In much of the open ocean, NPP is limited by nitrogen.But in the Gulf of Mexico, especially near the mouth of the Mississippi River, dead zones (regions of low or no oxygen, resulting in the death of marine organisms) form every summer.These dead zones result from
A) eutrophication caused by nitrogen fertilizer runoff from farms upstream.
B) very low nitrogen levels leading to inability of plants to reproduce.
C) an unknown combination of excess nutrients poisoning the system.
D) a lack of required nutrients, with the type of nutrient varying from year to year.
E) fertilizer production in the area producing smog, which limits photosynthesis.

Question

Quizplus · Accepted Answer

Dead zones in the Gulf of Mexico are caused by eutrophication, which is the excess accumulation of nutrients (mainly nitrogen and phosphorus) in the water. This excess nutrient supply comes from runoff of nitrogen-rich fertilizers used in agriculture and discharged from wastewater treatment plants. This leads to the excessive growth of algae and other planktonic organisms that consume oxygen during decomposition by bacteria, creating hypoxic (low-oxygen) conditions that can result in the death of marine organisms.

In Much of the Open Ocean, NPP Is Limited by Nitrogen.But