Particle Flux Dynamics in Oceanic Ecosystems

Particle flux dynamics in oceanic ecosystems describe the movement of organic and inorganic particles from the surface layers into the deep sea. These particles, generated through primary production, zooplankton grazing, physical aggregation and mineral ballasting, form marine snow that sinks through the water column. The balance between particle formation, transformation by microbial and faunal activity, and physical disaggregation governs the efficiency of downward export. This export underpins the biological carbon pump, whereby carbon fixed in the euphotic zone is sequestered at depth, influencing atmospheric CO₂ levels over seasons to millennia. Regional variability in temperature, ecosystem structure, nutrient regimes and mineral composition modulates sinking rates and remineralisation patterns. For example, diatom-rich blooms often produce large, rapidly sinking aggregates, while communities dominated by smaller phytoplankton yield slower-sinking material subject to enhanced degradation. The interaction of biological, chemical and physical processes shapes global carbon budgets and informs climate models. Understanding these dynamics is essential to predict changes in carbon sequestration under shifting ocean stratification, nutrient supply and ecosystem composition driven by climate change.

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Particle Flux Dynamics in Oceanic Ecosystems publication trend

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Technical terms

Particle flux: The downward transport rate of particulate matter, typically expressed as mass or radioactivity per unit area per unit time.

Biological carbon pump (BCP): The process by which photosynthetically fixed carbon is exported from the surface ocean to depth via sinking particles.

Particulate organic carbon (POC): Organic carbon contained within particles, including detritus, faecal pellets and aggregates.

Thorium-234 tracer: A naturally occurring radionuclide used to estimate sinking particle fluxes by measuring its disequilibrium with parent uranium-238.

Euphotic zone: The upper layer of the ocean where light is sufficient for photosynthesis.

Export efficiency: The fraction of primary production that is exported below the euphotic zone as sinking particles.

References

1. Combined Use of Short-Lived Radionuclides (234Th and 210Po) as Tracers of Sinking Particles in the Ocean. Annual Review of Marine Science (2023).
2. Biological Production of Distinct Carbon Pools Drives Particle Export Efficiency in the Southern Ocean. Geophysical Research Letters (2024).
3. Global database of ratios of particulate organic carbon to thorium-234 in the ocean: improving estimates of the biological carbon pump. Earth System Science Data (2020).