Marsh restoration carbon fix comes with a nitrogen tradeoff
Wilburn B, Ikeh R, Potapova M, Smyth A, Fountain M
Soil Health
Coastal marsh restoration projects are increasingly adding charcoal-like biochar to fight sea level rise, and this study shows that same fix can backfire on the wetland's natural water-filtering job.
Scientists are mixing biochar, a charcoal-like material, into rebuilt salt marshes to help them store more carbon and withstand rising seas. But when they tested it, marshes with older biochar lost most of their ability to break down excess nitrogen in the water, a process called denitrification. The biochar did shift which microbes lived in the soil and boosted carbon storage, but it came at the cost of one of the marsh's key pollution-filtering jobs.
Key Findings
Aged biochar reduced denitrification rates by 88%, while fresh biochar had no measurable effect on denitrification.
No detectable DNRA (an alternative nitrate reduction pathway) was observed in any treatment.
Biochar-amended sediments had higher relative abundances of Cyanobacteria and Truepera, greater carbon content, and distinct microbial functional profiles (more inferred fermentation, less sulfate reduction) compared to restoration sediments (F = 3.22, p = 0.026).
chevron_right Technical Summary
Adding biochar to restored California salt marsh sediments boosted carbon storage but cut the soil's ability to remove excess nitrogen, with aged biochar reducing denitrification by 88%.
Abstract Preview
Original paper
Biochar amendments in a California salt marsh restoration reduced denitrification and supported distinct microbial community functions.
Accelerated sea level rise, combined with human-induced changes to hydrology and sediment transport, threatens the long-term persistence of coastal wetlands. Sediment addition is increasingly used ...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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