Estuaries and Coasts

, Volume 41, Issue 3, pp 661–675 | Cite as

Effects of Docks on Salt Marsh Vegetation: an Evaluation of Ecological Impacts and the Efficacy of Current Design Standards

  • John M. LoganEmail author
  • Amanda Davis
  • Charles Markos
  • Kathryn H. Ford
Management Applications


Private docks are common in estuaries worldwide. Docks in Massachusetts (northeast USA) cumulatively overlie ~ 6 ha of salt marsh. Although regulations are designed to minimize dock impacts to salt marsh vegetation, few data exist to support the efficacy of these policies. To quantify impacts associated with different dock designs, we compared vegetation characteristics and light levels under docks with different heights, widths, orientations, decking types and spacing, pile spacing, and ages relative to adjacent control areas across the Massachusetts coastline (n = 212). We then evaluated proportional changes in stem density and biomass of the dominant vegetation (Spartina alterniflora and Spartina patens) in relation to dock and environmental (marsh zone and nitrogen loading) characteristics. Relative to adjacent, undeveloped habitat, Spartina spp. under docks had ~ 40% stem density, 60% stem biomass, greater stem height and nitrogen content, and a higher proportion of S. alterniflora. Light availability was greater under taller docks and docks set at a north-south orientation but did not differ between decking types. Dock height best predicted vegetation loss, but orientation, pile spacing, decking type, age, and marsh zone also affected marsh production. We combined our proportional biomass and stem elemental composition estimates to calculate a statewide annual loss of ~ 2200 kg dry weight of Spartina biomass (367 kg per ha of dock coverage). Managers can reduce impacts through design modifications that maximize dock height (> 150 cm) and pile spacing while maintaining a north-south orientation, but dock proliferation must also be addressed to limit cumulative impacts.


Aboveground biomass Cumulative impacts Light attenuation Shading Spartina Stem density 



We would like to thank Holly Williams, Alina Arnheim, Drew Collins, David Behringer, Christian Petitpas, Tay Evans, Katelyn Ostrikis, Jillian Carr, and Wesley Dukes for their assistance with field sampling. Vincent Manfredi provided equipment for grass measurements. Tara Rajaniemi (University of Massachusetts—Dartmouth) provided lab facilities for sample preparation. Brad Hubeny and the staff at the Salem State Viking Environmental Stable Isotope Lab performed isotope and elemental analyses.

Funding Information

This work was funded by a grant from the Massachusetts Bays National Estuary Program (MassBays).

Supplementary material

12237_2017_323_MOESM1_ESM.docx (27 kb)
Online Resource 1 (DOCX 26 kb)
12237_2017_323_MOESM2_ESM.docx (28 kb)
Online Resource 2 (DOCX 28 kb)
12237_2017_323_MOESM3_ESM.docx (32 kb)
Online Resource 3 (DOCX 32 kb)
12237_2017_323_MOESM4_ESM.docx (31 kb)
Online Resource 4 (DOCX 31 kb)


  1. Alexander, C. 2012. Field assessment and simulation of shading from alternative dock construction materials. Final Report. 18 March 2012. Accessed 5 Jan 2017.
  2. Alexander, C., and M. Robinson. 2004. GIS and field-based analysis of the impacts of recreational docks on the saltmarshes of Georgia. Skidaway Institute of Oceanography Technical Report. 40 pp. Accessed 5 Jan 2017.
  3. Alexander, C., and M. Robinson. 2006. Quantifying the ecological significance of marsh shading: the impact of private recreational docks in coastal Georgia. Submitted to Coastal Resources Division Georgia Department of Natural Resources Brunswick, GA. Accessed 5 Jan 2017.
  4. Barbier, E.B., S.D. Hacker, C. Kennedy, E.W. Koch, A.C. Stier, and B.R. Silliman. 2011. The value of estuarine and coastal ecosystem services. Ecological Monographs 81: 169–193.CrossRefGoogle Scholar
  5. Bartoń, K. 2016. MuMIn: Multi-Model Inference. R package version 1.15.6. Accessed 7 Jan 2017.
  6. Bertness, M.D. 1991. Zonation of Spartina patens and Spartina alterniflora in New England salt marsh. Ecology 72: 138–148.CrossRefGoogle Scholar
  7. Bertness, M.D., and A.M. Ellison. 1987. Determinants of pattern in a New England salt marsh plant community. Ecological Monographs 57: 129–147.CrossRefGoogle Scholar
  8. Bliven, S., and S. Pearlman. 2003. A guide to permitting small pile-supported docks and piers. Massachusetts Department of Environmental Protection, Bureau of Resource Protection, Wetlands/Waterways Program. 28 pp. Accessed 5 Jan 2017.
  9. Boesch, D.F., and R.E. Turner. 1984. Dependence of fishery species on salt marshes: the role of food and refuge. Estuaries 7: 460–468.CrossRefGoogle Scholar
  10. Broome, S.W., C.B. Craft, S.D. Struck, and M. San Clements. 2005. Effects of shading from bridges on estuarine wetlands. Final Report to U.S. Department of Transportation Research and Special Programs Administration. Accessed 9 Dec 2016.
  11. Burdick, D.M., and F.T. Short. 1999. The effects of boat docks on eelgrass beds in coastal waters of Massachusetts. Environmental Management 23: 231–240.CrossRefGoogle Scholar
  12. Burnham, K.P., and D.R. Anderson. 2002. Model selection and multimodel inference. 2nd ed. New York, NY: Springer.Google Scholar
  13. Burnham, K.P., D.R. Anderson, and K.P. Huyvaert. 2011. AIC model selection and multimodel inference in behavioral ecology: some background, observations, and comparisons. Behavioral Ecology and Sociobiology 65: 23–35.CrossRefGoogle Scholar
  14. Chmura, G.L., S.C. Anisfield, D.R. Cahoon, and J.C. Lynch. 2003. Global carbon sequestration in tidal, saline wetland soils. Global Biogeochemical Cycles 17: 1111.CrossRefGoogle Scholar
  15. Cifuentes, L.A., M.L. Fogel, J.R. Pennock, and J.H. Sharp. 1989. Biogeochemical factors that influence the stable nitrogen isotope ratio of dissolved ammonium in the Delaware Estuary. Geochemica et Cosmochimica Acta 53: 2713–2721.CrossRefGoogle Scholar
  16. Cohen, J. 1988. Statistical Power Analysis for the Behavioral Sciences. 2nd ed. Hillsdale: Lawrence Erlbaum Associates Publishers.Google Scholar
  17. Colligan, M., and C. Collins. 1995. The effect of open-pile structures on salt marsh vegetation. NOAA/NMFS Pre-publication Draft Report.Google Scholar
  18. COMAR. 2016. COMAR. Maryland Code of Regulations: piers and boathouses. Accessed 19 Sept 2016.
  19. Connecticut Department of Energy & Environmental Protection. 2015. Residential dock guidelines. Accessed 16 Nov 2016.
  20. Cribari-Neto, F., and A. Zeileis. 2010. Beta regression in R. Journal of Statistical Software 34: 1–24.CrossRefGoogle Scholar
  21. Culbertson, J.B., I. Valiela, M. Pickart, E.E. Peacock, and C.M. Reddy. 2008. Long-term consequences of residual petroleum on salt marsh grass. Journal of Applied Ecology 45: 1284–1292.CrossRefGoogle Scholar
  22. Deegan, L.A., and R.H. Garritt. 1997. Evidence for spatial variability in estuarine food webs. Marine Ecology Progress Series 147: 31–47.CrossRefGoogle Scholar
  23. Deegan, L.A., J.E. Hughes, and R.A. Rountree. 2000. Salt marsh ecosystem support of marine transient species. In Concepts and Controversies in Tidal Marsh Ecology, ed. M.P. Weinstein and D.A. Kreeger, 333–365. The Netherlands: Kluwer Academic Publisher.Google Scholar
  24. 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.CrossRefGoogle Scholar
  25. Duarte, C.M., J.J. Middelburg, and N. Caraco. 2005. Major role of marine vegetation on the oceanic carbon cycle. Biogeosciences 2: 1–8.CrossRefGoogle Scholar
  26. Galipaud, M., M.A.F. Gillingham, M. David, and F.X. Dechaume-Moncharmont. 2014. Ecologists overestimate the importance of predictor variables in model averaging: a plea for cautious interpretations. Methods in Ecology and Evolution 5: 983–991.CrossRefGoogle Scholar
  27. Gedan, K.B., A.H. Altieri, and M.D. Bertness. 2011. Uncertain future of New England salt marshes. Marine Ecology Progress Series 434: 229–237.CrossRefGoogle Scholar
  28. Gladstone, W., and G. Courtenay. 2014. Impacts of docks on seagrass and effects of management practices to ameliorate these impacts. Estuarine, Coastal and Shelf Science 136: 53–60.CrossRefGoogle Scholar
  29. Gleason, M.L., D.A. Elmer, N.C. Pien, and J.S. Fisher. 1979. Effects of stem density upon sediment retention by salt marsh cord grass, Spartina alterniflora loisel. Estuaries 2: 271–273.CrossRefGoogle Scholar
  30. Grice, A.M., N.R. Loneragan, and W.C. Dennison. 1996. Light intensity and the interactions between physiology, morphology and stable isotope ratios in five species of seagrass. Journal of Experimental Marine Biology and Ecology 195: 91–110.CrossRefGoogle Scholar
  31. Horrigan, S.G., J.P. Montoya, J.L. Nevins, and J.J. McCarthy. 1990. Natural isotopic composition of dissolved inorganic nitrogen in the Chesapeake Bay. Estuarine, Coastal and Shelf Science 30: 393–410.CrossRefGoogle Scholar
  32. Hothorn, T., K. Hornik, M.A. van de Wiel, and A. Zeileis. 2008. Implementing a class of permutation tests: the coin package. Journal of Statistical Software 28: 1–23.CrossRefGoogle Scholar
  33. Johnson, D.S., R.S. Warren, L.A. Deegan, and T.J. Mozdzer. 2016. Saltmarsh plant responses to eutrophication. Ecological Applications 26: 2647–2659.Google Scholar
  34. Kearney, V.F., Y. Segal, and M.W. Lefor. 1983. The effects of docks on salt marsh vegetation. Connecticut State Department of Environmental Protection. Connecticut: Hartford 22 pp.Google Scholar
  35. Kelty, R., and S. Bliven. 2003. Environmental and aesthetic impacts of small docks and piers. Workshop report: developing a science-based decision support tool for small dock management, phase 1: status of the science. NOAA Coastal Ocean Program Decision Analysis Series No. 22. National Centers for Coastal Ocean Science, Silver Spring, MD. 69 pp. Accessed 5 Jan 2017.
  36. Kennish, M.J. 2001. Coastal salt marsh systems in the U.S.: a review of anthropogenic impacts. Journal of Coastal Research 17: 731–748.Google Scholar
  37. Kneib, R.T. 2003. Bioenergetic and landscape considerations for scaling expectations of nekton production from intertidal marshes. Marine Ecology Progress Series 264: 279–296.CrossRefGoogle Scholar
  38. Koch, E.W., E.B. Barbier, B.R. Silliman, D.J. Reed, G.M.E. Perillo, S.D. Hacker, E.F. Granek, et al. 2009. Non-linearity in ecosystem services: temporal and spatial variability in coastal protection. Frontiers in Ecology and Environment 7: 29–37.CrossRefGoogle Scholar
  39. Logan, J.M., S. Voss, A. Davis, and K.H. Ford. 2017. An experimental evaluation of dock shading impacts on salt marsh vegetation in a New England estuary. Estuaries and Coasts. Scholar
  40. Long, M.H., J.E. Rheuban, P. Berg, and J.C. Zieman. 2012. A comparison and correction of light intensity loggers to photosynthetically active radiation sensors. Limnology and Oceanography: Methods 10: 416–424.Google Scholar
  41. MacFarlane, S.L., J. Early, T. Henson, T. Balog, and A. McClennen. 2000. A resource-based methodology to assess dock and pier impacts on Pleasant Bay, Massachusetts. Journal of Shellfish Research 19: 455–464.Google Scholar
  42. Macreadie, P.I., A.R. Hughes, and D.L. Kimbro. 2013. Loss of “blue carbon” from coastal salt marshes following habitat disturbance. PLoS ONE 8: e69244. Scholar
  43. Martinetto, P., M. Teichberg, and I. Valiela. 2006. Coupling of estuarine benthic and pelagic food webs to land-derived nitrogen sources in Waquoit Bay, Massachusetts, USA. Marine Ecology Progress Series 307: 37–48.CrossRefGoogle Scholar
  44. McClelland, J.W., and I. Valiela. 1998. Linking nitrogen in estuarine producers to land-derived sources. Limnology and Oceanography 43: 577–585.CrossRefGoogle Scholar
  45. McClelland, J.W., I. Valiela, and R.H. Michener. 1997. Nitrogen-stable isotope signatures in estuarine food webs: a record of increasing urbanization in coastal watersheds. Limnology and Oceanography 42: 930–937.CrossRefGoogle Scholar
  46. Medeiros, D.L., D.S. White, and B.L. Howes. 2013. Replacement of Phragmites australis by Spartina alterniflora: the role of competition and salinity. Wetlands 33: 421–430.CrossRefGoogle Scholar
  47. Mendelssohn, I.A., and J.T. Morris. 2000. Ecophysiological controls on the growth of Spartina alterniflora. In Concepts and controversies in tidal marsh ecology, ed. N.P. Weinstein and D.A. Kreeger, 59–80. The Netherlands: Kluwer Academic Publisher.Google Scholar
  48. Moore, K.A., and R.L. Wetzel. 2000. Seasonal variations in eelgrass (Zostera marina L.) responses to nutrient enrichment and reducted light availability in experimental ecosystems. Journal of Experimental Marine Biology and Ecology 244: 1–28.CrossRefGoogle Scholar
  49. Morris, J.T., K. Sundberg, and C.S. Hopkinson. 2013. Salt marsh primary production and its responses to relative sea level and nutrients. Oceanography 26: 78–84.CrossRefGoogle Scholar
  50. National Research Council. 2007. Mitigating shore erosion on sheltered coasts. Washington, D.C.: The National Academies Press.Google Scholar
  51. Needles, L.A., S.E. Lester, R. Ambrose, A. Andren, M. Beyeler, M.S. Connor, J.E. Eckman, B.A. Costa-Pierce, S.D. Gaines, K.D. Lafferty, H.S. Lenihan, J. Parrish, M.S. Peterson, A.E. Scaroni, J.S. Weis, and D.E. Wendt. 2015. Managing bay and estuarine ecosystems for multiple services. Estuaries and Coasts 38: 35–48.CrossRefGoogle Scholar
  52. New Hampshire Department of Environmental Services. 2009. Environmental fact sheet. Permitting of tidal docks. Accessed 15 Nov 2016.
  53. Oksanen, J., F.G. Blanchet, R. Kindt, P. Legendre, P.R. Minchin, R.B. O’Hara, G.L. Simpson, P. Solymos, M.H.H. Stevens, and H. Wagner. 2016. vegan: community ecology package. R package version 2.4-0. Accessed 7 Jan 2017.
  54. Patterson, M.M. 2003a. Residential docks and piers: inventory of laws, regulations, and policies for the southeastern United States. Accessed 5 Jan 2017.
  55. Patterson, M.M. 2003b. Residential docks and piers: inventory of laws, regulations, and policies for the New England region. Accessed 5 Jan 2017.
  56. Peralta, G., J.L. Pérez-Lloréns, I. Hernández, and J.J. Vergara. 2002. Effects of light availability on growth, architecture and nutrient content of the seagrass Zostera noltii Hornem. Journal of Experimental Marine Biology and Ecology 269: 9–26.CrossRefGoogle Scholar
  57. Peterson, M.S., and M.R. Lowe. 2009. Implications of cumulative impacts to estuarine and marine habitat quality for fish and invertebrate resources. Reviews in Fisheries Science 17: 505–523.CrossRefGoogle Scholar
  58. Pinheiro, J., D. Bates, S. DebRoy, D. Sarkar, and R Core Team. 2017. nlme: linear and nonlinear mixed effects models. R package version 3.1-131. Accessed 7 Jan 2017.
  59. R Core Team. 2016. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL Accessed 15 Nov 2016.
  60. Sanger, D.M., and A.F. Holland. 2002. Evaluation of the impacts of dock structures on South Carolina estuarine environments. Final report Submitted to: Office of Ocean and Coastal Resource Management South Carolina Department of Health and Environmental Control 1362 McMillan Avenue, Suite 400 Charleston, SC 29405. Accessed 5 Jan 2017.
  61. Sanger, D.M., A.F. Holland, and C. Gainey. 2004. Cumulative impacts of dock shading on Spartina alterniflora in South Carolina estuaries. Environmental Management 33: 741–748.Google Scholar
  62. 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: e27374. Scholar
  63. Spiess, A.N. 2014. Propagate: propagation of uncertainty. R package version 1.0-4. Accessed 7 Jan 2017.
  64. Struck, S.D., C.B. Craft, S.W. Broome, M.D. Sanclements, and J.N. Sacco. 2004. Effects of bridge shading on estuarine marsh benthic invertebrate community structure and function. Environmental Management 34: 99–111.CrossRefGoogle Scholar
  65. Symonds, M.R.E., and A. Moussalli. 2011. A brief guide to model selection, multimodel inference and model averaging in behavioural ecology using Akaike’s information criterion. Behavioral Ecology and Sociobiology 65: 13–21.CrossRefGoogle Scholar
  66. Teal, J.M. 1986. The ecology of regularly flooded salt marshes of New England: a community profile. U.S. Fish and Wildlife Service Biological Report 85 (7.4): 61 pp.Google Scholar
  67. The Savannah District U.S. Army Corps of Engineers. 2012. Joint public notice revision and reissuance of programmatic general permit 0083 for private single-family docks in Bryan, Brantley, Camden, Charlton, Chatham, Effingham, Glynn, Liberty, Long, McIntosh and Wayne Counties, Georgia. Accessed 5 Jan 2017.
  68. van Lent, F., J.M. Verschuure, and M.L.J. van Veghel. 1995. Comparative study on populations of Zostera marina L. (eelgrass): in situ nitrogen enrichment and light manipulation. Journal of Experimental Marine Biology and Ecology 185: 55–76.CrossRefGoogle Scholar
  69. Vasilas, B.L., J. Bowman, A. Rogerson, A. Chirnside, and W. Ritter. 2011. Environmental impact of long piers on tidal marshes in Maryland—vegetation, soil, and marsh surface effects. Wetlands 39: 423–431.CrossRefGoogle Scholar
  70. Wainright, S.C., M.P. Weinstein, K.W. Able, and C.A. Currin. 2000. Relative importance of benthic microalgae, phytoplankton and the detritus of smooth cordgrass Spartina alterniflora and the common reed Phragmites australis to brackish-marsh food webs. Marine Ecology Progress Series 200: 77–91.CrossRefGoogle Scholar
  71. Wigand, C., R.A. McKinney, M.L. Cole, G.B. Thursby, and J. Cummings. 2007. Varying stable nitrogen isotope ratios of different coastal marsh plants and their relationships with wastewater nitrogen and land use in New England, USA. Environmental Monitoring and Assessment 131: 71–81.CrossRefGoogle Scholar
  72. Wood, S.N. 2006. Generalized Additive Models: An Introduction with R. London: Chapman and Hall/CRC.CrossRefGoogle Scholar
  73. Ysebaert, T., S.-L. Yang, L. Zhang, Q. He, T.J. Bouma, and P.M.J. Herman. 2011. Wave attenuation by two contrasting ecosystem engineering salt marsh macrophytes in the intertidal pioneer zone. Wetlands 31: 1043–1054.CrossRefGoogle Scholar
  74. Zeileis, A., and T. Hothorn. 2002. Diagnostic checking in regression relationships. R News 2: 7–10.Google Scholar

Copyright information

© Coastal and Estuarine Research Federation 2017

Authors and Affiliations

  • John M. Logan
    • 1
    Email author
  • Amanda Davis
    • 1
  • Charles Markos
    • 1
  • Kathryn H. Ford
    • 1
  1. 1.Massachusetts Division of Marine FisheriesNew BedfordUSA

Personalised recommendations