(2024). Microbial remineralisation of the downward particle flux measured in the upper mesopelagic with the C-RESPIRE dual particle interceptor/incubator. SEANOE. https://doi.org/10.17882/100610
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Microbial remineralisation of the downward particle flux measured in the upper mesopelagic with the C-RESPIRE dual particle interceptor/incubator
The oceans’ biological pump plays a major role in the carbon cycle by transferring 5-10 Pg carbon annually out of the upper ocean. A relationship formulated >30 years ago – the ‘Martin curve’ – continues to be used to parameterize particle flux attenuation for the global ocean in models. Despite the almost universal adoption of this empirically-derived relationship, we have made little progress in understanding the drivers of C flux attenuation in over three decades.
The fundamental problem with obtaining a mechanistic understanding of the C flux attenuation curve is that it represents multiple processes that concurrently attenuate particle flux (zooplankton flux feeding, diurnal vertical migration, and microbial remineralization of settling particles). Disentangling these processes is further confounded by the likelihood that each process will have different patterns with depth, that may also vary regionally. Hence the way ahead to “deconstructing the Martin curve” is to separate these processes and their drivers.
We present a novel in situ approach (called C-RESPIRE) that first intercepts sinking particles (covered in attached microbes) in the upper Twilight Zone (~100-300 m depth), immediately isolates the particles from grazers, and then incubates them at depth during the same deployment. This approach, across multiple deployment depths, provides vertical profiles of rates of microbial remineralization of particle flux.
Disciplines
Biological oceanography, Chemical oceanography
Keywords
biological carbon pump, particle flux attenuation, microbial remineralization, mesopelagic zone, particle interceptor/incubator C-RESPIRE
Devices
The C-RESPIRE particle interceptor/incubator is designed to non-intrusively intercept sinking particles, concentrate them within a 1.45 L volume of (unpoisoned) filtered seawater, and then incubate them at in situ pressure and temperature (Boyd et al. 2015). C-RESPIRE consists of a titanium cylinder with a collection area of 0.0124 m2. At its entrance, a baffle limits the turbulence and resuspension of the sinking particles that ultimately settle into an indented rotating sphere (IRS). Pre-programmed rotations (typically every 5-10 minutes) of the IRS transfer particles into an inner chamber (1.45 L) equipped with an oxygen optode. The IRS ensures the exclusion of mesozooplankton, and isolation of the inner chamber when not rotating. The ~1-3 day particle collection phase promotes the accumulation of sinking particles in the chamber, along with their attached microbial consortia. This accumulation of sinking particles ensures that the remineralisation signature most closely corresponds to that of the attached microbial assemblage, as opposed to free-living heterotrophic bacteria potentially present in the <0.2-µm filtered seawater initially used to fill the inner chamber.
Boyd, P. W., McDonnell, A., Valdez, J., LeFevre, D., & Gall, M. P. RESPIRE: An in situ particle interceptor to conduct particle remineralization and microbial dynamics studies in the oceans’ Twilight Zone. Limnol. Oceanogr.: Methods 13(9), 494-508 (2015).
Data
| File | Size | Format | Processing | Access | end of embargo | |
|---|---|---|---|---|---|---|
111202.xlsx | 17 Ko | XLS, XLSX | Processed data | 2024-10-01 |
How to cite
Bressac M.
