Hypoxic Areas Such as in the Gulf of Mexico Develop

Hypoxic areas such as in the Gulf of Mexico develop when

A) oxygen levels fall below 5ppm.
B) large amounts of nitrate are added into the water.
C) die-off from a large phytoplankton bloom uses up the oxygen in water.
D) methyl-mercury is added to water.
E) oxygen levels fall below 5ppm, large amounts of nitrate are added into the water, and die-off from a large phytoplankton bloom uses up the oxygen in water.