Seasonal nitrogen fluxes of the Lena River Delta

Anthropogenic global warming is changing the global nitrogen cycle. The Arctic ecosystems, a oligotrophic region, are limited in nitrogen, , which is warming approximately twice as rapidly as the global average and therefore sensitive to changes in nitrogen cycling. Arctic warming intensifies thawing of permafrost soils, which releases their large organic nitrogen reservoir. Released organic nitrogen reaches hydrological systems and is transported by large rivers to the Arctic Ocean. We estimate the load of nitrogen supplied from terrestrial sources into the Arctic Ocean by sampling Lena River water along one of the major deltaic channels in winter and summer in 2019 and at a stationary location in the central delta over a one-year cycle. Additionally, we investigate the potential release of reactive nitrogen including nitrous oxide from soils. We found that the Lena Delta region added approximately 25% of total nitrogen to the river and transported mainly organic nitrogen to the ocean. This has the potential to increase the primary production locally in the river and downstream in the coastal ocean. The higher availability of inorganic nitrogen is the source to enhance N2O emissions from terrestrial and aquatic sources to the atmosphere