Question

In many temperate lakes, thermal energy from sunlight causes changes in the temperature of surface waters. These changes initiate a turnover, a mixing of waters that occurs in spring and fall.

Determine the correct order of events involved in seasonal turnover.
Drag the labels onto the flowchart of seasonal turnover. Labels may be used once, more than once, or not at all.
a. surface water warms to 4 C and sinks
b. water mixes, bringing oxygen to the bottom and nutrients to the surface
c. warm surface water is separated from cooler bottom water by thermocline
d. surface water cools to 4 C and sinks
e. water mixes, bringing oxygen to the bottom and nutrients to the surface

Answer 1

In temperate lakes, the correct order of events in seasonal turnover is: surface water warms and sinks, water mixes bringing oxygen to the bottom and nutrients to the surface, surface water cools and sinks, water mixes again with oxygen and nutrients, and a thermocline separates warm surface water from the cooler bottom water.

Step-by-step explanation:

The correct order of events involved in seasonal turnover in temperate lakes is as follows:

1. Surface water warms to 4 C and sinks - In springtime, as air temperatures increase, the surface ice melts, and the temperature of the surface water begins to approach 4°C. This warmer water becomes heavier and sinks to the bottom.
2. Water mixes, bringing oxygen to the bottom and nutrients to the surface - As the warmer surface water sinks, it displaces the cooler bottom water, bringing nutrients and sediments from the lake bottom to the surface and oxygen to the bottom.
3. Surface water cools to 4 C and sinks - In the fall, as air temperatures drop, the temperature of the surface water cools to 4°C. This colder water becomes heavier and sinks to the bottom, causing a turnover.
4. Water mixes, bringing oxygen to the bottom and nutrients to the surface - Similar to the spring turnover, as the colder surface water sinks, it displaces the water at the bottom, bringing oxygen to the bottom and nutrients to the surface.
5. Warm surface water is separated from cooler bottom water by thermocline - Throughout the entire turnover process, there exists a layer called the thermocline, which separates the warm surface water from the cooler bottom water.