Concept:The diagram shows nutrient enrichment of a water body causing excessive plant growth and oxygen loss, which is called eutrophication.
Explanation:Nitrates such as
NO3− enter the water from fertilisers or sewage.
These dissolved nutrients cause algae and aquatic plants to grow very quickly.
The thick algal layer covers the surface and blocks sunlight from reaching deeper water.
When the algae die, bacteria decompose them and use up much of the dissolved oxygen.
This drop in oxygen harms fish and other aquatic organisms.
This sequence of nutrient over-enrichment, algal bloom, and oxygen depletion is termed eutrophication.
It is not denitrification because denitrification converts nitrates into nitrogen gas.
It is not conservation, which is the protection of natural resources.
It is not global warming, which is the rise in Earth’s average temperature.
Answer:The phenomenon in the diagram is termed
C. eutrophication.
