Question

Thorough mixing of oxygen and nutrients within a lake occurs in

a. winter and summer.
b. winter and spring.
c. spring and summer.
d. spring and autumn.
e. summer and autumn.​

Answer 1

The thorough mixing of oxygen and nutrients within a lake occurs in spring and autumn (d). During these seasons, the temperature and light conditions in the lake are optimal for mixing. In spring, as the ice melts and water warms up, the water column becomes more uniform, allowing for better mixing. In autumn, as the water cools down, it becomes denser, which promotes vertical mixing and circulation. This mixing is important for distributing oxygen and nutrients throughout the lake, supporting the growth of organisms and maintaining a healthy ecosystem.

Step-by-step explanation:

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Answer 2

d. spring and autumn

Step-by-step explanation:

In temperate regions, lakes undergo a process called turnover, where the upper and lower layers of the lake mix together. This happens in the spring and autumn, when the surface water cools and becomes denser than the deeper water.

The cooler, denser water sinks, and the warmer, less dense water rises, mixing the two layers together. This mixing brings oxygen and nutrients from the surface to the deeper layers, and vice versa.

• In the winter, the surface water of a lake freezes, preventing the mixing of oxygen and nutrients.
• In the summer, the surface water warms up and becomes less dense than the deeper water, so the two layers do not mix.

So the answer is d. spring and autumn.