Magnitude of nitrate turbulent diffusion in contrasting marine environments

• Published in: Scientific reports Vol. 11; no. 1; p. 18804
• Main Authors: Mouriño-Carballido, Beatriz, Otero Ferrer, José Luis, Fernández Castro, Bieito, Marañón, Emilio, Blazquez Maseda, Mariña, Aguiar-González, Borja, Chouciño, Paloma, Graña, Rocío, Moreira-Coello, Víctor, Villamaña, Marina
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 22.09.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 704/829/2737; 704/829/826; Diffusion; Eddy diffusion; Entrainment; Euphotic zone; Humanities and Social Sciences; Marine environment; multidisciplinary; Nitrates; Nitrogen; Nitrogen fixation; Oceanic turbulence; Phytoplankton; Science; Science (multidisciplinary); Surface temperature
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-97731-4

Difficulties to quantify ocean turbulence have limited our knowledge about the magnitude and variability of nitrate turbulent diffusion, which constitutes one of the main processes responsible for the supply of nitrogen to phytoplankton inhabiting the euphotic zone. We use an extensive dataset of microturbulence observations collected in contrasting oceanic regions, to build a model for nitrate diffusion into the euphotic zone, and obtain the first global map for the distribution of this process. A model including two predictors (surface temperature and nitrate vertical gradient) explained 50% of the variance in the nitrate diffusive flux. This model was applied to climatological data to predict nitrate diffusion in oligotrophic mid and low latitude regions. Mean nitrate diffusion (~ 20 Tmol N y −1 ) was comparable to nitrate entrainment due to seasonal mixed-layer deepening between 40°N–40ºS, and to the sum of global estimates of nitrogen fixation, fluvial fluxes and atmospheric deposition. These results indicate that nitrate diffusion represents one of the major sources of new nitrogen into the surface ocean in these regions.