Scientists have discovered that future changes in air pollution and agricultural emissions could significantly alter the amount of nitrogen deposited into the world’s oceans, with cascading effects on marine ecosystems and climate. The new study shows that managing nitrogen pollution may require coordinated strategies rather than controlling individual pollutants separately.
The research was conducted by an international team of scientists using a global atmospheric chemistry model to simulate how nitrogen emissions may evolve between 2015 and 2050 under different socioeconomic and climate policy scenarios. Their findings reveal that global oceanic nitrogen deposition could change by as much as minus 24 percent to plus 6 percent depending on future emission pathways.
Atmospheric nitrogen deposition occurs when reactive nitrogen compounds released into the air by human activities such as fossil fuel combustion, fertilizer use, and livestock production eventually settle onto land or ocean surfaces. When this nitrogen reaches the ocean, it can act as a nutrient that stimulates the growth of phytoplankton, microscopic organisms that form the foundation of marine food webs and play an important role in the global carbon cycle.
Using the GEOS Chem global atmospheric chemistry transport model, the researchers analyzed how emissions of ammonia and nitrogen oxides influence nitrogen deposition to the oceans under several future scenarios from the CMIP6 climate modeling framework. The results suggest that changes in these emissions will alter not only the total amount of nitrogen reaching the oceans but also the balance between different chemical forms of nitrogen.
One of the most surprising findings was that reducing emissions of only one type of nitrogen compound can unintentionally increase deposition of another. This happens because ammonia and nitrogen oxides interact chemically in the atmosphere, shifting between gas and particle phases in ways that influence how easily they are transported and deposited.
“Many policies focus on reducing a single pollutant, but our results show that nitrogen compounds are strongly linked through atmospheric chemistry,” said the study’s corresponding author. “If we only control one species, such as nitrogen oxides or ammonia, we may unintentionally enhance the deposition of the other to the oceans.”
The study also estimated how these deposition changes could influence marine productivity. In 2015, atmospheric nitrogen deposition to the oceans was estimated at about 51 teragrams of nitrogen per year, supporting roughly 290 teragrams of carbon in ocean productivity. Under a low emission scenario consistent with strong climate mitigation, this nitrogen driven productivity could decline to about 222 teragrams of carbon by 2050. Under a high emission scenario, it could increase to approximately 306 teragrams.
However, the climate implications are not straightforward. The researchers found that changes in nitrogen driven ocean productivity are partly offset by changes in emissions of nitrous oxide, a potent greenhouse gas produced by marine microbial processes. These feedbacks highlight the complex links between atmospheric pollution, ocean ecosystems, and climate.
“Our findings highlight that nitrogen management should be viewed through an Earth system perspective,” the authors noted. “Policies aimed at improving air quality and reducing emissions can also reshape nutrient inputs to the oceans, with consequences for marine ecosystems and climate.”
The study emphasizes the need for integrated nitrogen management strategies that jointly reduce ammonia and nitrogen oxide emissions. Such coordinated approaches could more effectively limit nitrogen deposition to the oceans and avoid unintended environmental impacts.
The researchers say future studies should also consider how climate change itself may influence atmospheric chemistry, ocean circulation, and natural emissions, which could further modify global nitrogen deposition patterns in the coming decades.
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Journal Reference: Deng J, Guo Y, Lu N, Ye X, Zhao Y, et al. 2026. Evolving global oceanic nitrogen deposition under future emission pathways and responses to nitrogen emission reductions. Nitrogen Cycling 2: e013 doi: 10.48130/nc-0025-0025
https://www.maxapress.com/article/doi/10.48130/nc-0025-0025
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Nitrogen Cycling (e-ISSN 3069-8111) is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.
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Evolving global oceanic nitrogen deposition under future emission pathways and responses to nitrogen emission reductions
29-Jan-2026