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The UN Environment Programme reported 146 dead zones in 2004 in the world's oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometer (0.4 mi 2), but the largest dead zone covered 70,000 square kilometers (27,000 mi 2). A 2008 study counted 405 dead zones worldwide. [4] [2]
Eutrophication is a common phenomenon in coastal waters, where nitrogenous sources are the main culprit. [21] In coastal waters, nitrogen is commonly the key limiting nutrient of marine waters (unlike the freshwater systems where phosphorus is often the limiting nutrient).
This is the most common type of estuary in temperate climates. Well-studied estuaries include the Severn Estuary in the United Kingdom and the Ems Dollard along the Dutch-German border. The width-to-depth ratio of these estuaries is typically large, appearing wedge-shaped (in cross-section) in the inner part and broadening and deepening seaward.
More than 99 percent of all species, amounting to over five billion species, [7] that ever lived on Earth are estimated to be extinct. [8] [9] Estimates on the number of Earth's current species range from 10 million to 14 million, [10] of which about 1.2 million have been documented and over 86 percent have not yet been described. [11]
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients.It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. [1]
LME-based conservation is based on recognition that the world's coastal ocean waters are degraded by unsustainable fishing practices, habitat degradation, eutrophication, toxic pollution, aerosol contamination, and emerging diseases, and that positive actions to mitigate these threats require coordinated actions by governments and civil society ...
The off shore areas may be called the pelagic zone, the photic zone may be called the limnetic zone and the aphotic zone may be called the profundal zone. Inland from the littoral zone, one can also frequently identify a riparian zone which has plants still affected by the presence of the lake—this can include effects from windfalls, spring ...
Eutrophication of a lake can lead to algal blooms. Dystrophic lakes have high levels of humic matter and typically have yellow-brown, tea-coloured waters. [ 2 ] These categories do not have rigid specifications; the classification system can be seen as more of a spectrum encompassing the various levels of aquatic productivity.