S. Agusti, J.I. González-Gordillo, D. Vaqué, M. Estrada, M.I. Cerezo, G. Salazar, J.M. Gasol, C.M. Duarte
Nature Communications, 6:7608, (2015)
The role of the ocean as a sink for CO2 is partially
dependent on the downward transport of phytoplankton cells packaged
within fast-sinking particles. However, whether such fast-sinking
mechanisms deliver fresh organic carbon down to the deep bathypelagic
sea and whether this mechanism is prevalent across the ocean requires
confirmation. Here we report the ubiquitous presence of healthy
photosynthetic cells, dominated by diatoms, down to 4,000 m in the deep dark ocean. Decay experiments with surface phytoplankton suggested that the large proportion (18%)
of healthy photosynthetic cells observed, on average, in the dark
ocean, requires transport times from a few days to a few weeks,
corresponding to sinking rates (124–732 m d−1)
comparable to those of fast-sinking aggregates and faecal pellets.
These results confirm the expectation that fast-sinking mechanisms
inject fresh organic carbon into the deep sea and that this is a
prevalent process operating across the global oligotrophic ocean.