What Are Three Sources of Ocean Pollution?

Oceans cover more than two-thirds of this planet's surface, and most life is directly linked to it. The major food supply for many cultures comes directly from the ocean. Most of the oxygen in the atmosphere originally came from the photosynthesis process of ocean organisms. Global weather patterns are heavily influenced by the ocean tides and currents; most of the rainfall throughout the world comes from tropical ocean evaporation. Pollution continuously threatens the oceans' balance, and knowing the sources of that pollution is the first step to knowing how to stop it.

Oil Pollution

• At the time of publication, more than 700 million gallons of oil pollute the oceans every year. Surprisingly, major spills and offshore drilling account for less than 10 percent of that total. Natural seepage from untapped oil sources result in more pollution than spills and drilling do. Air pollution adds nearly 12 percent of the oil pollution annually. The main culprit, providing more than half of the oil pollutants in the ocean each year, is run-off from rivers and streams. The greatest effect on reducing oil pollution in the ocean would be controlling pollution of the land and the waters nearby. Oil pollution kills wildlife, damages marine and coastal ecosystems, and wreaks havoc on local economies dependent upon fishing.

Garbage Pollution

• In 2010, more than 7 million tons of garbage were estimated to have been illegally dumped into the ocean. Accurate numbers are difficult to attain, as culprits do not exactly line up to report their offenses. From garbage scows to cruise ships, the dumping of garbage at sea creates a multitude of problems. Sea life eat or become tangled in the refuse, causing injury or even death. Ships tangle propellers and rudders in the garbage, causing mechanical failures. Ocean dumping has become such a huge problem that there is a "garbage continent" twice the size of Texas floating around in the northern Pacific, and it continues to grow.

Sewage and Waste Pollution

• Treated and untreated sewage is dumped into the ocean from cities around the globe. Even in some developed areas (e.g., Halifax Harbor in Nova Scotia) raw sewage flows into the water. In underdeveloped areas, no treatment is available, thus untreated sewage continuously flows into waterways. Animal waste from livestock farms and manure fertilizing also contaminate streams, rivers and oceans. Sewage contaminated waters can contain microbes, which cause disease. A condition called "eutrophication" can also occur, where added nutrients from the waste causes an overabundance in the ecosystem. This stimulates algae and other plant growth. When algae and plants decay, the oxygen supply in the water is depleted and marine life can no longer survive.

Other Pollutants

• There are other causes of pollution as well. Toxic waste, industrial waste and chemical waste are significant concerns, poisoning water supplies and marine life. The problems compound throughout the food chain, and top-level predators, such as orca and tuna, have been found with extremely high levels of toxins.