Monday, June 23, 2008

Baltic Sea - Problem of marine dead zones

World Wildlife Fund has issued a warning that the spread of so-called "marine dead zones", where nothing can survive due to the lack of oxygen could cause the total collapse of Baltic Sea ecosystem. WWF also stated that since 1995 these marine dead zones dead zones around the world have been spreading at very fast rate, from 44 in 1995 to 169 today. Marine dead zones are mostly caused by an increase in chemical nutrients in the water, and chemical fertilizer is considered to be the prime cause of dead zones around the world. This process is called eutrophication.

This is how eutrophication works. Marine areas receive large quantities of nitrogen and phosphorus, mainly from agriculture. Nitrogen and phosphorus are rich nutrients that act as fertilizers, enhancing plant growth. This especially applies to algae that experience a significant population increase (so called algal bloom). Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water. When algae die and sink to the bottom bacteria that feed on the increasing mass of dead algae, sucks up all the available oxygen, creating anaerobic conditions.

Baltic Sea has serious problem with marine dead zones since seven of the world's 10 largest marine dead zones are located in the Baltic. WWF issued in its statement: "WWF demands quick and decisive action to reduce emissions, not least from agriculture around the Baltic Sea". The good news is that marine dead zones are reversible. For instance the Black Sea marine dead zone, that used to be the world's biggest marine dead zone in period from 1991 to 2001, largely disappeared after fertilizers became too expensive to use following the collapse of Soviet Union and the demise of centrally planned economies in Eastern and central Europe.

Marine dead zones are areas where the water at the sea floor has very low, or is completely without dissolved oxygen. Among the top 10 largest marine dead zones, seven is located in Baltic.

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