Ocean's Adversaries: Pollutants And Their Impact

Oceans are among the most valuable natural resources on Earth, governing the weather, cleaning the air, helping feed the world, and providing a living for millions. They are also home to most of the life on Earth, from microscopic algae to blue whales. However, human activity is causing significant harm to marine ecosystems through pollution. The leading source of ocean pollution is plastic, which accounts for 80% of all marine debris. Other major pollutants include nutrient pollution, nonpoint-source pollution, light pollution, noise pollution, and industrial pollution. These pollutants have far-reaching consequences for marine life, coastal economies, and human health.

Plastic pollution

Plastic is the leading source of ocean pollution. There are an estimated 170 trillion particles of plastic in the ocean, or roughly 21,250 pieces of plastic for every person on the planet. This number is expected to increase to 29 million metric tons per year by 2040 without ambitious action.

The majority of plastic pollution in the ocean is caused by littering. We use disposable plastic items (food wrappings, plastic bags, razors, bottles, etc.) and do not dispose of them properly, which causes them to end up in the waterways and eventually in the ocean. Some plastics and microplastics are also the product of improper manufacturing processes, and about 20% of the ocean’s plastic pollution comes from industrial fishing.

The most infamous example of plastic pollution in the ocean is the Great Pacific Garbage Patch, located between Hawaii and California. However, this patch represents only a fraction of the plastic trash in our oceans. In fact, plastic debris has been found at the bottom of the deepest ocean trench.

Plastic is harmful to marine life. It causes damage to animals when they come into contact with or ingest it, including suffocation, entanglement, laceration, infections, and internal injuries. It is estimated that roughly 100,000 marine animals die each year from either ingesting plastic or becoming entangled in plastic. Additionally, plastic can mimic fish eggs and other tiny organisms, which are then consumed by sea life. Once microplastics reach the ocean, they are nearly impossible to filter out without great cost or damage to marine life, so they become a near-permanent feature of the ecosystem.

To reduce plastic pollution, we can:

• Stop plastic pollution at the source
• Carry out beach cleanups
• Avoid agricultural runoff from entering the oceans
• Create business incentives to eliminate plastic use
• Develop and improve waste management laws
• Invest in plastic pollution innovations

Nutrient pollution

The primary sources of nutrient pollution are agricultural runoff and wastewater generated from lawns, both of which often contain fertilisers. Human activities, such as food production, fossil fuel burning, and wastewater discharge, have contributed to the increase in nitrogen and phosphorus compounds in the marine environment, particularly in coastal waters.

The consequences of nutrient pollution are severe. Eutrophication has caused a 70% reduction in hard corals in the Great Barrier Reef over the past century. Globally, there are now over 700 dead zones, covering an area of approximately 245,000 km². These zones, where most marine life cannot survive, result in the collapse of ecosystems and negatively impact coastal livelihoods such as fishing and tourism.

To address nutrient pollution, short-term solutions include planting trees and shrubs near water bodies to absorb excess nutrients. However, in the long term, we need to find alternatives to fertilisers in agriculture and horticulture to prevent further damage to marine ecosystems.

Nonpoint-source pollution

• Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas.
• Oil, grease, and toxic chemicals from urban runoff and energy production.
• Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks.
• Salt from irrigation practices and acid drainage from abandoned mines.
• Bacteria and nutrients from livestock, pet waste, and faulty septic systems.
• Atmospheric deposition and hydrologic modification.

Industrial pollution

Some of the worst impacts of industrial pollution include:

• Dead zones: Nutrient-packed fertilizers and sewage are making some environments uninhabitable.
• Chemical contamination: Insecticides, such as DDT, climb up the food chain, causing diseases and killing birds that consume marine animals.
• Poisoning of animals and humans: PFAS (a group of nearly 15,000 synthetic chemicals) are used to make heat, oil, stain, grease, and water-resistant materials. Once leaked into the ocean, they become part of marine mammal blood and eventually enter the human body.

Offshore oil and gas production, which accounts for one-third of the total value of the ocean economy, has a wide-ranging and pervasive impact on marine habitats and wildlife. From noise pollution to spills to habitat damage, the effects are devastating. The Deepwater Horizon oil spill in 2010, for example, led to the uncontrolled release of 5 million barrels of oil in the Gulf of Mexico, resulting in the immediate death of marine life and substantial financial losses for tourism and fishing industries. Studies have also found that the biodiversity of microbes was flattened at sites closest to the spill, indicating that the oil may have long-lasting impacts on the ecosystem for years to come.

Shipping, the second-largest sector economically, is responsible for approximately 3.1% of global greenhouse emissions, which are expected to increase by 50-250% from 2012 levels by 2050. Shipping also contributes to pollution, invasive species, habitat destruction, and marine mammal mortality through dumped and spilled oil and waste, ballast water discharges, ship strikes, noise pollution, and dredging for shipping channels.

Noise pollution

However, human activities such as shipping, boating, and energy exploration have become increasingly common along coasts, offshore, and in deep-ocean environments. The noise from these activities can travel long distances underwater, causing ocean noise levels to rise in many coastal and offshore habitats. This, in turn, can negatively impact marine animals and ecosystems.

Higher noise levels can reduce the ability of animals to communicate with potential mates, other group members, and their offspring. It can also make it harder for them to hear environmental cues that are vital for survival, such as those needed to avoid predators, find food, and navigate to preferred habitats.

To reduce noise pollution in the marine environment, policies are needed to reduce propeller noise from ships, mitigate the sounds of sonar equipment, seismic air guns, pile-driving, and construction, as well as develop quieter technologies.

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