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Marine Debris Assessment Expedition

July 20-25, 2009
aboard the R/V Manta



The surface of Stetson Bank is sprinkled with shrimp trawl nets, boat anchors, twisted metal, an engine block, vessel stabilizers, fishing line, and various other items.

Rusty anchor and chain sitting on the bottom about 80 feet underwater at Stetson Bank.
Rusty anchor and chain resting on the bottom in about 80 feet of water at Stetson Bank. Photo: Joyce & Frank Burek

All of these items pose potential threats to sanctuary resources:

  • Derelict fishing gear and other marine debris smother existing animals and create an unstable habitat for those organisms that survive the initial impact.
  • Marine debris can weaken the claystone substrate and associated communities with its initial impact or by scouring and scraping as it moves in the waves and currents after settling.  This leaves the substrate more vulnerable to erosion and fracturing by natural hazards, such as hurricanes.
  • Hurricane force wave action can dislodge marine debris, leading to additional habitat destruction in the sanctuary.
  • Derelict fishing gear has been documented as an entanglement threat to wildlife. Sanctuary staff removed monofilament line from around the back flippers of a loggerhead sea turtle, a threatened species, several years ago.
Fishing line lies wound in between the tubes of a sponge at Stetson Bank.
Fishing gear lies entangled in all sorts of habitat at Stetson Bank. Here a line is wound in and around the tubes of a sponge. Photo: Joyce & Frank Burek
  • Abandoned fishing gear poses a hazard to research activities.  Remotely operated vehicles, manned submersibles, and divers can easily become entangled in fishing line, which is clear and difficult to see underwater.

Bright Bank has been the target of extensive treasure salvage activities that have left marine debris scattered around the excavation sites.   It is one one of the sites included in a proposal to expand the sanctuary boundaries.

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Area of Operation

Northwestern Gulf of Mexico

Map of northwestern Gulf of Mexico showing the northeastern Texas coast and all of the Louisiana coast.  In the Gulf,  the locations of 15 different banks are marked and labeled.
There are numerous identified banks along the continental shelf in the northwestern Gulf of Mexico.

Stetson Bank

Stetson is one of three separate banks that form FGBNMS.  It was added to the sanctuary in 1996, four years after the sanctuary was originally designated.  

Map of northwestern Gulf of Mexico showing all of the Texas and Louisiana coastlines.  The three banks that make up the sanctuary are marked in white and labeled.
Stetson Bank is located about 30 miles northwest of West Flower Garden Bank and about 70 miles south southeast of Galveston, TX.

Like East and West Flower Garden Banks, Stetson sits atop a salt dome, similar to a small underwater mountain.  It is located on the continental shelf in the Gulf of Mexico, about 70 miles south southeast of Galveston, Texas.  Stetson Bank provides an ‘island’ of productive, shallow habitat for the growth of coral and sponge communities which in turn are home to an array of invertebrates, bony fishes, sharks, and turtles.

Stetson Bank is comprised of a main feature and an ‘outer ring’ consisting of claystone outcroppings. The primary area of Stetson Bank is protected within FGBNMS and the ‘outer ring’ is within a Habitat Area of Particular Concern (designated by the Gulf of Mexico Fishery Management Council).

Bathymetric map of Stetson Bank and the surrounding ring.  Red lines on the map show ROV tracks from previous expeditions.
Red lines on this map of Stetson Bank and the surrounding ring indicate the paths of Remotely Operated Vehicle (ROV) surveys conducted during earlier habitat characterization expeditions.

Recreational and commercial fishing, diving, boating, and other activities occur at and around Stetson Bank. Marine debris from these activities has been reported by divers and opportunistically documented through ROV habitat characterization surveys. However, accurate mapping, assessment and documentation of this debris have not been systematically conducted to date.

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Bright Bank

Bathymetric map of Bright Bank.  Black lines on map indicate the path of previous ROV surveys at this bank.
Black lines on this map of Bright Bank show ROV tracks from previous expeditions.

Located about 12 miles east of FGBNMS, Bright Bank is a site proposed for sanctuary boundary expansion. This bank also sits atop an underwater salt dome.  If time allows during this expedition, treasure salvage debris at Bright Bank will be accurately mapped, assessed, and documented. 

Excavation pit with an L shaped metal rod protruding from it.  This hole is located on the seafloor at Bright Bank.
Evidence of excavation activity at Bright Bank as seen during the Secrets of the Gulf expedition in 2007.

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Expedition Objectives

During this expedition marine debris surveys and mapping will be conducted and the identified debris will be assessed for its impact on the biological communities of Stetson Bank and Bright Bank. If feasible, priority debris items will be removed by divers, under the guidance of sanctuary staff. 

Monofilament line tangled in fire coral at Stetson Bank.

This project contributes to ongoing research on the impacts and occurrence of marine debris within Flower Garden Banks National Marine Sanctuary (FGBNMS) and other hard-bottom habitats in the northwestern Gulf of Mexico. The removal of marine debris, especially derelict fishing gear, will enhance the protection and restoration of the siltstone and claystone reef habitat of Stetson Bank.  Mapping, assessment and documention of marine debris at Bright Bank will lay the groundwork for possible future debris removal and restoration of the damaged habitat.

This expedition is part of an ongoing project supported by National Oceanic & Atmospheric Administration’s (NOAA) Marine Debris Program.  To learn more about the overall project, visit

One of the challenges for this project is the depth range at which much of the debris is located.  It is too deep for standard SCUBA diving operations.  To meet this challenge, the sanctuary research team recruited expert technical divers to assist with the work.

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Experimental Tasks

Fishing net caught on bottom habitat about 250 feet underwater along the Stetson ring.  Sediments cling to the net, but nothing else is able to settle on this moving object.
Fishing nets snagged on the bottom habitat of Stetson ring. Water movement causes these nets to wave about preventing anything new from settling and causing repeated contact with the surrounding habitat.

1. Conduct biological sampling of various organisms.

2. Map locations of marine debris within the shallow and deepwater portions of Stetson Bank:

  • use scientific mapping methodology commonly employed by archaeologists;
  • document debris with still and video footage;
  • note scientific names of observed species and their numbers, as well as the size of the area impacted, for a marine debris assessment.

3. Remove debris when it is possible to do so safely.

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Technical Diving

Doug Kesling sutied up for technical diving.
Doug Kesling suited up for technical diving.

Divers will use Open-Circuit Scuba with Trimix, Enriched Air Nitrox (EANx) and Oxygen.  SCUBA stands for Self-Contained, Underwater Breathing Apparatus.  It means the divers carry everything with them that they will need to breath for the time they are under water.  Open-Circuit means that all of the air the divers exhale will go into the surrounding water.  In Closed-Circuit systems (commonly known as ‘re-breathers’) the breathing gas is treated and re-circulated so the diver breathes it again.  Trimix and EANx are special mixes of gases that are used to minimize the risk of potential hazards, such as decompression sickness, nitrogen narcosis and oxygen toxicity when breathing compressed air at the depths being targeted on this mission.

The divers  will carefully follow the protocols and procedures outlined in NOAA’s Scientific Diving Standards and Safety Manual to insure everyone’s safety.  The team will also be supported by a diving medical technician onboard the primary dive vessel, R/V Manta.  They will even have a portable decompression chamber on board, although the goal is NOT to need it!

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Expedition Partners

NOAA Flower Garden Banks National Marine Sanctuary

NOAA Gray's Reef National Marine Sanctuary

NOAA Marine Debris Program

NOAA Thunder Bay National Marine Sanctuary

NOAA Undersea Research Center – University North Carolina, Wilmington

Georgia Aquarium

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If you have questions about this expedition, please contact the sanctuary by email.

weather report observations cool stuff get wet

Orange, branching gorgonian (soft coral) anchored in a bed of sponges and other sea life.
National Marine Sanctuary logo - a stylized whale tail above waves