AME 71:99-115 (2013)  -  DOI: https://doi.org/10.3354/ame01666

FEATURE ARTICLE
Seasonal variability of microbial respiration and bacterial and archaeal community composition in the upper twilight zone

M. G. Weinbauer1,2,*, J. Liu1,3, C. Motegi1,2, C. Maier1,2, M. L. Pedrotti1,2, M. Dai3, J. P. Gattuso1,2 

1Université Pierre et Marie Curie, UMR 7093, Laboratoire d’Océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
2CNRS, UMR 7093, Laboratoire d’Océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
3State Key Laboratory of Marine Environmental Science, Xiamen University, 361005 Xiamen, China

ABSTRACT: The mesopelagic (‘twilight’) zone of the ocean is the sandwich layer between euphotic surface waters and the deep ocean. The physical, chemical, and biological processes in this layer strongly influence the marine carbon cycle, although some surprising knowledge gaps remain, e.g. with respect to microbial communities. We therefore determined biological parameters such as microbial abundances, community respiration, and bacterial and archaeal community composition (as assessed by 16S rRNA gene PCR denaturing gradient gel electrophoresis, DGGE) over a seasonal time scale (at ca. 46 d intervals for 433 d) at a coastal mesopelagic site in the NW Mediterranean Sea (Point C, 300 m depth) and related them to physicochemical parameters. Some chemical and most biological parameters showed strong variability, thus confirming the emerging view that this water layer is more dynamic than previously thought. Community respiration was likely influenced by seasonal changes as indicated by its indirect relationship with water density. The high detected community respiration rates (0.23-1.65 µmol O2 l-1 d-1) confirm that the twilight zone plays a critical role as a hub between surface and deep water. Statistical analyses indicate that water stratification, dissolved organic carbon, and transparent exopolymeric particles were controlling factors of bacterial community composition, whereas the archaeal community was likely controlled by other mechanisms. A sequence analysis of DGGE bands and a literature comparison suggests some specificity of the mesopelagic zone regarding bacterial and archaeal community composition, thus further confirming the peculiarity of this water layer.


KEY WORDS: Mesopelagic · Transparent exopolymeric particles · Carbon cycle · Prokaryote · Virus · Flagellate


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Cite this article as: Weinbauer MG, Liu J, Motegi C, Maier C, Pedrotti ML, Dai M, Gattuso JP (2013) Seasonal variability of microbial respiration and bacterial and archaeal community composition in the upper twilight zone. Aquat Microb Ecol 71:99-115. https://doi.org/10.3354/ame01666

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