Ocean pollution is the combination of trash and chemicals which end up in the sea. Because most of the Earth’s surface is water, a large portion of land-based pollution ends up in the ocean.
In this article, we’re going to break down the ins and outs of ocean pollution, answering questions like:
- What is ocean pollution?
- How does ocean pollution impact the environment?
- What are the main sources of ocean pollution?
What is ocean pollution?
Ocean pollution, also called marine pollution, consists of a combination of pollutants which cause harm to marine organisms. Ocean pollution is made of:
- Debris & litter
- Chemicals
- Particulate matter
- Runoff
In some areas, ocean pollution is clearly visible, with trash littering the ocean’s surface. In other places, contamination may not be as visible, though there may be signs, like algae blooms and mass die offs.
Types of ocean pollution
Marine Litter
Marine litter is made of household and commercial trash that ends up in the ocean. Trash is often illegally dumped into the sea, and is then carried away by ocean currents. It tends to congregate on coastlines and in ocean gyres. Marine litter is made up of:
- Plastic waste
- Glass bottles
- Aluminum cans
- Ship litter
Some types of ocean litter, like driftwood and seaweed, are natural and pose no threat to the envrionment.
Plastic Pollution
Plastic pollution is related to marine litter, but is much more complex. Large plastic items break down into microplastics, and can take hundreds to thousands of years to completely dissolve. The majority of plastic pollution comes from a few main sources:
- Plastic bottles
- Plastic bags
- Microbeads
- Discarded fishing nets
Discarded fishing nets are the largest single source of plastic pollution, making up around 10% of ocean plastic. Microbeads are also especially concerning because their small size means they are often mistaken for plankton, and are consumed by small fish and filter feeders.
Runoff
Runoff consists of chemicals and sediments which drain into the ocean from land-based sources. Runoff can be urban or agricultural, and contains a range of chemicals, including:
- Nitrogen
- Phosphorus
- Potassium
- Silt & sediments
- Gasoline
- Motor Oil
- Heavy metals
Chemical Pollution
Chemical pollution of the oceans is usually a result of the direct discharge of pollutants from heavy industries, like mining and fossil fuel extraction. These industries might release their waste directly into the ocean. Chemical pollution includes:
- Raw sewage
- Oil spills
- Mining waste
Shipping Wastes
Ships often discharge their ballast water into the oceans. This water contains oils and compounds from the ships interior. Discharging ballast water can also enable the movement of invasive species, as organisms from one region are transported to another. Cargo ships also often lose their cargo, which escape into the ocean and become marine litter.
How does ocean pollution impact the environment?
Ocean pollution has a wide range of effects, owing to the vast size of the ocean and the varying nature of contaminants. Many forms of ocean pollution are still new, and have yet to be studied in depth.
Litter is often mistaken for food and is eaten by marine organisms. Plastic bags are notorious for being eaten by sea turtles, as they resemble jellyfish, a major food source for sea turtles. The trash gets lodged in the digestive system of the organism, which later dies due to sickness or asphixiation.
Marine litter can also cause physical injuries. Discarded fishing nets can entangle large animals like dolphins, sea turtles and sea lions. Researchers have found animals injured by broken glass and discarded fishing hooks.
Microplastics have become pervasive in the world’s oceans, and in some places, plastic particles are more numerous than plankton. Like marine litter, microplastics are often mistaken for food and eaten. Filter feeders are especially prone to this, as the particulate matter resembles krill or plankton. The chemicals in the plastics bioaccumalate, and harmful compounds like DDT and polystyrene can build up in fish and work their way up the food chain.
Excess nutrients from runoff can cause harmful algae blooms and fish die offs. Nutrients like nitrogen allow oxygen-depleting bacteria and algae to explode in number, creating anoxic conditions. Poisonous red tides are a result of agricultural runoff.
Oil Spills
Petroleum spills into the open ocean have become a highly publicized form of ocean pollution. Oil tankers and rigs sometimes have catastrophic failures which release millions of gallons of oil into the sea. Oil spills can spread over thousands of square miles of open ocean, covering everything in sight with a thick layer of oil.
The crude oil coats everything, from aquatic plants and animals, to the surface of the ocean, even down to the seafloor. The thick oily sludge decreases buoyancy, causing animals to sink. Birds are rendered unable to fly, and many die trying to pull themselves out of the oil.
The oil is also toxic to wildlife. Animals exposed to petroleum may suffer from liver and kidney malfunction, blindness, and dehydration.
Pacific Garbage Patch
Ocean currents carries most marine debris either to the coastline or into large rotating gyres in the middle of the ocean. The large gyres create dead zones of waste, often called garbage patches. The Pacific Garbage Patch is the largest, located in the northern Pacific Ocean. While the Pacific Garbage Patch isn’t a literal floating island of garbage, as many seem to believe, the area has a high concentration of microplastics and marine debris.
Sources of Ocean Pollution
Eighty percent of ocean pollution originates on land. This applies to every form of pollution, whether marine debris, plastics, or chemicals. Common land-based sources of ocean pollution include:
- Urban & agricultural runoff
- Illegal waste dumping
- Heavy industry
Ocean-borne pollutants are becoming more publicized, especially in the context of pollution from shipping. About ten percent of plastic pollution comes from fishing vessels, mainly in the form of discarded fishing nets. Maritime sources of ocean pollution include:
- Cargo ships
- Fishing vessels
- Cruise ships
- Oil wells
Conclusion
Ocean pollution has garnered increased attention over the past decade. The increased publicity around oil spills and plastic pollution has shed light on the devastation wrought on the world’s marine life. While several organizations have sprouted up to combat ocean pollution and raise awareness, the root causes have yet to be addressed. Countries in Africa and Southeast Asia continue to bear the brunt of the problem, where it’s common to see entire coastines covered with marine litter.