Key Findings
This research demonstrates how harnessing variation in plants and microbiomes could improve bioremediation (i.e., the process in which biological systems transform organic contaminants into less toxic byproducts). Researchers found that experimental microcosms with duckweeds rapidly transformed the organic contaminant benzotriazole. However, microcosms with duckweeds from rural sites, diverse microbiomes, or algae biotransformed a larger amount of benzotriazole.
About the Co-Author
Anna O'Brien, Assistant Professor, Molecular, Cellular, and Biomedical Sciences
Contact information: Anna.OBrien@unh.edu, 603-862-0157, The O’Brien Lab at UNH
This research first published in Water Research.
Researchers: A. O'Brien, Z. Yu, C. Pencer, M. Frederickson, G. LeFevre, E. Passeport
The continued urbanization of our human population and the associated expanding urban land area necessitates better management of urban ecological issues. One of these issues is the influx of contaminants into urban stormwater. For example, North American freshwater lakes in areas that use road salt have become much saltier, thereby threatening aquatic life. Winter brings more than just salt contamination too, as anti-corrosives (such as the organic compound benzotriazole) are commonly co-applied with salt. Natural and constructed wetlands are key tools in managing urban stormwater, largely because plants and microbes favor transformation of many organic pollutants into less dangerous products. However, constructed wetlands vary in effectiveness, suggesting that there is room for improvement. One potential source of improvement could be harnessing the diversity of microbiomes. Leveraging diverse microbiomes for applied purposes is often touted, but rarely practiced.
In this study, researchers used more than 2,500 constructed microcosms to demonstrate how naturally occurring and manipulable biological variation could be leveraged for water bioremediation in a model plant-microbiome-contaminant system: the common freshwater plant duckweed (Lemna minor) and co-occurring microbiomes from 50 different sites, with the winter co-contaminants benzotriazole and salt (sodium chloride). Benzotriazole is commonly used as an anti-corrosive and has a relatively long half-life, meaning it can persist without breaking down for a long time. While it is usually found in environments at concentrations below those affecting most aquatic organisms, its environmental fate is poorly understood.
In all of the experimental microcosms with duckweeds, the researchers saw extremely rapid transformation of benzotriazole. Normally, they would expect high levels of salt to interfere with biotransformation of organic contaminants, but benzotriazole was rapidly transformed even in concentrations of salt at urban runoff levels. However, the researchers would not expect all duckweeds and microbiomes to be equivalent if included in new constructed wetlands. Duckweeds from rural sites, duckweeds with diverse microbiomes, and duckweeds with added algae (Chlorella vulgaris) could help optimize benzotriazole removal and minimize byproduct toxicity.
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High Park in the city of Toronto, in Ontario, Canada, with duckweeds in the foreground. Image courtesy of Anna O’Brien.
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An image of duckweed shown in a 96-well plate. Image courtesy of Anne O’Brien.
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Microscopic image of duckweed (Lemna minor). Image courtesy of Anne O’Brien, Nicholas Deakin, Ph.D., Nikkon Instruments.
This project was funded by NSERC Discovery Grants and a University of Toronto XSeed Grant to MEF and EP, NSERC Canada Research Chair program grants to EP (950-230892), and by the Gordon and Betty Moore Foundation grant GBMF9356 to MEF. GHL acknowledges NSF CBET CAREER funding (1844720). The researchers thank Hollis Dahn for collecting two duckweed sources, and Frederickson lab members for useful discussion. Co-authors include A. O'Brien, Z. Yu, C. Pencer, M. Frederickson, G. LeFevre and E. Passeport.
