Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Nature Communications 6214 [9 ] 2021 fdi:010083323 ENG Nature Communications ISI:000712527000013 1 10.1038/s41467-021-26552-w https://www.documentation.ird.fr/hor/fdi:010083323 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2021-12/010083323.pdf 12 Horizon (IRD) The open ocean nitrogen cycle is being altered by increases in anthropogenic atmospheric nitrogen deposition and climate change. How the nitrogen cycle responds will determine long-term trends in net primary production (NPP) in the nitrogen-limited low latitude ocean, but is poorly constrained by uncertainty in how the source-sink balance will evolve. Here we show that intensifying nitrogen limitation of phytoplankton, associated with near-term reductions in NPP, causes detectable declines in nitrogen isotopes (delta N-15) and constitutes the primary perturbation of the 21st century nitrogen cycle. Model experiments show that similar to 75% of the low latitude twilight zone develops anomalously low delta N-15 by 2060, predominantly due to the effects of climate change that alter ocean circulation, with implications for the nitrogen source-sink balance. Our results highlight that delta N-15 changes in the low latitude twilight zone may provide a useful constraint on emerging changes to nitrogen limitation and NPP over the 21st century. 032 ; 021 UR182