Bacterivorous protists inhibit nitrification and N2O emissions in cadmium polluted soils via negative feedback loops

Xuehua Wang; Youjing Wang; Di Tong; Haochun Zhao; Caixian Tang; Jianming Xu

doi:10.1016/j.jhazmat.2024.136638

Bacterivorous protists inhibit nitrification and N₂O emissions in cadmium polluted soils via negative feedback loops

J Hazard Mater. 2024 Nov 24:483:136638. doi: 10.1016/j.jhazmat.2024.136638. Online ahead of print.

Authors

Xuehua Wang¹, Youjing Wang¹, Di Tong¹, Haochun Zhao¹, Caixian Tang², Jianming Xu³

Affiliations

¹ Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China.
² La Trobe Institute for Sustainable Agriculture and Food, Department of Animal, Plant & Soil Sciences, La Trobe University, Bundoora, VIC 3086, Australia.
³ Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China. Electronic address: jmxu@zju.edu.cn.

PMID: 39608070
DOI: 10.1016/j.jhazmat.2024.136638

Abstract

Understanding the soil nitrogen (N) process under increasing anthropogenic activities, i.e., heavy metal pollution and N fertilization is essential for optimizing soil N management and tackling environmental problems. However, few studies assess how ubiquitous soil protists influence N process from a multitrophic perspective. Here, we conducted microcosm experiments to investigate how phagotrophic protists (Colpoda steinii) influence the autochthonous bacterial flora proxy for N process to drive the N transformation processes under different Cd pollution levels (0-3 mg kg^-1) with or without N fertilization. Because of hormesis, Cd stimulated the net nitrification rate and N₂O emissions by up to 65 % and 100 %, respectively, and this stimulation was stronger after N addition. However, protists attenuated and even reversed the stimulation of Cd on the net nitrification rate and N₂O flux, especially after N addition by correspondingly reducing N fertilization-enhanced nitrifiers and denitrifiers, which were also metabolically active under Cd pollution. With this negative feedback loop, protists reduced the net nitrification rate and N₂O emissions by up to 91 % and 36 %, respectively. This study offers novel insights to assess the effects of heavy metal pollution on soil nutrient cycling regarding soil predation, providing strategies for increasing N-use efficiency in agricultural ecosystems.

Keywords: Colpoda steinii; Denitrifier; Hormesis; Nitrifier; Nitrous oxide.