So-Called "Dead Zones" in Coastal Oceans Are Associated with Nutrient

So-called "dead zones" in coastal oceans are associated with nutrient runoff and oxygen-depleted bottom waters. What causes the oxygen depletion?

A) Nutrient runoff causes population growth of cyanobacteria and algae, which consume oxygen via aerobic respiration.
B) Nutrient runoff causes population growth of cyanobacteria and algae which, in turn, support the growth of fish populations. Fish consume oxygen via aerobic respiration.
C) Nutrient runoff causes population growth of algae, which consume oxygen via aerobic respiration.
D) Nutrient runoff causes algae and cyanobacteria populations to grow. When they die, they are consumed by heterotrophic bacteria that consume oxygen via aerobic respiration.
E) Nutrient runoff causes the waters to warm, which causes them to lose oxygen.