Marine plastic pollution

An exhibit at the Mote Marine Laboratory that displays plastic bags in the ocean that look similar to jellyfish.

Plastic pollution in the ocean (also called ocean plastic pollution) is a term referring to pollution of the sea by plastics in general, ranging from large pieces of fishing gear that can entrap marine animals to the microplastics and nanoplastics that result from the breakdown or photodegradation of plastic waste in surface waters, rivers or oceans. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic. It is estimated that there is a stock of 86 million tons of plastic marine debris in the worldwide ocean as of the end of 2013, assuming that 1.4% of global plastics produced from 1950 to 2013 has entered the ocean and has accumulated there.

The 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh, largely through the rivers Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and the Mekong, and accounting for "90 percent of all the plastic that reaches the world's oceans." Asia was the leading source of mismanaged plastic waste, with China alone accounting for 2.4 million metric tons.

Discarded plastic bags, six pack rings, cigarette butts and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries. Aquatic life can be threatened through entanglement, suffocation, and ingestion. Fishing nets, usually made of plastic, can be left or lost in the ocean by fishermen. Known as ghost nets, these entangle fish, dolphins, sea turtles, sharks, dugongs, crocodiles, seabirds, crabs, and other creatures, restricting movement, causing starvation, laceration, infection, and, in those that need to return to the surface to breathe, suffocation.

Plastics accumulate because they don't biodegrade in the way many other substances do. They will photodegrade on exposure to the sun, but they do so properly only under dry conditions, and water inhibits this process. In marine environments, photodegraded plastic disintegrates into ever-smaller pieces while remaining polymers, even down to the molecular level. When floating plastic particles photodegrade down to zooplankton sizes, jellyfish attempt to consume them, and in this way the plastic enters the ocean food chain.

Types of sources and and amounts

The pathway by which plastics enters the world's oceans

Average estimated decomposition times of typical marine debris items. Plastic items are shown in blue.

Plastic waste entering the seas is increasing each year with much of the plastic entering the seas is in particles smaller than 5 millimetres. As of 2016 it was estimated that there was approximately 150 million tonnes of plastic pollution in the world's oceans, estimated to grow to 250 million tonnes in 2025. Another study estimated that in 2012, it was approximately 165 million tonnes. In 2020 a study found that the Atlantic Ocean contain approximately 10 times more plastic than was previously thought. The largest single type of plastic pollution (~10 %) and majority of large plastic in the oceans is discarded and lost nets from the fishing industry.

The Ocean Conservancy reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.

One study estimated that there are more than 5 trillion plastic pieces (defined into the four classes of small microplastics, large microplastics, meso- and macroplastics) afloat at sea. In 2020, new measurements found more than 10 times as much plastic in the Atlantic Ocean than previously estimated to be there.

In October 2019, when research revealed most ocean plastic pollution comes from Chinese cargo ships, an Ocean Cleanup spokesperson said: "Everyone talks about saving the oceans by stopping using plastic bags, straws and single use packaging. That's important, but when we head out on the ocean, that's not necessarily what we find."

Almost 20% of plastic debris that pollutes ocean water, which translates to 5.6 million tonnes, comes from ocean-based sources. MARPOL, an international treaty, "imposes a complete ban on the at-sea disposal of plastics". Merchant ships expel cargo, sewage, used medical equipment, and other types of waste that contain plastic into the ocean. In the United States, the Marine Plastic Pollution Research and Control Act of 1987 prohibits discharge of plastics in the sea, including from naval vessels. Naval and research vessels eject waste and military equipment that are deemed unnecessary. Pleasure crafts release fishing gear and other types of waste, either accidentally or through negligent handling. The largest ocean-based source of plastic pollution is discarded fishing gear (including traps and nets), estimated to be up to 90% of plastic debris in some areas.

Continental plastic litter enters the ocean largely through storm-water runoff, flowing into watercourses or directly discharged into coastal waters. Plastic in the ocean has been shown to follow ocean currents which eventually form into what is known as Great Garbage Patches. Knowledge of the routes that plastic follows in ocean currents comes from accidental container drops from ship carriers. For example, in May 1990 The Hansa Carrier, sailing from Korea to the United States, broke apart due to a storm, ultimately resulting in thousands of dumped shoes; these eventually started showing up on the U.S western coast, and Hawaii.

Plastic waste generation exceeds amount of plastic pollution being expelled from the ocean.

The impact of microplastic and macroplastic into the ocean is not subjected to infiltration directly by dumping of plastic into marine ecosystems, but through polluted rivers that lead or create passageways to oceans across the globe. Rivers can either act as a source or sink depending on the context. Rivers receive and gather majority of plastic but can also prevent a good percentage from entering the ocean. Rivers are the dominant source of plastic pollution in the marine environment contributing nearly 80% in recent studies. The amount of plastic that is recorded to be in the ocean is considerably less than the amount of plastic that is entering the ocean at any given time. According to a study done in the UK, there are "ten top" macroplastic dominant typologies that are solely consumer related (located in the table below). Within this study, 192,213 litter items were counted with an average of 71% being plastic and 59% were consumer related macroplastic items. Even though freshwater pollution is the major contributor to marine plastic pollution there is little studies done and data collection for the amount of pollution going from freshwater to marine. Majority of papers conclude that there is minimal data collection of plastic debris in freshwater environments and natural terrestrial environments, even though these are the major contributor. The need for policy change in production, usage, disposal, and waste management is necessary to decrease the amount and potential of plastic to enter freshwater environments.

Present study top ten	Litter rate in the UK (Elliott and Elliott, 2018)	Litter rate ranking
1) Food wrappers	Variable (e.g. crisp packets 3.7%; sweet wrappers 3.1%)	5
2) Bottles and lids	6.9%	6
3) Bags	Unknown	-
4) Cigarette butts	31.9%	2
5) Sanitary items	Variable (e.g. wet wipes 31.3%; Sanitary towels 21.3%)	1
6) Smoking-related packaging	Unknown	-
7) Cotton bud sticks	13.5% littered	3
8) Takeaway containers	5.1%	7
9) Cups	13.1%	4
10) Straws, stirrers, cutlery	Variable (e.g. Straws 3.1%, Cutlery 0.5%; stirrers 0.2%)	8

A 1994 study of the seabed using trawl nets in the North-Western Mediterranean around the coasts of Spain, France, and Italy reported mean concentrations of debris of 1,935 items per square kilometre. Plastic debris accounted for 77%, of which 93% was plastic bags.

Land-based sources of ocean plastic pollution

Further information: Plastic pollution § Major plastic polluter countries

Estimates for the contribution of land-based plastic vary widely. While one study estimated that a little over 80% of plastic debris in ocean water comes from land-based sources, responsible for 800,000 tonnes (880,000 short tons) every year. In 2015, it was calculated that 275 million tonnes (303 million short tons) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million tonnes (5.3 to 14 million short tons) entering the ocean – a percentage of only up to 5%.

In a study published by Science, Jambeck et al (2015) estimated that the 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh.

A source that has caused concern is landfills. Most waste in the form of plastic in landfills are single-use items such as packaging. Discarding plastics this way leads to accumulation. Although disposing of plastic waste in landfills has less of a gas emission risk than disposal through incineration, the former has space limitations. Another concern is that the liners acting as protective layers between the landfill and environment can break, thus leaking toxins and contaminating the nearby soil and water. Landfills located near oceans often contribute to ocean debris because content is easily swept up and transported to the sea by wind or small waterways like rivers and streams. Marine debris can also result from sewage water that has not been efficiently treated, which is eventually transported to the ocean through rivers. Plastic items that have been improperly discarded can also be carried to oceans through storm waters.

Nurdles

This section is an excerpt from Plastic pellet pollution.[edit]

Plastic "nurdle" pellets on a beach in southwest France, 2011

Plastic pellet pollution is a type of marine debris originating from the plastic particles that are universally used to manufacture large-scale plastics. In the context of plastic pollution, these pre-production plastic pellets are commonly known as 'nurdles'. These microplastics are created separately from the user plastics they are melted down to form, pellets. Loss can occur during both the manufacturing and transport stages. When released into the open environment, they create persistent pollution both in the oceans and on beaches. About 230,000 tonnes of nurdles are thought to be deposited in the oceans each year, where they are often mistaken for food by seabirds, fish and other wildlife. Due to their small size, they are notoriously difficult to clear up from beaches and elsewhere.

Microplastics

Microplastics in the surface ocean 1950-2000 and projections beyond, in million metric tonnes.

Polystyrene foam beads on an Irish beach

Great Pacific garbage patch — Pacific Ocean currents have created three "islands" of debris.

Example of microplastic collected by Oregon State University

A growing concern regarding plastic pollution in the marine ecosystem is the use of microplastics. Microplastics are little beads of plastic less than 5 millimeters wide, and they are commonly found in hand soaps, face cleansers, and other exfoliators. When these products are used, the microplastics go through the water filtration system and into the ocean, but because of their small size they are likely to escape capture by the preliminary treatment screens on wastewater plants. These beads are harmful to the organisms in the ocean, especially filter feeders, because they can easily ingest the plastic and become sick. The microplastics are such a concern because it is difficult to clean them up due to their size, so humans can try to avoid using these harmful plastics by purchasing products that use environmentally safe exfoliates.

Because plastic is so widely used across the planet, microplastics have become widespread in the marine environment. For example, microplastics can be found on sandy beaches and surface waters as well as in the water column and deep sea sediment. Microplastics are also found within the many other types of marine particles such as dead biological material (tissue and shells) and some soil particles (blown in by wind and carried to the ocean by rivers). Upon reaching marine environments, the fate of microplastics is subject to naturally occurring drivers, such as winds and surface oceanic currents. Numerical models are able to trace small plastic debris (micro- and meso-plastics) drifting in the ocean, thus predicting their fate.

Microplastics enter waterways through many avenues including deterioration of road paint, tire wear and city dust entering the waterways, plastic pellets spilled from shipping containers, ghost nets and other synthetic textiles dumped into the ocean, cosmetics discharged and laundry products entering sewage water and marine coatings on ships degrading.

Some microplastics leave the sea and enter the air, as researchers from the University of Strathclyde discovered in 2020. Some remain on the ocean's surface; microplastics account for 92% of plastic debris on the ocean's surface, according to a 2018 study. And some sink to the ocean floor. Australia's national science agency CSIRO estimated that 14 million metric tons of microplastics are already on the ocean floor in 2020. This represents an increase from a 2015 estimate that the world's oceans contain 93–236 thousand metric tons of microplastics and a 2018 estimate of 270 thousand tons.

The Ocean Conservancy has reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.

A study of the distribution of Eastern Pacific Ocean surface plastic debris (not specifically microplastic, although, as previously mentioned, most is likely microplastic) helps to illustrate the rising concentration of plastics in the ocean. By using data on surface plastic concentration (pieces of plastic per km²) from 1972 to 1985 (n=60) and 2002–2012 (n=457) within the same plastic accumulation zone, the study found the mean plastic concentration increase between the two sets of data, including a 10-fold increase of 18,160 to 189,800 pieces of plastic per km².

Arctic Ocean microplastics come mainly from Atlantic sources, especially Europe and North America.

A study found that microplastics from oceans have been found in sea breeze.

The ingestion of plastic by marine organisms has now been established at full ocean depth. Microplastic was found in the stomachs of hadal amphipods sampled from the Japan, Izu-Bonin, Mariana, Kermadec, New Hebrides and the Peru-Chile trenches. The amphipods from the Mariana Trench were sampled at 10,890 m and all contained microfibres.

Research studies

The extent of microplastic pollution in the deep sea has yet to be fully determined, and as a result scientists are currently examining organisms and studying sediments to better understand this issue. A 2013 study surveyed four separate locations to represent a wider range of marine habitats at depths varying from 1100-5000m. Three of the four locations had identifiable amounts of microplastics present in the top 1 cm layer of sediment. Core samples were taken from each spot and had their microplastics filtered out of the normal sediment. The plastic components were identified using micro-Raman spectroscopy; the results showed man-made pigments commonly used in the plastic industry. In 2016, researchers used an ROV to collect nine deep-sea organisms and core-top sediments. The nine deep-sea organisms were dissected and various organs were examined by the researchers on shore to identify microplastics with a microscope. The scientists found that six out of the nine organisms examined contain microplastics which where all microfibers, specifically located in the GI tract. Research performed by MBARI in 2013 off the west coast of North America and around Hawaii found that out of all the debris observed from 22 years of VARS database video footage, one-third of the items was plastic bags. This debris was most common below 2000 m depth. A recent study that collected organisms and sediments in the Abyssopelagic Zone of the Western Pacific Ocean extracted materials from samples and discovered that poly(propylene-ethylene) copolymer (40.0%) and polyethylene terephthalate (27.5%) were the most commonly detected polymers.

Another study was conducted by collecting deep-sea sediment and coral specimens between 2011 and 2012 in the Mediterranean Sea, Southwest Indian Ocean, and Northeast Atlantic Ocean. Of the 12 coral and sediment samples taken, all were found with an abundance of microplastics. Rayon is not a plastic but was included in the study due to being a common synthetic material. It was found in all samples and comprised 56.9% of materials found, followed by polyester (53.4%), plastics (34.1%) and acrylic (12.4%). This study found that the amount of microplastics, in the form of microfibres, was comparable to that found in intertidal or subtidal sediments. A 2017 study had a similar finding – by surveying the Rockall Trough in the Northeast Atlantic Ocean at a depth of more than 2200 meters, microplastic fibers were identified at a concentration of 70.8 particles per cubic meter. This is comparable to amounts reported in surface waters. This study also looked at micropollution ingested by benthic invertebrates Ophiomusium lymani, Hymenaster pellucidus and Colus jeffreysianus and found that of the 66 organisms studied, 48% had ingested microplastics in quantities also comparable to coastal species. A recent review of 112 studies found the highest plastic ingestion in organisms collected in the Mediterranean and Northeast Indian Ocean with significant differences among plastic types ingested by different groups of animals, including differences in colour and the type of prevalent polymers. Overall, clear fibre microplastics are likely the most predominant types ingested by marine megafauna around the globe.

In 2020 scientists created what may be the first scientific estimate of how much microplastic currently resides in Earth's seafloor, after investigating six areas of ~3 km depth ~300 km off the Australian coast. They found the highly variable microplastic counts to be proportionate to plastic on the surface and the angle of the seafloor slope. By averaging the microplastic mass per cm³, they estimated that Earth's seafloor contains ~14 million tons of microplastic – about double the amount they estimated based on data from earlier studies – despite calling both estimates "conservative" as coastal areas are known to contain much more microplastic. These estimates are about one to two times the amount of plastic thought to currently enter the oceans annually.

Toxic chemicals

Toxic additives used in the manufacture of plastic materials can leach out into their surroundings when exposed to water. Approximately 8000–19000 tonnes of additives are transported with buoyant plastic matrices globally with a significant portion also transported to the Arctic. Waterborne hydrophobic pollutants collect and magnify on the surface of plastic debris, thus making plastic far more deadly in the ocean than it would be on land. Hydrophobic contaminants are also known to bioaccumulate in fatty tissues, biomagnifying up the food chain and putting pressure on apex predators and humans. Some plastic additives are known to disrupt the endocrine system when consumed, others can suppress the immune system or decrease reproductive rates.

Floating debris can also absorb persistent organic pollutants from seawater, including PCBs, DDT, and PAHs. Plastic debris can absorb toxic chemicals from ocean pollution, potentially poisoning any creature that eats it. Aside from toxic effects when ingested some of these affect animal brain cells similarly to estradiol, causing hormone disruption in the affected wildlife. A study discovered, when plastics eventually decompose, they produce potentially toxic bisphenol A (BPA) and PS oligomer into the water. These toxins are believed to bring harm to the marine life living in the area. Bisphenol A (BPA) is a famous example of a plasticizer produced in high volumes for food packing from where it can leach into food, leading to human exposure. As an estrogen and glucocorticoid receptor agonist, BPA is interfering with the endocrine system and is associated with increased fat in rodents.

Accumulation sites

Pacific Garbage, Black sand beach, Maui, Hawaii

Plastic debris tends to accumulate at the center of ocean gyres. The North Pacific Gyre, for example, has collected the so-called "Great Pacific Garbage Patch", which is now estimated to be one to twenty times the size of Texas (approximately from 700,000 to 15,000,000 square kilometers). There could be as much plastic as fish in the sea. It has a very high level of plastic particulate suspended in the upper water column. In samples taken in 1999, the mass of plastic exceeded that of zooplankton (the dominant animal life in the area) by a factor of six.

Midway Atoll, in common with all the Hawaiian Islands, receives substantial amounts of debris from the garbage patch. Ninety percent plastic, this debris accumulates on the beaches of Midway where it becomes a hazard to the bird population of the island. Midway Atoll is home to two-thirds (1.5 million) of the global population of Laysan albatross. Nearly all of these albatross have plastic in their digestive system and one-third of their chicks die.

Garbage patches

This section is an excerpt from Garbage patch.[edit]

Trash washed ashore in Hawaii from the Great Pacific Garbage Patch

A garbage patch is a gyre of marine debris particles caused by the effects of ocean currents and increasing plastic pollution by human populations. These human-caused collections of plastic and other debris are responsible for ecosystem and environmental problems that affect marine life, contaminate oceans with toxic chemicals, and contribute to greenhouse gas emissions. Once waterborne, marine debris becomes mobile. Flotsam can be blown by the wind, or follow the flow of ocean currents, often ending up in the middle of oceanic gyres where currents are weakest.

Within garbage patches, the waste is not compact, and although most of it is near the surface of the ocean, it can be found up to more than 30 metres (100 ft) deep in the water. Patches contain plastics and debris in a range of sizes from Microplastics and small scale plastic pellet pollution, to large objects such as fishing nets and consumer goods and appliances lost from flood and shipping loss.

Garbage patches grow because of widespread loss of plastic from human trash collection systems. The United Nations Environmental Program estimated that "for every square mile of ocean" there are about "46,000 pieces of plastic". The 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh, largely through the rivers Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and the Mekong, and accounting for "90 percent of all the plastic that reaches the world's oceans". Asia was the leading source of mismanaged plastic waste, with China alone accounting for 2.4 million metric tons.

The best known of these is the Great Pacific Garbage Patch which has the highest density of marine debris and plastic. The Pacific Garbage patch has two mass buildups: the western garbage patch and the eastern garbage patch, the former off the coast of Japan and the latter between California and Hawaii. These garbage patches contain 90 million tonnes (100 million short tons) of debris. Other identified patches include the North Atlantic garbage patch between North America and Africa, the South Atlantic garbage patch located between eastern South America and the tip of Africa, the South Pacific garbage patch located west of South America, and the Indian Ocean garbage patch found east of South Africa listed in order of decreasing size.

In the Pacific Ocean

North Pacific Subtropical Convergence Zone

Main article: Great Pacific garbage patch

In the Pacific Gyre, specifically 20°N-40°N latitude, large bodies with floating marine debris can be found. Models of wind patterns and ocean currents indicate that the plastic waste in the northern Pacific is particularly dense where the Subtropical Convergence Zone (STCZ), 23°N-37°N latitude, meets a southwest–northeast line, found north of the Hawaiian archipelago.

In the Pacific, there are two mass buildups: the western garbage patch and the eastern garbage patch, the former off the coast of Japan and the latter between Hawaii and California. The two garbage patches are both part of the great Pacific garbage patch, and are connected through a section of plastic debris off the northern coast of the Hawaiian islands. It is approximated that these garbage patches contain 90 million tonnes (100 million short tons) of debris. The waste is not compact, and although most of it is near the surface of the pacific, it can be found up to more than 30 metres (100 ft) deep in the water.

Research published in April 2017 reported "the highest density of plastic rubbish anywhere in the world" on remote and uninhabited Henderson Island in South Pacific as a result of the South Pacific Gyre. The beaches contain an estimated 37.7 million items of debris together weighing 17.6 tonnes. In a study transect on North Beach, each day 17 to 268 new items washed up on a 10-metre section. The study noted that purple hermit crabs (Coenobita spinosus) make their homes in plastic containers washed up on beaches.

Environmental impacts

See also: Marine pollution § Plastic debris, and North Atlantic garbage patch

Model results for the count density of planktonic plastic particles (red is more dense)

The litter that is being delivered into the oceans is toxic to marine life, and humans. The toxins that are components of plastic include diethylhexyl phthalate, which is a toxic carcinogen, as well as lead, cadmium, and mercury.

Plankton, fish, and ultimately the human race, through the food chain, ingest these highly toxic carcinogens and chemicals. Consuming the fish that contain these toxins can cause an increase in cancer, immune disorders, and birth defects.

The majority of the litter near and in the ocean is made up of plastics and is a persistent pervasive source of marine pollution. In many countries improper management of solid waste means there is little control of plastic entering the water system. According to Dr. Marcus Eriksen of The 5 Gyres Institute, there are 5.25 trillion particles of plastic pollution that weigh as much as 270,000 tonnes (2016). This plastic is taken by the ocean currents and accumulates in large vortexes known as ocean gyres. The majority of the gyres become pollution dumps filled with plastic.

Research on floating plastic debris in the ocean was the fastest-growing topic among 56 sustainability topics examined in a study of scientific publishing by 193 countries over 2011 to 2019. Over nine years, global research documenting this phenomenon ballooned from 46 (2011) to 853 (2019) publications.

Marine ecosystems

Concern among experts has grown since the 2000s that some organisms have adapted to live on floating plastic debris, allowing them to disperse with ocean currents and thus potentially become invasive species in distant ecosystems. Research in 2014 in the waters around Australia confirmed a wealth of such colonists, even on tiny flakes, and also found thriving ocean bacteria eating into the plastic to form pits and grooves. These researchers showed that "plastic biodegradation is occurring at the sea surface" through the action of bacteria, and noted that this is congruent with a new body of research on such bacteria. Their finding is also congruent with the other major research undertaken in 2014, which sought to answer the riddle of the overall lack of build up of floating plastic in the oceans, despite ongoing high levels of dumping. Plastics were found as microfibres in core samples drilled from sediments at the bottom of the deep ocean. The cause of such widespread deep sea deposition has yet to be determined.

The hydrophobic nature of plastic surfaces stimulates rapid formation of biofilms, which support a wide range of metabolic activities, and drive succession of other micro- and macro-organisms.

Effects on animals

Plastic waste has reached all the world's oceans. This plastic pollution harms an estimated 100,000 sea turtles and marine mammals and 1,000,000 sea creatures each year. Larger plastics (called "macroplastics") such as plastic shopping bags can clog the digestive tracts of larger animals when consumed by them and can cause starvation through restricting the movement of food, or by filling the stomach and tricking the animal into thinking it is full. Microplastics on the other hand harm smaller marine life. For example, pelagic plastic pieces in the center of our ocean’s gyres outnumber live marine plankton, and are passed up the food chain to reach all marine life.

Plastic pollution has the potential to poison animals, which can then adversely affect human food supplies. Plastic pollution has been described as being highly detrimental to large marine mammals, described in the book Introduction to Marine Biology as posing the "single greatest threat" to them. Some marine species, such as sea turtles, have been found to contain large proportions of plastics in their stomach. When this occurs, the animal typically starves, because the plastic blocks the animal's digestive tract. Sometimes marine mammals are entangled in plastic products such as nets, which can harm or kill them.

Entanglement

Sea turtle entangled in a ghost net

Entanglement in plastic debris has been responsible for the deaths of many marine organisms, such as fish, seals, turtles, and birds. These animals get caught in the debris and end up suffocating or drowning. Because they are unable to untangle themselves, they also die from starvation or from their inability to escape predators. Being entangled also often results in severe lacerations and ulcers. It was estimated that at least 267 different animal species have suffered from entanglement and ingestion of plastic debris. It has been estimated that over 400,000 marine mammals perish annually due to plastic pollution in oceans. Marine organisms get caught in discarded fishing equipment, such as ghost nets. Ropes and nets used to fish are often made of synthetic materials such as nylon, making fishing equipment more durable and buoyant. These organisms can also get caught in circular plastic packaging materials, and if the animal continues to grow in size, the plastic can cut into their flesh. Equipment such as nets can also drag along the seabed, causing damage to coral reefs.

Ingestion

The remains of an albatross containing ingested flotsam

Many animals that live on or in the sea consume flotsam by mistake, as it often looks similar to their natural prey. Plastic debris, when bulky or tangled, is difficult to pass, and may become permanently lodged in the digestive tracts of these animals. Especially when evolutionary adaptions make it impossible for the likes of turtles to reject plastic bags, which resemble jellyfish when immersed in water, as they have a system in their throat to stop slippery foods from otherwise escaping. Thereby blocking the passage of food and causing death through starvation or infection.

Many of these long-lasting pieces end up in the stomachs of marine birds and animals, including sea turtles, and black-footed albatross. This results in obstruction of digestive pathways, which leads to reduced appetite or even starvation. In a 2008 Pacific Gyre voyage, Algalita Marine Research Foundation researchers began finding that fish are ingesting plastic fragments and debris. Of the 672 fish caught during that voyage, 35% had ingested plastic pieces.

In samples taken from the North Pacific Gyre in 1999 by the Algalita Marine Research Foundation, the mass of plastic exceeded that of zooplankton by a factor of six.

Mammals and fish

A 2021 literature review published in Science identified 1,288 marine species that are known to ingest plastic. Most of these species are fish.

Sea turtles are affected by plastic pollution. Some species are consumers of jelly fish, but often mistake plastic bags for their natural prey. This plastic debris can kill the sea turtle by obstructing the oesophagus. Baby sea turtles are particularly vulnerable according to a 2018 study by Australian scientists.

So too are whales. Large amounts of plastics have been found in the stomachs of beached whales. Plastic debris started appearing in the stomach of the sperm whale since the 1970s, and has been noted to be the cause of death of several whales. In June 2018, more than 80 plastic bags were found inside a dying pilot whale that washed up on the shores of Thailand. In March 2019, a dead Cuvier's beaked whale washed up in the Philippines with 88 lbs of plastic in its stomach. In April 2019, following the discovery of a dead sperm whale off of Sardinia with 48 pounds of plastic in its stomach, the World Wildlife Foundation warned that plastic pollution is one of the most dangerous threats to sea life, noting that five whales have been killed by plastic over a two-year period.

Some of the tiniest bits of plastic are being consumed by small fish, in a part of the pelagic zone in the ocean called the Mesopelagic zone, which is 200 to 1000 metres below the ocean surface, and completely dark. Not much is known about these fish, other than that there are many of them. They hide in the darkness of the ocean, avoiding predators and then swimming to the ocean's surface at night to feed. Plastics found in the stomachs of these fish were collected during Malaspina's circumnavigation, a research project that studies the impact of global change on the oceans.

A study conducted by Scripps Institution of Oceanography showed that the average plastic content in the stomachs of 141 mesopelagic fish over 27 different species was 9.2%. Their estimate for the ingestion rate of plastic debris by these fish in the North Pacific was between 12,000 and 24,000 tonnes per year. The most popular mesopelagic fish is the lantern fish. It resides in the central ocean gyres, a large system of rotating ocean currents. Since lantern fish serve as a primary food source for the fish that consumers purchase, including tuna and swordfish, the plastics they ingest become part of the food chain. The lantern fish is one of the main bait fish in the ocean, and it eats large amounts of plastic fragments, which in turn will not make them nutritious enough for other fish to consume.

Another study found bits of plastic outnumber baby fish by seven to one in nursery waters off Hawaii. After dissecting hundreds of larval fish, the researchers discovered that many fish species ingested plastic particles. Plastics were also found in flying fish, which are eaten by top predators such as tunas and most Hawaiian seabirds.

Deep sea animals have been found with plastics in their stomachs.

Birds

Northern gannet on Helgoland, trapped in their own nests, build only of old nets and other plastic waste.

Plastic pollution does not only affect animals that live solely in oceans. Seabirds are also greatly affected. In 2004, it was estimated that gulls in the North Sea had an average of thirty pieces of plastic in their stomachs. Seabirds often mistake trash floating on the ocean's surface as prey. Their food sources often has already ingested plastic debris, thus transferring the plastic from prey to predator. Ingested trash can obstruct and physically damage a bird's digestive system, reducing its digestive ability and can lead to malnutrition, starvation, and death. Toxic chemicals called polychlorinated biphenyls (PCBs) also become concentrated on the surface of plastics at sea and are released after seabirds eat them. These chemicals can accumulate in body tissues and have serious lethal effects on a bird's reproductive ability, immune system, and hormone balance. Floating plastic debris can produce ulcers, infections and lead to death. Marine plastic pollution can even reach birds that have never been at the sea. Parents may accidentally feed their nestlings plastic, mistaking it for food. Seabird chicks are the most vulnerable to plastic ingestion since they can't vomit up their food like the adult seabirds.

Great Blue Heron capturing a fish in a plastic bags -- birds and other wildlife regularly consume plastic when it gets entangled with or confused with food.

After the initial observation that many of the beaches in New Zealand had high concentrations of plastic pellets, further studies found that different species of prion ingest the plastic debris. Hungry prions mistook these pellets for food, and these particles were found intact within the birds' gizzards and proventriculi. Pecking marks similar to those made by northern fulmars in cuttlebones have been found in plastic debris, such as styrofoam, on the beaches on the Dutch coast, showing that this species of bird also mistake plastic debris for food.

An estimate of 1.5 million Laysan albatrosses, which inhabit Midway Atoll, all have plastics in their digestive system. Midway Atoll is halfway between Asia and North America, and north of the Hawaiian archipelago. In this remote location, the plastic blockage has proven deadly to these birds. These seabirds choose red, pink, brown, and blue plastic pieces because of similarities to their natural food sources. As a result of plastic ingestion, the digestive tract can be blocked resulting in starvation. The windpipe can also be blocked, which results in suffocation. The debris can also accumulate in the animal's gut, and give them a false sense of fullness which would also result in starvation. On the shore, thousands of birds corpses can be seen with plastic remaining where the stomach once was. The durability of the plastics is visible among the remains. In some instances, the plastic piles are still present while the bird's corpse has decayed.

Similar to humans, animals exposed to plasticizers can experience developmental defects. Specifically, sheep have been found to have lower birth weights when prenatally exposed to bisphenol A. Exposure to BPA can shorten the distance between the eyes of a tadpole. It can also stall development in frogs and can result in a decrease in body length. In different species of fish, exposure can stall egg hatching and result in a decrease in body weight, tail length, and body length.

Reduction efforts

Further information: Plastic pollution § Reduction efforts, and Marine debris § Debris removal

Collection in the ocean

Plastics pollution in the oceans might be irreversible.

The organization "The Ocean Cleanup" is trying to collect plastic waste from the oceans by nets. There are concerns from harm to some forms of sea organisms, especially Neuston.

Plastic-to-fuel conversion strategy

The Clean Oceans Project (TCOP) promotes conversion of the plastic waste into valuable liquid fuels, including gasoline, diesel and kerosene, using plastic-to-fuel conversion technology developed by Blest Co. Ltd., a Japanese environmental engineering company. TCOP plans to educate local communities and create a financial incentive for them to recycle plastic, keep their shorelines clean, and minimize plastic waste.

In 2019, a research group led scientists of Washington State University found a way to turn plastic waste products into jet fuel.

Also, the company "Recycling Technologies", has come up with a simple process that can convert plastic waste to an oil called Plaxx. The company is led by a team of engineers from the university of Warwick.

Other companies working on a system for converting plastic waste to fuel include GRT Group and OMV.

Policies and legislation

The trade in plastic waste has been identified as the main cause of marine litter. Countries importing the waste plastics often lack the capacity to process all the material. As a result, the United Nations has imposed a ban on waste plastic trade unless it meets certain criteria.

History

Terminology

Plastic soup

The term "plastic soup" was coined by Charles J. Moore in 1997, after he found patches of plastic pollution in the North Pacific Gyre between Hawaii and California. This Great Pacific Garbage Patch had previously been described in 1988 by scientists who used the term neuston plastic to describe "The size fraction of plastic debris caught in nets designed to catch surface plankton (hereafter referred to as neuston plastic)", and acknowledged that earlier studies in the 1970s had shown that "neuston plastic is widespread, is most abundant in the central and western North Pacific, and is distributed by currents and winds".

The term is sometimes used to refer only to pollution by microplastics, pieces of plastic less than 5mm in size such as fibres shed from synthetic textiles in laundry: the British National Federation of Women's Institutes passed a resolution in 2017 headlined "End Plastic Soup" but concentrating on this aspect of pollution.

The Amsterdam-based Plastic Soup Foundation is an advocacy group which aims to raise awareness of the problem, educate people, and support the development of solutions.

As of January 2019, the Oxford English Dictionary did not include the terms plastic soup, neuston plastic or neustonic plastic, but it defined the term microplastic (or micro-plastic) as "Extremely small pieces of plastic, manufactured as such (in the form of nurdles or microbeads) or resulting from the disposal and breakdown of plastic products and waste" and its illustrative quotations all relate to marine pollution, the earliest being a 1990 reference in the South African Journal of Science: "The mean frequency of micro-plastic particles increased from 491 m-1 of beach in 1984 to 678 m-1 in 1989".

See also

• Plastic pollution
• Great Pacific Garbage Patch
• Marine debris