BUSCADOR RECOLECTA

Digital.CSIC. Repositorio Institucional del CSIC

oai:digital.csic.es:10261/316210

Microbes in the dark ocean are exposed to hydrostatic pressure increasing with depth. Activity rate measurements and biomass production of dark ocean microbes are, however, almost exclusively performed under atmospheric pressure conditions due to technical constraints of sampling equipment maintaining in situ pressure conditions. To evaluate the microbial activity under in situ hydrostatic pressure, we designed and thoroughly tested an in situ microbial incubator (ISMI). The ISMI allows autonomously collecting and incubating seawater at depth, injection of substrate and fixation of the samples after a preprogramed incubation time. The performance of the ISMI was tested in a high-pressure tank and in several field campaigns under ambient hydrostatic pressure by measuring prokaryotic bulk 3H-leucine incorporation rates. Overall, prokaryotic leucine incorporation rates were lower at in situ pressure conditions than under to depressurized conditions reaching only about 50% of the heterotrophic microbial activity measured under depressurized conditions in bathypelagic waters in the North Atlantic Ocean off the northwestern Iberian Peninsula. Our results show that the ISMI is a valuable tool to reliably determine the metabolic activity of deep-sea microbes at in situ hydrostatic pressure conditions. Hence, we advocate that deep-sea biogeochemical and microbial rate measurements should be performed under in situ pressure conditions to obtain a more realistic view on deep-sea biotic processes., This study was supported by JSPS KAKENHI Grant (23651004) to M.U., the Austrian Science Fund (FWF) project I486-B09 and Z194 and the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC grant agreement No. 268595 (MEDEA project) to G.J.H., FWF project P27696-B22 to E.S., FWF project P23221-B11 to T.R., and the Axencia Galega de Innovación (GAIN, Xunta de Galicia, Spain) through IEO-GAIN Programme Contracts (Contratos Programa) and GRC grant (INGO7A 2018/2) to Plankton ecology and biogeochemistry (“Ecologia Plantónica y Biogeoquímica”, EPB) research group (https://epb-research-group.mozello.es/). C.A. was supported by JSPS Postdoctoral Fellowships for Research Abroad (H26–168) and the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie No. 701324. The comments of two reviewers are gratefully acknowledged and helped to improve an earlier version of the manuscript., Peer reviewed