Arctic coastal nutrient limitation linked to tundra greening

Abstract Nutrients supplied by upwelling, mixing, and inflow from adjacent oceans and terrestrial nutrient inputs are key factors regulating primary production in Arctic fjords and coastal areas. However, the contribution of terrestrial nutrient input to marine primary production remains poorly understood. Tundra biomes are highly sensitive to climate change, and vegetation responses to warming such as Arctic greening could modify terrestrial nutrient inputs to fjords and coastal areas. Here we analyze long–term measurements from northeast Greenland, revealing that climate–induced terrestrial greening has increased by 20% from 1999–2021, leading to a 77% decline in terrestrially–derived nitrate input from land to the coastal ecosystem, and a 39% decrease in phytoplankton biomass in the coastal ecosystem. These changes indicate an overall climate–driven decline in nitrate export via terrestrial rivers to the sea, and this oligotrophication may have major consequences for future Arctic coastal ecosystems.