Causes of sea pollution
Causes of sea pollution
Waste and residues resulting from navigation at sea are considered pollutants that testify to the negative impact of humans on the seas, and the source of these wastes may be from marine activities; such as fishing boats, and cargo carriers, but 80% of them come from land sources; Many of these pollutants are from plastic waste and manufactured materials, which are waste left by humans to end up in seawater; These wastes may be dumped directly in the water, or on beaches, or high areas, miles away from the seas, to be transferred with the running rain water to drain in them. 
In general, this waste affects marine organisms that may end up in death if swallowed or unable to move because of it, and it also affects the aesthetic views of the seas and oceans, and reducing them can recycle waste, and reduce the use of plastic materials as much as possible, in addition To dispose of the waste by placing it in its correct place, making sure that the places of collection outside are completely closed. 
Oil and chemicals
Oil pollution can cause the destruction of marine ecosystems, oil usually reaches seawater with running water from cities and urban areas, and from the filling and unloading of fuel in boats at ports, as well as oil spills that occur from disasters that may occur to oil tankers in the seas and oceans , and oil spills during the transportation or manufacture of oil constitute about 8% of the total causes of sea pollution due to oil, while oil spills associated with boat fuel constitute about 24% of them, and the following are the most important sources of sea pollution with oil: 
- Use of oil and its derivatives : Oil and its derivatives are widely used, especially in cities and urban areas; It is used as a fuel in cars, planes , agricultural machinery, boats and marine vessels, among others; The remains scattered on the roads travel through surface running waters to eventually reach the seas, in addition to the fuel produced by aircraft when it is disposed of in the air, which reaches the seas.
- Oil transportation : In 1989, a navigational error in the oil tanker Exxon Valdez caused the spillage of about 34,000 tons of crude oil into sea waters, which harmed huge numbers of animals and sea birds, and the cost of cleaning it was more than 2.5 billion dollars. Despite the high amount of oil transported overseas, spills associated with oil transportation have become rare in recent times.
- Oil exploration and extraction : The production and exploration of oil and natural gas are important sources of oil pollution in sea waters. In 2010, an explosion occurred in the Deepwater Horizon platform for extracting oil in the Gulf of Mexico, which caused tens of thousands of barrels of crude oil to spill daily for more than a hundred days, and as a result, the oil covered an area of more than 6,475 square kilometers of sea water, This is considered the largest marine oil spill in history. 
- Natural seepage from the deep sea : One of the reports issued by the National Research Council report Oil in the Sea III revealed that the main natural source of oil in the seas is the seepage resulting from the geological formations under the seabed, which is the source of about 60 % of it is in the seas in the waters of North America, and 45% of its source is in the world, and the remaining percentage is from human influence.
When plastic waste is disposed of in the wrong way, it accumulates and negatively affects the surrounding ecosystems; This is because plastic is a material that is not biodegradable, and instead it breaks down into smaller pieces that persist in the environment for centuries, and these particles can cause the death of marine organisms if ingested;  These particles cause the death of millions of animals, including endangered species, and can accumulate in their bodies. 
Small plastic particles when they reach the oceans and seas remain just below the surface of the water, and move with ocean currents to be concentrated in eddies and form patches of plastic in the oceans that are usually difficult to determine their size, but some of them have been estimated to contain about two million pieces of microplastic per square mile. 
Many industries release tons of hazardous emissions into the atmosphere every year. These pollutants are transmitted through the air and reach the seas and oceans through atmospheric precipitation, when suspended particles from them fall into the air with rainwater and snow, and some industrial facilities also contribute, Wastewater purification plants, and mining activities pollute aquatic environments by dumping residues of toxic chemicals directly into seawater.  
Fertilizer and Nutrients
Water rich in nutrients and fertilizer residues may reach the waters of the seas and oceans even from remote areas; In several ways, as follows: 
- Fertilizers and nutrients seep from agricultural land usually through surface water courses to large rivers, to carry these nutrients to seas and oceans, as happens in the Mississippi River in the United States of America; During the last half of the twentieth century, the amount of accumulated nitrogen in it tripled.
- Fertilizers seep through the soil after irrigation or rain into aquifers , then reach coastal waters with the flow of groundwater, and these elements move with ocean currents.
- Nutrients can be deposited directly from the air directly into the ocean or into the water running towards it.
An increase in nutrients such as nitrogen and phosphorous in the seas and oceans stimulates the growth of algae and marine plants in a phenomenon called eutrophication, and when these plants die and decompose at the bottom, they consume most of the oxygen in the water, which leads to its deficiency, thus eliminating marine life in those areas. 
Most of the sewage water in some countries, such as the United States of America, reaches the seas and oceans after being treated by treatment plants before being discharged there. In return, it may be stored in special tanks if this is not possible. However, failure to maintain these tanks may lead to water pollution. Groundwater that may flow into surface water or coastal water, causing pollution, and sometimes sea water may be polluted due to leakage resulting from inefficient sewage facilities, treatment plants, and sewage systems, due to their old age, or due to some accidents that may be exposed to them. 
When seawater is contaminated with feces, it often dissipates and disappears within several days, but its stay on the beach gives a longer chance for bacteria and pathogens to survive, as well as the excrement left by animals and livestock on the soil, which may move with running rainwater and streams to cause beach and seawater pollution. 
Domestic sewage water contains bacteria, viruses, chemicals, and nutrients, so direct exposure to water contaminated with sewage water through swimming or drinking in it causes many health damages; Such as rashes, pain in the ear and stomach, diarrhea and vomiting, and many other diseases. Diseases transmitted through contaminated water are also a major cause of death in developing countries. On the other hand, pollution of sea water with sewage water causes many economic effects; It causes pollution of fish and shellfish , and polluted water reduces the water's suitability for swimming and boat traffic, and can cause beach closures and affect the tourism sector. Diseases resulting from water pollution also lead to higher health care costs and lost days of work due to disease. 
Overview of seas and oceans
The seas and oceans cover more than 70% of the surface of the planet, and they have a great impact on it; It controls the weather, contributes to purifying the air of pollutants, and is an essential source of food and natural resources. It is also home to many forms of life on Earth; Where many types of living organisms live, starting from microorganisms , to the largest animal on this planet, the blue whale , and it is worth noting that the seas differ from the oceans because they are smaller in size, and they are usually located within the area where the land meets the oceans.  
Human activities have brought about remarkable changes in the seas and oceans in recent times. Its waters have become a site for gathering various forms of pollutants, which include emissions of harmful gases to the atmosphere, plastic waste and non-degradable waste, in addition to oil leaking into the seas and oceans, and many other pollutants that affect them very quickly and pose a threat to environmental and human health.  Among the most important of these pollutants are the following:
- "Pollution in the Ocean", www.aquariumofpacific.org,1-5-2009، Retrieved 14-4-2020. Edited.
- Mariann Lloyd-Smith, Joanna Immig (1-10-2018), "OCEAN POLLUTANTS GUIDE"، www.ipen.org, Retrieved 14-4-2020.
- Patrick Johnston, Priyanka Ketkar, "Plastic Pollution and Our Oceans: What Everyone Should Know"، camd.northeastern.edu, Retrieved 30-4-2020. Edited.
- Simon Harding (2016), MARINE DEBRIS: UNDERSTANDING, PREVENTING AND MITIGATING THE SIGNIFICANT ADVERSE IMPACTS ON MARINE AND COASTAL BIODIVERSITY, Canada: the Secretariat of the Convention on Biological Diversity , Page 19, 20. Edited.
- "Water Pollution", www.ohio.k12.ky.us, Retrieved 15-4-2020. Edited.
- NOAA (3-4-2019), "What's the difference between an ocean and a sea?"، www.oceanservice.noaa.gov, Retrieved 14-4-2020. Edited.
- Melissa Denchak (22-1-2018), "Ocean Pollution"، www.nrdc.org, Retrieved 14-4-2020