Tidal marsh degradation has been attributed to a number of different causes, but few studies have examined multiple potential factors at the same sites. Differentiating the diverse drivers of marsh loss is critical to prescribing successful interventions for conservation and restoration of this important habitat. We evaluated two hypotheses for vegetation loss at two marshes in Long Island Sound (LIS): (1) marsh submergence, caused by an imbalance between sea-level rise and marsh accretion, and (2) defoliation associated with herbivory by the purple marsh crab, Sesarma reticulatum. At our western LIS site, we found no evidence of herbivory: crabs were scarce, and crab-exclusion cages provided no benefit. We attribute degradation at that site to submergence, a conclusion supported by topographic and hydrologic data showing that loss of vegetation occurred only in wetter parts of the marsh. In contrast, at our central LIS site, our observations were consistent with herbivory as a driving force: There were substantial populations of Sesarma, crab-exclusion cages allowed plants to thrive, and vegetation loss took place across a variety of elevations. We also analyzed soil conditions at both sites, in order to determine the signatures of different degradation processes and assess the potential for restoration. At the submergence site, unvegetated soils exhibited high bulk density, low organic content, and low soil strength, posing significant biogeochemical challenges to re-colonization by vegetation. At the herbivory site, unvegetated soils had a characteristic “riddled-peat” appearance, resulting from expansion and erosion of Sesarma burrow networks. The high redox potential and organic content of those soils suggested that revegetation at the herbivory site would be likely if Sesarma populations could be controlled before erosion leads to elevation loss.
Herbivory Marsh submergence Sea level rise Sesarma reticulatumLong Island Sound
This is a preview of subscription content, log in to check access.
This study was supported by funding from Connecticut Sea Grant, the Sounds Conservancy, the Jubitz Endowment, and the Carpenter-Sperry Fund. We would like to thank Jonas Karosas, Helmut Ernstberger, Brad Erkkila, Katharine Cooper, Jamie O’Connell, Michelle Camp, and Bunyod Holmatov for assistance in the field and lab.
Altieri, A.H., M.D. Bertness, T.C. Coverdale, N.C. Herrmann, and C. Angelini. 2012. A trophic cascade triggers collapse of a salt-marsh ecosystem with intensive recreational fishing. Ecology 93: 1402–1410.CrossRefGoogle Scholar
Altieri, A.H., M.D. Bertness, T.C. Coverdale, E.E. Axelman, N.C. Herrmann, and P.L. Szathmary. 2013. Feedbacks underlie the resilience of salt marshes and rapid reversal of consumer-driven die-off. Ecology 94: 1647–1657. doi:10.1890/12-1781.1.
Anisfeld, S.C., T.D. Hill, and D.R. Cahoon. 2016. Elevation dynamics in a restored versus a submerging salt marsh in Long Island Sound. Estuarine, Coastal and Shelf Science 170: 145–154. doi:10.1016/j.ecss.2016.01.017.CrossRefGoogle Scholar
Bertness, M.D., C.P. Brisson, M.C. Bevil, and S.M. Crotty. 2014a. Herbivorsy drives the spread of salt marsh die-off. Plos One 9: e92916.CrossRefGoogle Scholar
D’Alpaos, A., S.M. Mudd, and L. Carniello. 2011. Dynamic response of marshes to perturbations in suspended sediment concentrations and rates of relative sea level rise. Journal of Geophysical Research-Earth Surface 116: F04020. doi:10.1029/2011jf002093.Google Scholar
Davidson, T.M., and C.E. de Rivera. 2010. Accelerated erosion of saltmarshes infested by the non-native burrowing crustacean Sphaeroma quoianum. Marine Ecology: Progress Series 419: 129–136. doi:10.3354/meps08836.CrossRefGoogle Scholar
Day, J.W., G.P. Shaffer, L.D. Britsch, D.J. Reed, S.R. Hawes, and D. Cahoon. 2000. Pattern and process of land loss in the Mississippi Delta: a spatial and temporal analysis of wetland habitat change. Estuaries 23: 425–438.CrossRefGoogle Scholar
Deegan, L.A., D.S. Johnson, R.S. Warren, B.J. Peterson, J.W. Fleeger, S. Fagherazzi, and W.M. Wollheim. 2012. Coastal eutrophication as a driver of salt marsh loss. Nature 490: 388–392. doi:10.1038/nature11533.CrossRefGoogle Scholar
DeLaune, R.D., J.A. Nyman, and W.H. Patrick Jr. 1994. Peat collapse, ponding and wetland loss in a rapidly submerging coastal marsh. Journal of Coastal Research 10: 1021–1030.Google Scholar
Elmer, W.H., J.A. LaMondia, S. Useman, I.A. Mendelssohn, R.W. Schneider, M.M. Jimenez-Gasco, R.E. Marra, and F.L. Caruso. 2013. Sudden vegetation dieback in Atlantic and Gulf Coast salt marshes. Plant Disease 97: 436–445. doi:10.1094/pdis-09-12-0871-fe.CrossRefGoogle Scholar
Fagherazzi, S., G. Mariotti, P.L. Wiberg, and K.J. McGlathery. 2013. Marsh collapse does not require sea level rise. Oceanography 26: 70–77.CrossRefGoogle Scholar
Hughes, Z.J., D.M. FitzGerald, C.A. Wilson, S.C. Pennings, K. Wieski, and A. Mahadevan. 2009. Rapid headward erosion of marsh creeks in response to relative sea level rise. Geophysical Research Letters 36: 5. doi:10.1029/2008gl036000.CrossRefGoogle Scholar
Kirwan, M.L., G.R. Guntenspergen, A. D’Alpaos, J.T. Morris, S.M. Mudd, and S. Temmerman. 2010. Limits on the adaptability of coastal marshes to rising sea level. Geophysical Research Letters 37, L23401. doi:10.1029/2010gl045489.CrossRefGoogle Scholar
Kirwan, M.L., A.B. Murray, J.P. Donnelly, and D.R. Corbett. 2011. Rapid wetland expansion during European settlement and its implication for marsh survival under modern sediment delivery rates. Geology 39: 507–510. doi:10.1130/g31789.1.CrossRefGoogle Scholar
Mariotti, G., and S. Fagherazzi. 2013. Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise. Proceedings of the National Academy of Sciences of the United States of America 110: 5353–5356. doi:10.1073/pnas.1219600110.CrossRefGoogle Scholar
Morris, J.T., P.V. Sundareshwar, C.T. Nietch, B. Kjerfve, and D.R. Cahoon. 2002. Responses of coastal wetlands to rising sea level. Ecology 83: 2869–2877.CrossRefGoogle Scholar
Rybczyk, J.M., and D.R. Cahoon. 2002. Estimating the potential for submergence for two wetlands in the Mississippi River Delta. Estuaries 25: 985–998.CrossRefGoogle Scholar
Seiple, W., and M. Salmon. 1982. Comparative social-behavior of 2 grapsid crabs, Sesarma-reticulatum (Say) and Sesarma-cinereum (Bosc). Journal of Experimental Marine Biology and Ecology 62: 1–24. doi:10.1016/0022-0981(82)90213-1.CrossRefGoogle Scholar
Shepard, C.C., C.M. Crain, and M.W. Beck. 2011. The protective role of coastal marshes: a systematic review and meta-analysis. Plos One 6.Google Scholar
Smith, S.M., and C.W. Green. 2015. Sediment suspension and elevation loss triggered by Atlantic mud fiddler crab (Uca pugnax) bioturbation in salt marsh dieback areas of southern New England. Journal of Coastal Research 31: 88–94. doi:10.2112/jcoastres-d-12-00260.1.CrossRefGoogle Scholar
Smith, S.M., K.C. Medeiros, and M.C. Tyrrell. 2012. Hydrology, Herbivory, and the Decline of Spartina patens (Aiton) Muhl. in Outer Cape Cod Salt Marshes (Massachusetts, USA). Journal of Coastal Research 28: 602–612. doi:10.2112/jcoastres-d-10-00175.1
Smith, S.M., M.C. Tyrrell, and M. Congretel. 2013. Palatability of salt marsh forbs and grasses to the purple marsh crab (Sesarma reticulatum) and the potential for re-vegetation of herbivory-induced salt marsh dieback areas in Cape Cod (Massachusetts, USA). Wetlands Ecology and Management 21: 263–275. doi:10.1007/s11273-013-9298-2.CrossRefGoogle Scholar
Swanson, R.L., and R.E. Wilson. 2008. Increased tidal ranges coinciding with Jamaica Bay development contribute to marsh flooding. Journal of Coastal Research 24: 1565–1569. doi:10.2112/07-0907.1.CrossRefGoogle Scholar
Turner, R.E. 2004. Coastal wetland subsidence arising from local hydrologic manipulations. Estuaries 27: 265–272.CrossRefGoogle Scholar
Wilson, C.A., Z.J. Hughes, and D.M. FitzGerald. 2012. The effects of crab bioturbation on Mid-Atlantic saltmarsh tidal creek extension: geotechnical and geochemical changes. Estuarine, Coastal and Shelf Science 106: 33–44. doi:10.1016/j.ecss.2012.04.019.CrossRefGoogle Scholar