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NCCOS Research Project

Restoring Injured Seagrass Beds with New Methods for Re-Grading and Fertilization

Region(s) of Study: U.S. States and Territories / Florida
Primary Contact(s): amy.Uhrin@noaa.gov
This project began in 2000 and is ongoing

Vessel groundings in shallow waters can damage fragile seagrass habitats, sometimes permanently. We are conducting scientific studies to assess new intervention methods of sediment re-grading and nutrient fertilization to accelerate the recovery of the climax seagrass. The development of science-based restoration tools for seagrass is an essential part of the process supporting NOAA’s conservation, restoration and litigation efforts in the Florida Keys National Marine Sanctuary (FKNMS).    

Why We Care

Every year the FKNMS experiences over 500 vessel groundings in shallow-water seagrass habitats. Natural recovery from vessel groundings can take years to decades and in some cases recovery may never occur and the injuries may eventually expand. Often they are physically unstable and lose their capacity to support the nutrition and growth of the climax species.

Section 312 of the National Marine Sanctuary Act requires the resource trustee (NOAA) to seek compensation from responsible parties for the injuries including both primary and compensatory restoration of damaged seagrass beds.

Seagrasses are the most abundant shallow-water benthic marine habitat in FKNMS supporting ecologically and economically valuable commercial and recreational fisheries, a wide diversity of marine species and wildlife, including several endangered and threatened species.

Vessel groundings are one of the most severe disturbances that occur in this habitat because:

  • Plants are damaged and destroyed
  • Sediments are excavated and redistributed
  • The local environment is destabilized
  • The cumulative loss of habitat from this type of injury continues to expand
  • Natural recovery is often uncertain.

What We’re Doing

We conducted observational, manipulative, and monitoring studies to evaluate the severity of the disturbance, natural recovery rates, and restoration methods to offset the effects and accelerate recovery.  We learned that deeply excavated sediment disturbances were more likely to prevent the recovery of the desire climax species, turtlegrass (Thalassia testudinum ) and that recovery could be accelerated by re-grading the injuries with native sediments.  We expected that the excavated injuries and re-graded conditions were nutrient depleted, so we conducted experiments to test different combinations of sediment fill and fertilization.  We learned that we could get faster-growing opportunistic seagrasses to accelerate recovery of these injury sites by installing bird stakes within the injury sites to receive phosphorous-rich droppings of roosting birds.

Next Steps

We are currently engaged in ongoing work to:

  • Test different methods of deploying fill material in blowholes
  • Conduct a cost/benefit analysis of different sediment fill techniques
  • Calculate seagrass recovery horizons in sediment filled restoration sites
  • Continue to support FKNMS and NOAA trustee in NMSA Section 312 litigations.

Additional Resources

Products, Datasets & Reports


  • Fonseca, Mark S., Whitfield, Paula E., Kenworthy, W. Judson, Colby, David, R., Julius, Brian E.  2004. Use of two spatially explicit models to determine the effect of injury geometry on natural resource recovery.  Aquatic Conservation: Marine and Freshwater Ecosystems 14:281-298

Peer-Reviewed Publications

Uhrin, A.V., Kenworthy, W.J, and M.S. Fonseca, M.S.  In Press.  Understanding uncertainty in seagrass injury recovery: an information-theoretic approach.  Ecological Applications.  [doi:10.1890/10-0761.1]

Uhrin, A. V., M. S. Fonseca, and W. J. Kenworthy.  2009. Preliminary Comparison of Natural Versus Model-predicted Recovery of Vessel-generated Seagrass Injuries in Florida Keys National Marine Sanctuary.  Marine Sanctuaries Conservation Series NMSP-09-03.  U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries, Silver Spring, MD. 13 pp.

Di Carlo, G and W.J. Kenworthy.  2008.  Evaluation of belowground biomass recovery in physically disturbed seagrass meadows.  Oecologia 158:285-298.

Hammerstrom, KK, W.J. Kenworthy, P.E. Whitfield, M. Merello. 2007.  Response and recovery dynamics of seagrasses Thalassia testudinum and Syringodium filiforme and macroalgae in experimental motor vessel disturbances.  Marine Ecology Progress Series 345:83-92.

Kirsch, K.D., K.A. Barry,  M.S. Fonseca, P.E. Whitfield, S.R. Meehan, W. Judson Kenworthy, and B.E. Julius.  2005.  The Mini-312 Program-an expedited damage assessment and restoration process for seagrasses in the Florida Keys National Marine Sanctuary.  Journal of Coastal Research SI40:109-119.

McNeese, P.L., C.R. Kruer, W.J. Kenworthy, A.C. Schwartzschild, P. Wells and J. Hobbs.  2006.  Topogroaphic restoration of boat grounding damage at the Lignumvitae Submerged Land Management Area.  Pp. 131-146 in S.F. Treat & R.R. Lewis III (eds.) Seagrass Restoration: Success, Failure, and the Cost of Both.  Lewis Environmental Services, Inc., Velrico, FL.

Whitfield, P.E., W. Judson Kenworthy, Michael J. Durako, Kamille K. Hammerstrom, and Manuel F. Merello.  2004.  Recruitment of Thalassia testudinum Seedlings into Physically Disturbed Seagrass Beds.  Marine Ecology Progress Series 267:121-131.

Kenworthy, W.J.  Fonseca, M.S., Whitfield, P.E., Hammerstrom, K.  2002.  Analysis of seagrass recovery in experimental excavations and propeller-scar disturbances in the Florida Keys National Marine Sanctuary.  Journal of Coastal Research 37:75-85.

Whitfield, P.E., Kenworthy, W.J., Fonseca, M.S., Hammerstrom, K.  2002. The Role of a Hurricane in expansion of disturbances initiated by motor vessels on subtropical seagrass banks.  Journal of Coastal Research 37:86-99.

Fonseca, M.S., W.J. Kenworthy, B.E. Julius, S. Shutler, and S. Fluke.  2002.  Seagrasses, pp. 149-770 In M. R. Perrow and A.J. Davy (eds.), Handbook of Ecological Restoration. University Press, Cambridge.

Fonseca, M.S., B.E. Julius, W. Judson Kenworthy.  2000.  Integrating biology and economics in seagrass restoration: How much is enough and why?  Ecological Engineering 15:227-237.

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