Environment International (Feb 2023)

Molecular transformation of organic nitrogen in Antarctic penguin guano-affected soil

  • Libin Wu,
  • Ming Sheng,
  • Xiaodong Liu,
  • Zhangqin Zheng,
  • Steven D. Emslie,
  • Ning Yang,
  • Xueying Wang,
  • Yaguang Nie,
  • Jing Jin,
  • Qiaorong Xie,
  • Shuang Chen,
  • Donghuan Zhang,
  • Sihui Su,
  • Shujun Zhong,
  • Wei Hu,
  • Junjun Deng,
  • Jialei Zhu,
  • Yulin Qi,
  • Cong-Qiang Liu,
  • Pingqing Fu

Journal volume & issue
Vol. 172
p. 107796

Abstract

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Organic nitrogen (ON) is an important participant in the Earth’s N cycle. Previous studies have shown that penguin feces add an abundance of nutrients including N to the soil, significantly changing the eco-environment in ice-free areas in Antarctica. To explore the molecular transformation of ON in penguin guano-affected soil, we collected guano-free weathered soil, modern guano-affected soil from penguin colonies, ancient guano-affected soil from abandoned penguin colonies, and penguin feces from the Ross Sea region, Antarctica, and Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) was used to investigate the chemical composition of water-extractable ON. By comparing the molecular compositions of ON among different samples, we found that the number of ON compounds (>4,000) in weathered soil is minimal, while carboxylic-rich alicyclic-like molecules (CRAM-like) are dominant. Penguin feces adds ON into the soil with > 10,000 CHON, CHONS and CHN compounds, including CRAM-like, lipid-like, aliphatic/ peptide-like molecules and amines in the guano-affected soil. After the input of penguin feces, macromolecules continue to degrade, and other ON compounds tend to be oxidized into relatively stable CRAM-like molecules, this is an important transformation process of ON in guano-affected soils. We conclude the roles of various forms of ON in the N cycle are complex and diverse. Combined with previous studies, ON eventually turns into inorganic N and is lost from the soil. The lost N ultimately returns to the ocean and the food web, thus completing the N cycle. Our study preliminarily reveals the molecular transformation of ON in penguin guano-affected soil and is important for understanding the N cycle in Antarctica.

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