Question

90. Which of the below statements best describes a “winterkill”?

• A. a) Death of polar bears due to lack of food resources
  
• B. b) Loss of fish in winter because of lack of oxygen
  
• C. c) Excessively low temperature in the Polar Regions
  Leading to loss of life
  
• D. d) None of the above

Answer 1

The correct option is B b) Loss of fish in winter because of lack of oxygen


B)

Explanation:

Winterkill is a term used to describe the loss of fish in winter because of lack of oxygen in a water body.

Submerged vegetation and algae create oxygen through the process of photosynthesis. During the winter, oxygen production is often reduced because ice and snow on the lake limit the amount of sunlight reaching vegetation. In small, shallow lakes the available oxygen can quickly be used up by live plants that consume oxygen in the evening, fish, and by bacteria that feed on dead and decaying vegetation.

When the oxygen level declines, less tolerant fish species, and fish in poor condition overall, can begin to suffocate.