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Closing loopholes in the nitrogen cycle: Nitrification now and in the future

Project Description

Project Rationale:
Nitrification (= oxidation) of ammonia (NH3) back to nitrate (NO3-) is an important regenerative step in the nitrogen cycles of both marine and terrestrial systems. In the ocean, it was initially believed to only occur at depth away from the sunlit surface zone, and this separation was used to develop a methodology, known as the f-ratio, to understand export production (1). Subsequently, improvements in analytical techniques led to more widespread measurements of nitrification being made which suggested that it actually occurred at high rates in the surface ocean, with implications for the f-ratio method (2). More recent work has focused on the competition for ammonia between autotrophic phytoplankton and chemoautotrophic nitrifiers, and how the availability of nitrate mediates a community’s affinity for ammonia, suggesting a more complex picture (3). With changes in the availability of nutrient species under a warmer, more stratified ocean, it is expected that this present-day balance in NH3 consumption will shift. Separately, it has also been suggested that ocean acidification may negatively impact nitrification since ammonia exists in a pH-sensitive chemical balance with ammonium (NH4+), with nitrifying bacteria preferring the former substrate for their growth.

Funding Notes

You can apply for fully-funded studentships (stipend and fees) from INSPIRE if you:
Are a UK or EU national.
Have no restrictions on how long you can stay in the UK.
Have been 'ordinarily resident' in the UK for 3 years prior to the start of the project.

Please click View Website for more information on eligibilty and how to apply


(1) Eppley, R. W. & Peterson, B. J.: Particulate organic matter flux and planktonic new production in the deep ocean. Nature 282, 677–680 (1979).
(2) Yool, A., Martin, A. P., Fernandez, C. & Clark, D. R.: The significance of nitrification for oceanic new production. Nature 447, 999–1002 (2007).
(3) Wan, X.S., Sheng, H.-796 X., Dai, M., Zhang, Y., Shi, D., Trull, T.W., Zhu, Y., Lomas, M.W., & Kao, S.-J.: Ambient nitrate switches the ammonium consumption pathway in the euphotic ocean. Nat. Comm., 9, 915 (2018).

How good is research at University of Southampton in Earth Systems and Environmental Sciences?

FTE Category A staff submitted: 68.62

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