Why are the bottom waters of some lakes anoxic?
A)The respiration of sinking organic particles reduces oxygen in deep waters.
B)Physical stratification keeps bottom waters from mixing with oxygen-rich surface waters.
C)Runoff of fertilizers from agriculture can increase the amount of primary production and hence respiration in the lake.
D)All of these choices are correct.

Question

Quizplus · Accepted Answer

All of these choices are correct. The respiration of sinking organic particles reduces oxygen in deep waters, physical stratification keeps bottom waters from mixing with oxygen-rich surface waters, and runoff of fertilizers from agriculture can increase the amount of primary production and hence respiration in the lake. These factors combine to create an anoxic environment in the bottom waters of some lakes.

Why Are the Bottom Waters of Some Lakes Anoxic