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Marine debris, also known as marine litter, is human-created solid material that has deliberately or accidentally been released in or the ocean. Floating oceanic debris tends to accumulate at the center of and on , frequently washing aground, when it is known as beach litter or tidewrack. Deliberate disposal of wastes at sea is called ocean dumping. Naturally occurring debris, such as driftwood and , are also present. With the increasing use of plastic, human influence has become an issue as many types of (petrochemical) plastics do not Biodegradation quickly, as would natural or organic materials. The largest single type of plastic pollution (~10%) and majority of large plastic in the oceans is discarded and Ghost net from the fishing industry. Waterborne plastic poses a serious threat to fish, , , and , as well as to boats and coasts.
Dumping, container spillages, litter washed into and and wind-blown landfill waste all contribute to this problem. This increased water pollution has caused serious negative effects such as discarded fishing nets capturing animals, concentration of plastic debris in massive marine garbage patches, and increasing concentrations of contaminants in the food chain.
In efforts to prevent and mediate marine debris and pollutants, laws and policies have been adopted internationally, with the UN including reduced marine pollution in Sustainable Development Goal 14 "Life Below Water". Depending on relevance to the issues and various levels of contribution, some countries have introduced more specified protection policies. Moreover, some non-profits, NGOs, and government organizations are developing programs to collect and remove plastics from the ocean. However, in 2017 the UN estimated that by 2050 there will be more plastic than fish in the oceans if substantial measures are not taken.
A wide variety of man-made objects can become marine debris; , , , rope, medical waste, glass and plastic bottles, cigarette stubs, Lighter, , polystyrene, ghost net, and various wastes from cruise ships and Oil platform are among the items commonly found to have washed ashore. Six-pack rings, in particular, are considered emblematic of the problem.
The U.S. military used ocean dumping for Dud, including Bomb, Unexploded ordnance (UXO), Land mine and Chemical weapon from at least 1919 until 1970. Millions of pounds of ordnance were disposed of in the Gulf of Mexico and off the coasts of at least 16 states, from New Jersey to Hawaii (although these, of course, do not wash up onshore, and United States is not the only country who has practiced this).
Eighty percent of marine debris is plastic. Plastics accumulate because they typically do not biodegradation as many other substances do. They photodegradation on exposure to sunlight, although they do so only under dry conditions, as water inhibits photolysis. In a 2014 study using computer models, scientists from the group 5 Gyres, estimated 5.25 trillion pieces of plastic weighing 269,000 tons were dispersed in oceans in similar amount in the Northern and Southern Hemispheres.
Litter, made from diverse materials that are lighter than surface water (such as , metals and some plastics), have been found to spread over the floor of seas and open oceans, where it can become entangled in and interfere with other Benthos, or even become buried under sediment, making Marine salvage extremely difficult, especially due to the wide area of its dispersal compared to shipwrecks. Plastics that are usually negatively buoyant can sink with the adherence of phytoplankton and the aggregation of other organic particles. Other oceanic processes that affect circulation, such as coastal storms and offshore convection, play a part in transferring large volumes of particles and debris. Submarine topographic features can also augment downwelling currents, leading to the retention of microplastics at certain locations.Woodall, L. C., Sanchez-Vidal, A., Canals, M., Paterson, G. L., Coppock, R., Sleight, V., ... & Thompson, R. C. (2014). The deep sea is a major sink for microplastic debris. Royal Society open science, 1(4), 140317. .
A Deep-sea Debris database by the Global Oceanographic Data Center of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), showing thirty years of photos and samples of marine debris since 1983, was made public in 2017. From the 5,010 dives in the database, using both ROVs and deep-sea submersibles, 3,425 man-made debris items were counted. The two most significant types of debris were macro-plastic, making up 33% of the debris found – 89% of which was single-use – and metal, making up 26%. Plastic debris was found at the bottom of the Mariana Trench, at a depth of 10,898m, and plastic bags were found entangled in hydrothermal vent and cold seep communities.
An estimated 10,000 Containerization at sea each year are lost by , usually during storms. One spillage occurred in the Pacific Ocean in 1992, when thousands of rubber ducks and other toys (now known as the "Friendly Floatees") went overboard during a storm. The toys have since been found all over the world, providing a better understanding of . Similar incidents have happened before, such as when Hansa Carrier dropped 21 containers (with one notably containing buoyant Nike shoes).
In 2007, MSC Napoli beached in the English Channel, dropping hundreds of containers, most of which washed up on the Jurassic Coast, a World Heritage Site. A 2021 study following a 2014 loss of a container carrying printer cartridges calculated that some cartridges had dispersed at an average speed of between 6 cm and 13 cm per second. A 1997 accident of Tokio Express ship off the British coast resulted in loss of cargo container holding 5 million Lego pieces. Some of the pieces became valued among collectors who searched the beaches for Lego dragons. It also provided valuable insight in studying marine plastic degradation.
In Halifax Harbour, Nova Scotia, 52% of items were generated by recreational use of an urban park, 14% from sewage disposal and only 7% from shipping and fishing activities. Around four-fifths of oceanic debris is from rubbish blown onto the water from , and urban runoff.
Some studies show that marine debris may be dominant in particular locations. For example, a 2016 study of Aruba found that debris found the windward side of the island was predominantly marine debris from distant sources. In 2013, debris from six beaches in Korea was collected and analyzed: 56% was found to be "ocean-based" and 44% "land-based".
In the 1987 Syringe Tide, medical waste washed ashore in New Jersey after having been blown from Fresh Kills Landfill. On the remote sub-Antarctic island of South Georgia, fishing-related debris, approximately 80% plastics, are responsible for the entanglement of large numbers of Antarctic fur seals..
Thirteen companies have an individual contribution of 1% or more of the total branded plastic observed in the audit events: The Coca-Cola Company, PepsiCo, Nestlé, Danone, Altria, Bakhresa Group, Wings, Unilever, Mayora Indah, Mondelez International, Mars, Incorporated, Salim Group, and British American Tobacco. All 13 companies produce food, beverage, or tobacco products. The top company, The Coca-Cola Company, was responsible for 11% (CI95% = 10 to 12%), significantly greater than any other company. The top 5 companies were responsible for 24% of the branded plastic; 56 companies were responsible for greater than 50% of the branded plastic; and 19,586 companies were responsible for all of the branded plastic. The contributions of the top companies may be an underestimation because there were brands that were not attributed to a company, and there were many unbranded objects.
Additionally, have been known to use pieces of beach litter as a shell when they cannot find an actual seashell of the size they need.
There are also projects that stimulate fishing boats to remove any litter they accidentally fish up while fishing for fish.
Elsewhere, "trash traps" are installed on small rivers to capture waterborne debris before it reaches the sea. For example, South Australia's Adelaide operates a number of such traps, known as "trash racks" or "gross pollutant traps" on the Torrens River, which flows (during the wet season) into Gulf St Vincent.
In lakes or near the coast, manual removal can also be used. Project AWARE for example promotes the idea of letting dive clubs clean up litter, for example as a diving exercise.
Once a year there is a diving marine debris removal operation in Scapa Flow in Orkney, run by Ghost Fishing UK, funded by World Animal Protection and Fat Face Foundation. Daily Telegraph 28 September 2017, page 31
Cleanup of marine debris can be stymied by inadequate collaboration across levels of government, and a patchwork of regulatory authorities (responsibility often differs for the ocean surface, the seabed, and the shore). For example, there are an estimated 1600 abandoned and derelict boats in the waters of British Columbia. In 2019 Canada's federal government passed legislation to make it illegal to abandon a vessel but enforcement is hampered because it is often difficult to determine who owns an abandoned boat since owners are not required to have a license – licensing is a provincial government responsibility. The Victoria-based non-profit Dead Boats Disposal Society notes that lack of enforcement means abandoned boats are often left to sink, which increases the cleanup cost and compounds the environmental hazard (due to seepage of fuel, oil, plastics, and other pollutants).
Another method to gather artificial litter has been proposed by The Ocean Cleanup's Boyan Slat. He suggested using platforms with arms to gather the debris, situated inside the current of gyres. The SAS Ocean Phoenix ship is somewhat similar in design.
In June 2019, Ocean Voyages Institute, conducted a cleanup utilizing GPS trackers and existing maritime equipment in the North Pacific Subtropical Convergence Zone setting the record for the largest mid-ocean cleanup accomplished in the North Pacific Gyre and removed over 84,000 pounds of polymer nets and consumer plastic trash from the ocean.
In May/June 2020, Ocean Voyages Institute conducted a cleanup expedition in the Gyre and set a new record for the largest mid-ocean cleanup accomplished in the North Pacific Gyre which removed over 170 tons (340,000 pounds) of consumer plastics and ghostnets from the ocean. Utilizing custom designed GPS satellite trackers which are deployed by vessels of opportunity, Ocean Voyages Institute is able to accurately track and send cleanup vessels to remove ghostnets. The GPS Tracker technology is being combined with satellite imagery increasing the ability to locate plastic trash and ghostnets in real time via satellite imagery which will greatly increase cleanup capacity and efficiency.
Another issue is that removing marine debris from the ocean can potentially cause more harm than good. Cleaning up microplastics could also accidentally take out plankton, which are the main lower level food group for the marine food chain and over half of the photosynthesis on earth.Parker, Laura. "With Millions of Tons of Plastic in Oceans, More Scientists Studying Impact." National Geographic. National Geographic Society, 13 June 2014. Web. 3 April 2016. One of the most efficient and cost effective ways to help reduce the amount of plastic entering our oceans is to not participate in using single-use plastics, avoid plastic bottled drinks such as water bottles, use reusable shopping bags, and to buy products with reusable packaging.
Ocean dumping is controlled by international law, including:
On 11 April 2013 in order to create awareness, artist Maria Cristina Finucci founded the Garbage Patch State at UNESCO –Paris in front of Director General Irina Bokova. First of a series of events under the patronage of UNESCO and of Italian Ministry of the Environment.
Forty-eight plastics manufacturers from 25 countries, are members of the Global Plastic Associations for solutions on Marine Litter, have made the pledge to help prevent marine debris and to encourage recycling.
Plastic debris from inland states come from two main sources: ordinary litter and materials from open dumps and landfills that blow or wash away to inland waterways and wastewater outflows. The refuse finds its way from inland waterways, rivers, streams and lakes to the ocean. Though ocean and coastal area cleanups are important, it is crucial to address plastic waste that originates from inland and landlocked states.
At the systems level, there are various ways to reduce the amount of debris entering our waterways:
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