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Ocean pollution from mining, transportation, and a range of human activities puts pressure on marine life in many ways. Ocean pollution also exposes people to a variety of health risks.  Among other issues, heavy metals like mercury concentrations in fish that people eat. Plastic garbage in the oceans kills marine life and fouls the beaches where people like to relax. Contaminated water discharged from sewer pipes also causes diseases.

This post relates 15 key facts about ocean pollution in areas like impacts, trends, and numbers. Human action is not the only source of ocean pollution of course, but agriculture, industry, and transportation do generate a huge amount of waste that gets into oceans. Wikipedia contained some interested, and unsettling, facts about ocean pollution around the world.

Human Activity Produces a Massive Amount of Plastic Garbage

An estimated 110 million tons of plastic garbage has found its way into the oceans. Trash tends to stay put until consumed by marine life or cleaned up. The plastic that isn’t consumed by mistake can endanger sea birds, sea turtles, and fish, mostly because they become entangled in string and plastic bags.

Fertilizers Pollute Coastal Ocean Waters

Millions of tons of fertilizer meant for crops end up in the oceans, either because it ran directly into the nearest salt water or because the fertilizer ran into a river. There are over 400 “eutrophication zones” around the world, where fertilizer run off has led to enhanced plant growth, low oxygen levels and a lack of marine animals.

There is a Huge Dead Zone in the Gulf of Mexico:

Fertilizer and pesticide runoff from farms, yards, and golf courses find its way into the water. Some of that runoff inevitably ends up in the Oceans. The fertilizer periodically creates “dead zones” where low oxygen levels kill or drive away marine life. The Gulf of Mexico had a dead zone of over 7,700 square miles in 2008. In 2017, a dead zone the size of New Jersey developed. The Chesapeake Bay had a dead zone created by runoff from western Maryland and northern Virginia.

Ocean Acidification Threatens the World’s Biggest Carbon Sink:

Some natural and artificial carbon dioxide emissions end up being captured by growing plants. A large amount of carbon dioxide also ends up dissolved in the oceans. Ocean acidification reduces the capacity of the oceans to hold carbon dioxide.

The Oceans Conceal Huge Stocks of Methane Gas:

The seas contain trillions of tons of minerals that trap methane gas under the sea. The methane clathrates lie under the sediments at the sea floor where they keep a huge amount of this potent greenhouse gas out of the atmosphere.

Oil Spills are Relatively Minor Sources

Leaking oil tankers and burning oil well platforms get headlines, but the oil released in these events is not even close to being a major source of ocean pollution. In fact, most ocean pollution comes from highly distributed sources, like millions of yards, landfills, mines, recreational boats, ships, and factories.

Windblown Dust is a Threat to Coral Reefs

Dust naturally blows out to sea from many sources, deserts naturally being a major one. Human activity that contributes to desertification and some forms of agriculture can make high winds likely to carry more dust out to sea. The United States Geological Survey blames that dust on some damage to coral reefs around the world.

Ships Disrupt Local Ecosystems by Dumping Water

Large cargo ships and passenger ships may take on ballast water that they dump in a port. While this water is often harmless, it can introduce non-native species like zebra mussels and exotic jellyfish. These creatures can decimate local ecosystems, and have done so.

Oyster Reefs Save Estuaries

Oysters and other mussels are harmed by ocean pollution, but can also help clean the ocean in some places. In estuaries, oysters can filter nitrogen out of the water and can filter other solids. The idea of pollution control using shellfish beds has been tested at least once, in a Swedish project.

Heavy Metal Contamination

Compounds containing mercury, arsenic, lead, and cadmium leak into seawater from natural sources, but mostly from industrial sources. Those compounds tend to concentrate in sea life that people eat. Tiny animals like mussels and sea anemones absorb the chemicals, bigger creatures eat the small animals, and popular fishes like tuna absorb even more of the contaminants.

The Great Pacific Garbage Patch is One of Several

News about a giant patch of floating plastic trash generating a surge of interest in plastic contamination in the ocean. What many people may forget is this – there are several garbage patches. Ocean currents can dump plastic trash in areas where there is little circulation. The result is a huge garbage patch that looks like the remains of a sunken garbage barge.

Underwater Noise Pollution:

We usually think of toxic chemicals and garbage when we think of ocean pollution. However, the oceans can be noisy, just like cities. This is not a problem except where extremely noisy human activity. The engines of passing ships, active sonar used by navy ships, and seismic surveys used in oil exploration all contribute to increased noise.

Noise Pollution Makes Animals Louder:

Just as humans tend to speak up in noisy environments, animals may have to “speak up” to be heard over active sonars and other human sources of noise. Whales, for example, use their songs to communicate about prey, potential danger, and more. When their communications are masked by artificial noise, they must try harder. Other marine creatures that use sound to communicate also raise their voices.

Ocean Mining is a Growing Source of Minerals and Pollution

Hydrothermal vents have become a new source of minerals, but raise new pollution concerns. Sulfide deposits rich in metals like gold and copper can be recovered from near those vents. Unfortunately, the mining operations can disrupt the ecosystem in a couple of ways, by chewing up the habitat of organisms that live on the seabed and by dumping silt into the water. Filter-feeding organisms can be injured ingesting too much silt.

Most Ocean Pollution Comes from Millions of Scattered Sources

Spectacular events like huge oil spills or the Fukushima nuclear disaster get a huge amount of media attention. But most of the plastic garbage, heavy metals, and nutrient pollution comes from millions of farms, factories, sewer pipes, lawns, landfills, and leaky old boats around the world.