Ocean Pollution: What Is It, Its Main Causes & Solutions?

Ocean Pollution
Photo by James Thornton on Unsplash

Estimated reading time: 12 minutes

Human activities are having a huge impact on the planet. We know the climate is warming, and we are seeing the effects all around us in the floods, fires and other threatening events that are occurring more and more frequently. We also know that wild habitats are being lost at an alarming rate. And we know that there is pollution not just in the air, earth and rivers but in the oceans, too. It’s certainly very worrying but it’s not too late to protect our planet. It’s all about the choices we make.

What Is Ocean Pollution?

Quite simply, it is any man-made ‘thing’ in the oceans that causes a negative effect. As we’ll see, that can take a multitude of forms, from the toxic oil spills we read about in newspapers to issues we may never have considered, such as noise. Whatever form it takes, pollution has consequences for the animals who live in the ocean and depend on it. And when the oceans suffer, we suffer too, because oceans produce more than half of the world’s oxygen, while also acting as climate regulators. It is clear that our health and wellbeing are intertwined with the health and wellbeing of aquatic animals.

What Causes Ocean Pollution?

All marine pollution is caused by people. The more general term ‘water pollution’ encompasses a wider range but even then, most of it is caused by people.

What Are 7 Things That Pollute The Ocean?

There are so many ocean pollutants but these are our Sinful Seven. And don’t worry! We’ll cover how we can each make a positive difference to our oceans later on.

Plastic Waste

Have you seen those tragic images of animals who have died through ingesting plastic, or by getting caught up in it? If so, you’ll know just how damaging plastics can be. The problem is we produce vast amounts and very little gets recycled. Forty percent of the plastic produced each year is single-use, and although much of it has a lifespan of just a few minutes, it will linger in the environment, causing untold damage, for hundreds of years.

The biggest plastic polluter isn’t plastic bags, food wrappers and straws, however. It is the fishing industry.
It discards or loses more than 640,000 tons of nets, lines, pots and traps into the sea every year, which is the same weight as 55,000 double-decker buses.


There are some natural causes of oceanic mercury pollution, such as volcanic eruptions and forest fires, but the main culprit is human activity. Burning coal and petroleum is the biggest problem, which makes manufacturing and animal farming, which are very energy-intensive, key polluters. Another cause is gold mining, which is responsible for around one quarter of all mercury use.

It’s long been known that mercury “bioaccumulates” in fish. That means the toxin is stored in the bodies of small fish who ingest it, and when they get eaten, the mercury they contain gets stored in the larger fish, and so mercury accumulates in fish as it passes along the food web. If people eat those larger fish, they ingest all that mercury. The World Health Organization says “Exposure to mercury – even small amounts – may cause serious health problems, and is a threat to the development of the child in utero and early in life.”

One Canadian study of 259 foods found that of all of them, fish contained the most mercury. It has been found in almost every sea creature from scallops and lobsters to mackerel and tuna.

Petroleum Pollutants

Oil spills are absolutely devastating to the marine ecosystem. In 2010, the largest ever accidental oil spill occurred when BP’s Deepwater Horizon oil platform in the Gulf of Mexico ignited and sank. Eleven people were killed, more were injured, and the effects on oceanic animals were both severe and long-lasting.

Over the next three months, approximately 134 million gallons of oil spilled into the ocean, leaving 1,300 miles of coastline from Texas to Florida coated. It covered diving seabirds who lost their waterproofing and drowned as a result. It covered endangered turtles, reducing their ability to move, which caused exhaustion and made them vulnerable to predators. And all 21 species of cetaceans found in the Gulf were exposed to it, causing lung problems and compromised immune function.

Although this may have been the biggest spill, smaller spills happen regularly. The oceans pay a heavy price for our reliance on oil.


It comes as a shock to many that raw sewage is discharged directly into the rivers and oceans, and yet it happens all the time and all over the world. In fact, more than 80 percent of all sewage is discharged into the environment without treatment.

And it’s not just human sewage. The vast quantities of poop produced by the world’s billions of farmed animals is also discharged – accidentally or deliberately – into the environment, and from there it gets into waters. The nutrients in slurry fuel algal blooms which starve the water of oxygen and kill all aquatic life. The animal farming industry is thought to be responsible for some of the worst “ocean dead zones’ in the world.

Dangerous Microorganisms

One type of bacteria is on the rise in our oceans, and it is one that can prove fatal to people: Vibrio. It is found throughout the ocean but proliferates in warmer waters, which is one more reason why climate breakdown is going to affect us. Those who ingest this pathogen can suffer typical food poisoning symptoms including nausea and cramps, and in severe cases it can even cause death. Of the 80,000 Americans who fall ill with vibriosis each year, most were infected by eating sea creatures.

Ocean Noise

Many marine animals use sound to communicate, navigate, defend territory and to find food and a mate. But the more human activity there is in and under the water, the more disruption there is to these animals’ lives. The cacophony is now so bad that it is harming and killing wild animals.

Prof Carlos Duarte of King Abdullah University of Science and Technology in Saudi Arabia, who led an impact assessment of oceanic noise says: “Marine animals can only see across tens of metres at most, and can smell across hundreds of metres, but they can hear across entire ocean basins. The scientific literature, when read carefully, provides compelling evidence of human-caused noise being a major source of disruption to the marine ecosystem.”

His team analysed more than 500 studies and found widespread significant harm to marine mammals, such as whales, seals and dolphins, as well as to fish and invertebrates. Commercial tankers, the navy and the world’s fishing fleet all contribute to this devastating noise pollution.

Light Pollution

The light from coastal human habitation is also having an impact on the animals who live in the ocean. Researchers from the University of Plymouth in the UK found that 76 percent and 70 percent of green and blue lights respectively reached the sea floor. These are present in the LEDs of street lighting but underwater, they create an ‘artificial skyglow’. This disrupts the natural biological cycles of marine animals who rely on the light of the moon to regulate their sleep, reproduction, consumption patterns and protection from predators.

With 75 percent of the world’s megacities now located in coastal regions and coastal populations being projected to more than double by 2060, it’s clear that the impact on our marine friends is only going to deteriorate.

How Much Pollution Is In The Ocean?

According to the National Oceanic and Atmospheric Administration, billions of pounds of trash and other pollutants enter the oceans each year. It’s a stratospherically large amount.

How Does Ocean Pollution Affect Marine Life?

The various kinds of pollution can impact animals in many different ways, none of them positive.


Fish ingest mercury and other toxins into their bodies, which can impact their reproduction. They are disoriented by light and sound pollution, which – along with other forms of pollution – affect many of the behaviors that their survival depends on, including exploration, sociability, memory, learning, appetite, boldness, and foraging. They may be killed by oil spills or by ingesting plastics or other pollutants. They may die as a result of loss of oxygen due to sewage and agricultural run-off.

Sea Turtles

Sea turtles are at great risk of ingesting plastic, which can cause internal blockages, leading the animals to die from malnutrition or starvation. They also get entangled in plastic and other debris from fishing gear. Chemical and other pollutants can build up in their tissues, leading to immunosuppression, disruption of the endocrine function, and organ damage. Sea turtles are also extremely sensitive to light and noise, which drive them away from critical nesting and foraging habitats. Coastal development is a serious problem for our turtle friends.


Seabirds are also at risk from ingesting plastic and becoming entangled in it. One study of 34 seabird species found that 74 percent of them had ingested plastic. Even ingesting just a small amount can have long-term impacts on their health.

Seabirds are also particularly vulnerable to oil pollution, and while the headline-grabbing disasters cause serious damage, vessels that routinely clean out their fuel tanks at sea have an even greater impact. The oil suffocates birds and can destroy the water-proofing of their feathers, resulting in hypothermia and drowning. If ingested, it can damage birds’ internal organs and affect their metabolism.

Marine Mammals

One hundred thousand marine mammals – including whales, dolphins, porpoises, seals and sea lions – die every year as a result of plastic pollution alone, either from ingesting it or getting caught in plastic-based fishing gear.

A high concentration of pollutants in the tissues of marine mammals is also associated with organ anomalies, impaired reproduction, and immune function.

Noise pollution is a serious issue for them, too, which can diorient them, and cause them to become stranded on land. In just one awful incident, 14 beaked whales washed ashore in the Canary Islands. They were all bleeding from their ears from surfacing too quickly to evade a predator that was – in all likelihood – a naval sonar test. All of them died.

Mussels, Clams, Coral, And Oysters

These special aquatic animals are vital cleaners of the ocean: they filter water, removing pollutants. Oysters can filter an extraordinary 200 liters of water a day, while clams can filter 20 liters. But the pollution that causes the seas to warm also makes them more acidic, and this has caused a significant drop in the number of shellfish. It’s climate pollution and the fishing industry that is killing shellfish.

How Does Ocean Pollution Affect Humans?

Individually, those who eat fish can become sick from the pollutants they contain, but on a bigger scale, we all depend on the health of the ocean for a habitable planet, and so we would be wise to care for it. A 2019 report by the International Monetary Fund calculated how much carbon dioxide was absorbed by microorganisms in the sea. They found that it “is equivalent to the amount… captured by 1.70 trillion trees – four Amazon forests’ worth.” The same study found that protecting large marine animals such as whales, dolphins, and sharks is even more important for the climate than planting trees because these animals accumulate carbon in their bodies throughout their long lives. When they die, it sinks to the bottom of the ocean with them where it is stored for hundreds of years.

Ocean Pollution Facts And Statistics

  • More than 70 percent of marine animal entanglements involve abandoned plastic fishing nets
  • Of the 79,000 metric tons of plastic in the “Great Pacific Garbage Patch”, most of it is abandoned fishing gear
  • There is more microplastic in the ocean than stars in the Milky Way
  • Over one million seabirds are killed by ocean pollution each year
  • It’s estimated that 250,000 seabirds, 2,800 sea otters, 300 harbour seals, 250 bald eagles and up to 22 orcas were killed by the Exxon Valdez oil spill in Alaska
  • Aside from oil spills, approximately 706 million gallons of waste oil enter the ocean every year, with over half coming from land drainage and the improper disposal of used motor oil
  • Agricultural fertilizer is a serious ocean pollutant, which – along with sewage and farmed animal slurry – causes eutrophication and ocean dead zones
  • Ocean dead zones have quadrupled in size since 1950
  • Until the 1970s, dumping chemicals and garbage into the oceans was a common practice. People thought it would just “disappear”

Ocean Pollution Solutions

It’s clear we are affecting the oceans in myriad ways, and while we may not toss our garbage into the ocean, we may unwittingly be paying companies to do it on our behalf. The industries that most need to be curtailed for the sake of our oceans are: plastics, oil, animal agriculture and fishing.

What You Can Do

  1. We can reduce our plastic use to the bare minimum and recycle whatever we do have to use.
  2. We can walk, cycle or use public transport wherever possible to reduce our reliance on oil. We can buy electric cars and use green energy to heat our homes and offices. These are more expensive and so not available to everyone but this brings us to point 3.
  3. We can lobby our political representatives on plastic use, marine conservation zones, tighter limits on fishing quotas, sanctions for dumping sewage into waterways, and making green energy and electric cars more affordable. Governments must be pressed to take action on these issues!
  4. We can stop eating meat. The slurry run-off from all those animal farms is a significant contributor to ocean dead zones and the deaths of sea creatures.
  5. We can stop eating fish. The oceans need to heal. Not only does the mass extraction of billions of animals upset the delicate ecosystems but the fishing industry is responsible for more than half of oceanic plastic pollution.


As we come to understand the wide-ranging impact humans are having on the planet, the damage done to oceans often gets overlooked. This may not be surprising. After all, we can see the impact of climate breakdown on land, but we tend not to go out into the ocean to measure the damage done there. Nonetheless, it is happening, and the one thing driving it all is human behavior. More precisely, it is that many in the Global North consume too much, and often choose the more damaging products.

Wherever we have meaningful choices, we should use them to protect this beautiful, diverse, and fragile planet. And if we do that, we may just find ourselves happier and healthier, too.

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