Marine or Ocean Pollution | Meaning, Types & Causes

What is Marine or Ocean Pollution?

Marine pollution, ocean pollution or sea pollution is said to occur when toxic & harmful substances, debris, garbage or trash enters ocean or sea. Marine pollution is now a matter of concern all around the globe. The pollution is growing vigorously without any measure to prevent it. Harmful chemicals and trash are the two main reasons that are spreading marine pollution at an unbelievable rate. Statistics show that 80% of the pollution is derived from the land. Industrial and residential waste, windblown debris and agricultural runoff are some of the other reasons for marine pollution. Marine pollution is often confused and mixed with other similar terms. Marine pollution, ocean pollution, sea pollution all are of similar kind and used interchangeably. Broadly all of these can be clubbed under water pollution.

Nutrient pollution mainly refers to the contamination of harmful chemicals leading to the hazardous effects on human health and the environment. In this case, excess nutrients, phosphates, and nitrates stimulate the growth of algae over the water surface leading to eutrophication. Many toxic tiny chemical particles adhere to the plankton that is consumed by other aquatic animals. Thus these dangerous chemicals came back to us in the form of environmental food chains. Moreover, these pesticides are causing mutations and terminal diseases like cancer.

Marine Pollution - Ocean Pollution

The lethal metals that are discharged into the water are consumed by animals. And therefore, there is a huge change in their tissues, reproduction, behavior, biochemistry, and growth due to metal consumption. In this article, we are going to discuss the causes and effects of marine pollution, and policies or laws that have been surpassed to prevent it.

Related: Types of Pollution, Environmental Education, Importance of environmental education

Different Ways of how Marine Pollution occurs?

In several ways, the input sources of marine pollution into the ecosystem can be identified. There are mainly five types of inputs for the pollution and they are:

  1. Direct Discharge of waste
  2. Land Runoff
  3. Pollution by ship
  4. Pollution through atmosphere
  5. pollution due to mining in the deep sea

Direct Discharge of Waste 

Industrial wastes are discharged from the urban sewage into the rivers which in turn get submitted to the sea. It can be in the form of plastics or hazardous chemicals. China, Indonesia, Sri Lanka, Egypt, Nigeria, the Philippines, Vietnam, Thailand, Malaysia, and Bangladesh are the major emitters of plastic into the ocean.

Mining of different metals like gold, copper, coal, etc is another cause of marine pollution. Minerals like copper, when get mixed in the water, can alter the life development of coral polyps. According to a report by USEPA, 40% of the water bodies in the western USA are contaminated due to mining.

Land Runoff

Runoff due to the construction of buildings and infrastructure carries particles laden with nitrogen, phosphorus, heavy metals, carbon, petroleum, and minerals. When the runoffs are eliminated in the water, it gives birth to phytoplankton and algal blooms. These algae use up all the oxygen (a situation called hypoxic) leading to the death of fish, dolphins, and turtles.

Pollution by Ship

Oil spills by ships are one of the major reasons for marine pollution globally. Crude oil contains PAH (Polycyclic Aromatic Hydrocarbons) is very difficult to remove and remain in the marine environment for years.

Tankers discharging oil tank’s ballast water, disposal of engine oil from the down sewers, and leaking pipelines are the chief poignant of marine pollution. Sometimes cargo ships intentionally discharge harmful and illegal chemical wastes into the ocean in spite of violation of foreign and domestic regulations.

According to statistics, almost 10000 containers are lost during storms under the sea causing noise pollution and multiplication of harmful algae and invasive species.

Pollution through the Atmosphere

Plastics and dust are blown by the atmosphere into the sea. Dust from different desserts like Sahara, Gobi, and the Taklamakan is blown towards the Atlantic and the Pacific Ocean.

However, nowadays, global warming is raising the temperature of the atmosphere due to which carbon dioxide levels are also increasing. High levels of CO2 are making the oceans acidic in nature. As a result of this, the aquatic ecosystem is getting hampered and is getting lesser in numbers.

Pollution Due to Mining in the Deep Sea

This is the recent mineral retrieval process from the bottom of the ocean floor. It generally takes place around polymetallic nodules or extinct and active hydrothermal vents. These types of vents are present around 1400 to 3700 meters beneath the surface of the sea. Precious metals like manganese, gold, copper, silver, and zinc are mined through the vents by the use of hydraulic pumps and are brought to the surface.

If this mining lasts for some more years, experts are convinced that it will result in the turbulence of the benthic layer, increase the water toxicity levels and sediment plumes. Plumes will have the greatest adverse effect on the ocean in the coming years. The fine floating particles from the plumes due to tailing will enhance the turbidity of the water, thus blocking the filter-feeding gears of the oceanic organisms.

Different Types of Marine Pollution

Some of the most common types of marine pollution are:

  1. Eutrophication
  2. Acidification
  3. Toxins
  4. Debris of Plastic


Eutrophication is the increase in the chemical compounds in the ecosystem due to the presence of excessive phosphorus and nitrogen. Rivers containing fertilizers, human and livestock wastes, chemicals, and many harmful elements dump themselves into the ocean. This results in the creation of hypoxia and dead zone.

The southern coast of the US, East Asia, West Europe, and Japan- all these areas are identified with 375 hypoxic zones. Due to eutrophication, there is a huge production of algae that consumes all the oxygen of the surface, resulting in the death of mammals and fish in the ocean.

According to a study in 2008, it has been found that the accumulation of reactive nitrogen in the ocean is more dangerous than the accretion of Carbon Dioxide in the environment.

The only solution for eutrophication is to refurbish the population of oysters and shellfish in the sea. Oysters consume algae, reduces the level of nitrogen and filter out all the solids present in the water. Shellfish enhance the water quality by reducing all the phytoplanktons lost due to denitrification.


The ocean absorbs carbon dioxide from the environment. Due to an increasing level of this carbon dioxide, oceans are becoming highly acidic. This is a cause of concern as the structures like corals that are made up of calcium carbonate will get dissolved and will affect the capability to form shells by the fish.

Sea absorbs almost 25% of the global carbon dioxide level and half the release of anthropogenic carbon. Rising ocean acidification will weaken the ability to sink carbon giving rise to more global warming.

Another reason for marine acidification is methane clathrate which will be released due to excessive ocean temperature. In 2004, almost one and five million cubic km of the ocean floor are covered with this gas. This number is equal to 500 to 2500 Gt carbon. Now you can imagine where this is going.


Innumerable toxins like PCBs, TBT, DDT, heavy metals, radioactive wastes, dioxins, furans, and pesticides do not disintegrate speedily in the ocean. These toxins mount up inside the tissues of many aquatic animals through a process called bioaccumulation. Bioaccumulation results in many deformations and unnatural death of the organisms.

Debris of Plastic

Plastics are gathering in the ocean since the end of World War II and now contain 80% of the ocean debris. It is estimated that the total mass of the plastic present in the entire marine world is nearly about 100,000,000 tonnes!

Anything made of plastic can entangle oceanic creatures, restricting the movement, causing starvation, suffocation, infection and ultimately resulting in a painful death. Debris of plastics tends to gather at the center of the ocean. The north pacific gyre has collected so much plastic that the zone is almost 21 times the size of Texas City.

Additives used in plastic materials are more deadly in the ocean than the land. They enter the body of the organisms and disrupt the endocrine system. It can also suppress the reproduction and immune system of the body.

Microplastics are also equally harmful as plastics. Due to their small size of less than 5 mm, they are mainly used in face scrubs, cleansers and hand soaps. The microbeads are harmful to filter feeders as they can swallow this plastic and become sick.

Rules and Regulations to Control Marine Pollution

The following Acts and Regulations are passed to control marine pollution all over the world.

  • Federal Water Pollution Act was signed in 1948 to control marine pollution in the USA
  • The Council on Environmental Quality has passed the Marine Protection, Research, and Sanctuaries Act in 1972 to control dumping into the ocean
  • In the year 1973 and 1978, a treaty called MARPOL 73/78 was signed to manage pollution by the oil vessels
  • In 1982, UNCLOS was founded to control and restrict the number of pollutants and toxins from all the ships that come internationally
  • United Nation’s 14 Goal – Life Below Water focuses on reducing the marine pollution (United Nations)

People are becoming more aware of global warming and doing their part to reduce it. Many countries are taking action to reduce the use of plastics. In 2018, a report by the United Nations shows that more than 65 countries across the world have banned the use of plastic items. However, it is every person’s responsibility to maintain the basic cleanliness and not to pollute the environment. It is ‘we ourselves’ who can bring this change to the environment and get the marine pollution stopped.

Some facts and figures about marine pollution

  1. Oceans cover over 75% of the Earth surface. They are home to over 99% of the living space on the planet by volume.
  2. Oceans remains unexplored to a great extent. They contain nearly 0.2 million identified species but actual figures might be much more.
  3. Over 40% of the oceans are affected due to pollution, reduced fisheries, loss of coastal habitats. Most of the reasons for such large loss remains human activities.
  4. Oceans not only supports large number of species but also absorbs as much as 30% of the carbon dioxide produced by human activities.
  5. More than 3 billion people depend directly or indirectly on oceans. Market value of marine and coastal resources is over 3 trillion USD.

Related: Strategic Environmental Assessment (SEA), environmental degradation, Environmental Sustainability, Sustainable Development Goals

Tags: Marine Pollution, Water Pollution, Ocean Pollution, Sea Pollution, Plastic Pollution, Aquatic life, aquatic pollution, Marine pollution Facts, Aquatic life, underwater pollution