The Top 6 Ocean Pollutants

You might have guessed it already: the top ocean pollutant is plastic with 79 to 199 million tonnes of it in our oceans, and further an estimated 9-14 million tonnes entering each year.

The question is, is it the only ocean pollutant?

Well, no, there are a couple of others as well, which are causing, if not equal but significant, damage to the oceans.

The main ones include nutrient pollution, non-point source pollution, light pollution, noise pollution, and industrial pollution. They contaminate the water, kill marine life, and destroy marine habitats. 

In this post, we’ll discuss each of these ocean contaminants in detail and share a few ways in which you can contribute to reducing them. Let’s dive in! 

Plastic Pollution

Our planet has a plastic problem. It’s literally everywhere, but the biggest victim is the ocean. You can find plastic floating on water’s surface to thousands of meters deep. Let’s look at the top plastic pollutants in detail: 

Single Use Plastic

According to United Nations Environment Programme (UNEP), 89% of macro plastic debris in the oceans is single-use plastic. Not only that, but they have also reached the world’s deepest ocean trench, Mariana Trench, which is 10,898m from the water surface. 

Plastic in Mariana Trench | Image via Science Direct

This shows that the plastic products we use for mere minutes are reaching the deepest parts of the ocean, from where it is virtually impossible to clean them, specifically if they turn into microplastics. They are going to stay there for centuries and suffocate marine life and contaminate their habitats. 

Non-recyclable Plastic

Most of the plastic entering the oceans becomes unusable for recycling because of the degradation from ocean salt and the sun’s radiation, which make it discolored, brittle, and fragmented. Currently, it is estimated that approximately 80% of the plastic on the land is Ocean Bound Plastic (OBP), which is the non-recyclable plastic found within 50 km of the coast. 

The only way to stop it from entering the oceans is to collect it from the source. A strategy through which we, at CleanHub, have succeeded in stopping thousands of tons of plastic from entering the oceans. 

We collect them from houses, businesses, and the environment in the coastal areas, segregate them into recyclable and non-recyclable waste and recover them in the best possible way. Head over to our live dashboard to get the most recent numbers of the impact that we’ve made so far. 

Fishing Gear

Each year, approximately, 100 million pounds of plastic becomes part of ocean pollution from industrial fishing activities. This number only represents the lost fishing gear, the voluntary disposal and abandonment are yet to be studied. 

So, what happens to the oceans due to this lost fishing gear? Here’s the answer:

  • The lost gear continues ghost fishing, which means that it continues fishing and killing marine animals.
  • It introduces invasive species causing harm to the ecosystem and the food chain.
  • As it is degraded under sun exposure and sea salt-action, it releases toxins and chemicals that contaminate the water.
  • It breaks down into microplastics, a process during which GHGs are emitted.
  • It destroys sensitive habitats, such as coral reefs.
  • It hinders navigation.

Cigarette Butts

It’s common knowledge that cigarette butts contain harmful chemicals. Nonetheless, smokers discard them here and there into nature, and they end up in the oceans, granting them the top position as the most common ocean pollutants: according to the Building a Clean Swell 2018 Report, the Ocean Conservancy collected 2,412,151 cigarette butts in their 2017 International Coastal Cleanup.

Cigarette butts are made from Cellulose Acetate, a type of plastic that takes more than 10 years to decompose

The San Diego University conducted a study by placing a single cigarette butt with tobacco traces in one liter of water. It killed 50% of the fish. You can only imagine the impact of the plastic and the trapped toxins in the cigarette butt filters on the ocean water, the air, and marine life!

Food Wrappers

The next on the list of most abundant plastic ocean pollutants found in the 2017 International Coastal Cleanup were food wrappers. They are made of numerous different types of plastics, but the most common ones are polyolefins and polyester: The Ocean Conservancy collected a total of 1,739,743 food wrappers.

The food wrappers are generally non-recyclable, so the best way to get rid of them in daily life is to choose products that are packaged in reusable sustainable materials. If finding such food items is difficult, then buy in bulk, so that you reduce the amount of plastic involved in packaging. 

Plastic Bottles

The third most abundant plastic item in the 2017 International Coastal Cleanup by the Ocean Conservancy was plastic beverage bottles, which were 1,569,135 in total.

You can play your part in reducing this number by recycling the plastic bottles that you use. Generally, they are made from polyethylene terephthalate (PET), which is acceptable in the majority of recycling programs. You can check a plastic bottle’s material through the resin ID code on the side of the bottle.

Another thing that you can do is completely cut out water bottles by using reusable beverage bottles

Bottle Caps

Bottle caps stood at number four on the list of the most common plastic ocean pollutants, with 1,091,107 items.

Bottle caps are generally colorful and small, so marine animals mistake them for food, and end up consuming them, which causes digestive issues, and sometimes, kills them.

The most concerning issue with bottle caps is that most of the recycling facilities don’t accept them, so generally, recycling isn’t the way forward with them. The best strategy is to stop using plastic beverage bottles and replace them with reusable bottles, so you don’t create plastic pollution through plastic beverage bottles or their caps.  

Plastic Grocery Bags

The number fifth on the list of most abundant plastic items in the ocean is plastic grocery bags. They stood at 757,523.

Eliminating this type of waste is quite simple. All you have to do is get a reusable grocery bag or tote bag. These tote bags are not only environmentally friendly, but they are also quite trendy and will give your outfit an extra oomph. 

Nutrient Pollution

Nutrient pollution or eutrophication is a process in which excess nutrients, generally nitrogen and phosphorus enter the water bodies, and act as fertilizers, causing high algal growth, which restricts sunlight and oxygen from entering the water, resulting in a reduction in dissolved oxygen levels, which creates dead or hypoxic zones.  

So, where do these excess nutrients come from?

The excess nutrients come from the agricultural runoff, or the wastewater generated from lawns, both of which generally contain fertilizer remnants.  

Currently, there are 415 dead or hypoxic zones throughout the world, with the largest one in the Arabian Sea, covering the entire Gulf of Oman, which has an area of 165,000 square kilometers (63,700 square miles).

Non-point Source Pollution

80% of the ocean pollution comes from the land, with one of the biggest sources being non-point source pollution. 

Non-point source pollution is a form of pollution in which pollutants enter the oceans through numerous small sources, such as farms, boats, and septic tanks. They could be both natural and anthropogenic. 

General causes of non-point source pollution include:

  • Oil runoff from transportation sources and home drainage. To put this in perspective, the massive oil spills are only responsible for 5% to 12% of the oil present in the oceans, the rest is from non-point sources. 
  • The dirt and soil from agricultural lands and construction sites through the air.  
  • Herbicides, fertilizers, insecticides, and other chemicals from agricultural and residential farming or gardening practices
  • Acid drainage from industrial sources and abandoned mines
  • Bacterial and nutrient runoff from livestock, residential wastewater, and pet wastes.  

Light Pollution

Light doesn’t seem like a massive source of pollution in comparison to plastic or chemicals, but it has completely modified numerous marine life habitats, specifically the ones around coastal areas. Here’s how:

  • Light disrupts the circadian rhythm of marine animals, which in turn has an impact on their migration, reproduction, and feeding patterns.
  • Artificial light at night makes small fishes more susceptible to attacks from predators
  • Light pollution hinders the hatching of fish eggs. A study showed that none of clownfish eggs hatched when they were exposed to artificial light. 

Noise Pollution

The majority of marine mammals communicate through sounds, so they don’t appreciate the extra loud and persistent sounds made by ships, sonar devices, and other industrial procedures. These communications help them migrate, hunt and reproduce. Many of these mammals even use sound waves to help them see! 

Image via AWI

Here are a few ways in which marine animals are immensely affected by noise pollution:

  • In 2000, in the Bahamas, 17 stranded beaked whales lost their life due to the active mid-frequency sonar used by a US Navy ship’s passage.
  • Noise pollution causes hemorrhaging in various organs of marine animals, which either seriously injures or kills them.
  • It causes temporary or permanent deafness, which makes it impossible for numerous marine animals to feed, avoid prey, or reproduce. 
  • Instigates avoidance and aggressive behavior
  • Noise pollution masks biologically meaningful sounds resulting in the loss of calls of predators or potential mates. 

Industrial Pollution

Industrial pollution includes heavy chemicals, such as acids and alkaline wastes, scrap metals, sludge, and coal ash, to name a few. Here’s how this waste impacts marine life and the water:

  • Nutrient-packed fertilizers and sewage cause eutrophication and create dead zones
  • Insecticides, such as DDT, climb up the food chain, cause diseases, and even kill the birds that consume marine animals. The bald eagle was the biggest victim in this regard as it ended up on the endangered species list of the United States Fish and Wildlife. 
  • PFAS, a chemical that is used to make heat, oil, stain, grease, and water-resistant materials, ends up in the ocean and becomes part of marine mammal blood, and eventually, enters the human body


Oceans desperately need our help to counter the endless pollution entering them from various sources. The top 6 ocean pollutants are plastic, nutrients from fertilizer runoff, non-point sources, light, noise, and industrial chemicals. 

Plastic, as always, tops the list, with fishing gear, cigarette butts, food wrappers, plastic bottles, bottle caps, and plastic bags being the highest contributors. 

Just like plastic, the other pollution sources are also disrupting marine life. From getting strangled to losing sight, marine animals desperately need us to give them a break. It’s high time we cut down on plastic and evaluate our lifestyles so we could make a difference. Even a small environmentally-positive change counts! 

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