Marine plastic pollution
Marine plastic pollution is a type of marine pollution by plastics, ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic. Microplastics and nanoplastics result from the breakdown or photodegradation of plastic waste in surface waters, rivers or oceans. Recently, scientists have uncovered nanoplastics in heavy snow, more specifically about 3,000 tons that cover Switzerland yearly.
It is approximated 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. Global consumption of plastics is estimated to be 300 million tonnes per year as of 2022, with around 8 million tonnes ending up in the oceans as macroplastics. Approximately 1.5 million tonnes of primary microplastics end up in the seas. Around 98% of this volume is created by land-based activities, with the remaining 2% being generated by sea-based activities. It is estimated that 19–23 million tonnes of plastic leaks into aquatic ecosystems annually. The 2017 United Nations Ocean Conference estimated that the oceans might contain more weight in plastics than fish by the year 2050.
Oceans are polluted by plastic particles ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. This material is only very slowly degraded or removed from the ocean so plastic particles are now widespread throughout the surface ocean and are known to be having deleterious effects on marine life. 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. There are various types of ocean plastics causing problems to marine life. Bottle caps have been found in the stomachs of turtles and seabirds, which have died because of the obstruction of their respiratory and digestive tracts. Ghost nets are also a problematic type of ocean plastic as they can continuously trap marine life in a process known as "ghost fishing".
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 Yangtze, Indus, Yellow River, Hai, Nile, Ganges, Pearl River, Amur, Niger, and 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 Ocean Conservancy has reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.
Plastics accumulate because they do not 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, photo-degraded 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.
Solutions to marine plastic pollution, along with plastic pollution within the whole environment will be intertwined with changes in manufacturing and packaging practices, and a reduction in the usage, in particular, of single or short-lived plastic products. Many ideas exist for cleaning up plastic in the oceans including trapping plastic particles at river mouths before entering the ocean, and cleaning up the ocean gyres.
Scope of the problem
Marine pollution caused by plastic substances is recognized as an issue of the highest magnitude, from a pollution perspective. A majority of plastics used in people's day to day lives are never recycled. Single use plastics of this kind contribute significantly to the 8 million tons of plastic waste found in the ocean each year. If this trend continues, by the year 2050 there will be more plastic than fish in the ocean by weight. In just the first decade of the century, more plastic has been created than all the plastic in history up until the year of 2000 and a majority of that plastic is not recycled. One estimate of the historic production of plastic gives a figure of 8,300 million metric tonnes for global plastic production up to 2015, of which 79% have been accumulated in landfills or the natural environment. According to the IUCN, this number has grown to 14 million tons of plastic. There is an estimated 15 to 51 trillion pieces of plastic amongst all of the world's oceans stretching from the top of ocean to the seafloor. Oceans are Earth's deepest and most extensive basins with average depths of the abyssal plains being about 4 km beneath sea level. Gravity will naturally move and transfer materials from land to the ocean, with the ocean becoming the end-repository. Oceanic plastic pollution is remarkable for the sheer ubiquity of its presence, from ocean trenches, within deep sea sediment, on the ocean floor and ocean ridges to the ocean surface and coastal margins of oceans. Even remote island atolls can have beaches loaded with plastic from a faraway source. At the ocean surface, plastic debris is concentrated within circular structures of large areal extent, called ocean gyres. Ocean gyres form within all oceans, due to alternating patterns of zonal winds that drive equatorward interior transport in the subtropics, and poleward interior transport in subpolar oceans. Ocean currents concentrate plastic waste within the gyres.Plastics have been increasingly manufactured because of their flexible, molding and durable qualities, which provides plastic with a myriad of useful applications. Plastics are remarkably resistant to natural weathering processes that break down many other materials at the Earth's surface. Ocean processes, including storms, wave action, ocean currents, hydration, and surface exposure to the atmospheric weathering processes and ultraviolet radiation, tend to break plastic particles into ever-decreasing sizes, rather than organically digest or chemically alter plastic substances. Estimates of the total number and weight of plastic across five ocean gyre plastic concentration zones are of the order of 5.25 trillion particles weighing almost 300,000 tons. The reduction in size of plastic particles to the millimeter and micro-scales allow plastic to settle within deep sea sediments, with perhaps four times as much plastic ending up within sediments compared to surface ocean waters. Plastics are now a part of complex biogeochemical cycles with living organisms, such as cetaceans, seabirds, mammals, and bacteria, ingesting plastic.
Over 300 million tons of plastic are produced every year, half of which is used in single-use products like cups, bags, and packaging. It is estimated that 19–23 million tonnes of plastic leaks into aquatic ecosystems annually. It is impossible to know for sure, but it is estimated that about 150 million metric tons of plastic exists in our oceans. Plastic pollution makes up 80% of all marine debris from surface waters to deep-sea sediments. Because plastics are light, much of this pollution is seen in and around the ocean surface, but plastic trash and particles are now found in most marine and terrestrial habitats, including the deep sea, Great Lakes, coral reefs, beaches, rivers, and estuaries. Submarine canyons are important accumulation sites as well, contributing to the transfer of such debris to the deep sea. The most eye-catching evidence of the ocean plastic problem are the garbage patches that accumulate in gyre regions. A gyre is a circular ocean current formed by the Earth's wind patterns and the forces created by the rotation of the planet. There are five main ocean gyres: the North and South Pacific Subtropical Gyres, the North and South Atlantic Subtropical Gyres, and the Indian Ocean Subtropical Gyre. There are significant garbage patches in each of these.
Larger plastic waste can be ingested by marine species, filling their stomachs and leading them to believe they are full when in fact they have taken in nothing of nutritional value. This can bring seabirds, whales, fish, and turtles to die of starvation with plastic-filled stomachs. Marine species can also be suffocated or entangled in plastic garbage.
Macroplastic waste can break can weather into smaller fragments of plastic debris, known as microplastics when they are smaller than 5mm in size. Sunlight exposure, temperature, humidity, waves, and wind begin to break the plastic down into pieces smaller than five millimeters long. Plastics can also be broken down by smaller organisms who will eat plastic debris, breaking it down into small pieces, and either excrete these microplastics or spit them out. In lab tests, it was found that amphipods of the species Orchestia gammarellus could quickly devour pieces of plastic bags, shredding a single bag into 1.75 million microscopic fragments. Although the plastic is broken down, it is still a man-made material that does not biodegrade. It is estimated that approximately 90% of the plastics in the pelagic marine environment are microplastics. There are also primary sources of microplastics, such as microbeads and nurdles. These microplastics are frequently consumed by marine organisms at the base of the food chain, like plankton and fish larvae, which leads to a concentration of ingested plastic up the food chain. Plastics are produced with toxic chemicals, so these toxic substances enter the marine food chain, including the fish that some humans eat.