Early View
Research Article

Resilience to multiple stressors in an aquatic plant and its microbiome

Anna M. O'Brien

Corresponding Author

E-mail address: anna.obrien@utoronto.ca

Department of Ecology and Evolutionary Biology, University of Toronto

Author for correspondence (e‐mail:

anna.obrien@utoronto.ca

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Zhu Hao Yu

Department of Chemical Engineering and Applied Chemistry, University of Toronto

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Dian‐ya Luo

Department of Ecology and Evolutionary Biology, University of Toronto

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Jason Laurich

Department of Ecology and Evolutionary Biology, University of Toronto

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Elodie Passeport

Department of Chemical Engineering and Applied Chemistry, University of Toronto

Department of Civil and Mineral Engineering, University of Toronto

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Megan E. Frederickson

Department of Ecology and Evolutionary Biology, University of Toronto

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First published: 26 December 2019

Abstract

Premise

Outcomes of species interactions, especially mutualisms, are notoriously dependent on environmental context, and environments are changing rapidly. Studies have investigated how mutualisms respond to or ameliorate anthropogenic environmental changes, but most have focused on nutrient pollution or climate change and tested stressors one at a time. Relatively little is known about how mutualisms may be altered by or buffer the effects of multiple chemical contaminants, which differ fundamentally from nutrient or climate stressors and are especially widespread in aquatic habitats.

Methods

We investigated the impacts of two contaminants on interactions between the duckweed Lemna minor and its microbiome. Sodium chloride (salt) and benzotriazole (a corrosion inhibitor) often co‐occur in runoff to water bodies where duckweeds reside. We tested three L. minor genotypes with and without the culturable portion of their microbiome across field‐realistic gradients of salt (3 levels) and benzotriazole (4 levels) in a fully factorial experiment (24 treatments, tested on each genotype) and measured plant and microbial growth.

Results

Stressors had conditional effects. Salt decreased both plant and microbial growth and decreased plant survival more as benzotriazole concentrations increased. In contrast, benzotriazole did not affect microbial abundance and even benefited plants when salt and microbes were absent, perhaps due to biotransformation into growth‐promoting compounds. Microbes did not ameliorate duckweed stressors; microbial inoculation increased plant growth, but not at high salt concentrations.

Conclusions

Our results suggest that multiple stressors matter when predicting responses of mutualisms to global change and that beneficial microbes may not always buffer hosts against stress.