Elevation change and the vulnerability of Rhode Island (USA) salt marshes to sea-level rise
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Salt marshes persist within the intertidal zone when marsh elevation gains are commensurate with rates of sea-level rise (SLR). Monitoring changes in marsh elevation in concert with tidal water levels is therefore an effective way to determine if salt marshes are keeping pace with SLR over time. Surface elevation tables (SETs) are a common method for collecting precise data on marsh elevation change. Southern New England is a hot spot for SLR, but few SET elevation change datasets are available for the region. Our study synthesizes elevation change data collected from 1999 to 2015 from a network of SET stations throughout Rhode Island (RI). These data are compared to accretion and water level data from the same time period to estimate shallow subsidence and determine whether marshes are tracking SLR. Salt marsh elevation increased at a mean overall rate of 1.40 mm year−1 and ranged from −0.33 to 3.36 mm year−1 at individual stations. Shallow subsidence dampened elevation gain in mid-Narragansett Bay marshes, but in other areas of coastal RI, subsurface processes may augment surface accretion. In all cases, marsh elevation gain was exceeded by the 5.26 mm year−1 rate of increase in sea levels during the study period. Our study provides the first SET elevation change data from RI and shows that most RI marshes are not keeping pace with short- or long-term rates of SLR. It also lends support to previous research that implicates SLR as a primary driver of recent changes to southern New England salt marshes.
KeywordsNew England Resilience Surface elevation table Accretion
We would like to thank all the staff, students, and volunteers who helped install and read SETs and marker horizons across the RI network. In particular, this includes James Lynch, Robin Weber, Daisy Durant, Erin King, Rhonda Smith, Benjamin Gaspar, Jennifer White, Kevin Rogers, Dr. Larry Ward, and Alison Bowden. We would also like to thank Robin Weber for creating Fig. 1, Philippe Hensel for advice on SET data analysis and interpretation, Elizabeth Watson for guidance on manuscript preparation, and Jordan Mora for SET elevation change data from the Waquoit Bay National Estuarine Research Reserve. Financial support was provided in part by a grant under the Federal Coastal Zone Management Act, administered by the Office of Ocean and Coastal Management, National Oceanic and Atmospheric Administration, Silver Spring, MD. Additional funding was provided by the U.S. Fish and Wildlife Service LMRD program, Inventory and Monitoring effort and the Hurricane Sandy DOI #30 “Stronger Coast” project. The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the US Fish and Wildlife Service.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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