Microplastics alter nitrous oxide production and pathways through affecting microbiome in estuarine sediments

Area of Science:

• Environmental Science
• Microbiology
• Biogeochemistry

Background:

• Microplastics (MPs) are pervasive pollutants in estuarine environments.
• MPs significantly impact microbial ecosystems and biogeochemical processes.
• Nitrous oxide (N₂O), a potent greenhouse gas, is a key intermediate in microbial nitrogen cycling, but MP regulation of its production and pathways is unclear.

Purpose of the Study:

• To investigate the effects of traditional petroleum-based and biodegradable MPs on microbial N₂O production and its pathways in estuaries.
• To compare the impact of different MP types, including polylactic acid (PLA), polyvinyl chloride (PVC), and polyethylene (PE), on N₂O emissions.

Main Methods:

• Utilized dual-isotope (¹⁵N-¹⁸O) labeling technique to trace N₂O pathways.
• Employed molecular methods to analyze microbial communities and functional genes.
• Assessed N₂O production rates alongside sediment chemical and microbiological properties.

Main Results:

• Both traditional and biodegradable MPs enhanced sedimentary N₂O production, with varying pathway dominance.
• Biodegradable PLA MPs showed a greater promotion of N₂O production compared to PE and PVC.
• PLA promoted N₂O via nitrifier nitrification (NN) and heterotrophic denitrification (HD); PE via nitrifier denitrification and HD; PVC via NN.
• MPs enriched nitrifying bacteria in all treatments and denitrifying bacteria in PLA and PE treatments, altering nitrogen cycling.

Conclusions:

• MPs promote sedimentary N₂O production in estuaries.
• Emerging biodegradable MPs, particularly PLA, may significantly increase estuarine N₂O emissions.
• This enhanced N₂O release has implications for accelerating global climate change.