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Marine pollution refers to ocean contamination, especially with man-made waste or byproducts. This is considered to be a severe problem by many environmentalists, since it can have detrimental and lasting effects on the global marine ecosystem. There are several types of marine pollution, each of which has the potential to harm the delicate balance of life.
A number of sources can generate marine pollution. Sources that directly dump waste into the water are known as point sources. Non-point source pollution is harder to recognize, and therefore harder to regulate. This occurs when pollution comes from several hard-to-pinpoint sources, such as the debris blown into the ocean by gusts of wind.
Marine debris usually includes plastic litter discarded by humans, either intentionally or accidentally. This marine pollution can be harmful to marine life, such as fish or dolphins. Animals can become tangled up in things like old fishnets or plastic six pack holders, or they can suffocate if they get trapped in a plastic bag. If the debris resembles an animal's food, it could also be ingested, and most likely, the animal will not be able to digest it.
Garbage and other marine debris sometimes ends up covering the coastlines of islands in the middle of ocean gyres, which are large circulating ocean currents. Hawaii, for example, is in the middle of the North Pacific Gyre. Because of the massive amount of debris found here, it is often referred to as the Great Pacific Garbage Patch. One major source of marine debris is containers that fall off ships, the contents of which end up on shores all over the world.
Ships and other ocean vessels are main contributors to marine pollution. Oil spills can harm marine life and often take months or even years to clean up. These vessels can also introduce non-native species of animals, plants, and micro-organisms to new habitats when they dump their ballast waters. This can lead to an unbalanced ecosystem as these new species prey on and compete with the native species in the area.
Ships, large boats, and submarines are also a major source of noise pollution in the oceans and seas. Since sound travels farther in water than it does in air, noises like sonar can travel for miles. This can cause problems in animals that rely on noise to communicate with each other or find prey.
Toxins, such as chemicals, certain metals, and radioactive waste, are another form of marine pollution. These poisonous substances often have harmful effects on marine life and can accumulate in their bodies. Mercury, which is a waste product of certain types of power plants, accumulates in fish. Albacore tuna and swordfish with high levels of mercury are considered unsafe to eat, especially for nursing mothers, pregnant woman, and children.
Chemical nutrients, like nitrogen and phosphorus used in fertilizers, accidentally released into the ocean also contribute to marine pollution. These often make it into bodies of water because of agricultural runoff. Excess amounts of these types of nutrients can cause excessive algae growth. This process, known as eutrophication, can often lead to less oxygen in the water.
The amount of oxygen in the water also decreases as the water gets warmer. This can happen when water that is used as a coolant by industrial manufacturers and power plants is dumped into rivers and oceans. Since the warmer water contains less oxygen, some species find it harder to survive and may die off. This type of marine pollution is called thermal pollution.
Acidification of the world's oceans is another concern of many environmentalists. The ocean naturally absorbs carbon dioxide, and since the amount of carbon dioxide in the atmosphere is increasing, the amount that the ocean is absorbing is also increasing. The result is a lower pH level in the oceans, which can disrupt the delicate marine ecosystem. Many researchers believe more acidic waters can make it harder for some shellfish to form their shells. Disappearing coral reefs are also blamed on ocean acidification.