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

• Published in: Environment International
• Main Authors: 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
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: Organic nitrogen; FT-ICR MS; Soil; Penguin guano; Antarctic ice-free areas; Environmental sciences; GE1-350; Antarctic; Ross Sea; Guano; Antarc*; Antarctica
• Online Access: https://doi.org/10.1016/j.envint.2023.107796; https://doaj.org/article/54d81d825ce843d194418df284d7c7ae

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.