Journal
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
Volume 95, Issue -, Pages 131-138Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.dsr.2014.10.014
Keywords
Mesopelagic zone; Microbial respiration; Prokaryotic growth efficiency; Temperature; Indian Ocean; South Atlantic Ocean
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Funding
- INGENIO CONSOLIDER program [CDS2008-00077]
- Spanish National Research Council (CSIC)
- BBVA Foundation, Spain
- Project HotMix [CTM2011-30010-C02/MAR]
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We have measured both prokaryotic heterotrophic production (PHP) and respiration (R), then providing direct estimates of prokaryotic growth efficiencies (PGE), in the upper mesopelagic zone (300-600 m) of the South Atlantic and Indian Oceans. Our results show that in situ R ranged 3-fold, from 87 to 238 mu mol C m(-3) d(-1). In situ PHP rates were much lower but also more variable than R (ranging from 0.3 to 9.1 mu mol C m(-3) d(-1)). The derived in situ PGE values were on average similar to 1.4% (from 0.3% to 3.7%), indicating that most of the organic substrates incorporated by prokaryotes were respired instead of being used for growth. Together with the few previous studies on PGE published before for the Atlantic Ocean and Mediterranean Sea, our findings support the hypothesis that the global mesopelagic zone represents a key remineralization site for export production in the open ocean. We also found a strong correlation between R and PGE with temperature across a gradient ranging from 8.7 to 14.9 degrees C. The derived Q(10), value of 3.7 suggests that temperature variability in the mesopelagic zone plays a significant role in the remineralization of organic matter. (C) 2014 Elsevier Ltd. All rights reserved.
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