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- Importance of Guam's reefs
- Health of Guam's reefs
- - Health intro
- - Reef health tour
- - - - Northern reefs
- - - - East-central and southeastern reefs
- - - - Apra Harbor reefs
- - - -Southwestern reefs
- - - - Western reefs
- Threats to Guam's reefs
- - Algae overgrowth
- - Anchor damage
- - Coral bleaching
- - Crown of thorns outbreaks
- - Debris
- - Disease
- - Divers/snorkelers/ swimmers
- - Illegal fishing
- - Kayaks and other human-powered watercraft
- - Ocean acidification
- - Overharvesting
- - Sedimentation
- - Sewage discharge
- - Stormwater runoff
- - Terpios sponge
- - Vessel groundings
- - Windsurf boards and kiteboards
- Current management
- Recommendations
- Get involved

Although not considered a major threat, as it is in places like the northwestern Hawaiian Islands, marine debris continues to negatively impact Guam’s reefs. Marine debris is a term given to any man-made object that is discarded, disposed of, or abandoned that enters the coastal or marine environment. Among the most common types of marine debris are plastics, glass, metal, rubber, styrofoam, fishing nets, and derelict vessels.

As reported in the 2008 State of the Coral Reef Ecosystems of Guam, data collected during International Coastal Cleanup events held annually on Guam indicate that most of the marine debris found on the beaches and in the coastal waters of Guam is generated locally. The majority of this debris is from land-based activities, such as barbecues, festivals, sports and days at the beach. Litter washed from streets, parking lots and storm drains also contributes to the debris found on Guam’s shores and on Guam's nearshore reefs.

While litter is unsightly and can have negative impacts on marine life, perhaps one of the most destructive types of marine debris on Guam are discarded fishing nets. These nets are occasionally found wrapped around coral colonies, especially on Guam's reef flats, with broken branches evident and partial or full colony mortality apparently a result of abrasion and smothering. According to the 2008 State of the Coral Reef Ecosystems of Guam report, nearly 200 fishing nets were collected during the 2006 International Coastal Cleanup. The Guam Department of Agriculture's Division of Aquatic and Wildlife Resources also reported removing numerous abandoned fishing nets since 2004. More recently, members of the local NGO, the Marine Awareness Foundation, and students from the Guam Community College and the University of Guam have removed several nets from Guam's nearshore waters.

More information about the threat of marine debris will be provided in the near future.