Impact of intensifying nitrogen limitation on ocean net primary production is fingerprinted by nitrogen isotopes

Nat Commun. 2021 Oct 28;12(1):6214. doi: 10.1038/s41467-021-26552-w.

Abstract

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 (δ15N) and constitutes the primary perturbation of the 21st century nitrogen cycle. Model experiments show that ~75% of the low latitude twilight zone develops anomalously low δ15N 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 δ15N changes in the low latitude twilight zone may provide a useful constraint on emerging changes to nitrogen limitation and NPP over the 21st century.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Climate Change
  • Nitrogen Cycle
  • Nitrogen Isotopes / analysis*
  • Nitrogen Isotopes / metabolism
  • Oceans and Seas
  • Phytoplankton / metabolism
  • Seawater / analysis*

Substances

  • Nitrogen Isotopes