Human activities have a profound impact on the planet’s oceans, and most of the pollution affecting marine life does not come from the sea. Pollutants, such as toxic chemicals and plastic waste, were developed, purchased, and used on land before being deposited in the ocean.

Although most people are aware of the enormous volume of plastic trash polluting our waterways, few may know about the other pollutants affecting marine animals. We’ll discuss the four primary types of ocean pollution, but we’ll focus on the lesser-known contaminants before examining chemical and plastic pollution.


The 4 Types of Ocean Pollution

1. Noise Pollution

industrial shipping
Image Credit: Pawel Grzegorz, Pixabay

Sound travels faster in water, and marine animals that depend on sound for navigating, mating, and foraging, are being assaulted with high-decibel blasts from Navy sonar, seismic air guns, and shipping vessel propellers. Military ordinance testing, aircraft carrier takeoffs, wind farm construction, and underwater explosions also create an unlivable environment for sea creatures, but they’re not as frequent or disruptive.


The U.S. Navy uses powerful sonar for navigation and detecting enemy ships and mines. The devices are particularly disruptive to whales because the sonar frequencies mask whale sounds and cause them to be disoriented. At 235 decibels, the sonar’s noise can be heard by whales miles away.

When these sensitive mammals try to escape the sound, some try to surface too quickly and experience decompression sickness and auditory structure injuries. Others flee, hoping to find a safer environment, but since they’re confused, they often travel into shallow water, become stranded, and die.

Possible Improvements:

Although the Navy is unlikely to limit its use of sonar anytime soon, they can limit the damage they inflict on marine life by restricting sonar tests to specific areas. Spawning sites, feeding areas, and nursery regions could be off-limits to sonar to prevent reproductive failure and death.

Seismic Air Guns

The sound emitted from a seismic air gun is louder than practically any other human-made noise. The deafening blast from the guns sends fish and whales fleeing for safety and destroys nearby zooplankton and krill populations.

The guns are used by geological research vessels and companies searching for oil and gas. In one day, up to 40 seismic tests occur on the open water, and along the eastern coast of the United States, over 5 million seismic blasts happen every year.

Air guns emit 260 decibels of sound, which is exponentially louder than the 160-decibel takeoff from the space shuttle. When several rows of ships use seismic testing, they minimize the livable environment of the marine animals. Seismic blasts disrupt the way invertebrates navigate, mask whale communication, and lead to collisions with ships when the sound hides the propeller noise.

Possible Improvements:

Environmental agencies have sued the National Marine Fisheries Service to reduce seismic air gun testing. The groups claim that the agency has neglected to protect marine life under the Endangered Species Act by allowing seismic testing. Limiting where testing can occur and developing effective alternatives to air guns will benefit the marine environment.

Merchant Ships

Although the 190-decibel sound from a large ship’s propellers is not as intense as sonar or air guns, it’s more common since international commerce has significantly increased since the 1970s. The low-frequency propeller noise forces fish, mammals, and invertebrates to move away from their favorite feeding zones. It also masks whale sounds they depend on for breeding and locating food.

When marine vessels were restricted from leaving ports after the terrorist attack on New York in 2001, the underwater noise dropped by 6 decibels. Although that doesn’t sound like much, researchers tested the level of stress hormones in whale feces after the attack and discovered the whales were less stressed by the quieter underwater environment.

Possible Improvements:

Unlike other environmental changes such as climate change and resource conservation, ocean noise pollution can be reduced with simple, short-term solutions. Since shipping noise is one of the most prevalent offenders, conservation groups suggest focusing on it first. Reducing traveling speeds, which alters the underwater frequency, can significantly benefit marine life.

Shipping companies can also adjust their routes to avoid sensitive areas and use more efficient marine engines. The U.S. Navy and the International Maritime Organization are committed to developing quieter ships that reduce anthropogenic ocean noise.

2. Light Pollution

offshore oil and gas powerplant
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Another lesser-known form of pollution ravaging the seas is light pollution. Like noise pollution, light pollution has only increased in the last 50 years as coastal cities have expanded their populations, and more deep-sea projects are conducted.

The adverse effects of bright lights on nocturnal creatures living on land are well documented, but scientists have only recently tested marine animals. 1n 1994, researchers discovered that the light pollution from a nearby tourist resort and paper mill on a Turkish beach prevented 60% of the loggerhead turtle hatchlings from reaching the ocean.

Hatchlings use visual cues in their environment to navigate safely to the surf, but artificial lights and even bonfires can make them disoriented. In 1979, a group of 500 green sea turtle hatchlings perished when they were attracted to an unattended bonfire on Ascension Island. Artificial light disrupts the predatory and reproductive habits of seals and other marine animals.

Possible Improvements:

Restricting new construction near coastal breeding grounds and reducing the intensity of artificial lighting near the ocean can limit the light pollution’s detrimental effects.

3. Chemical Pollution

top view of chemically polluted ocean
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Many of the chemicals and toxic compounds we produce and use eventually make their way into our embattled oceans. After heavy rains, runoff from storm drains carries the contaminants to estuaries and rivers, which then flow into the sea. From 2003 to 2012, the number of toxins in the world’s oceans increased by 12%. These chemicals are primarily responsible for polluting the sea:

  • Fertilizers
  • Pharmaceutical products
  • Industrial chemicals
  • Herbicides and pesticides
  • Sewage
  • Detergents and household cleaners

Sunblock and skincare products also contaminate the ocean on a much smaller scale than the biggest offenders listed above. Coastal areas experience phosphorus and nitrogen pollution from agricultural runoff, and 20% of the nitrogen fertilizer used on farmland reaches the ocean from surface runoff. Also, 60% of the fertilizer escapes into the atmosphere by volatilization.

Possible Improvements:

North America and most of Europe have tightened their restrictions and penalties for chemical dumping, but the problem has only worsened in the Pacific Ocean. In China, the 14,000 farming operations are loosely regulated, and meat production has increased significantly since the dawn of the 21st century. Increased production has led to more manure and fertilizer seeping into the ocean.

Fewer than 10% of Chinese farms have pollution controls. Until the world’s leaders prioritize chemical pollution control, the problem will only worsen. Although the effects of agriculture on marine life have been devastating, most of the world has not embraced sustainable farming with fewer chemicals.

4. Plastic Pollution

plastic floating in ocean
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Are you familiar with the Great Pacific Garbage Patch? Also called the Pacific trash vortex, it’s a massive collection of plastic and marine debris that has accumulated in two locations in the Pacific Ocean between Japan and the west coast of the United States. The Eastern Garbage Patch is in the North Pacific, several miles from the California coast, and the Western Garbage Patch rests near Kuroshio, Japan.

The immense trash heaps highlight the problem of plastic pollution in the ocean. Of course, plastic water bottles are part of the problem, but microbeads from wellness products, single-serving plastic containers and utensils, and discarded electronics contribute to the mass of waste. Small bits of plastic have been discovered in the digestive systems of marine animals and even in glacial ice.

Possible Improvements:

The Ocean Cleanup is an environmental organization that has developed a revolutionary cleanup system that aims to reduce the Great Pacific Garbage Patch by 90% by 2040. The system uses a long tube stretched across the water to remove the plastic and marine debris. Other inventions, such as the Seabin, are designed to remove plastic and oil sheens from marinas and ports.

Floating skimmers and stationary devices have effectively removed plastic around ports, and some U.S. cities like San Francisco have banned plastic bottles and containers to reduce pollution. Although the ocean is saturated with plastic trash, the situation seems to be improving as government agencies and the general public become more aware of the issue.

Final Thoughts

Although marine animals provide us with food, medical breakthroughs, jobs, and countless commercial products, we continue to assault their hearing, sight, digestion, and overall health. Ocean pollution is a troubling issue that kills marine organisms and affects our health and economic systems.

Imposing restrictions on chemical dumping, shipping routes, traveling speeds, marine construction, and intrusive exploratory devices are small steps to cleaning the oceans. Cleanup projects and advanced marine equipment can also improve the seas’ condition, but marine creatures will continue to suffer until every nation commits to improvements.

Featured Image Credit: Naja Bertolt Jensen, Unsplash