Water: Marine Debris
Marine Debris Impacts
Marine debris impacts the environment, economy, and human health and safety. The extent of the impacts is determined by the type of marine debris and where it settles in the ocean (e.g., submerged, floating, or within a sensitive habitat). Fishing nets, plastic bags, and tires can sink to the ocean floor and break and smother coral reefs. Fishing line can float along the ocean surface and catch vessel propellers causing costly damage. A syringe can wash up on the beach and be stepped on by a beachgoer resulting in a wound and possibly an infection. Regardless of the type or the location of the marine debris, it can have serious impacts.
Environmental impacts are wide ranging and can be both direct and indirect. Direct impacts occur when marine life is physically harmed by marine debris through ingestion or entanglement (e.g., a turtle mistakes a plastic bag for food) or marine debris physically alters a sensitive ecosystem (e.g., a fishing net is dragged along the ocean floor by strong ocean currents and breaks and smothers a coral reef). Environmental impacts can also be indirect, such as when a marine debris cleanup results in ecological changes.
Direct Environmental Impacts
Seabirds, sea turtles, fish, and marine mammals often ingest marine debris that they mistake for food. Ingesting marine debris can seriously harm marine life. For example, whales and sea turtles often mistake plastic bags for squid, and birds often mistake plastic pellets for fish eggs. Moreover, a study of 38 green turtles found that 61 percent had ingested some form of marine debris including plastic bags, cloth, and rope or string (Bugoni et al., 2001).
At other times, animals accidentally eat the marine debris while feeding on natural food. Ingestion can lead to starvation or malnutrition when the marine debris collects in the animal's stomach causing the animal to feel full. Starvation also occurs when ingested marine debris in the animal's system prevents vital nutrients from being absorbed. Internal injuries and infections may also result from ingestion. Some marine debris, especially some plastics, contain toxic substances that can cause death or reproductive failure in fish, shellfish, or any marine life. In fact, some plastic particles have even been determined to contain certain chemicals up to one million times the amount found in the water alone (Moore, C., 2002).
Marine life can become entangled in marine debris causing serious injury or death. Entanglement can lead to suffocation, starvation, drowning, increased vulnerability to predators, or other injury. Marine debris can constrict an entangled animal's movement which results in exhaustion or development of an infection from deep wounds caused by tightening material. For example, volunteers participating in the 2008 International Coastal Cleanup event discovered 443 animals and birds entangled or trapped by marine debris (2008 ICC Report, Ocean Conservancy).
The direct impacts of marine debris are not limited to mobile animals. Plants, other immobile living organisms, and sensitive ecosystems can all be harmed by marine debris. Coral reefs can be damaged by derelict fishing gear that breaks or suffocates coral. Plants can be smothered by plastic bags and fishing nets. The ocean floor ecosystems can be damaged and altered by the movement of an abandoned vessel or other marine debris.
Indirect Environmental ImpactsEcosystem Alteration
Efforts to remove marine debris can harm ecosystems. Mechanical beach raking uses a tractor or other mechanical device to remove marine debris from beaches and marine shorelines and can adversely impact shoreline habitats. This removal technique can be harmful to aquatic vegetation, nesting birds, sea turtles, and other types of aquatic life. Beach raking also can contribute to beach erosion and disturbance of natural vegetation when the raking is conducted too close to a dune.
Marine debris can contribute to the transfer and movement of invasive species. Floating marine debris can carry invasive species from one location to another. Invasive species use the marine debris as a type of "raft" to move from one body of water to another. In a study performed by the British Antarctic Survey in 2002, it was estimated that man-made debris found in the oceans has approximately doubled the number of different species found in the subtropics (Barnes, D.K., 2002).
Marine debris can harm three important components of our economy: tourism, fishing, and navigation. Economic impacts are felt through loss in tourism dollars and catch revenue, as well as costly vessel repairs.
Marine debris is unsightly and unwelcoming to beachgoers, which can result in lost revenue from tourism. In severe cases, marine debris can even cause beach closures. The costs to remove and dispose of the marine debris can be high and the loss of tourism dollars can be even higher. In an attempt to stop the draining of trash to the ocean, the Los Angeles County's Department of Public Works and the Flood Control District spends $18 million each year on street sweeping, catch basin cleanouts, cleanup programs, and litter prevention and education efforts (L.A. County Boards of Supervisors Staff Report, 2007).
Fisheries experience significant economic impacts from marine debris. Commercial fisheries are impacted when commercial fish and shellfish become bycatch in lost fishing nets or other fishing gear. This type of bycatch can result in both immediate losses in the standing stock of available seafood, and decreases in the long-term sustainability of the stock due to negative impacts on its reproductive ability. For example, the Gulf States Marine Fisheries Commission has predicted blue crab ghost fishery leads to a loss of up to 4 to 10 million crabs a year in Louisiana alone (Virginia Institute of Marine Science, 2006). Fisheries also can be financially affected when fishing gear and vessels are entangled or damaged by marine debris. The high cost of replacing fishing gear and vessels, as well as loss of days at sea for fishing, can cause small fisheries to go out of business.
Floating marine debris is a navigational hazard that entangles propellers and clogs cooling water intake valves. Repairing boats damaged by marine debris is both time consuming and expensive.
Human Health and Safety Impacts
Marine debris impacts humans by endangering health and safety. Beachgoers can be injured by stepping on broken glass, cans, needles or other items. Similar to marine organisms, swimmers and divers can also become entangled in abandoned netting and fishing lines. Passengers on vessels that strike or become entangled in floating or submerged marine debris may be injured or killed if the vessel is damaged or disabled.