What is marine pollution?
Marine pollution is the result of pollution of the oceans. Until the 70s it was popularly believed that due to the large amount of water in the oceans, it had the ability to dilute all pollutants without generating consequences in the environment. During those years all kinds of chemicals, untreated sewage, and even radioactive waste were dumped into the seas, in the hope that they would disappear into the deep blue.
However, far from being diluted, these pollutants have been accumulating both in the water and in the trophic chains and, in addition, they have managed to be distributed throughout the planet to places where human activity is not so present, such as the Mariana Trench or Antarctica.
Causes of marine pollution
The causes of pollution of the oceans and seas or marine pollution are diverse and numerous. Below are those that cause a greater impact on saltwater or marine ecosystems:
Pesticides and herbicides
Although they are mainly used on land they can reach the seas through rivers and groundwater. They can decrease the populations of phytoplankton, algae and marine plants causing a decrease in dissolved oxygen in the water. In addition, they can bioaccumulate in tissues and move up the trophic chain, as well as cause alterations in behavior and reproduction, and cause damage to the immune, endocrine and neurological systems of animals (crustaceans, fish, mammals, birds).
Fertilizers and detergents
Both cause nutrient enrichment of the waters (eutrophication), since they are mostly composed of nitrogen (fertilizers) and phosphorus (fertilizers and detergents). When these reach the bodies of water the algae that live in them begin to grow and form a layer of biomass that prevents the entry of sunlight and the renewal of oxygen and therefore making life impossible in these eutrophicated areas.
All kinds of chemicals can be found in the ocean as a result of intentional dumping or transport from continents and coasts. This range extends from heavy metals and radioactive waste from industries to medicines, drugs and hormones among others. The effects of these substances are death by poisoning in the most extreme cases, the appearance of malformations, different metabolic and behavioral disorders and bioaccumulation in the trophic chain being able to reach us again.
They reach the ocean through discharges, drainage of inland waters or other human activities (fishing boats, boats, cruise ships, etc.). When an oil spill occurs, animals (fish, birds) die asphyxiated, in addition it prevents the entry of sunlight and the components from its decomposition can affect the behavior and physiology of organisms.
In many cases, wastewater from populations and industries is discharged without any control. This favors eutrophication due to the enrichment of the waters with organic matter and nutrients, as well as the entry of chemicals and even microorganisms and parasites destabilizing aquatic communities and increasing the level of toxicity of the water.
Plastics and microplastics
One of the most polluting elements on the planet. Plastics can cause wounds, malformations and amputations in animals when they get hooked somewhere on the body. Large plastics (bags, straws, bottles) are mistaken for food by animals. Its intake causes the obstruction of the airways and can die from asphyxiation, in other cases they are entangled in the stomach and intestines so the animal ends up dying because it cannot feed or be able to expel them.
Microplastics (plastics smaller than 5 mm) such as nurdles (raw materials for the manufacture of plastics), glitter, cosmetic microspheres and other small plastic fragments have been found in the digestive systems of fish, birds and even humans as a result of their movement through the food chain. But the problem of plastics goes much further, being organic compounds are able to absorb toxics from the environment so once ingested they accumulate in tissues and move through the food chain.
They are those nets that are lost or thrown into the sea. When they are left adrift, animals such as turtles, birds, dolphins and sharks become entangled in them becoming their executioners. They can cause major injuries, lacerations and death as animals cannot move and escape.
Sound from sonars, submarines, ships, and oil and mining facilities can spread over miles through the marine environment. This directly affects large mammals such as whales, porpoises or dolphins that use ultrasound to migrate, feed, reproduce or communicate.
Consequences of marine pollution
The consequences of pollution are very diverse and are already being felt.
As a result of plastic pollution, islands made entirely of plastic have emerged. The Great Pacific Garbage Patch was discovered in 1997 and occupies an area larger than that of Spain, France and Germany combined, is located between Hawaii and California and is estimated to weigh 80,000 metric tons. In addition, in recent years several more patches have been detected, another in the southern Pacific Ocean near the coasts of Chile and Peru, and another in the north of the Atlantic Ocean near the US coasts. These plastic islands are maintained by the existence of vortices created by ocean gyres, a type of circular water current.
Eutrophication and lack of oxygen
As we have explained before, one consequence of discharges of wastewater and other chemicals is eutrophication. Due to the proliferation of algae the oxygen dissolved in the water is depleted so that almost no organism can survive in those conditions of anoxia. In addition, in these circumstances other toxic substances such as nitrogen oxides, greenhouse gases more powerful than carbon dioxide, can be released. These eutrophic areas are known as dead zones, among the more than 400 that are estimated to highlight the Gulf of Mexico.
On the other hand, industries contribute doubly to ocean pollution, not only with the waste they generate but also with the greenhouse gas emissions that are causing acidification of our oceans. Naturally, CO2 dissolves in the water of the oceans releasing protons as a result of this reaction causing a decrease in the pH of the water and therefore an acidification of it. This acidification affects the calcification processes hindering the formation of calcium carbonate. This has resulted in the bleaching of corals and the weakness of the calcareous structures that protect and shape mollusks, crustaceans and different microorganisms (diatoms, coccolithophores, fominifera).
Loss of biodiversity due to marine pollution
Finally, it should be noted as one of the worst consequences of marine pollution the loss of biodiversity, since in the end all these agents (plastics, chemicals, metals) and processes (eutrophication, acidification) negatively affect marine life. Unfortunately, the species that are suffering the most from the consequences of marine pollution are the species that are already in danger of extinction to which more pressure is added. Do not forget that many of these species that are disappearing are those at the top of the trophic pyramid, such as large predators (orcas, sharks, turtles, seals) and their disappearance would trigger negative effects on communities.