Read the passage and answer the following question.
In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their field in order to enhance the yield. Soon they discovered that, the water body was completely covered with green floating plants and fishes started dying in large numbers.
What is the cause for excessive growth of plants and death of fish in the lake?

Eutrophication

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Water pollution

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Water purification

No worries! We‘ve got your back. Try BYJU‘S free classes today!

None of the above

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is A Eutrophication
If fertilizers were added to their field in order to enhance the yield, it will seep into the nearby water body. This will enhance the growth of algae causing eutrophication.
Eutrophication is the ecosystem's response to the addition of artificial or natural substances, mainly phosphates, through detergents, fertilizers, or sewage, to an aquatic system.
One example is the "bloom" or a great increase of phytoplankton in a water body as a response to increased levels of nutrients. Negative environmental effects include hypoxia, the depletion of oxygen in the water, which may cause death to aquatic animals.

Suggest Corrections

Similar questions

Question 27
In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their field in order to enhance the yield. Soon they discovered that the waterbody was completely covered with green floating plants and fishes started dying in large numbers.
Analyze the situation and give reasons for excessive growth of plants and death of fish in the lake.

Q. In a village, farmers started cultivating crops all around a lake which was always filled with water. They added lot of materials W to the soil in their fields to increase the yield of crops. Soon they found that the whole surface of water in the lake was covered with a green layer made up of tiny organisms X. After some time, the fish present in the lake started dying in large numbers because they could not get sufficient Y due to a process Z which had occurred in lake water and drained out all the Y present in the water of lake.
(a) What do you think materials W are?
(b) Name (i) X, and (ii) Y.
(c) What is the process Z known as?
(d) What happens during the process Z which uses up all the Y present in lake water?
(e) What does this example tell us about the use of materials like W?

The farmers use large amounts of a substance P in the fields to increase the crop yield. The excess of P dissolves in water and runs into a lake. The substance P causes rapid growth of tiny green water plants Q in the lake which cover the whole lake like a green sheet. When the plants Q die, the organisms called R decompose them by utilizing S dissolved in lake water. The amount of dissolved S in water decreases too much due to which the fish living in lake suffocate and die. What are P, Q, R and S?

Fishes died within a few days in a lake near a village. Following are the possible reasons for this:

(a) Lot of urea and phosphate fertilisers used in crops in the vicinity

(b) Spraying agricultural fields with degradable pesticides

(d) Phytoplankton population declined in the lake

What are the two main causes of fish mortality in the lake?

Q. A lake near a village suffered heavy mortally of fishes within a few days. Consider the following reasons for this.

(A) Lots of urea and phosphate fertilizers were used in the crops in the vicinity.

(B) The area was sprayed with DDT by an aircraft.

(D) Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.

Which two of the above were the main causes of fish mortality in the lake?

Join BYJU'S Learning Program