{
  "id": 8128172,
  "title": "Fossil plankton shells reveal reduced nitrogen fixation in warmer oceans 3 million years ago",
  "url": "https://urgent.news/2026/09/18/fossil-plankton-shells-reveal-reduced-nitrogen-fixation-in-warmer",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-18T00:00:05.000Z",
  "source": {
    "name": "Phys.org",
    "slug": "phys-org",
    "url": "https://phys.org/news/2026-09-fossil-plankton-shells-reveal-nitrogen.html"
  },
  "original_language": "en",
  "account": "Researchers have discovered that in the warm late Pliocene era, nearly 3 million years ago, the process of natural nitrogen fixation in the tropical Atlantic Ocean decreased significantly. Nitrogen fixation is the conversion of nitrogen gas into a form usable by marine life, and it is vital for the ocean's food web. The study, published in Nature Communications, analyzed fossil shells of foraminifera, microscopic organisms that incorporated nitrogen into their shells as they grew. The findings reveal a connection between nitrogen fixation and another key process, denitrification, which removes nitrogen from the ocean and returns it to the atmosphere. During the late Pliocene, denitrification also decreased, leading to a decline in nitrogen fixation. When denitrification slowed in the Pacific Ocean, less phosphorus reached the Atlantic, causing nitrogen fixation to decline as well. This pattern persisted even as the ocean's overall nitrogen balance remained relatively stable. The researchers note that the ocean's nitrogen cycle may remain balanced under future climate changes, although the nutrient supply to different regions might vary. Another interesting pattern emerged when the scientists looked at the relationship between nitrogen fixation and Earth's Milanković cycles, which are periodic variations in Earth's orbit around the sun. They found that during colder interglacial periods, higher sea levels flooded continental shelves, promoting local nitrogen fixation as microbes removed nitrogen from the water and left phosphorus behind. However, when sea levels fell during glacials, exposing the shelves, phosphorus sources dwindled, and nitrogen fixation declined in the Caribbean. Overall, these findings help scientists understand the long-term context of Atlantic nitrogen fixation and demonstrate that the driving force behind this process shifts between warmer and cooler climates.",
  "summary": "Nitrogen is a key nutrient because it fuels the growth of plankton, which forms the basis of the marine food web. Two opposing processes determine the global nitrogen cycle: nitrogen fixation and denitrification.",
  "key_points": [
    "Nitrogen fixation in tropical Atlantic Ocean declined 3 million years ago",
    "Foraminifera shells show reduced nitrogen fixation during late Pliocene era",
    "Denitrification decrease linked to nitrogen fixation decline in Pliocene"
  ],
  "editors_take": "The decline in nitrogen fixation in warmer oceans 3 million years ago reveals a climate-dependent shift in the ocean's nitrogen cycle, where nutrient supply and regional variations may persist under future climate changes.",
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}