Importance of salt fingering for new nitrogen supply in the oligotrophic ocean.
The input of new nitrogen into the euphotic zone constrains the export of organic carbon to the deep ocean and thereby the biologically mediated long-term CO2 exchange between the ocean and atmosphere. In low-latitude open-ocean regions, turbulence-driven nitrate diffusion from the ocean's interior and biological fixation of atmospheric N2 are the main sources of new nitrogen for phytoplankton productivity. With measurements across the tropical and subtropical Atlantic, Pacific and Indian oceans, we show that nitrate diffusion (171±190 μmol m(-2) d(-1)) dominates over N2 fixation (9.0±9.4 μmol m(-2) d(-1)) at the time of sampling. Nitrate diffusion mediated by salt fingers is responsible for ca. 20% of the new nitrogen supply in several provinces of the Atlantic and Indian Oceans. Our results indicate that salt finger diffusion should be considered in present and future ocean nitrogen budgets, as it could supply globally 0.23-1.00 Tmol N yr(-1) to the euphotic zone.
Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36310 Vigo, Spain.
B
B
Fernández-Castro
Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36310 Vigo, Spain.
B
B
Mouriño-Carballido
Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36310 Vigo, Spain.
E
E
Marañón
Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36310 Vigo, Spain.
P
P
Chouciño
Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Vigo, Apdo. 1552, 36390 Vigo, Spain.
J
J
Gago
Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Málaga, Puerto Pesquero s/n, Apdo. 285, 29640 Fuengirola (Málaga), Spain.
T
T
Ramírez
Departament d'Ecologia, Universitat de Barcelona, A. Diagonal 643, 08028 Barcelona, Spain.
M
M
Vidal
Instituto Español de Oceanografía (IEO), Centro Oceanográfico de A Coruña, Apdo. 130, 15080 A Coruña, Spain.
A
A
Bode
Institut de Ciències del Mar, CSIC, Pg. Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain.
D
D
Blasco
Institut de Ciències del Mar, CSIC, Pg. Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain.
S-J
SJ
Royer
Institut de Ciències del Mar, CSIC, Pg. Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain.
M
M
Estrada
Institut de Ciències del Mar, CSIC, Pg. Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain.
R
R
Simó
D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism*; D000458:Cyanobacteria / Q000378:metabolism; D004058:Diffusion; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D009586:Nitrogen Fixation; D009792:Oceans and Seas; D054300:Oscillatoria / Q000378:metabolism; D010839:Phytoplankton / Q000378:metabolism*; D054712:Salinity; D012623:Seawater / Q000737:chemistry*; D012965:Sodium Chloride; D013696:Temperature
D009566:Nitrates; D002245:Carbon Dioxide; D012965:Sodium Chloride; D009584:Nitrogen