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Jack mackerel caught by a Chilean purse seiner Fishing down the food web. Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the species becoming increasingly underpopulated in that area.
Topsoil runoff from farm, central Iowa (2011). Water pollution in the United States is a growing problem that became critical in the 19th century with the development of mechanized agriculture, mining, and manufacturing industries—although laws and regulations introduced in the late 20th century have improved water quality in many water bodies. [1]
Cyanobacteria (blue-green algae) bloom on Lake Erie (United States) in 2009. These kinds of algae can cause harmful algal bloom. A harmful algal bloom (HAB), or excessive algae growth, sometimes called a red tide in marine environments, is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, water deoxygenation, mechanical damage to ...
Eutrophication can be a natural process and occurs naturally through the gradual accumulation of sediment and nutrients. Naturally, eutrophication is usually caused by the natural accumulation of nutrients from dissolved phosphate minerals and dead plant matter in water. [29] [30] Natural eutrophication has been well-characterized in lakes.
The term fish kill, known also as fish die-off, refers to a localized mass die-off of fish populations which may also be associated with more generalized mortality of aquatic life. [ 1 ] [ 2 ] The most common cause is reduced oxygen in the water, which in turn may be due to factors such as drought , harmful algal bloom , overpopulation , or a ...
A practical definition of water pollution is: "Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses." [1]: 6 Water is typically referred to as polluted when it is impaired by anthropogenic contaminants.
Water pollution in the United States is a growing problem that became critical in the 19th century with the development of mechanized agriculture, mining, and manufacturing industries—although laws and regulations introduced in the late 20th century have improved water quality in many water bodies. [80]
The transfer of parasites from open-net cage salmon farming, especially sea lice, has reduced numbers of wild salmon. The European Commission (2002) concluded, "The reduction of wild salmonid abundance is also linked to other factors but there is more and more scientific evidence establishing a direct link between the number of lice-infested wild fish and the presence of cages in the same ...