DOI 10.1002/lom3.10528 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.
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Publisher's official version | 13 | 1 Mo | ||
Fig. S1. Deployment of ISMI mounted on Niskin rosette frame (a) and attached on a ship's winch cable (b). Incubation with 10 L folding bags (c) and a 12 L titanium tank (d and e) are also possible.... | - | 27 Mo | ||
Fig. S2. CAD image of ISMI sampling bottle. | - | 360 Ko | ||
Fig. S3. CAD image of rosette tubing clamp unit. | - | 2 Mo | ||
Fig. S4. Programming of ISMI. An example of prepared setting sheet (a). Blue filled boxes are the data needed as input in the ROCS-com software. Wiring scheme showing the connections of the ... | 1 | 40 Ko | ||
Fig. S5. Distribution of a dye-solution of variable density prepared with artificial seawater (ASW) of a density of 1.03 g cm−3.Horizontal (a, b) and vertical (g) setup of ISMI detached bottles.... | - | 6 Mo | ||
Fig. S6. 3H-leucine uptake kinetics determined on samples collected from several depths in the Southern Ocean (a) and North Atlantic Ocean (b). In the Southern Ocean samples, saturating substrate .... | 1 | 44 Ko | ||
Table S1. Locations, date and temperature and salinity of samples used in this study. | - | 25 Ko | ||
Table S2. Comparison of leucine incorporation rates (pmol leu L−1 h−1) from samples incubated in detached ISMI bottles and polypropylene centrifuge tubes. Incubations were conducted at in situ ... | - | 19 Ko | ||
Table S3. Leucine incorporation rates (pmol leu L−1 h−1) of representative samples incubated at atmospheric pressure (atm.) and in situ pressure conditions. | - | 19 Ko |
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