Understanding Ocean Oil Pollution: Main Human Causes

Oil pollution in the ocean is a pressing issue that has garnered significant attention due to its detrimental effects on marine ecosystems and coastal regions. The primary causes of oil pollution in the ocean are a combination of factors, including major oil spills, the cumulative impact of smaller spills and leaks, intentional dumping of excess oil, and natural seeps through fractures in the seafloor. While accidents involving tankers, barges, pipelines, and drilling rigs are the most common sources of large-scale spills, smaller spills during activities like refueling ships or changing car oil also contribute to the problem. Oil pollution poses a severe threat to marine life, coastal habitats, and human activities, necessitating sound scientific approaches for cleanup, measurement of impacts, and ecosystem restoration.

Major oil spills

Another notable major oil spill occurred on April 20, 2010, when an explosion took place on the Deepwater Horizon drilling platform in the Gulf of America, resulting in the deaths of 11 people. Before the well was capped three months later, approximately 134 million gallons of oil had spilled into the ocean—the equivalent of over 200 Olympic-sized swimming pools. The restoration process has been long and challenging, with an $8.8 billion settlement reached in 2016, and work still ongoing. The Deepwater Horizon spill has provided valuable insights into the science of oil spills and their impact on the ocean, with advancements being made in the decade since.

The location, time of year, environmental sensitivity, and type of oil all play a role in determining the overall significance of a spill. Even small spills can cause significant harm, depending on where they occur. For instance, a spill in Tampa in August 1993 had a major impact on recreational beaches and shoreline vegetation. Despite the passage of time, the photos from this incident are still used to illustrate the complexities of shoreline cleanup.

The Oil Pollution Act of 1990 established that those responsible for oil spills can be held accountable for the cleanup and restoration costs. This process, known as Natural Resource Damage Assessment (NRDA), involves federal, state, and tribal agencies working together with the responsible party to select restoration projects, often with input from the public. Over the years, NOAA has helped recover billions of dollars from those at fault to fund restoration projects for the ocean and Great Lakes.

While major oil spills like Exxon Valdez and Deepwater Horizon tend to capture the most attention, it's important to recognize that thousands of smaller oil spills occur each year, contributing to the overall problem of ocean oil pollution. These smaller spills can accumulate over time, impacting the ocean ecosystem just as severely as the larger, more publicized incidents.

Small oil spills and leaks on land

While large oil spills are major, dangerous disasters, thousands of smaller oil spills occur each year, some spilling less than a barrel of oil. These small spills and leaks on land contribute to ocean oil pollution. They occur during activities such as oil extraction, transportation, and storage, and gradually accumulate over time.

Drilling blowouts are another cause of small oil spills and leaks on land. They occur when there is a sudden release of oil and gas from a well during drilling operations, often resulting in a large eruption of oil and gas that can be difficult to control. Before the creation of the Environmental Protection Agency (EPA) in 1970, the Secretary of Interior was responsible for responding to onshore oil incidents. Now, the EPA responds to onshore spills, while the U.S. Coast Guard responds to offshore spills.

In addition to small spills and leaks, intentional dumping of excess oil also contributes to ocean oil pollution. This can occur when companies or individuals dispose of oil products improperly, such as by dumping them into waterways or onto land where they can eventually make their way into the ocean.

The impact of small oil spills and leaks on land can be significant, especially when they occur in sensitive environments like beaches, mangroves, and wetlands. These areas are home to a diverse range of plant and animal life, which can be severely affected by even small amounts of oil pollution. Small spills and leaks can harm sea creatures, ruin beaches, and make seafood unsafe to eat.

Intentional dumping of excess oil

Oil pollution in the ocean is caused by a combination of factors, including major oil spills, the cumulative effect of smaller oil spills and leaks on land, and the intentional dumping of excess oil. While the Exxon Valdez and BP oil spills have garnered significant media attention, it is important to note that ships purposefully dump more oil and sludge into the oceans. This act of intentional dumping of excess oil has been enabled by corrupt ship captains and engineers who use a "magic pipe" to dump oil under the water line rather than disposing of it on land as is legally required.

The Caribbean Princess cruise ship, for example, was caught and convicted of using such a pipe to secretly flush its used oil and other toxic liquids into the ocean. Oil logs from the company's other ships also indicated that oil dumping was a widespread practice. This act of intentional dumping is not a new phenomenon. In 1973, the tanker Zoe Colocotronis ran aground off the coast of Puerto Rico, and the master ordered 1.5 million gallons of crude oil to be released to help get the vessel off the reef.

Historically, ships at sea have sometimes intentionally dumped some of their cargo to save the ship and prevent a complete loss. Aircraft in distress may also sometimes intentionally dump fuel to reduce landing weight. While the dumped fuel is thought to vaporize rapidly, this technique is rare due to environmental concerns.

The National Academy of Sciences estimates that up to 810,000 tons of fuel oil sludge and oily bilge waste are illegally dumped into the world's oceans by commercial shipping each year. This intentional dumping of excess oil contributes significantly to ocean pollution and poses a severe threat to marine life and ecosystems.

Natural seeps

The amount of oil released from natural seeps is difficult to determine due to the quick spread of oil in seawater. However, recent studies have provided improved data and estimates. For instance, the annual global oil seepage rate is now estimated to be between 200,000 and 2,000,000 tonnes, with the Gulf of Mexico and Southern California being significant contributors.

Discharge from oil and gas operations

Oil pollution in the ocean is caused by a combination of factors, including major oil spills, the cumulative effect of small oil spills and leaks on land, and the intentional dumping of excess oil. While no single factor can be held solely responsible, major oil spills have an immediate and catastrophic impact on marine ecosystems. These incidents release massive amounts of oil directly into the ocean, causing significant damage to marine life and coastal habitats.

Oil spills are often the result of accidents during the extraction of oil, a process that involves the implementation of a huge amount of infrastructure, including lengthy pipelines, oil rigs, and increased ship traffic. The construction of this infrastructure can, in itself, cause damage to and destruction of important habitats, such as seagrass beds, kelp forests, coral reefs, and deep-sea ecosystems. The extraction of oil can also cause accidents in the form of huge oil spills, as seen in the Deepwater Horizon drilling platform explosion in the Gulf of America in 2010, which resulted in approximately 134 million gallons of oil spilling into the ocean.

However, it is important to note that the cumulative effect of smaller oil spills and leaks from activities such as oil extraction, transportation, and storage also contributes significantly to ocean oil pollution. The facilities built for oil extraction, including roads, pipelines, and rigs, can further harm sensitive marine biodiversity and interfere with the movement of migratory animals such as whales and dolphins.

Technological advancements in offshore oil and gas exploration and development have led to the use of high-performance non-aqueous drilling fluids (NADFs) that function more efficiently than conventional water-based drilling fluids (WBDFs) in complex and deep drilling operations. While regulations in many countries permit the disposal of drilling waste by discharge into the marine environment under certain conditions, this practice can still cause environmental disturbances.

The discharge of drill cuttings and associated drilling fluids from offshore oil and gas operations can contain toxic substances like polycyclic aromatic hydrocarbons (PAHs) and mercury, which are harmful to marine organisms and ecosystems. The specific regulations and limitations regarding the discharge of these cuttings vary across different regions and countries. For example, in the US, Group III Synthetic-Based Fluid (SBF) associated drill cuttings are permitted for ocean discharge if they meet certain Effluent Limitations Guidelines (ELG) on concentrations of oil and PAHs.

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