De-oxygenated zones are areas where algal blooms, triggered by nutrients from sources including fertilizer run off, sewage, animal wastes and atmospheric deposition from the burning of fossil fuels, can remove oxygen from the water.
The low levels of oxygen in the water make it difficult for fish, oysters and other marine creatures to survive as well as important habitats such as sea grass beds.
Experts claim that the number and size of deoxygenated areas is on the rise with the total number detected rising every decade since the 1970s. They are warning that these areas are fast becoming major threats to fish stocks and thus to the people who depend upon fisheries for food and livelihoods.
Some dead zones are fleeting whereas others can persist for large sections of the year.
In 2004, UNEP reported in its Global Environment Outlook Year Book, an estimated 149 sites known to have experienced or be suffering 'dead zones'.
Some of the earliest recorded dead zones were in places like Chesapeake Bay in the United States, the Baltic Sea, the Kattegat, the Black Sea and the northern Adriatic Sea. Others have been reported in Scandinavian fjords.
The most well known area of depleted oxygen is in the Gulf of Mexico. Its occurrence is directly linked to nutrients or fertilizers brought to the Gulf by the Mississippi River.
Others have been appearing off South America, China, Japan, south east Australia and New Zealand. Research by a team led by Professor Robert Diaz at the College of William and Mary, Virginia Institute of Marine Science in Gloucester Point, Virginia, whose work contributed to the GEO Year Book, now estimate that the number has climbed to 200 sites.
Professor Diaz told UNEP in advance of the Global Programme Action Global (GPA) for the Protection of the Marine Environment from Land-Based Sources (GPA) meeting in Beijing that the full list of new or newly-registered sites would be available in early 2007.
But he said among them were ones in the Archipelago Sea, Finland; the Fosu Lagoon, Ghana; the Pearl River Estuary and the Changjiang River, China; the Mersey Estuary, United Kingdom; the Elefsis Bay, Aegean Sea, Greece; Paracas Bay, Peru; Mondego River, Portugal; Montevideo Bay, Uruguay and the Western Indian Shelf. Nitrogen exports to the marine environment from rivers are expected to rise globally by 14 percent by 2030 when compared with the mid 1990s, says the report.
Something should be done with this problem of ours. The concern is not only a domestic one but it concerns all of us. It's a global issue. Its even so disheartening to note that here in our country, it is not given due importance by the government agencies concerned. All they do is lip service, all propaganda and no actions at all. Take Mactan Channel for instance. Time is running out and action should be done to save it. In our own little ways let us help and do our share in helping mother nature. This is our only home.
Jesson J. Morata
Blk. 6 San Miguel Pusok
Lapu-Lapu City