Reduced N(2) fixation in the tropical Atlantic Ocean during the warm late Pliocene.

N2 fixation in the tropical Atlantic decreased during the late Pliocene’s warm period and increased in the late Pleistocene, indicating climate-driven shifts in ocean nitrogen cycling.

• Why it matters: Understanding how oceanic nitrogen sources and sinks respond to past climate changes is crucial for predicting future nutrient dynamics and marine productivity under global warming.
• What they did: Using foraminifera-bound N isotope records from the tropical Atlantic, the study analyzed nitrogen fixation over the past 2.8 million years, focusing on periods of climate variability.
• The result: Findings reveal that N2 fixation decreased during the late Pliocene’s warmth and increased later, suggesting that marine nitrogen budgets may adjust under warming by balancing reductions in both nitrogen fixation and denitrification.