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 seagrass recovery. 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.
Why We Care
Every year the Florida Keys National Marine Sanctuary (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 the affected areas 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, and 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 desired 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.
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.