Weathered plastic bits disrupt nitrogen cycling in coastal wetland soils
Chen R, Ruan S, Liu C, Chen F, Zhang Y
Soil Health
The salt marshes and mudflats that filter runoff before it reaches the coast rely on a delicate microbial nitrogen cycle, and this study shows plastic litter that's been sitting in the environment for a while throws that cycle further off balance than fresh plastic ever would.
Scientists buried two kinds of plastic pieces, some brand new and some weathered by sun and salt water, into tidal wetland soil and watched what happened over three months. The weathered plastic did more damage: it made the soil more acidic, changed its chemistry, and disrupted the balance between two groups of microbes that convert ammonia into forms plants and ecosystems can use. That's a problem because this ammonia-processing step is a bottleneck in the nitrogen cycle that wetland plants and the whole coastal food web depend on.
Key Findings
High-concentration aged polypropylene microplastics reduced total ammonia oxidation rates by about 31.4% after 90 days compared to untreated soil.
Aged microplastics increased ammonia oxidation activity from archaea (AOA) while decreasing it from bacteria (AOB), shifting the microbial balance.
Aged plastics lowered soil pH, raised organic carbon content, increased the Fe2+/Fe3+ ratio, and boosted sulfide accumulation, all of which likely drove the microbial shifts.
chevron_right Technical Summary
Microplastics that have weathered in the environment do more damage to coastal wetland soil chemistry than fresh plastic, cutting the soil's ability to process ammonia by nearly a third and throwing off the microbes that manage nitrogen there.
Abstract Preview
Original paper
Environmentally aged microplastics alter archaeal and bacterial roles in ammonia oxidation of intertidal soils.
Increasing microplastic pollution in intertidal wetlands poses significant risks to global nitrogen cycling. As microplastics inevitably undergo environmental aging, their impacts on soil physicoch...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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Microplastics are persistent synthetic particles (1 μm to 5 mm) that accumulate in terrestrial and aquatic environments. For plant science, these particles are important because they can be taken up by plant roots and potentially affect plant physiology, growth, and ecosystem function.
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