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Abstract A considerable amount of particulate carbon produced by oceanic photosynthesis is exported to the deep-sea by the “gravitational pump” (~6.8 to 7.7 Pg C/year), sequestering it from the atmosphere for centuries. How particulate organic carbon (POC) is transformed during export to the deep sea however is not well understood. Here, we report that dominant suspended prokaryotes also found in sinking particles serve as informative tracers of particle export processes. In a three-year time series from oceanographic campaigns in the Pacific Ocean, upper water column relative abundances of suspended prokaryotes entrained in sinking particles decreased exponentially from depths of 75 to 250 m, conforming to known depth-attenuation patterns of carbon, energy, and mass fluxes in the epipelagic zone. Below ~250 m however, the relative abundance of suspended prokaryotes entrained in sinking particles increased with depth. These results indicate that microbial entrainment, colonization, and sinking particle formation are elevated at mesopelagic and bathypelagic depths. Comparison of suspended and sinking particle-associated microbes provides information about the depth-variability of POC export and biotic processes, that is not evident from biogeochemical data alone.
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Constraining growth rates and the ratio of living to nonliving particulate carbon using beam attenuation and adenosine‐5′‐triphosphate at Station ALOHA
Abstract Carbon is not only the foundation of all life on our planet, but also an element that persists in detrital material long after living organisms die. Quantifying the relative amount of living and nonliving carbon in suspended particles in the ocean is challenging and rarely done; yet it is key to understanding the fate of organic matter and informing food web models. Here, we use particulate adenosine‐5′‐triphosphate (ATP) and particulate carbon (PC) data collected as a component of the Hawaii Ocean Time‐series program to show that living particles comprise only ~ 26–42% of the total PC pool in the surface waters of the North Pacific Subtropical Gyre, regardless of time of year. Diel‐resolving particulate beam attenuation data are then used in conjunction with PC and ATP data to constrain living particle net growth rates for this system, yielding rates of ~ 0.5–0.7 d−1year‐round. These estimates are realistic and consistent with previous microscopy and incubation‐based work in the region.
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- Award ID(s):
- 1756517
- PAR ID:
- 10361003
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography Letters
- Volume:
- 6
- Issue:
- 5
- ISSN:
- 2378-2242
- Page Range / eLocation ID:
- p. 243-252
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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