Biological and physical influences on marine snowfall at the equator

2017

Article référencé dans le Web of Science WOS:000414031600016

Kiko R., Biastoch A., Brandt P., Cravatte Sophie, Hauss H., Hummels R., Kriest I., Marin Frédéric, McDonnell A. M. P., Oschlies A., Picheral M., Schwarzkopf F. U., Thurnherr A. M., Stemmann L.

Nature Geoscience, 2017, 10 (11), p. 852-858 ISSN 1752-0894

High primary productivity in the equatorial Atlantic and Pacific oceans is one of the key features of tropical ocean biogeochemistry and fuels a substantial flux of particulate matter towards the abyssal ocean. How biological processes and equatorial current dynamics shape the particle size distribution and flux, however, is poorly understood. Here we use high-resolution size-resolved particle imaging and Acoustic Doppler Current Profiler data to assess these influences in equatorial oceans. We find an increase in particle abundance and flux at depths of 300 to 600 m at the Atlantic and Pacific equator, a depth range to which zooplankton and nekton migrate vertically in a daily cycle. We attribute this particle maximum to faecal pellet production by these organisms. At depths of 1,000 to 4,000 m, we find that the particulate organic carbon flux is up to three times greater in the equatorial belt (1 degrees S-1 degrees N) than in off-equatorial regions. At 3,000 m, the flux is dominated by small particles less than 0.53 mm in diameter. The dominance of small particles seems to be caused by enhanced active and passive particle export in this region, as well as by the focusing of particles by deep eastward jets found at 2 degrees N and 2 degrees S. We thus suggest that zooplankton movements and ocean currents modulate the transfer of particulate carbon from the surface to the deep ocean.

Limnologie physique / Océanographie physique [032] ; Ecologie, systèmes aquatiques [036]

ATLANTIQUE ; PACIFIQUE ; ZONE EQUATORIALE

Fonds IRD [F B010071367]

fdi:010071367