Pollution of the marine environment occurs from a number of sources. Industrial, agricultural and domestic pollutants find their way into the oceans either through spillages and dumping at sea or via rivers. A range of chemicals such as persistent organic pollutants are known to damage the immune and neurological systems of many marine species, and plastic waste is often fatal to fish, sea birds and other marine creatures who ingest it. Oil spills from tankers and rigs have devastating consequences for sea birds and marine mammals, and can cause damage to tropical coral reefs and fish populations. Scientists are also concerned about the impacts of a wide range of chemicals now being found in marine ecosystems, including pharmaceuticals and synthetic musks used in detergents and personal care products. The effects of these pollutants further exacerbate the stresses facing a large variety of marine species from overfishing and the impacts of climate change.
A serious consequence of marine pollution is the creation of dead zones in coastal areas, where oxygen levels become so depleted that very little marine life can exist. Dead zones are caused by an increase in chemical nutrients (particularly nitrogen and phosphorus) in the water, which lead to blooms in algae and a loss of oxygen. This process is known as eutrophication. A well known example is the large dead zone in the Gulf of Mexico, caused by nutrients from fertiliser and animal waste which enter the Mississippi River as it passes through a number of major farming states. The number of marine dead zones is increasing around the world, causing significant problems for the health of marine ecosystems as well as impacting on the viability of the fishing industry.
Fresh Water Pollution
Globally, fresh water pollution is also a serious problem, particularly in relation to eutrophication. As with coastal dead zones, an increase in nitrogen and phosphorus entering rivers, canals and lakes can result in algal blooms, which have a big impact on water quality and freshwater ecosystems. In the UK high levels of phosphate from fertiliser and household waste, particularly detergents, leads to a spate of algal blooms every summer. Some of these blooms are formed by blue-green algae, which can become toxic and harmful to wildlife, livestock and people. Freshwater algal blooms are an international problem, affecting freshwater species, water quality, lakeside tourism and leisure activities and posing risks to health.
Sewage and waste water from domestic and industrial sources is a major source of water pollution of rivers, lakes and coastal areas around the world. Many industrial facilities use freshwater to carry waste from plants into rivers and lakes, which can contaminate surface and groundwater supplies, affecting drinking water quality and ecosystem health. Regulation to protect water sources varies, and in some countries booming industrialisation is the cause of significant pollution. For example, China faces serious problems with water pollution due to its expanding manufacturing industries, including a range of persistent pollutants entering river systems from industrial textile plants and lead and cadmium contamination from the production of materials for mobile phones.
Fresh water pollution poses a substantial risk to human and ecosystem health, and exacerbates the problem of water scarcity in some countries.