The sea pollution it is one of the most serious threats facing life on Earth. Thus, the main source of oxygen is marine phytoplankton, which is drastically affected by pollution..
In addition, the seas are inhabited by numerous species whose life is directly compromised by the action of various pollutants. On the other hand, the seas are a source of food for humans, which decrease or lose quality due to pollution.
Sea pollution is caused by pollutants such as plastics, agrochemicals (fertilizers, pesticides), and urban and industrial sewage. Likewise, oil and its derivatives, marine navigation wastes, acid rain and others are pollutants..
The fundamental cause of sea pollution is anthropic activity, especially industrial and agricultural activities and the generation of waste in cities. All this results in eutrophication phenomena, which deplete the oxygen dissolved in water..
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Plastics are the main pollutant in the seas, with concentrations of 5.1 mg of plastic polymers per square meter of marine area. They are degraded by solar radiation and release toxic substances into the water, such as dioxins..
Another group of high impact pollutants in the seas are agrochemicals, which mainly include fertilizers and pesticides (herbicides, insecticides and others). These compounds come from the residues dragged by runoff water due to irrigation and rain, from the cultivated fields..
These pollutants reach the seas through both domestic and industrial sewage. Detergents are used for cleaning tasks, thanks to their ability to dissolve fats and this makes them dangerous pollutants for marine life.
They reach the sea through untreated urban and industrial wastewater and block gaseous exchange by reducing dissolved oxygen in the water, forming a surface cover. This is due to the fact that they are substances less dense than water and hydrophobic (they do not mix with water) and therefore they float..
Human and animal feces are the main polluting organic waste, coming from urban sewage and animal farms. These wastes not only contribute to eutrophication processes, but also incorporate disease-causing microorganisms into the water..
Crude oil and its derivatives are very problematic marine pollutants, due to their negative effect on ecosystems and the difficulty in eliminating them. This is less dense than water, so it forms superficial layers that affect the oxygenation of the water, in addition to adhering to the feathers of seabirds and the body of other animals..
One of the broadest groups of marine pollutants, and at the same time with the greatest impact due to their toxicity, are heavy metals. There are more than 50 elements considered heavy metals, capable of reaching the sea from various sources.
Among these, the use of fossil fuels such as coal and oil stands out, as well as mining, metalworking and electronics. Mercury is one of the most common polluting heavy metals, like cadmium, arsenic and lead.
The main route of pollution of the sea are rivers as well as runoff water that carries all kinds of waste. These wastes include untreated urban and industrial wastewater, as well as agricultural waste..
The different industrial branches generate a great diversity of waste that, if not treated properly, can end up in the sea. The textile and chemical industries are the ones that generate the most polluting effluents, although so do the electronics, metalworking and thermoelectric industries..
The emission of combustion gases such as nitrogen oxides, sulfur dioxide and COtwo pollutes the atmosphere. These gases then react with water vapor and form acids such as nitric, sulfuric and carbonic, which precipitate with the rain and reach the sea, acidifying the water..
Large amounts of inorganic chemicals are used in modern agriculture in the form of fertilizers and pesticides. A large part of these products are washed (leaching) and end up carried by surface waters to the sea.
Once there, many pesticides exert direct toxic effects on living organisms, but additionally, they provide nitrates and phosphates..
Accidents that occur on offshore platforms and tanker ships cause oil spills. Then the currents carry the waste to the coast, impregnating everything with oil, affecting marine fauna, the fishing industry and tourism..
It is estimated that around 6,000,000 tons of waste fall into the sea carried by polluted rivers or directly by coastal activities. Most of this waste is plastics, but sewage also carries detergents, oils, fats and organic waste.
According to some estimates, 20% of the waste that pollutes the seas comes from maritime traffic. This includes litter dumped into the sea from pleasure and passenger cruise ships, war fleets, merchant marine and fishing fleets..
Sea pollution is a direct cause of the death of a large number of marine organisms, either by intoxication, mechanical asphyxia or others. An example of this is the disappearance of coral reefs, due to the fact that coral polyps are very susceptible to contamination..
In the same way, the pollution of the coasts of the seas by solid waste and eutrophication, causes the removal or death of various species.
It is caused especially by fertilizers, pesticides, detergents and organic matter that contribute unusual amounts of nitrogen and phosphorus to the water. These compounds are nutrients that facilitate the excessive development of populations of phytoplankton, cyanobacteria and macroalgae..
By increasing these populations, they cover the surface reducing the entry of sunlight and the exchange of gases between the sea and the atmosphere. Then, the photosynthesis of algae and underwater plants and the dissolved oxygen in the water are reduced, causing the massive death of organisms..
Eutrophication processes, as well as the contamination of marine organisms with heavy metals and other toxic substances, leads to a decrease in food. Shoals of fish decrease or move to other areas as the marine environment deteriorates.
On the other hand, contaminated marine animals such as fish, crustaceans and mollusks, are no longer an option for human consumption.
Sea pollution is a source of diseases, ranging from skin problems when bathing on polluted beaches, to serious poisoning problems. One of the most frequent and documented cases is poisoning from the consumption of seafood contaminated with mercury.
This causes the so-called Minamata disease, with serious neurological problems, especially in children. Likewise, there are frequent cases of poisoning from consuming animals contaminated by algae toxins that proliferate in an exaggerated way due to eutrophication.
The economic impact of marine pollution covers various spheres of the economy, since it affects the food industry, but also tourism. In the latter case, the pollution of the beaches is influenced by either solid waste, toxic substances or the proliferation of algae due to eutrophication..
The first element to solve the problem of marine pollution is to develop public awareness of the problem. This allows promoting individual changes in habits that imply polluting and generating a mass of social pressure for governments to take the necessary measures..
The previous point is the basis for implementing changes in consumer habits and in the economic development model. If current forms and rates of consumption continue, it is difficult to reduce marine pollution.
A sustainable development model is required that takes into account the ecological balance within its variables.
To achieve global solutions, it is necessary in turn to reach international agreements to reduce marine pollution. This taking into account that the oceans and seas are an interconnected system, whose pollution is not reduced to a national problem..
The ultimate goal is to reduce the amount of solid and liquid waste that reaches the seas and pollutes them. This involves recycling, reusing and reducing waste as well as sewage treatment and waste management in the shipping industry..
There are systems that allow the capture and removal of waste in rivers, preventing its arrival at sea, in addition to recovering freshwater ecosystems.
In those cases where there is contamination, it is necessary to implement remedial measures (implement technological solutions to decontaminate marine environments). This ranges from simple beach cleaning days to more technologically complex alternatives for the management of oil or plastic spills in the seas..
They are found in ocean gyres (central areas of ocean currents circuits) and litter is made up mainly of degraded plastic fragments. 6 garbage islands have been detected, two in the Atlantic, one in the Pacific, one in the Indian Ocean as well as in the Mediterranean and the Caribbean..
Being an inland sea (semi-closed basin) and highly populated, the impact of pollution is very relevant. The amount of pollutants that the Mediterranean Sea receives, especially from its European side, is enormous, given the industrial and urban concentration.
By some estimates, more than 600,000 tons of sewage are discharged each year, including mineral oils, medicine waste, mercury, lead and phosphates. In addition, there is an island of garbage near the island of Elba, of about 900 km² and around 3,500,000 tons of plastic.
It is an inland sea open to the North Sea, subject to great pollution whose basin is surrounded by 10 northern European states. The large amount of agricultural pollutants annually generates a proliferation of algae that covers 377,000 kmtwo.
A large area of the Gulf of Mexico is a dead zone due to a shortage of dissolved oxygen in the water. This is caused by the eutrophication phenomenon, a consequence of the large amount of agrochemical residues carried into the gulf by the Mississippi River..
The large amount of solid and liquid waste that is thrown into the sea from its coasts generates significant sources of pollution. Thus, there is an island of garbage between the Yucatan peninsula and the island of Cuba with around 25,000 pieces of plastic / Kmtwo as well as another less dense, located around the island of Jamaica.
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