Abstract
The major biogeochemical cycles of marine ecosystems are driven by solar energy. Energy that is initially captured through photosynthesis is transformed and transported to great ocean depths via complex, yet poorly understood, energy flow networks. Herein we show that the chemical composition and specific energy (Joules per unit mass or organic carbon) of sinking particulate matter collected in the North Pacific Subtropical Gyre reveal dramatic changes in the upper 500 m of the water column as particles sink and age. In contrast to these upper water column processes, particles reaching the deep sea (4000 m) are energy-replete with organic carbon-specific energy values similar to surface phytoplankton. These enigmatic results suggest that the particles collected in the abyssal zone must be transported by rapid sinking processes. These fast-sinking particles control the pace of deep-sea benthic communities that live a feast-or-famine existence in an otherwise energy-depleted habitat.
Highlights
The major biogeochemical cycles of marine ecosystems are driven by solar energy
Photosynthesis is the primary source of both organic carbon and energy, but the subsequent pathways and mechanisms for carbon cycling and energy dissipation are less well understood
In the present study, we observed that the elemental compositions and specific energy values for sinking particulate matter (SPM) collected in the upper mesopelagic zone (300–500 m) were fundamentally distinct from SPM collected at an abyssal (4000 m) depth
Summary
The major biogeochemical cycles of marine ecosystems are driven by solar energy. Energy that is initially captured through photosynthesis is transformed and transported to great ocean depths via complex, yet poorly understood, energy flow networks. In contrast to these upper water column processes, particles reaching the deep sea (4000 m) are energyreplete with organic carbon-specific energy values similar to surface phytoplankton These enigmatic results suggest that the particles collected in the abyssal zone must be transported by rapid sinking processes. Photosynthesis is typically estimated by measuring O2 production or CO2 reduction per unit volume and per unit time during incubation experiments[4,5] These O2 or CO2 fluxes alone are insufficient to track energy within the surface ocean, or to quantify potential energy export from the sunlit zone of maximum production into the mesopelagic and abyssal zones in the form of sinking particulate matter (SPM). Measurements of the enthalpy of SPM can provide reasonable estimates of the total energy (measured in Joules), specific energy (J mg−1 mass or J mg−1 OC) and downward energy transport (J m−2 d−1) associated with SPM collected at different depths in the water column
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