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Carbon storage in the Mississippi River delta enhanced by environmental engineering

Nature Geoscience volume 10, pages 846851 (2017) | Download Citation

Abstract

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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Acknowledgements

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.

Author information

Affiliations

  1. Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, USA

    • Michael R. Shields
    • , Thomas S. Bianchi
    • , Jack A. Hutchings
    •  & Jason H. Curtis
  2. Jackson School of Geosciences, University of Texas, Austin, Texas 78712, USA

    • David Mohrig
  3. Land Use and Environmental Change Institute, University of Florida, Gainesville, Florida 32611, USA

    • William F. Kenney
  4. Louisiana Universities Marine Consortium, 8124 Highway 56, Chauvin, Louisiana 70344, USA

    • Alexander S. Kolker
  5. Department of Earth and Environmental Sciences, Tulane University, New Orleans, Louisiana 70118, USA

    • Alexander S. Kolker

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Contributions

M.R.S., T.S.B. and D.M. determined the sampling strategy. M.R.S. and A.S.K. collected the cores. M.R.S. and J.H.C. conducted the laboratory analyses. M.R.S. and J.A.H. conducted the data processing and statistical analyses. M.R.S., T.S.B., D.M., J.A.H., W.F.K., A.S.K. and J.H.C. critically analysed the results and wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Michael R. Shields.

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https://doi.org/10.1038/ngeo3044