It's the time of year when dead zones are prominent all over the northern hemisphere. Their causes are varied: massive runoff of fertilizer from agricultural fields and other lands; extreme rainfall that flushes more pollutants than normal; extreme drought that reduces inflows, concentrating harmful substances in certain water bodies; ocean current shifts suspected to be linked to global climate change; and combinations of these.
Whatever the cause, the result is large swaths of oceans or lakes that are sharply depleted in or completely devoid of oxygen, ruining their normal ability to support much life. The death traps can last for weeks or months, and can result in major biological changes that may endure for years.
The number of documented dead zones around the world is climbing quickly, rising from about 150 sites three years ago to about 250 anticipated by the end of this year. They are occurring off extensive stretches of the US Atlantic, Gulf, and Pacific coasts, and in the Caribbean, Central and South America, Europe, the Middle East, Africa, India, China, Japan, Korea, Australia, and New Zealand. Often they occur near the mouths of major rivers. For a map and more information, contact Robert Diaz  of the Virginia Institute of Marine Science, 804-684-7364.
Some starting points for background on, and people who can talk about, a few of the more prominent US dead zones include:
- NOAA: press release, July 17, 2007, "NOAA and Louisiana scientists say Gulf of Mexico 'dead zone' could be largest since measurements began in 1985." 
- Associated Press: July 29, 2007, "'Dead zone' in Gulf of Mexico Among Top 3 Ever Mapped." 
- Houston Chronicle: Aug. 1, 2007, by Eric Berger, "Summer Deluge Gives Rise to Texas 'Dead Zone' In Gulf." 
- Chesapeake Bay Program: July 2007 forecast;  frequently-sampled data on oxygen content. 
- Chesapeake Bay Foundation: John Surrick,  443-482-2045; July 26, 2005, "July Survey Finds More Than 1/3 Of Bay Is A 'Dead Zone'." 
- Associated Press: July 30, 2007, "'Dead Zone' Returns To Oregon Coast." 
- NASA: July 27, 2006, "Marine 'Dead Zone' Off Oregon Is Spreading." 
- Associated Press: Oct. 30, 2006, by Jeff Barnard, "Ocean Dead Zone Off Oregon Dissipating." 
- EPA: Lake Erie 'Dead Zone'  and The Great Lakes: An Environmental Atlas and Resource Book, Chapter Four, The Great Lakes Today Concerns. 
- NASA: Science Focus on Creeping Dead Zones. 
- For much more information, see the TipSheet of Aug. 2, 2006.