Question

Two lakes, A and B are identical in all aspects except that lake A has a higher temperature. Which of the following is true?
(A) A has a higher rate of oxygen dissolution
(B) B has a higher rate of oxygen dissolution
(C) Oxygen dissolution of both is the same
(D) Both have some BOD

Answer 1

Hint: The process of eutrophication, which happens when the environment becomes enriched with nutrients, increases the quantity of plant and algae development in estuaries and coastal waters, is what causes harmful algal blooms, dead zones, and fish kills. Higher temperature can be an indicator of higher nutrient enrichment in the lake thus the process of eutrophication must be taking place.

Step by step solution:

The main environmental repercussions of eutrophication include a rise in suspended particles brought on by widespread macroalgal blooms, a decrease in water clarity, and an increase in precipitation rates that led to the obliteration of benthic habitats by shading submerged vegetation.
Eutrophication can be divided into two categories based on its underlying cause: artificial eutrophication and natural eutrophication. Excess nutrients (mostly nitrates and phosphates) enhanced water runoff to water bodies and is the first of the four stages of eutrophication. An algal bloom is brought on by the rapid proliferation of algae. generation of poisons and dissolved oxygen depletion.
The natural process of eutrophication is brought on by the buildup of nutrients in lakes and other bodies of water. Human activity is the primary cause of anthropogenic eutrophication. Humans employ fertilizers to supply agricultural farms, golf courses, lawns, and other surfaces with nutrients. Rains wash these fertilizers away, and eventually, they end up in lakes and rivers and other bodies of water.
Nutrient enrichment will lead to more organic matter in the water body due to which metabolism is very fast inside the lake, metabolism requires higher oxygen demand and thus increases BOD of water, also metabolic processes releases heat as well. So if a lake had higher temperature that means it has undergone metabolism which clearly means it had higher oxygen demand.

So, option (B) is correct.
Note: To lessen eutrophication, one of two strategies might be used: Narrow down the source of the nutrients (e.g. by phosphate stripping at sewage treatment works).