The Dead Zone by Archer and Sahl

Part II – What Affects the Dissolved Oxygen Content of Water?

“Hey guys, look at these maps of the Dead Zone I got from Professor Gracia,” said Sue, walking up to her friends sitting at the lunch table in the student cafeteria. “What I don’t get is why this particular area should have such low dissolved oxygen concentrations.”

Sue handed the maps to her friend Paula, a physics major. Paula stopped eating her sandwich long enough to give them a look.

“There must be some physical cause,” Paula said. “I can’t imagine anything else that could affect the dissolved oxygen content of water so dramatically.”

“Oh, come on,” said Sue’s friend Zack. “Living organisms should have a huge impact—aren’t all the fish busy consuming oxygen in the water?”

“Well, of course you would think of that, you’re a biology major,” said Sue. “But let’s be systematic. What are all the physical and biological influences we can think of that could affect how much oxygen is dissolved in the water?”

Questions

1. What physical forces or conditions affect the dissolved oxygen content of water?

2. What are the biological processes that can affect dissolved oxygen concentration?

3. What might cause each identified condition to fluctuate over the seasons?

4. If you had to choose, which of the conditions you’ve identified seem most likely to be the primary cause of hypoxia in the Gulf? Why?

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