River deltas have contributed to atmospheric carbon regulation throughout Earth history, but functioning in the modern era has been impaired by reduced sediment loads, altered hydrologic regimes, increased global sea-level rise and accelerated subsidence. Delta restoration involves environmental engineering via river diversions, which utilize self-organizing processes to create prograding deltas. Here we analyse sediment cores from Wax Lake delta, a product of environmental engineering, to quantify the burial of organic carbon. We find that, despite relatively low concentrations of organic carbon measured in the cores (about 0.4%), the accumulation of about 3 T m−2 of sediment over the approximate 60 years of delta building resulted in the burial of a significant amount of organic carbon (16 kg m−2). This equates to an apparent organic carbon accumulation rate of 250 ± 23 g m−2 yr−1, which implicitly includes losses by carbon emissions and erosion. Our estimated accumulation rate for Wax Lake delta is substantially greater than previous estimates based on the top metre of delta sediments and comparable to those of coastal mangrove and marsh habitats. The sedimentation of carbon at the Wax Lake delta demonstrates the capacity of engineered river diversions to enhance both coastal accretion and carbon burial.
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We thank the Gulf Coast Association of Geological Societies (GCAGS) for the student grant that supported our field work. The Jon and Beverly Thompson Chair in Geological Sciences at University of Florida provided support for the laboratory analyses.
The authors declare no competing financial interests.
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Shields, M., Bianchi, T., Mohrig, D. et al. Carbon storage in the Mississippi River delta enhanced by environmental engineering. Nature Geosci 10, 846–851 (2017). https://doi.org/10.1038/ngeo3044
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