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Marine pollution: causes and consequences

The oceans represent more than 70% of the earth’s surface and are home to 97% of the water that exists on the planet. Due to the large volume they occupy, around 99% of the total land volume, these large masses of salt water represent the home of thousands of plant species, animals, bacteria and other microorganisms, as well as an important source of natural resources ( energy, food, minerals, etc.). Unfortunately, the human being has found another way to take advantage of these immense aquatic spaces, to turn them into the new human landfills which results in the pollution of the oceans .

If you want to know more information about what marine pollution is, its causes and consequences, in this AgroCorrn article we will explain it to you in detail.

You may also be interested in: Causes and consequences of water pollution
  1. What is marine pollution
  2. Causes of marine pollution
  3. Consequences of marine pollution

What is marine pollution

Marine pollution is the result of ocean pollution . Until the 1970s there was a popular belief that due to the large amount of water in the oceans, it had the ability to dilute all pollutants without generating consequences for 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 accumulated both in the water and in the food chains and, in addition, they have managed to be distributed throughout the planet, reaching places where human activity is not so present, such as the Mariana Trench. or Antarctica.

For this reason, we have long celebrated World Seas Day to raise awareness of the problem and help improve the situation.

Causes of marine pollution

The causes of ocean and sea pollution or marine pollution are diverse and numerous. Those that cause the greatest impact on saltwater or marine ecosystems are detailed below :

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 the nutrient enrichment of the waters (eutrophication), since they are mainly composed of nitrogen (fertilizers) and phosphorus (fertilizers and detergents). When these reach the water masses, 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 makes life impossible in these eutrophied areas.

Chemical products

All kinds of chemicals can be found in the ocean as a result of deliberate spills 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, which can reach us again.


They reach the ocean through discharges, the drainage of continental waters or by other human activities (fishing boats, motorboats, cruise ships, etc.). When an oil spill occurs, animals (fish, birds) die asphyxiated, it also prevents the entry of sunlight and the components from its decomposition can affect the behavior and physiology of organisms.

sewage water

In many cases, wastewater from towns 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 injuries, malformations and amputations in animals when they get caught in any part of the body. Large plastics (bags, straws, bottles) are mistaken for food by animals. Its ingestion causes the obstruction of the respiratory tract and can die from suffocation, in other cases they become entangled in the stomach and intestines so the animal ends up dying by not being able to feed or 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 tracts of fish, birds and even humans as a result of movement of these by the trophic chain. But the problem of plastics goes much further, being organic compounds they are capable of absorbing toxins from the environment so that once ingested they accumulate in the tissues and move through the food chain.

Phantom networks

They are those nets that are lost or thrown into the sea. When left adrift, animals such as turtles, birds, dolphins and sharks become entangled in them, becoming their executioners. They can cause serious injuries, lacerations and death as animals cannot move and escape. In the main image of this article we can see a sea turtle entangled in one of these nets.

Noise pollution

Sound from sonars, submarines, ships, and oil and mining facilities can travel for 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. You can learn more about this in this other AgroCorrn article on Noise pollution affects fish .

Consequences of marine pollution

The consequences of pollution are very diverse and are already being noticed.

The plastic islands

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 greater than that of Spain, France and Germany combined, it is located between Hawaii and California and it is estimated that its weight would amount to 80,000 metric tons. Furthermore, several more patches have been detected in recent years, another in the southern Pacific Ocean near the coasts of Chile and Peru, and another in the northern Atlantic Ocean near the US coasts. These plastic islands are maintained by the existence of vortices created by oceanic gyrations, a type of circular water current.

In this other article we explain what plastic islands are and how they are formed .

Eutrophication and lack of oxygen

As we have explained before, a consequence of the discharge of sewage and other chemicals is eutrophication . Due to the proliferation of algae, the dissolved oxygen in the water is depleted so that almost no organism can survive in these anoxic conditions. In addition, other toxic substances such as nitrogen oxides, greenhouse gases more powerful than carbon dioxide, can be released under these circumstances. These eutrophic zones are known as dead zones, among the more than 400 that are estimated, the one in the Gulf of Mexico stands out.

Ocean acidification

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 an acidification of our oceans. In a natural way, CO2 dissolves in ocean water, 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 the corals and the weakness of the calcareous structures that protect and shape mollusks, crustaceans and different microorganisms (diatoms, coccolithophores, fominifers).

Loss of biodiversity due to marine pollution

Finally, the loss of biodiversity must be pointed out as one of the worst consequences of marine pollution , 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. It should not be forgotten that many of these species that are disappearing are those that are found at the top of the trophic pyramid, such as large predators (killer whales, sharks, turtles, seals) and their disappearance would trigger negative effects on communities.

As a final reflection, it is worth highlighting the need to create a general awareness of the conservation of the oceans and consider them, not as our landfills, but as sources of health and well-being because we must not forget that human beings have a very close relationship with the seas and That is why in the end everything that is thrown into them will be returned to us. So if we care about our health, we should also care about the health of the oceans.

If you want to read more articles similar to Marine pollution: causes and consequences , we recommend that you enter our Pollution category .

Maria Anderson

Hello, I am a blogger specialized in environmental, health and scientific dissemination issues in general. The best way to define myself as a blogger is by reading my texts, so I encourage you to do so. Above all, if you are interested in staying up to date and reflecting on these issues, both on a practical and informative level.

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