The situation described is a classic example of eutrophication, a process driven by the enrichment of water by nutrient salts that causes structural changes to the ecosystem such as increased production of algae and aquatic plants.

Here's a step-by-step analysis:

1. The farmers in the village started using fertilisers in their fields. These fertilisers are rich in nutrients like nitrogen and phosphorus.

2. When these nutrients are added to the soil, they don't stay there. Rain or irrigation water can cause these nutrients to leach out of the soil and run off into nearby water bodies, in this case, the lake.

3. The sudden influx of nutrients into the lake causes an excessive growth of plants and algae, a phenomenon known as an algal bloom. This is why the lake is covered with green floating plants.

4. The rapid growth of these plants and algae leads to a competition for light and space. The plants at the surface block the sunlight from reaching the plants and algae below.

5. As a result, the plants and algae below the surface die off because they can't photosynthesise without sunlight. When these organisms die, they start to decompose.

6. The process of decomposition uses up oxygen in the water. This leads to a significant decrease in the oxygen levels in the lake.

7. Fish and other aquatic organisms need oxygen to live. With the decrease in oxygen levels, these organisms start to die off in large numbers.

8. This process continues, leading to a dead zone in the lake where no life can survive due to lack of oxygen.

So, the excessive growth of plants is caused by the nutrient-rich runoff from the fields, and the death of the fish is caused by the decrease in oxygen levels due to decomposition of dead plants and algae.

Question

The situation described is a classic example of eutrophication, a process driven by the enrichment of water by nutrient salts that causes structural changes to the ecosystem such as increased production of algae and aquatic plants.

Here's a step-by-step analysis:

1. The farmers in the village started using fertilisers in their fields. These fertilisers are rich in nutrients like nitrogen and phosphorus.

2. When these nutrients are added to the soil, they don't stay there. Rain or irrigation water can cause these nutrients to leach out of the soil and run off into nearby water bodies, in this case, the lake.

3. The sudden influx of nutrients into the lake causes an excessive growth of plants and algae, a phenomenon known as an algal bloom. This is why the lake is covered with green floating plants.

4. The rapid growth of these plants and algae leads to a competition for light and space. The plants at the surface block the sunlight from reaching the plants and algae below.

5. As a result, the plants and algae below the surface die off because they can't photosynthesise without sunlight. When these organisms die, they start to decompose.

6. The process of decomposition uses up oxygen in the water. This leads to a significant decrease in the oxygen levels in the lake.

7. Fish and other aquatic organisms need oxygen to live. With the decrease in oxygen levels, these organisms start to die off in large numbers.

8. This process continues, leading to a dead zone in the lake where no life can survive due to lack of oxygen.

So, the excessive growth of plants is caused by the nutrient-rich runoff from the fields, and the death of the fish is caused by the decrease in oxygen levels due to decomposition of dead plants and algae.

Knowee AI · Accepted Answer