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 compared with other samples, in which 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 reveals the molecular transformation of ON in penguin guano-affected soil, which is important for understanding the N cycle in Antarctica.
Graphical abstract
Citation: Wu, L.B.#, Sheng, M.#, Liu, X.D.*, Zheng, Z.Q., Emslie, S.D., Yang, N., Wang, X.Y., Nie, Y.G., Jin, J., Xie, Q.R., Chen, S., Zhang, D.H., Su, S.H., Zhong, S.J., Hu, W., Deng, J.J., Zhu, J.L., Qi, Y.L., Liu, C.-Q., Fu, P.Q.*, 2023. Molecular transformation of organic nitrogen in Antarctic penguin guano-affected soil. Environment International 172, 107796. https://doi.org/10.1016/j.envint.2023.107796
