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Human influences on the environment

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Question 44

The graphs show changes in the concentration of nitrate and Secchi depth measurements in a reservoir over a 20-year period from 2000 to 2020.

Two line graphs side-by-side. The left graph is titled 'Nitrate concentration over time'. The x-axis is labeled 'Year' with intervals from 2000 to 2020 in steps of 5 years (2000, 2005, 2010, 2015, 2020). The y-axis is labeled 'Nitrate concentration in mg/L' ranging from 0 to 15. The plotted line shows a steady linear increase: 2.0 mg/L in 2000, 4.5 mg/L in 2005, 7.0 mg/L in 2010, 9.5 mg/L in 2015, and 12.0 mg/L in 2020. The right graph is titled 'Secchi depth over time'. The x-axis is labeled 'Year' with the same scale from 2000 to 2020. The y-axis is labeled 'Secchi depth in metres' ranging from 0 to 10. The plotted line shows a curve that decreases rapidly and then levels off: 8.0 m in 2000, 5.5 m in 2005, 2.5 m in 2010, 1.2 m in 2015, and 1.1 m in 2020.

a.

Describe the relationship between nitrate levels and Secchi depth over this 20-year period.

[3]
b.

Over this 20-year period, the population of trout (a species of fish) in the reservoir decreased significantly. Explain how the changes in nitrate levels could cause this decrease in trout population.

[5]

Human influences on the environment Questions

  1. IGCSE
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  3. /Human influences on the environment