BUSCADOR RECOLECTA

Digital.CSIC. Repositorio Institucional del CSIC

oai:digital.csic.es:10261/345854

Bulk dark dissolved inorganic carbon (DIC) fixation rates were determined and compared to microbial heterotrophic production in subsurface, meso- and bathypelagic Atlantic waters off the Galician coast (NW Iberian margin). DIC fixation rates were slightly higher than heterotrophic production throughout the water column, however, more prominently in the bathypelagic waters. Microautoradiography combined with catalyzed reporter deposition fluorescence in situ hybridization (MICRO-CARD-FISH) allowed us to identify several microbial groups involved in dark DIC uptake. The contribution of SAR406 (Marinimicrobia), SAR324 (Deltaproteobacteria) and Alteromonas (Gammaproteobacteria) to the dark DIC fixation was significantly higher than that of SAR202 (Chloroflexi) and Thaumarchaeota, in agreement with their contribution to microbial abundance. Q-PCR on the gene encoding for the ammonia monooxygenase subunit A (amoA) from the putatively high versus low ammonia concentration ecotypes revealed their depth-stratified distribution pattern. Taken together, our results indicate that chemoautotrophy is widespread among microbes in the dark ocean, particularly in bathypelagic waters. This chemolithoautotrophic biomass production in the dark ocean, depleted in bio-available organic matter, might play a substantial role in sustaining the dark ocean's food web., Funding for the sampling and analyses was provided by the projects ‘Biodiversidade Funcional do Microplancton nas profundidades mariñas de Galicia’ (BIO-PROF, Ref. 10MMA604024PR, 2010–2012, Xunta de Galicia) and ‘Fuentes de Materia Orgánica y Diversidad Funcional del Microplancton en las aguas profundas del Atlántico Norte’ (MODUPLAN, Plan Nacional I + D+I) to MMV. Additional funding was provided by the Axencia Galega de Innovación (GAIN, Xunta de Galicia) through IEO-GAIN Programme Contracts (Contratos Programa). EGF was supported by the BIO-PROF and MODUPLAN projects. ES received funding by the Austrian Science Fund (FWF) project P27696-B22 and GJH was funded by the Austrian Science Fund (FWF) projects I486-B09 and Z194-B17 and the European Research Council under the European Community's Seventh Framework Program (FP7/2007–2013)/ERC grant agreement No. 268595 (MEDEA project). This work is in partial fulfilment of the requirements for a Ph.D. degree from the Universidade de A Coruña by E.G.-F., Peer reviewed