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As massive as the Earth’s oceans are, the amount of pollution that enters the water from both man-made and natural activities is affecting marine ecosystems throughout the world. Most of the pollutants that enter the ocean come from the land, according to the National Oceanographic and Atmospheric Administration. Animals often eat these pollutants which, in turn, means humans will as well. There are many causes of ocean pollution, including:


Runoff from the land comes from both urban and agricultural areas. Often referred to as non-point source pollution, it can originate from various sources like cars and trucks, septic tanks, farms, and timber harvesting operations. Chemicals that end up on roads and highways flow over and under the ground with rain water, as do pesticides, fertilizers, and carbon-, nitrogen-, and phosphorous-rich particulates, eventually reaching the ocean. Inland mining can cause an influx of mineral and soil deposits. These travel through rivers and estuaries, making soil a real threat to marine ecosystems. Runoff can even smother marine plants and coral reefs.

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Anything from litter and debris to dust can make it into the ocean by way of the wind. This causes objects, such as plastic, to be suspended in the water and never decompose.

Intentional Discharge

Toxic waste, including mercury, released by manufacturing plants enters the sea and the food chain, making its way up to larger species consumed by humans. Agricultural toxins can be direct biological hazards and problematic as they raise ocean temperatures, which can end up being too high for some animals and plants to survive. Discharge of plastic is a problem as well. Scientists have estimated that up to 100,000,000 metric tons of plastic trash are in the world’s oceans, which doesn’t degrade very easily.

Scientists have estimated that up to 100,000,000 metric tons of plastic trash are in the world’s oceans

The impacts of discarded fishing nets and other plastics include entanglement of wildlife, potentially restricting their movement, injuring, or even starving them. Dolphins, turtles, crabs, crocodiles, sharks, and sea birds are especially vulnerable. Sewage passed directly into the ocean, including human waste and mining materials, is a problem as well.

Atmospheric Pollutants

Various types of pollutants can get in the water through rain. One menace, in particular, is carbon dioxide, which has built up with climate change. The oceans are absorbing the excess and becoming more acidic. This has been particularly troublesome for calcium carbonate structures such as corals, then, cannot regenerate or regrow. About 1 million species depend on thriving coral habitats. In addition, the excess CO2 can dissolve the shells of various marine animals.

Oil Spills

Ships and platforms release large amounts of oil every year. However, oil isn’t the only pollutant that comes from ships, which may also discharge fuel, plastic, and human waste. Crude oil is one of the most difficult to clean up. It is also toxic, suffocating, and devastating to marine life. Ships also cause noise pollution, disrupting the balance of life for marine animals such as dolphins and whales that use echolocation. Crates lost during storms, accidents, and other emergencies pollute the ocean as well.

Deep-Sea Mining

The ocean floor is a valuable source of gold, silver, copper, and zinc, but mining under the sea is a major source of pollution. Sulfide deposits created when these substances are drilled can have environmental impacts that aren’t fully understood. Material leaks and corrosion of equipment only exacerbate the problem.

Effects of Pollutants in the Ocean

The overabundance of pollution has a variety of consequences. One of these is excess nitrogen and phosphorous. Although plants require these to grow, too high a concentration can cause algal blooms, in which algae overrun the ecosystem. Once these organisms start to sink and decompose, oxygen is depleted. Dead zones are created because marine life cannot survive in that environment. Fish and other forms of life that can swim away leave; other species that cannot move die off.

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Debris in the water, whether or not chemically harmful, can be hazardous. It can kill all kinds of marine life. Discarded metal cans and plastic, broken glass, fishing gear, and parts of ships can harm people who come in contact with them. Beaches can become littered with trash that came from thousands of miles away, affecting human health and recreation. If there is enough debris in the water, it can even make it dangerous for ships to navigate.

Once the smallest organisms consume pollutants, their predators consume them as well. Plastics, garbage, heavy metals, and chemicals make their way up the food chain, ultimately accumulating in seafood that people catch and eat. Coastal pollution contaminates mussels and other shellfish that seafood industries rely on.

[caption id=”attachment_541” align=”alignnone” width=”700”] 100506-N-6070S-819 Gulf of Mexico (May 6, 2010) – Dark clouds of smoke and fire emerge as oil burns during a controlled fire in the Gulf of Mexico. The U.S. Coast Guard working in partnership with BP PLC, local residents, and other federal agencies conducted the “in situ burn” to aid in preventing the spread of oil following the April 20 explosion on Mobile Offshore Drilling Unit Deepwater Horizon. (U.S. Navy photo by Mass Communication Specialist 2nd Class Justin Stumberg/Released)[/caption]

Other specific effects of ocean pollution on sea life include:
  • Oil covering the feathers of birds and the gills of fish.
  • Skin and eye irritation, and lung and liver problems, from oil deposits and byproducts.
  • Reproductive system failure from exposure to poisonous industrial and agricultural chemicals.
  • The fatty tissues of fish can hold onto toxic substances which people then consume.

Despite the detrimental effects of pollution, the problem persists. About 8 million metric tons of plastic end up in the oceans every year, according to EcoWatch, while other studies have estimated as many as 12.7 million metric tons may have washed into the ocean in 2010. A total of 192 countries were considered, but the plastic that gets washed away is from those with high populations and poor waste management.

Improved infrastructure can limit the amount of pollution. Also, nations throughout the world have issued regulations to limit it as well. The degree of success has been variable. From changing the habits of people and businesses, to environmental organizations advocating awareness, we must address marine pollution. The impacts will not abate unless something is done to reverse the current trends.

Sources: Conserve Energy Future, Scubadiverlife.com, NOAA, EcoWatch