Question

What are the primary ways dissolved oxygen is lost from an aquatic ecosystem?

1. Through respiration by aquatic organisms.
2. Through the air-water interface.
3. Through photosynthesis by aquatic plants.
4. Through absorption by the substrate at the bottom of the water body.

• A. i, ii
• B. All
• C. ii only
• D. ii, iii

Answer 1

Answer:

A. i, ii

• Oxygen in the terrestrial ecosystems occurs in the atmosphere along with other gases in a certain fixed concentration.

• In aquatic ecosystems it is dissolved in water, where its concentration varies constantly depending on factors that influence the input and output of oxygen in water.

• Dissolved oxygen escapes the water body through air-water interface and through respiration of organisms (fish, decomposers, zooplanktons, etc).

• When the dissolved oxygen level falls below 3-5 ppm, many aquatic organisms will die.