Stories tagged dead zone
A massive algae bloom is choking China’s Yellow Sea and threatening some Olympic events. Many Chinese cities dump untreated sewage into the Sea. Rich in nutrients, the sewage makes the algae grow like crazy. The problem goes beyond the inconvenience to boaters. The growing algae changes the near-shore habitat. And when all this algae dies, the bacteria that decays it sucks oxygen out of the water, killing fish and creating a dead zone.
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The deadly cycle: Farming > River > Dead Zone > SHARKS!Did you know that the food we grow up here in the Midwest might cause shark attacks down in the Gulf of Mexico? Okay, I might be getting a little sensational but here is my train of thought.
- We do a ton of farming up here in the central states. This requires lots of fertilizer which in many cases eventually runs into the Mississippi River.
- The nutrients in this fertilizer flow down to the Gulf of Mexico where they cause a huge area of low oxygen in the water causing fish who can't swim long distances to die.
- Other fish that can migrate, like sharks, get the heck outta dodge and end up swimming around in larger numbers in beach areas where people swim.
It gets worse. Just today, the BBC is reporting that scientists think that this year's dead zone could grow to 8,500 sq miles, the biggest ever!
I wonder what the "tipping point" is for this issue? I'm not seriously too worried about the shark attacks. But the environmental impacts of the dead zone are huge. How bad will this have to get before people start talking about the issue of fertilizer run-off around the water cooler? Then again, maybe we can get some positive public action during the upcoming shark week, but I am guessing agricultural practices won't exactly be their focus...alas.
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Dead Zone - Great resource on the science behind the Dead Zone from none other than...us, the Science Museum of Minnesota.
Scientists are studying a 70-mile "dead zone" off the coast of Oregon.
First noticed in 2002, the dead zone is larger this year than in previous years.
What is a dead zone? It's an large area of water that's very low in oxygen and can't support life. (Scientists call this "hypoxia.") Dead zones are caused by the explosive growth of tiny aquatic plants called phytoplankton. When the phytoplankton die, they are decomposed by bacteria. Massive numbers of bacteria use up the oxygen in the water. Any animals that can swim out of the low-oxygen water--like many fish--do so. Others--some fish, many crabs, and others--suffocate because they can't get enough oxygen to live.
Dead crabs: Dead Dungeness crabs on beach, Oregon Coast (Photo by Jane Lubchenco)
In this case, the phytoplankton blooms are caused when north winds cause upwelling in the water column. The cooler water is rich in nutrients, providing a feast for the phytoplankton. When the wind dies down, the upwelling stops, and many phytoplankton die a natural death. Their decomposition results in water that is deadly because it lacks oxygen needed for life.
This year, the upwelling started in April, stopped in May, and started up again in June. The off-and-on upwelling creates a thick mat of organic material that rots and uses up the oxygen in the water. Then, when a new upwelling occurs, the oxygen-depleted water moves toward shore, killing the plants and animals that can't get out of its way.
Measuring oxygen levels: Chris Holmes (left) and Dr. Francis Chan (right), PISCO researchers measuring oxygen levels off the Oregon coast from the OSU research vessel Elakha (Photo by Jane Lubchenco)
So, why the upwelling? Jane Lubchenco, professor of marine ecology at Oregon State University and a member of the Pew Oceans Commission, told the Associated Press:
"We are seeing wild swings from year to year in the timing and duration of the winds that are favorable for upwelling. ... This increased variability in the winds is consistent with what we would expect under climate change."
Global warming is also the suspect in dead zones off Namibia, South Africa, and Peru.
(The dead zone in the Gulf of Mexico at the mouth of the Mississippi River is caused by agricultural runoff containing fertilizers. The river carries all those nutrients into the Gulf, creating algal blooms that use up all the oxygen.)
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