We collaborated with Gray’s Reef National Marine Sanctuary managers and NOAA’s Marine Debris Program personnel to determine where marine debris accumulates in the sanctuary and what factors lead to the buildup. By knowing where debris is most likely to occur, the staff of the sanctuary can more efficiently clean up the material. This project resulted in the implementation of a long-term marine debris monitoring project within the sanctuary to determine patterns of accumulation over time.

Why We Care
Marine debris has been documented as a growing problem affecting many areas in U.S. coastal waters. However, off the U.S. southeast Atlantic coast, debris levels were unknown despite the area’s potential vulnerability from the level of human activity and the particular seafloor characteristics. The U.S. South Atlantic Bight region has a broad, sandy continental shelf interspersed with patchy hard bottom or limestone ledges that are home to a diversity of reef fish and bottom-dwelling invertebrates, such as sponges, corals, and tunicates. Off the Georgia coast, NOAA’s Gray’s Reef National Marine Sanctuary (GRNMS) contains a range of seafloor characteristics that are representative of the entire bight, including a high relief and live habitats densely colonized by invertebrates. The seafloor thus supports high fish densities that in turn attract increasing numbers of recreational fishers and divers, making the region susceptible to marine debris deposition.

What We Did
We conducted marine debris surveys as part of a recent biological assessment of GRNMS (see 2007 report below).

What We Found
We determined that debris:

• Was significantly more common on the densely colonized ledge sites than on sand or sparsely colonized live bottom.
• Correlated with the level of boating activity and physical characteristics, such as ledge height.

We used these results to construct spatial predictive models to map debris density and worked with the sanctuary personnel to design and establish a long-term monitoring program to quantify accumulation rates and impacts of marine debris at the densely colonized ledge habitat.

Our spatial predictive maps helped managers identify and clean up debris-prone areas and to determine how frequently clean ups should occur. The GRNMS managers have also expanded outreach programs to educate the public and sanctuary users about the importance of reducing the amount of marine debris reaching these sensitive ocean habitats.

Follow Up
The GRNMS staff and volunteers continue to a perform the marine debris survey each year to track accumulation rates. This information is being used to further refine models and cleanup timelines.