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The lake became polluted because a farmer used a lot of fertiliser on his crops - Edexcel - GCSE Biology - Question 6 - 2014 - Paper 1
Question 6
The lake became polluted because a farmer used a lot of fertiliser on his crops. Complete the sentence by putting a cross (X) in the box next to your answer. The p... show full transcript
Worked Solution & Example Answer:The lake became polluted because a farmer used a lot of fertiliser on his crops - Edexcel - GCSE Biology - Question 6 - 2014 - Paper 1
Step 1
The process by which the lake has become polluted is called:
Answer
Eutrophication (A) is the correct answer. This process occurs when excess nutrients, particularly nitrogen and phosphorus from fertilisers, enter the water. These nutrients promote algal blooms which can deplete oxygen levels in the water, leading to fish death.
Step 2
Explain why the overuse of fertiliser by the farmer caused the fish in the lake to die.
Answer
The overuse of fertiliser results in nutrient runoff into the lake, leading to excessive growth of algae, known as algal blooms. When these algae die, they decompose, a process that consumes dissolved oxygen in the water. As oxygen levels drop, fish and other aquatic organisms may suffocate, leading to their death. Moreover, some algae can produce toxins that are harmful to fish and other wildlife, further exacerbating the situation.