Nitrogen input modulates the effects of coastal acidification on nitrification and associated N2O emission

Highlights

• N input influenced the response of nitrifying microbes to coastal acidification.
• Elevated N input alleviated the inhibitory effect of acidification on nitrification.
• Increase of N input intensified the production of N₂O under coastal acidification.
• Metatranscriptome data further provided microbial evidence at transcriptional level.

Abstract

Acidification of coastal waters, synergistically driven by increasing atmospheric carbon dioxide (CO₂) and intensive land-derived nutrient inputs, exerts significant stresses on the biogeochemical cycles of coastal ecosystem. However, the combined effects of anthropogenic nitrogen (N) inputs and aquatic acidification on nitrification, a critical process of N cycling, remains unclear in estuarine and coastal ecosystems. Here, we showed that increased loading of ammonium (NH₄⁺) in estuarine and coastal waters alleviated the inhibitory effect of acidification on nitrification rates but intensified the production of the potent greenhouse gas nitrous oxide (N₂O), thus accelerating global climate change. Metatranscriptomes and natural N₂O isotopic signatures further suggested that the enhanced emission of N₂O may mainly source from hydroxylamine (NH₂OH) oxidation rather than from nitrite (NO₂⁻) reduction pathway of nitrifying microbes. This study elucidates how anthropogenic N inputs regulate the effects of coastal acidification on nitrification and associated N₂O emissions, thereby enhancing our ability to predict the feedbacks of estuarine and coastal ecosystems to climate change and human perturbations.

Zhou J., Zheng Y., Hou L., Qi L., Mao T., Yin G., Liu M., 2024. Nitrogen input modulates the effects of coastal acidification on nitrification and associated N2O emission. Water Research 261: 122041. doi: 10.1016/j.watres.2024.122041. Article (subscription required).

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