Which of the following activities is most directly related to the dead zones in the Gulf of
Mexico just west of the Mississippi River?
farming in the Midwest
Which of the following farming practices were recommended to mitigate the dead zone in the
Gulf of Mexico just west of the Mississippi River?
increased use of no-till farming (nitrogen retention) and decreased fertilizer use
Adding fertilizer to most aquatic systems results in
increased growth of phytoplankton and hypoxic conditions.
Noticing large amounts of algal growth in her small farm pond, a farmer adds about 20 grass
carp to feed on the abundant algae and plants. After several years, the carp grow large, exceeding
20 pounds each in size. Late one summer, the farmer notices that the carp and most of the other
fish are dead. The water also smells very bad. Which one of the following is the most likely
explanation for the death of these fish?
bacteria feeding on the large volume of carp feces depleted the oxygen
In the regions of the dead zone in the Gulf of Mexico just west of the Mississippi River delta,
oxygen levels are
highest at the bottom of the ocean, where the algae do not get enough sunlight to survive.
About one hundred years ago, cities began to address the problems of sewage disposal by
dumping sewage into nearby rivers via storm water drainage systems. One of the results of this
strategy was that
people living downriver of these cities were more likely to experience contamination of their
drinking water sources.
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