09 Jul 2020

09 Jul 2020

Review status: a revised version of this preprint is currently under review for the journal ESurf.

Biophysical controls of marsh soil shear strength along an estuarine salinity gradient

Megan N. Gillen1,2,3, Tyler C. Messerschmidt4, and Matthew L. Kirwan4 Megan N. Gillen et al.
  • 1Department of Geology, William & Mary, Williamsburg, VA 23187-8795, USA
  • 2Earth, Atmospheric, and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
  • 3Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  • 4Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA 23062-1346, USA

Abstract. Sea-level rise, saltwater intrusion, and wave erosion threaten coastal marshes, but the influence of salinity on marsh erodibility remains poorly understood. We measured the shear strength of marsh soils along a salinity and biodiversity gradient in the York River estuary in Virginia to assess the direct and indirect impacts of salinity on marsh erodibility. We found that soil shear strength was higher in monospecific salt marshes (5–36 kPa) than biodiverse freshwater marshes (4–8 kPa), driven by differences in belowground biomass and rooting structure. However, we also found that shear strength at the marsh edge was controlled by sediment characteristics, rather than vegetation or salinity, suggesting that inherent relationships may be obscured in more dynamic environments. Our results indicate that freshwater marsh soils are weaker than salt marsh soils, and suggest that salinization of freshwater marshes may lead to simultaneous losses in biodiversity and erodibility.

Megan N. Gillen et al.

Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Megan N. Gillen et al.

Data sets

Shear Stress, Biomass, Bulk Density, Organic Matter on the Bank of the York River, VA 2018 Megan N. Gillen, Tyler C. Messerschmidt, and Matthew L. Kirwan

Megan N. Gillen et al.


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Short summary
We measured the shear strength of marsh soils along an estuarine salinity gradient to determine salinity's influence on marsh erodibility. Our work is one of the first studies to directly examine the relationship between salinity and marsh erodibility. We find that an increase in salinity correlates to higher soil shear strength values, indicating that salt marshes may be more resistant to erosion. We also show that both belowground biomass and soil properties drive shear strength differences.