Pollution in the Sea

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garbage in the sea off Japan
More than two out of every five people lives 60 miles or less from a sea coast. These people have a profound effect on the oceans and marine ecosystems. Many tourist resorts are built as close to the sea as possible. Garbage, untreated sewage and waste from construction of building tourist resorts is threatening the beauty and ecology of many small island nations.

Pollution has also taken a heavy toll, rendering the oceans less resilient to climate change. Runoff from nitrogen-rich fertiliser, killer microbes, and hormone-disrupting chemicals, for example, have all contributed to the mass die-off of corals, crucial not just for marine ecosystems but a lifeline for hundreds of millions of people too.

Most sea pollution comes from off from the land. The main sources are waste from farm animals, fertilizers, human sewage, eroded soil, runoff from irrigated fields and lawns with fertilizers and pesticides, runoff from urban landscape containing motor oil, sediment and animal wastes, overtaxed sewage and septic systems, air -borne particles from factories and vehicles dumped in the sea. River sediments contain petroleum runoff and mercury from power plant emissions.

Much of the pollution is in the form of basic nutrients such as nitrogen, carbon, iron and phosphoreus compounds. Millions of tons of carbons dioxide and nitrogen oxide, produced by burning fossils fuels enter the ocean every day.

Sources of maritime pollution: 1) sewage (30 percent); 2) farm run off (20 percent); 3) air pollutants (20 percent); 4) industrial wastewater (10 percent); 5) maritime transportation (10 percent); 6) offshore oil (6 percent); 7) litter (5 percent).

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures

Negative Impact of Humans of the Oceans

Juliet Eilperin wrote in the Washington Post: Humans have mined resources from the remote and rocky coast of Peru and Chile for more than a century and a half, gathering the guano deposits of seabirds for fertilizer and gunpowder. Those seabirds flourished on anchoveta in the coastal waters, while Peruvians in the highlands ate the same fish as dried snacks. [Source: Juliet Eilperin, Washington Post October 23, 2011]

Now fishing vessels haul 7.5 million tons of the small silvery fish out of the water every year. Almost all the catch is reduced to fish oil and fish meal, which is fed to pigs, poultry and salmon being raised thousands of miles away to satisfy demand in the industrialized and rapidly-growing developing world. The Peruvian seabird population that used to number in the tens of millions has dropped to 2 million. “These fish are an important source of food, and the basis of the ecosystem,” said Peruvian conservation biologist Patricia Majluf. “It’s part of the global syndrome of misuse of resources.”

Famous 1971 Minamata Bay photo
by William Eugene Smith of mercury poisoning
As the global population reaches the 7-billion mark, these sort of ecological distortions are becoming more pronounced and widespread. Sometimes local needs are depleting water, fish and forests; other times food and fuel needs in one region of the world are transforming ecosystems in another. Under either scenario, however, expanding human demands are placing pressure on resources, particularly on world water supply and fisheries. In the end, according to National Geographic fellow Barton Seaver, the world’s growing population will have to learn how to live better within its means. “We’re not going to find more fish; we’re not going to plow more rain forest to create more calories,” Seaver said. “I would rather have my anchoveta in all its briny, delicious, shiny glory than through a pork chop on my plate.”

One study found that one in 20 people who go in the sea around the world get sick from untreated water. In some places coastal waters are so polluted that people who swim in them risk getting diarrhea-causing gastrointestinal illnesses and sinus and upper respiratory infections. Most problems occur if the water is swallowed. Skin contact can result in rashes and infections of open wounds. In the worst cases people who stay in tainted water too long can contact viral myocarditis, a dangerous inflammation of the heart muscle.

Nutrient Pollution

Nutrient pollution is the process where too many nutrients, mainly nitrogen and phosphorus, are added to bodies of water and can act like fertilizer, causing excessive growth of algae. Nutrients can run off of land in urban areas where lawn and garden fertilizers are used. Pet and wildlife wastes are also sources of nutrients. [Source: NOAA]

This process is also known as eutrophication. Excessive amounts of nutrients can lead to more serious problems such as low levels of oxygen dissolved in the water. Severe algal growth blocks light that is needed for plants, such as seagrasses, to grow. When the algae and seagrass die, they decay. In the process of decay, the oxygen in the water is used up and this leads to low levels of dissolved oxygen in the water. This, in turn, can kill fish, crabs, oysters, and other aquatic animals.

Nutrients come from a variety of different sources. They can occur naturally as a result of weathering of rocks and soil in the watershed and they can also come from the ocean due to mixing of water currents. Scientists are most interested in the nutrients that are related to people living in the coastal zone because human-related inputs are much greater than natural inputs. Because there are increasingly more people living in coastal areas, there are more nutrients entering our coastal waters from wastewater treatment facilities, runoff from land in urban areas during rains, and from farming. All of these factors can lead to increased nutrient pollution.


Mercury and the Sea

Mercury in the food chain
Coal-fired power plants are the primary source of atmospheric mercury. As particles it can fall quickly to earth but as an aerosol it can float for hundreds or even thousands of kilometers and fall all over the globe. When mercury falls into the sea or other waterways, bacteria can transform it into highly toxic methyl mercury, which is absorbed in very minute amounts by plankton, shellfish anchovies, sardines and other small fish, which in turn pass it up the food chain.

Each time a large fish consumers its prey, the mercury from the smaller fish lodge in the tissues of the larger fish. At the top of the food chain, fish such as mackerel, tuna, swordfish and sharks — as well as dolphins and whales — can have thousands of times more mercury than sardines or shellfish can. High concentration of mercury are also found in land animals that feed on fish such as eagles, loons, mink, otters and alligators.

Mercury is a dangerous heavy metal linked to health problems with children and birth defects and brain deformities. One of the problems with eating fish though is that many fish that are said to be healthy are also high mercury. Fish at the top of the food chain such as sharks, king mackerel, tilefish and swordfish have the highest mercury levels. Tuna has moderate amounts. Albacore turn has ore than light tuna. The levels in salmon are low. Studies have show that people who eat a lot of whale sometimes have high levels of mercury.

Pure DDT and Barrels Of Pollutants Found on the Ocean Floor off Los Angeles

The largest manufacturer of DDT in the U.S. once used the ocean as a huge dumping ground and that as many as half a million barrels of its acid waste was been poured straight into the water. The Los Angeles Times reported: Scientists have discovered that much of the DDT — which had been dumped largely in the 1940s and ’50s — never broke down. The chemical remains in its most potent form in startlingly high concentrations, spread across a wide swath of seafloor larger than the city of San Francisco. [Source: Rosanna Xia, Los Angeles Times, March 24, 2023]

“We still see original DDT on the seafloor from 50, 60, 70 years ago, which tells us that it’s not breaking down the way that [we] once thought it should,” said UC Santa Barbara scientist David Valentine. “And what we’re seeing now is that there is DDT that has ended up all over the place, not just within this tight little circle on a map that we referred to as Dumpsite Two.”

Public calls for action have intensified since The Times reported in 2020 that DDT (dichlorodiphenyltrichloroethane), banned in 1972, is still haunting the marine environment today. Significant amounts of DDT-related compounds continue to accumulate in California condors and local dolphin populations, and a recent study linked the presence of this once-popular pesticide to an aggressive cancer in sea lions.

The findings so far have been one stunning development after another. A preliminary sonar-mapping effort led by the Scripps Institution of Oceanography identified at least 70,000 debris-like objects on the seafloor. The U.S. Environmental Protection Agency, after combing through thousands of pages of old records, discovered that other toxic chemicals — as well as millions of tons of oil drilling waste — had also been dumped decades ago by other companies in more than a dozen areas off the Southern California coast.

Shipping Pollution

Like all modes of transportation that use fossil fuels, ships produce carbon dioxide emissions that significantly contribute to global climate change and acidification. Besides carbon dioxide ships also release a handful of other pollutants that contribute to the problem. [Source: europe.oceana.org]

The shipping industry is responsible for a significant proportion of the global climate change problem. More than three percent of global carbon dioxide emissions can be attributed to ocean-going ships. This is an amount comparable to major carbon-emitting countries — and the industry continues to grow rapidly.

In fact, if global shipping were a country, it would be the sixth largest producer of greenhouse gas emissions. Only the United States, China, Russia, India and Japan emit more carbon dioxide than the world’s shipping fleet. Nevertheless, carbon dioxide emissions from ocean-going vessels are currently unregulated.

Along with CO2, ships emit various global warming pollutants, including black carbon (BC), nitrogen oxides (NOx) and nitrous oxide (N2O). These pollutants all contribute to global climate change either directly, by acting as agents that trap heat in the atmosphere, or indirectly by aiding in the creation of additional greenhouse gases.

Ocean Noise

A study published in September 2019 reported that most of the plastic bottles washing up on the shores of Inaccessible Island, a remote island the middle of the South Atlantic between Argentina and South Africa , probably come from Chinese merchant ships. According to AFP, The study offers evidence that the vast garbage patches floating in the middle of oceans, are less the product of people dumping single-use plastics in waterways or on land, than they are the result of merchant marine vessels tossing their waste overboard by the ton. The authors of the study published in the Proceedings of the National Academy of Sciences, or PNAS, collected thousands of pieces of waste during visits to the tiny island in 1984, 2009 and again in 2018.

Ocean Noise

Ocean noise refers to sounds made by human activities that can interfere with or obscure the ability of marine animals to hear natural sounds in the ocean. Many marine organisms rely on their ability to hear for their survival. Sound is a highly efficient means of communication underwater and is the primary way that many marine species gather and understand information about their environment. Many aquatic animals use sound to find prey, locate mates and offspring, avoid predators, guide their navigation and locate habitat, as well as to listen and communicate with each other. [Source: NOAA]

Over the last century, human activities such as shipping, recreational boating, and energy exploration have increased along our coasts, offshore, and deep ocean environments. Noise from these activities can travel long distances underwater, leading to increases and changes in ocean noise levels in many coastal and offshore habitats.

These rising noise levels can negatively impact ocean animals and ecosystems. Higher noise levels can reduce the ability of animals to communicate with potential mates, other group members, their offspring, or feeding partners. Noise can also reduce an ocean animal's ability to hear environmental cues that are vital for survival, including those key to avoiding predators, finding food, and navigating to preferred habitats.

See Whales and Sonar


20120517-run off_from_this_pipe_in_the_U_S__Virgin_Islands.jpg HAZMAT is an abbreviation for “hazardous materials” — substances in quantities or forms that may pose a reasonable risk to health, property, or the environment. HAZMATs include such substances as toxic chemicals, fuels, nuclear waste products, and biological, chemical, and radiological agents. HAZMATs may be released as liquids, solids, gases, or a combination or form of all three, including dust, fumes, gas, vapor, mist, and smoke. [Source: NOAA]

HAZMAT spills have caused health problems, injuries, and even death in people and animals, and have damaged buildings, homes, property, and the environment. Given such dire consequences, it is reasonable to conclude that one may not encounter HAZMATs on a daily basis. The truth, however, is that many products containing hazardous chemicals are routinely used and stored in homes, and are transported every day on the nation's highways, railroads, waterways, and pipelines.

Thousands of incidents occur each year in which HAZMATs are released into the environment as a result of accidents or natural disasters. In addition to potentially harming people and the environment, spills in coastal waters may cause substantial disruption of marine transportation with potential widespread economic impacts. Both coastal and inland spills are called HAZMAT incidents, and are routinely addressed by first responders like firefighters and local law enforcement.

Under the National Contingency Plan, NOAA provides scientific support to the Federal On-Scene Coordinator for oil and other HAZMAT spills, and participates in emergency response activities in coastal and near-coastal waters. NOAA's Office of Response and Restoration responds to 120-150 HAZMAT incidents each year. Most are oil spills originating from leaking pipelines or vessel collisions, as well as hurricanes and drilling well blowouts, such as the 2010 Deepwater Horizon spill in the Gulf of Mexico. For the thousands of minor incidents handled by first responders, NOAA and the U.S. Environmental Protection Agency collaborate on tools like the CAMEO software suite that offer fast access to chemical properties and other relevant information.

Pollution from Many Sources in a Florida Estuary

Abigail Tucker wrote in Smithsonian magazine: Long considered North America’s most diverse estuary, River Lagoon in on Florida’s east coast may now be dying. Pollution has thinned the dinoflagellate blooms, and the light from thousands of new houses drowns out the remaining brightness. Animals once wreathed in blue fire are ailing, too. Many dolphins are afflicted by a flesh-eating fungus that corrodes their skin; others are infected by viruses and have severely suppressed immune systems. Luxurious sea grass beds grow bald, leaving conch and periwinkle snails without shelter. Mammoth algae blooms stink like rotting eggs. The shellfish industry is in shambles. [Source: Abigail Tucker, Smithsonian magazine, March 2013]

These ills are not unique to Florida waters. Two abysmal assessments of the ocean’s overall health — the Pew Ocean Report in 2003 and the U.S. Commission on Ocean Policy’s in 2004 — spurred famed marine biologist Edith Widder to leave her longtime position as a senior scientist at Florida’s Harbor Branch Oceanographic Institute and start the environmental organization ORCA. “Ever since I did my first dive, I’ve been asking why is there all that light in the ocean and what is it used for,” she says. “More recently, I’ve come around to figuring out what we can use it for.”

The lagoon is a dense green world, interrupted here and there by the pastel crags of Floridian architecture. A wisp of an egret wanders the shore and pelicans on top of pilings appear sunk in contemplation. Fingers of mangrove roots protrude from the inky banks. More than 150 miles long, the lagoon is a home to logjams of manatees, a rest stop for migratory birds and a nursery for bull and bonnet sharks. But water that 30 years ago was gin clear now looks more like bourbon.

jellyfish swarm
The sources of pollution here are discouragingly diverse: There’s airborne mercury from China, fertilizer and pesticide runoff from inland citrus and cattle farms, even the grass clippings from local lawns. “There are literally thousands of chemicals being released into our environment and nobody is keeping track of them,” Widder says. So much of the surrounding wetlands have been paved and drained that the lagoon is fast becoming a sink for the land’s poisons. It’s hard to imagine a bright future for the place.

To protect the lagoon, Widder has designed ocean monitors that track currents, rainfall and other variables, mapping where water comes from and where it goes in real time. She wants this network to one day span the world — “the wired ocean.”

Now she’s studying the lagoon’s most polluted parts, which she identifies with the help of bioluminescent life-forms. Wearing yellow kitchen gloves, we shovel gray-green muck from the foot of ORCA’s dock, an area that Widder has never tested before. A lab assistant homogenizes the sample in a paint mixer, then retrieves a vial of freeze-dried bioluminescent bacteria. It’s Vibrio fischeri, the same strain that the fireshooter squid uses for its deep-sea dragon breath. She drops it, along with little drips of the lagoon mud, into a Microtox machine, which monitors the light. We can’t see it with our naked eyes, but the healthy bacteria are glowing at first.

“The light output of bacteria is directly linked to the respiratory chain,” Widder explains. “Anything that interferes with respiration in the bacteria quenches the light.” Interfering substances include pesticides, herbicides, petroleum byproducts and heavy metals, and the more they quench the light, the more toxic they are. Widder and the lab assistant don’t think the mud from outside the door will prove too toxic, but they are wrong: Within half an hour, readings show that the bacteria’s living lights are dim, and in the most concentrated samples, they have burned out.

Image Sources: Wikimedia Commons; YouTube, NOAA

Text Sources: National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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