via oxygen consumption, ranged from about $300 to 60 \mu mol C m^{-3} d^{-1}$ from ~100 m depth to the NADW. Prokaryotic growth efficiencies of ~2% in the deep waters (depth range 1,200-4,000 m) indicate that the prokaryotic carbon demand exceeds dissolved organic matter input and surface primary production by 2 orders of magnitude. Cell-specific prokaryotic production was rather constant throughout the water column, ranging from $15 to 32 \times 10^{-3} fmol C cell^{-1} d^{-1}$ in the eastern and from $35 to 58 \times 10^{-3} fmol C cell^{-1} d^{-1}$ in the western basin. Along with increasing cell-specific respiration towards the deep water masses and the relatively short turnover time of the prokaryotic community in the dark ocean (34-54 d), prokaryotic activity in the meso- and bathypelagic North Atlantic might be higher than previously assumed.