title: Uptake-release dynamics of the inorganic and organic carbon pool mediated by planktonic prokaryotes in the deep Mediterranean Sea.
abstract: Understanding the ecosystem functioning in the dark portion of the ocean is a challenge that microbial ecologists are still facing. Due to the large volume, the global deep Ocean plays a central role in the regulation of climate, possibly buffering the rise of atmospheric carbon dioxide if processes of CO2fixation compensate for respiration. We investigated the rates of several prokaryotic activities (dissolved and particulate primary production, heterotrophic carbon production and respiration) in meso- and bathypelagic waters of the Mediterranean Sea, covering all sub-basins. Chemosynthesis was the main process for C uptake. The rates of organic C (OC) excretion (or viral-induced cell lysis) inferred from the dissolved primary production measurements were noteworthy, being comparable to particulate primary production, and possibly contributing to the formation of non-sinking particulate organic matter. Inorganic C fixation rates were significantly higher than those reported for other deep-sea systems, probably as a consequence of the persistently higher temperature of dark Mediterranean waters or to phylogenetically diverse communities involved in the process. Primary production was negatively correlated with dissolved organic carbon concentration and showed an inverse pattern to heterotrophic carbon production, indicating a niche partitioning between heterotrophs and autotrophs. In sum, the deep Mediterranean Sea harbors active autotrophic communities able to fix inorganic carbon faster than the heterotrophic carbon production rates.
authors.affiliation: OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Oceanography Division, via A. Piccard 54, Trieste, 34151, Italy.
authors.forename: Mauro
authors.identifier: 0000-0002-5660-6832
authors.initials: M
authors.lastname: Celussi
authors.affiliation: OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Oceanography Division, via A. Piccard 54, Trieste, 34151, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Malfatti
authors.affiliation: Institute of Environmental Science and Technology, Autonomous University of Barcelona (UAB), Bellaterra, 08193, Spain.|ICREA, Pg. Lluis Companys 23, Barcelona, 08010, Spain.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ziveri
authors.affiliation: OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Oceanography Division, via A. Piccard 54, Trieste, 34151, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Giani
authors.affiliation: OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Oceanography Division, via A. Piccard 54, Trieste, 34151, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Del Negro
mesh_terms: D052818:Autotrophic Processes; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002980:Climate; D017753:Ecosystem; D052836:Heterotrophic Processes; D008522:Mediterranean Sea; D010802:Phylogeny; D010933:Plankton / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011387:Prokaryotic Cells / Q000145:classification / Q000378:metabolism*; D012623:Seawater / Q000032:analysis
chemical_list: D002245:Carbon Dioxide; D002244:Carbon