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NCCOS Research Project

Benthic Habitat Mapping for Buck Island Reef National Monument, St. Croix

This project began in April 2010 and was completed January 2012

Summary:

We developed benthic habitat maps for the Buck Island Reef National Monument, north of St. Croix in the U.S. Virgin Islands. The bathymetry (depth) data we collected was used to update nautical charts in the area, and the related habitat maps we developed are being used by local managers to plan research projects and site-related infrastructure inside the Monument, such as placing receivers for the acoustic tracking of fish and turtles. 

Why We Care

Buck Island Reef National Monument is a marine protected area situated on the north side of St. Croix and managed by the National Park Service. This marine protected area encompasses a mosaic of seagrass, algal, mangrove, and coral reef habitats. These habitats provide sources of food and refuge for a diversity of juvenile and adult marine organisms. In addition to providing habitat, these marine resources also provide valuable ecosystem services to the local community, including shoreline protection, fisheries replenishment, recreation, and tourism.

While the shallow-water habitats (<30 m) were mapped previously, the moderate to deep-water habitats (>30–1,800 m) inside the Monument had never been characterized. Consequently, there was a need to fill this information gap to provide local managers and scientists a baseline understanding of these benthic communities. A baseline is required to develop long-term strategies to conserve and protect these valuable natural resources.

What We Did

We developed benthic habitat maps from aerial photographs, light detection and ranging (LiDAR) imagery, and four types of multibeam echosounder (MBES) imagery for 98 percent of Buck Island Reef National Monument by combining manual interpretation with a novel object- and pixel-based classification technique. We used six types of imagery to characterize the seafloor because the Monument includes a wide range of depths (0–1,830 m).

The accuracy of habitat classes shallower than 50 meters was similar to those reported for other NOAA benthic habitat mapping efforts, ranging from 81.4 percent to 94.4 percent. These maps were also reviewed and edited by local experts—the National Park Service, the USVI Department of Planning and Natural Resources, the University of the Virgin Islands, and the Nature Conservancy—before being finalized. The final deliverables for this project included the benthic habitat maps, source imagery, and georeferenced underwater videos and photos. This project was funded by the National Park Service.

What We Found

The majority of the Monument is deeper than 30 meters with two distinct areas:

  1. The Bank/Shelf is composed mostly of hard bottom habitats colonized by various forms of algae. A quarter of the Bank/Shelf is also colonized by >10 percent live coral cover; and
  2. The Shelf Escarpment is dominated by uncolonized sand and mud. Mesophotic and deep-water corals were rare on areas of exposed bedrock.

 

Next Steps/Benefits of our Work

The bathymetry data was used to update nautical charts in the area. The habitat maps are being used by local managers to plan research projects and site-related infrastructure inside the Monument (e.g., placing receivers for the acoustic tracking of fish and turtles). These maps may also be used in the future to:

  • Update the Monument’s management plan, including evaluating different zoning options for multiple-use areas.
  • Evaluate the efficacy of management actions taken by Monument managers.
  • Map ecosystem services and estimate the economic value of goods and services across the seascape.
  • Understand seascape requirements for species and identify the most productive and diverse seascape types.
  • Predict habitat suitability for priority species to help target monitoring efforts and prioritize action strategies.

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