Substrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming

Zhen-Zhen Zheng,Wenchao Deng,Ehui Tan,Dalin Shi,Shuh-Ji Kao,Min Nina Xu,Minhan Dai,Li-Wei Zheng,Yao Zhang,David A Hutchins

doi:10.1038/s41467-020-17366-3

Zhen-Zhen Zheng, Wenchao Deng + Show 8 more

Open Access

https://doi.org/10.1038/s41467-020-17366-3

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Abstract

In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry. Here, we show divergent thermal response patterns for marine AO across a wide onshore/offshore trophic gradient. We find ammonia oxidizer community and ambient substrate co-regulate optimum temperatures (Topt), generating distinct thermal response patterns with Topt varying from ≤14 °C to ≥34 °C. Substrate addition elevates Topt when ambient substrate is unsaturated. The thermal sensitivity of kinetic parameters allows us to predict responses of both AO rate and Topt at varying substrate and temperature below the critical temperature. A warming ocean promotes nearshore AO, while suppressing offshore AO. Our findings reconcile field inconsistencies of temperature effects on AO, suggesting that predictive biogeochemical models need to include such differential warming mechanisms on this key nitrogen cycle process.

Highlights

In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry
Within the temperature range of ~14 to ~34 °C in our incubations, the observed ammonia oxidation rate (AOR) at the ambient substrate level (AORambient, see Methods) varied over 3 orders of magnitude, from 0.5 to ~4000 nM d−1, across a wide spectrum of ambient ammonium levels ranging from 14 nM to 96 μM (Fig. 1)
The Type III pattern was observed at station JLR3, N2, N3 and J1, for which the their optimum temperatures (Topt) of the AOR varied from 20 to 29 °C, with rates decreasing toward both higher and lower temperatures (Fig. 1c, g–i)

Summary

Introduction

In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry. The Type III pattern was observed at station JLR3 (outer estuary), N2 (shelf), N3 and J1 (basin), for which the Topt of the AOR varied from 20 to 29 °C, with rates decreasing toward both higher and lower temperatures (Fig. 1c, g–i).

Results

Conclusion