Marine Pollution and its Harmful Effects
Marine pollution is a diversified term. Several factors have created the present dilapidated condition of the sea. Sources are many but the solutions are few. Because oceans are part of the food chain, marine pollution affects a wide spectra of species, including humans. Ocean and human life is so inextricably interwoven that the effects of marine pollution are drastically visible on human life.
The effects that have been making headlines across the world include global warming, the melting of polar ice caps, the extinction of endangered marine species, etc. What are these effects caused by? How do the endangered marine species become extinct? How does marine pollution affect the food chain? Let’s explore the major sources of human pollution and how the oceans are affected by it.
Addition Of Nutrients & Pathogens
When organic matter is disposed of into the sea, the matter absorbs dissolved oxygen which reduces the level of oxygen in the ocean that marine organisms require. This organic matter also feeds algae blooms that are already present in the water, stimulating their growth. This decomposing algae not only depletes the oxygen content but also releases toxic substances that are harmful to marine organisms. The toxins can even enter food chain through fish or other sea organisms, which in turn, can poison humans. The main sources of organic matter pollution are sewage plants, forestry, farming, and also airborne nitrogen oxides from automobiles and power plants. Algae blooms that feed on human sewage also causes discoloration of water due to the decomposition of matter. Algae blooms can choke fish gills and even poison them with the chemicals created from the decomposition process.
Human sewage also contain bacteria and pathogens that contaminate the coastal areas by accumulating on shores and beaches. This might even enter the food chain or spread diseases like cholera, typhoid, or other dangerous diseases. One more source of pathogens is the water used to wash livestock that is disposed into the sea. This water contains high level of germs and bacteria.
Also, ocean organisms like mussels, oysters and clams that are consumed as food have a tendency of concentrating pathogens in their gut. Consumption of these foods will increase the possibility of food poisoning, creating possible health risks to many people around the world.
Oil is the most dangerous form of marine pollutant. Its effects are not only the most harmful but are also permanent. The oil spills that we hear about are not the only source of oil pollution. Oil finds its way into the sea through many ways such as automobiles, waste discharge of heavy industries, and also from offshore structures. Even the slightest type of contamination can kill the larvae of marine animals and also spread diseases. The chemical ingredients of oil causes physiological changes in the organisms leading to changes in behavior.
Larger oil spills are the worst type of marine pollution.The thick oil sticks to the body of marine organisms making them incapable of performing some necessary functions. Sea birds are the ones most affected by oil spills as the oil sticks to their wings, rendering them flightless. As the density of oil is less that water, it floats on the top, forming a thick impermissible membrane. This thick layer prevents marine organisms to come to the surface for sunlight and oxygen, and eventually will kill them. As the layer is black and opaque,the sunlight cannot pass through the surface. This prevents the marine plants to photosynthesize sunlight into energy.
Tar balls formed due to the coagulation of oil, water, and other debris is washed onto the shore, causing harm to human and coastal life that relies on the water and beaches for food.
Sediments, Plastics, and Foreign Species
Sediments from dredging and mining makes the sea water cloudy, preventing sunlight to reach the marine plants on the sea bed (much like oil spills). When heavy sediments settle on the ocean floor can bury fish and other delicate species such as coral reefs. These sediments can also clog fish gills and smother a large part of the marine ecosystem.
Sources of plastics include landfills, waste disposal from plastic industries, plastic garbage from ships, and litter on beaches. Plastics can stick to marine life and affect their breathing or swimming. When settled on the sea bed, the plastics can also smother any life that calls the sea floor home. Discarded fishing nets can continue to catch huge numbers of fish. Small plastic fragments can be mistaken as food by fish or other sea life which can kill them by filling up or damaging their stomach or other digestive organs. Another common piece of plastic that holds together 6 packs of soda cans are infamous for getting stuck around the necks of birds, sea turtles, and other marine life.
Different parts of the oceans have different inhabitants. Thousands of gallons of water, along with any local species in the water, is transported by ships in their ballast tanks. When the water is released in a different area, the foreign species in the transported water can kill off native species.
Chemical, Radioactive, and Thermal Pollution
Discarded radioactive materials from nuclear submarines and military waste have been a major source of radioactivity in the oceans, which causes fatal harm to marine life. They can also enter the food chain as some organisms like shell fish concentrate radioactivity in their bodies which are later consumed by humans.
Pesticides like DDT, PCBs etc can enter the oceans through city waste water and industrial discharges from farms and forests. Pesticides are easily absorbed by marine organisms causing numerous defects and reproductivity problems. Pesticides that enter the food chain pose great risks to humans who consume fish and sea food.
Thermal pollution is when high or low temperature water is discharged from an industrial source. The difference in temperatures can kill corals and other sensitive marine organisms that are not developed to handle the different temperatures.
Hofer, T.N., Abessa, T.M.S., Acquiar, V.M.C., Alfonso, J.A. & Neto, J.A.B. (2008) Marine Pollution: New Research. New York: Nova Science Publishers.