Marine pollution & its causes

Marine pollution is the release of by-products of human activity that cause harm to natural marine ecosystems. Eighty percent of pollution to the marine environment comes from the land. One of the biggest sources is called nonpoint source pollution, which occurs as a result of runoff. Nonpoint source pollution includes many small sources, like septic tanks, cars, trucks, and boats, plus larger sources, such as farms, ranches, and forest areas. Millions of motor vehicle engines drop small amounts of oil each day onto roads and parking lots. Much of this, too, makes its way to the sea.  This kind of pollution can have serious economic and health impacts by killing marine life and damaging habitats and ecosystems. Marine pollution includes a range of threats including from land-based sources, oil spills, untreated sewage, heavy siltation, eutrophication (nutrient enrichment), invasive species, persistent organic pollutants (POP’s), heavy metals from mine tailings and other sources, acidification, radioactive substances, marine litter, overfishing and destruction of coastal and marine habitats. Some common marine waste includes:

    1.    Sewage, Waste, and Fertilizers

Sewage, animal waste, and chemical fertilizers all have a high content of nitrogen and phosphorus. Artificially high levels of these substances in the water promote excessive growth of microscopic or macroscopic plants, in a process called eutrophication . When these plants accumulate, die, and decay, they cause low oxygen content in the water. Even if sewage is treated to remove solids, the liquid discharged contains high levels of nitrogen and phosphorus. Intensive cultivation of animals in feedlots, or application of more fertilizer than a crop can absorb, also cause runoff rich in nitrogen and phosphorus that find their way into rivers and estuaries. Vehicle exhausts and industrial chimneys are large sources of

nitrogen compounds that are transported in the atmosphere and deposited in coastal waters.

When pesticides are incorporated into the marine ecosystem, they quickly become absorbed into marine food webs. Once in the food webs, these pesticides can cause mutations, as well as diseases, which can be harmful to humans as well as the entire food web.

2.  Metals and Organic Contaminants

Toxic metals can also be introduced into marine food webs. These can cause a change to tissue matter, biochemistry, behaviour, reproduction, and suppress growth in marine life. Also, many animal feeds have a high fish meal or fish hydrolysate content. In this way, marine toxins can be transferred to land animals, and appear later in meat and dairy products.

Industry  produces organic compounds such as polychlorinated biphenyls (PCBs) and various pesticides. These accumulate in the fatty tissue of plants and animals low in the food chain, and as they pass through the food web to larger and long-lived animals, there is an increase in concentration of the substances in their fat, a process known as bioaccumulation.

3.  Oil Spill

The most serious types of oil pollution occur when an oil tanker goes ashore or hits a reef and spills its contents. As the oil drifts ashore, great damage is done to beaches, rocky shores, salt marshes, or mangrove forests. 
Chronic low levels of oil pollution, resulting from accidental spills when loading or unloading, or from washing out oil tanks, are widespread and of significant concern.
Oil spills cause huge damage to the marine environment - but in fact are responsible for only around 12% of the oil entering the seas each year. According to a study by the US National Research Council, 36% comes down drains and rivers as waste and runoff from cities and industry.

4.  Solid Waste

Solid garbage also makes its way to the ocean. Plastic bags, balloons, glass bottles, shoes, packaging material – if not disposed of correctly, almost everything we throw away can reach the sea. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic - a component that has been rapidly accumulating since the end of World War II.j The mass of plastic in the oceans may be as high as one hundred million metric tons. This garbage can also come back to shore, where it pollutes beaches and other coastal habitats.

5.  Acidification

The oceans are normally a natural carbon sink, absorbing carbon dioxide from the atmosphere. Because the levels of atmospheric carbon dioxide are increasing, the oceans are becoming more acidic. The potential consequences of ocean acidification are not fully understood, but there are concerns that structures made of calcium carbonate may become vulnerable to dissolution, affecting corals and the ability of shellfish to form shells.

1.  6.  Industrial  Waste

 Industry is a huge source of water pollution, it produces pollutants that are extremely harmful to people and the environment.

• Many industrial facilities use freshwater to carry away waste from the plant and into rivers, lakes and oceans.
• Pollutants from industrial sources include:

v  Asbestos – This pollutant is a serious health hazard and carcinogenic. Asbestos fibres can be inhaled and cause illnesses such as asbestosis, mesothelioma, lung cancer, intestinal cancer and liver cancer.

v  Lead – This is a metallic element and can cause health and environmental problems. It is a non-biodegradable substance so is hard to clean up once the environment is contaminated. Lead is harmful to the health of many animals, including humans, as it can inhibit the action of bodily enzymes.

v  Mercury – This is a metallic element and can cause health and environmental problems. It is a non-biodegradable substance so is hard to clean up once the environment is contaminated. Mercury is also harmful to animal health as it can cause illness through mercury poisoning.

v  Nitrates – The increased use of fertilisers means that nitrates are more often being washed from the soil and into rivers and lakes. This can cause eutrophication, which can be very problematic to marine environments.

v  Phosphates – The increased use of fertilisers means that phosphates are more often being washed from the soil and into rivers and lakes. This can cause eutrophication, which can be very problematic to marine environments.

v  Sulphur – This is a non-metallic substance that is harmful for marine life.

v  Oils – Oil does not dissolve in water, instead it forms a thick layer on the water surface. This can stop marine plants receiving enough light for photosynthesis. It is also harmful for fish and marine birds.

v  Petrochemicals – This is formed from gas or petrol and can be toxic to marine life.

   7.    Noise Pollution 

 Pollution is not always physical. In large bodies of water, sound waves can carry undiminished for miles. The increased presence of loud or persistent sounds from ships, sonar devices, oil rigs, and even from natural sources like earthquakes can disrupt the migration, communication, hunting, and reproduction patterns of many marine animals, particularly aquatic mammals like whales and dolphins. 

FAQs
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