The garbage islands They are areas of the oceans where a large amount of solid waste accumulates due to particular characteristics of the currents. The main component of these islands is the plastic that comes mostly from the coastal areas.
Its formation begins with the accumulation of solid waste in the coastal areas that are dragged out to sea by the tide and ocean currents. Likewise, waste directly thrown into the sea by cargo, fishing and passenger ships is added..
The floating debris is carried by the currents following their natural patterns so they converge towards the center of the circuit. The first time the formation of the garbage islands was visualized was in 1997.
This huge accumulation of waste (mainly plastic) represents a serious environmental problem. Thus, macroplastic (large pieces such as bags, containers or others) becomes deadly traps for many marine species.
On the other hand, microplastic (2-5 mm fragments) is ingested by marine fauna and causes mechanical damage in addition to releasing toxic substances. Microplastic is a material to which bacteria, toxic algae, chemicals such as DDT, hydrocarbons and metals adhere..
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Since the beginning of the 80s of the twentieth century, there had been a warning of the increase in plastic waste carried by the sea currents. However, the problem of the so-called garbage islands became known just a little over 20 years ago..
The first direct evidence was given by the American Charles Moore (ship captain and surfer) in 1997. Moore was sailing through areas far from the frequent routes in the North Pacific Ocean and detected an unusual amount of plastic debris.
During 1999 the first scientific work was published warning of the phenomenon known as the great patch of garbage in the Pacific. Since then, six large garbage islands have been detected (three in the Pacific Ocean, two in the Atlantic and one in the Indian Ocean)..
Garbage patches are not islands per se but vast oceanic areas with no defined boundaries covered with floating and submerged debris. Most of these wastes are pellet-shaped or rice-grain-sized pieces of plastic called plastic soup..
These garbage islands vary in extension from 700,000 km² to 15 million km², containing between 6 and 100 million tons of plastic. Regarding their location, they are located in the interior of the great circuits of ocean currents..
In the vertical dimension they extend in a strip approximately 30 m deep, forming two main zones:
Garbage islands are located in international waters in areas far from commercial maritime routes. For this reason, the problem has not been detected until a few years ago and no country is responsible for its solution..
Garbage patches are not easy to study because of their location away from common shipping lanes. On the other hand, its monitoring by satellites is not feasible due to the transparency of plastic, which is its main constituent..
Additionally, most of the plastic present consists of small particles in the greater proportion submerged and the area lacks defined limits. Therefore, according to the criteria and the measurement methods, they are assigned very variable extensions and masses of waste..
During 2009 the 5 Gyres Institute (Instituto 5 Giros) as an initiative of various researchers to study the islands of garbage in the oceans. Currently, the institute is internationally recognized and is supported by organizations such as the UN (United Nations Organization).
Most of the waste (approximately 80%) comes from coastal areas, both on the mainland and on the islands. While the other 20% originates from maritime transit (mainly fishing fleets).
It is estimated that about 8 million tons of garbage reach the oceans annually. These wastes deposited in the coastal areas are carried away by the tide and currents and become part of the circuit of the great ocean currents..
When observing the main currents of the planet's oceans, it is noted that they form a system of rotation that borders the coastal areas. This rotation creates a vortex or convergence zone towards the center of the system, causing floating debris to be located towards that zone..
The subtropical ocean gyres are systems of currents generated by wind flows in the Pacific, Atlantic and Indian oceans. These systems move from the tropics to the poles and in both oceans there are gyrations in the north and in the south..
Air masses heat up at the equator, rise, and are swept westward by the effect of the Earth's rotation. As these air masses rise, they cool and begin to descend around 30 ° latitude, heading east..
This circuit of winds creates a huge mass of air that rotates in a clockwise direction in the northern hemisphere. On the other hand, in the southern hemisphere the rotary movement occurs in the opposite direction.
The rotating air mass creates a high pressure system that depresses the ocean surface and drives a slow ocean-scale surface current. This current moves with the air forming a spiral that has light or calm winds in the center.
Due to this pattern of movement of the oceanic gyres, floating debris tends to converge towards the central zone of the current. In this way, floating pieces of plastic and other debris accumulate and form islands or oceanic garbage patches..
The wastes that make up these islands are polluting elements of the ocean environment. Most of them are plastic fragments that represent a danger to marine fauna..
Many marine animals ingest plastic by drowning, as in the case of turtles. Other animals suffer complications and even death from the large amounts of plastic that end up accumulating in their digestive tract..
Some groups affected by the plastic accumulated in the garbage islands are various species of sharks and cetaceans. In addition, filter-feeding organisms have been observed that are transparent with colored plastic fragments in their bellies..
The populations of albatrosses (family Diomedeidae) living near the eastern garbage island (North Atlantic) are seriously affected by plastic. Large amount of plastic has been found in the digestive tract of dead albatrosses.
Likewise, it is estimated that 40% of albatross chicks die because their parents feed them microplastics that they mistake for food..
Some of the macroplastic elements are large such as bags, nets, containers and become deadly traps where marine animals are trapped..
During an expedition in 2002, scientific photographers captured underwater images of jellyfish entangled in frayed lines of plastic. On the other hand, the expedition of 5 Gyres Institute in 2010 he located fish trapped in bottles.
Microplastics
Microplastics are fragments of 2 to 5 mm in diameter that are generated by the decomposition of plastic in the sea. These fragments are easily ingested by marine species causing alterations and even death..
Thus, the development of granulomas in blue mussels caused by the ingestion of microplastics has been verified.
Some researchers have pointed out that the most serious problem with these floating microplastic fragments is their toxic potential. Many of these wastes secrete substances that negatively affect marine life.
For example, plastics release dioxins and bisphenol A affect the reproductive processes of many species.
On the other hand, microplastics absorb pathogens (bacteria and toxic algae) and various harmful substances that can be consumed by marine fauna. Other toxic substances include DDT, PCBs, hydrocarbons, metals, and other toxic hydrophobic (water-rejecting) chemicals..
In addition, there is a danger of bioaccumulation (accumulation of toxins along the food chain as one organism ingests another). Therefore, human health can be affected by consuming marine animals contaminated by microplastics and their toxins..
Large areas covered in debris affect the penetration of sunlight. This situation alters the life cycles of plankton that is the base of the oceanic food chain..
Two islands or garbage patches have been detected in the North Pacific Ocean, although some treat them as a single North Atlantic garbage island. Depending on the criteria to make the estimate, an area between 700,000 km² and 15 million km² is indicated..
One of these islands is the eastern garbage patch, located between San Francisco and the Hawaiian Islands. The other is the western garbage patch off the coast of Japan..
This was the first island or garbage patch detected in the ocean and about which we have more information. It is located in the turn of the North Atlantic, between the Hawaiian Islands and California (USA), about 1,000 km from Hawaii.
Its vortex rotates clockwise and its extension is calculated between 1.6 to 3.4 million km². On the other hand, it is estimated that it contains between 6 million to 100 million tons of waste..
It is located in front of Japan and is somewhat smaller than the previous one..
It is located between the coasts of Chile to the east and the coasts of Australia and the islands of Oceania to the west. Its vortex rotates counterclockwise. It reaches an approximate area of 1 million km².
It is located in the center of the North Atlantic, between Bermuda to the west and the Azores islands to the east, in the so-called Sargasso Sea. Its vortex rotates clockwise.
It is located between the coasts of South America (Argentina, Uruguay and Brazil) and the coasts of the Gulf of Bengal and Cape of Good Hope (Africa). Its vortex rotates counterclockwise.
It was discovered in 2010 and is located on the coasts of South Africa and Madagascar and the coasts of Australia, in the central Indian Ocean. Its vortex rotates counterclockwise.
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