Marine Debris in Reef Habitats

Florida Keys National Marine Sanctuary

Lost Fishing Gear is Common in Sanctuary Waters 

Marine debris is one of the most widespread and persistent forms of pollution affecting the world’s ocean and coastal waters. 

Plastics, lost fishing gear, derelict vessels and other marine debris can find its way into even the most remote ocean waters where 

it can harm marine life. While most debris originates from activities taking place at sea, coastal communities also contribute 

significantly to this global threat. In the Florida Keys, where 

recreational and commercial fisheries have existed for over 100 

years, lost fishing gear and other marine debris have accumulated 

on the seafloor. Lost or abandoned fishing gear and other trash 

entangles and harms stony corals, sea fans, sponges, sea turtles, 

manatees and other marine life. It also degrades seagrass, hardbottom, coral reef and mangrove habitats and detracts from 

the natural beauty of the islands. For these and other reasons, 

citizens and resource managers of the Florida Keys National 

Marine Sanctuary are concerned about the environmental 

impacts of all marine debris.

Scientists Document Prevalence of Marine Debris

Coral researchers from Nova Southeastern University (NSU)

Oceanographic Center (formerly with University of North 

Carolina Wilmington) began conducting Keys-wide surveys of 

marine debris in 2000 during their assessments of corals, 

sponges and other benthic (bottom-dwelling) marine life. Since 

then, debris data have been recorded in 2008, 2010-11, and 2012. The 2012 surveys were conducted in collaboration with scientists 

from the sanctuary, National Park Service and Florida Fish and Wildlife Conservation Commission and included 600 coral reef and 

hard-bottom sites from Biscayne National Park to Key West. 

This long-term study has documented the widespread and damaging impacts of marine debris in sanctuary waters. In 2012, more 

than 1,000 debris items were recorded at survey sites whose area totaled about nine acres. Marine debris was present at 64% of 

the 600 study sites. Debris recovered from the seafloor weighed 1,000 pounds and included 2,027 feet of fishing line and 6,561 

feet of lobster and crab trap line. 

To inventory marine debris, science divers swam along a 50 foot transect tape placed on the seafloor at each survey site and 

recorded the debris items found within 3.3 feet on either side of the tape. They noted when debris was causing tissue damage to 

corals, sea fans or other benthic organisms from either entanglement or abrasion. Whenever removing debris would not cause 

additional harm, it was retrieved and weighed. The lengths of monofilament line, leaders and wire, as well as lobster and crab 

trap line, were measured. The sampling design made it possible to compare the prevalence and amount of debris among habitats 

and inside and outside of sanctuary protected zones (Sanctuary Preservation Areas (SPAs), Research-only Areas and Ecological 

Reserves).

Patch Reefs are Laden with More Debris than Other Reef Habitats

Similar to previous survey years, in 2012 hook-and-line angling gear was the most frequent type of debris recorded, making up 

45% of the total number of items. Angling gear consisted of monofilament line, hooks, wire leaders and lead sinkers. This type of 

gear was found in all habitats surveyed and in nearly all of the sanctuary protected zones where fishing is prohibited. Angling gear 

was particularly prevalent on patch reef habitat, being found on 48% of inshore and mid-channel patch reefs including those in 

Western Sambo Ecological Reserve, Hen and Chickens SPA and Cheeca Rocks SPA.

http://floridakeys.noaa.gov

Team OCEAN volunteers use kayaks to collect marine debris.
Lost lobster and crab trap fishing gear made up 42% of the total 

number of items found in the 2012 survey, making it the second most 

abundant type of debris. Trap gear consisted mostly of lost and broken 

lines, wooden slats, plastic trap throats and cement weights. This 

type of gear was found in all habitat types from inshore patch reefs to 

deeper fore reefs, but was substantially more prevalent on patch reefs, 

being found on 48% of inshore patch reefs and 46% of all offshore 

patch reefs. 

Glass bottles, plastics, metals, as well as anchors and other trash made 

up the third and least common category of debris. Items in this “other” 

category were found at 17% of sites. The prevalence of glass bottles and 

“other” debris was greatest on patch reefs, but also great on popular 

shallow, high-relief spur and groove reefs. The large amount of debris 

found on patch reefs suggests that they are heavily used by people. 

Over the past decade, mean densities of marine debris found inside 

and outside of sanctuary protected zones have tended to be similar. In 2012, though, mean densities of all debris types for all 

habitats were 1.7 times greater in study areas outside of zones compared to areas inside zones. Fishing and entry restrictions in 

protected zones may partially account for reduced debris inside zones. Occasionally, fresh (un-fouled) hook-and-line angling gear 

was found inside protected zones, suggesting illegal fishing had recently taken place there. Movement of debris by currents and 

people fishing along zone boundaries could also account for the presence of un-fouled gear inside zones. 

Fishing Line and Trap Rope Cause Damage to Reef Corals

The 2012 data indicate that while lost angling gear was the most prevalent debris category, the impact of entangled trap debris on 

marine life, especially trap rope, was greater than for other types of debris. Trap debris was responsible for 63% of the impacts to 

marine life, while angling gear was responsible for 32%. The remaining injuries to benthic organisms came from marine debris other 

than fishing gear. Sea fans, sea whips and other soft corals sustained 

48% of the injuries, followed by stony corals, then sponges.

No-Trap Zones Protect Threatened Corals

In 2006, NOAA Fisheries Service listed elkhorn and staghorn corals 

as threatened species under the Endangered Species Act. Long-term 

declines in these corals are thought to be caused by a combination of 

factors. A Florida Fish and Wildlife Conservation Commission study 

documented that lobster traps moved several meters during storms and 

caused harm to corals and other marine life living attached to the seafloor. 

In 2012 NOAA Fisheries implemented 60 relatively small no-trap zones 

surrounding the known stands of elkhorn and staghorn coral in federal 

waters of the Keys. These zones are expected to help protect elkhorn and 

staghorn from trap damage, giving them a better chance for recovery.

People Can Help Reduce Marine Debris

Over the years, volunteers with the sanctuary’s Team OCEAN program 

and other groups have organized many coastal and underwater clean-up 

events to collect marine debris from the waters and shorelines of the Keys. 

Between 2007 and 2012, Team OCEAN volunteers have recovered more 

than 36,000 pounds of marine debris from the waters of the sanctuary. 

While clean-ups have been successful in removing large volumes of trash, 

debris still accumulates where it can harm marine life. Discharging trash 

or other items into sanctuary waters is against regulations and can be 

avoided if people properly dispose of (and recycle) their trash. 

Principal Investigators: Drs. Steven Miller and Mark Chiappone, Nova Southeastern University Oceanographic Center 

Primary Funding Sources: NOAA Coral Reef Conservation Program, Endangered Species Acts Project, FKNMS

Written by: Nancy Diersing, Florida Keys National Marine Sanctuary

Publication Date: June 2013

Lobster traps can move during storms and damage corals.

Photo: Nova Southeastern University 

While boating, fishing or diving, take a few 

simple steps to keep marine debris out 

of sanctuary waters and away from Keys’ 

shorelines.

Boaters – Stow your trash in a designated 

container with a tight-fitting lid before 

getting underway. Use a boat hook to 

retrieve trash floating on the water’s surface.

Divers and snorkelers – Collect bottles, 

cans and other trash for proper disposal. 

Be careful not to damage marine life when 

retrieving debris. 

Anglers – Consider selecting fishing 

locations where you have less chance 

of entangling corals. Bring back all 

monofilament line, hooks and other 

gear. Recycle (or dispose of) fishing line 

at designated locations to keep it from 

entangling pelicans and other wildlife.

Everyone: Participate in Team OCEAN and 

other coastal and underwater clean-up events.