Consider the following statements regarding dissolved oxygen (DO) in
brackish water ecosystems:
1. It is generally well oxygenated in shallow brackishwater lakes.
2. It is highest during the night and lowest during the day in brackishwater
ecosystems.
3. It is depleted due to excess bacteria load, industrial effluents, and
turbidity in brackishwater ecosystems.

Which of the above statements is/are correct?
(a) 1 only
(b) 1 and 3 only
(c ) 2 and 3 only
(d) 1 , 2 and 3

Question

Consider the following statements regarding dissolved oxygen (DO) in
brackish water ecosystems:
1. It is generally well oxygenated in shallow brackishwater lakes.
2. It is highest during the night and lowest during the day in brackishwater
ecosystems.
3. It is depleted due to excess bacteria load, industrial effluents, and
turbidity in brackishwater ecosystems.

Which of the above statements is/are correct?
(a) 1 only
(b) 1 and 3 only
(c ) 2 and 3 only
(d) 1 , 2 and 3

ONLiNE UPSC · Accepted Answer

Statement 1 is correct: Shallow brackishwater lakes typically have good oxygenation because the water is well-mixed, allowing more oxygen to diffuse throughout the water column.

Statement 2 is not correct: Oxygen is generally highest during the day due to photosynthesis and lowest at night, when photosynthesis stops but respiration continues.

Statement 3 is correct: The depletion of dissolved oxygen (DO) in brackishwater ecosystems is mainly caused by excess bacteria load, industrial effluents, and turbidity. High organic material from bacteria and pollutants increases oxygen consumption during decomposition. Industrial effluents further promote bacterial activity, which depletes oxygen. Additionally, turbidity reduces light penetration, limiting photosynthesis and further decreasing oxygen production.

Aquatic Ecosystems

Dissolved Oxygen in Brackish Water Ecosystems

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M Question 1	⏱ 0
Consider the following statements regarding dissolved oxygen (DO) in brackish water ecosystems: 1. It is generally well oxygenated in shallow brackishwater lakes. 2. It is highest during the night and lowest during the day in brackishwater ecosystems. 3. It is depleted due to excess bacteria load, industrial effluents, and turbidity in brackishwater ecosystems. Which of the above statements is/are correct? (a) 1 only (b) 1 and 3 only (c ) 2 and 3 only (d) 1 , 2 and 3