Marine pollution is the introduction of any substance to the ocean that harms or changes its physical, chemical or biological properties. It can kill marine organisms, interfere with natural systems, and hurt human activities such as tourism, fishing and agriculture.
Plastic pollution is a big problem for our oceans. It is hard to break down and can cause many problems for animals, including entanglement.
Marine pollution refers to any substance that enters the ocean from human activities and harms marine life or changes the physical, chemical or biological state of the sea. It is mainly caused by humans, including waste from homes and businesses, litter on beaches, discarded fishing gear, toxic chemicals and oil spills. The majority of this pollution comes from land, but human activity on ships and oil platforms also contributes.
Plastic pollution can suffocate and kill marine animals that ingest it or become entangled in it. It also pollutes the environment by releasing chemicals into the water and changing its temperature. Chemicals such as polychlorinated biphenyls, dioxins and brominated flame retardants from consumer products, industrial processes and cleaning products can be ingested by marine organisms and move up the food chain to humans.
Other harmful substances in the ocean include fertilizers and pesticides that wash into the water from agricultural runoff, industrial chemical spills, and sewage and toxins released by ships. The rising levels of carbon dioxide in the atmosphere have an impact on the ocean through acidification, warming and deoxygenation.
Noise pollution is another form of marine pollution, as sound waves from shipping and sonar devices interfere with the natural noises that marine animals use to navigate, communicate and hunt for food. This can alter their behavior and lead to stress, disease, behavioral changes and death.
Trash and debris enters the ocean via rivers, septic tanks, farms, ranches and motor vehicles. These materials pollute the water and harm marine animals, plants and ecosystems. They can contaminate the food chain. They also cause a reduction in the level of oxygen in ocean water causing severe health problems for marine life. Some chemical pollutants such as mercury, industrial chemicals and pesticides harm the ecosystem. They can enter the bodies of sea animals through their skin or ingest them from the food they eat. Some chemical pollutants do not break down easily such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) and can build up in the tissues of marine creatures in a process called bioaccumulation.
Nitrogen and phosphorous pollution (also known as eutrophication) comes from agricultural runoff. These chemicals enter the water and stimulate an overgrowth of algae which causes a dead zone in the sea. They can also lead to the release of harmful algal blooms affecting human health.
Plastic pollution is one of the biggest challenges in ocean conservation. It can ensnare and suffocate marine wildlife and block sunlight that is vital for photosynthesis. It can also interfere with marine communication and behavior. Some marine species that have been impacted by plastic include dolphins, seabirds and turtles. A warmer climate can also release legacy pollutants from glaciers and permafrost and increase the acidity of the ocean threatening coral reefs and other calcareous sea creatures.
Efforts to prevent marine pollution focus on reducing the amount of waste that enters the ocean in the first place. This can be done by reducing the use of plastic bags and bottles, using reusable water bottles and cloth shopping bags, and implementing regulations on shipping and oil and gas development to reduce the risk of spills. Prevention also includes promoting sustainable practices and restoring depleted marine habitats.
Plastic and other man-made pollutants are a significant problem in the world’s oceans, with over 80% of them coming from land-based activities (WWF, n.d.). This waste, which doesn’t biodegrade, can entangle marine mammals and birds, restrict their movements, cause injury or even death. Discarded fishing nets, for example, can restrict the movement of dolphins, seals and turtles or strangle them. Plastics also contain toxic chemicals, such as polychlorinated biphenyls and polybrominated diphenyl ethers, which accumulate in the bodies of marine animals. These toxicants are passed up the food chain, causing health problems in people who eat contaminated seafood.
Other marine pollutants include fertilisers, which cause algae blooms that rob the ocean of oxygen and destroy coral reefs. Oil spills kill marine mammals and birds, and crude oil permeates seabird feathers, preventing them from flying or feeding their young. The increasing absorption of carbon dioxide in the ocean causes ocean acidification, which ruins coral reefs and other calcareous species, destroys shellfish embryos, and disrupts the marine food web.
Marine pollution is caused by a variety of sources, including chemical pollutants such as mercury, synthetic chemicals and petroleum wastes; biological threats, such as harmful algae blooms; and trash and debris. The majority of these chemicals and items – more than 80% — enter the ocean from land, via rivers, sewage, atmospheric deposition or marine transportation. The continental shelf is particularly vulnerable to contamination because most inputs come from the land.
Another source of marine pollution is wind-blown dust and debris, such as plastic bags, sand and dirt. These pollutants often collect in large “patches” called ocean gyres. Changing society’s use of disposable plastic products is essential, but a full transition will take time.
Many of these pollutants have toxic effects on water animals, such as cancer, damage to tissues and cells, and failure of reproductive organs. These chemicals can also be passed up the food chain to humans, which consume contaminated seafood, leading to serious health problems.
The main problem is that many of these pollutants do not break down or disperse in the ocean environment, so they continue to accumulate. These substances are known as persistent, bioaccumulative and toxic (PBT) chemicals. They include dioxins, furans, pesticides, phenols and radioactive wastes. These chemicals can have a devastating impact on the ecosystem, kill marine organisms, endanger human health and harm economies worldwide.