Eutrophication sequence?
Reveal answer
Fertiliser → algal bloom → light blocked → plants die → bacteria decompose → O₂ falls → fish die.
Key words: algal bloom · bacteria
5(d) HUMAN INFLUENCES ON THE ENVIRONMENT · RECALL
5.17 Eutrophication
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Which minerals cause eutrophication?
Reveal answer
Nitrates and phosphates.
Key words: nitrates · phosphates
Why do plants die under an algal bloom?
Reveal answer
Algae block light → no photosynthesis.
Key words: light
What uses the oxygen in eutrophication?
Reveal answer
Respiring bacteria.
Key words: bacteria
How can farmers reduce eutrophication?
Reveal answer
Right timing + right amount + buffer strips.
Key words: buffer
What is an algal bloom?
Reveal answer
Rapid growth of algae.
Key words: rapid
Why does O₂ stay high while algae grow?
Reveal answer
Algae photosynthesise → release O₂.
Key words: photosynthesise
Source of phosphates besides fertiliser?
Reveal answer
Detergents / sewage.
Key words: detergents
What is meant by the term eutrophication?
Reveal answer
Enrichment of water with mineral ions, leading to excessive plant and algal growth and oxygen depletion.
Key words: eutrophication
What is meant by the term leaching?
Reveal answer
Washing of soluble ions through soil by water.
Key words: leaching
What is meant by the term algal bloom?
Reveal answer
A rapid increase in algae in a body of water.
Key words: algal bloom
Sewage pollution and eutrophication: for Main input, give the sewage pollution and the eutrophication from fertiliser.
Reveal answer
Sewage pollution: Organic matter (and pathogens). Eutrophication from fertiliser: Mineral ions such as nitrate and phosphate.
Key words: Main input
Sewage pollution and eutrophication: for First change, give the sewage pollution and the eutrophication from fertiliser.
Reveal answer
Sewage pollution: Bacteria feed directly on the organic matter. Eutrophication from fertiliser: Algal bloom blocks light.
Key words: First change
Sewage pollution and eutrophication: for Cause of oxygen fall, give the sewage pollution and the eutrophication from fertiliser.
Reveal answer
Sewage pollution: Bacterial respiration. Eutrophication from fertiliser: Bacterial respiration decomposing dead plants and algae.
Key words: Cause of oxygen fall
Sewage pollution and eutrophication: for Health risk, give the sewage pollution and the eutrophication from fertiliser.
Reveal answer
Sewage pollution: Pathogens in drinking water. Eutrophication from fertiliser: Some algal blooms release toxins.
Key words: Health risk
True or false, and why? “The algae use up the oxygen.”
Reveal answer
False. Algae photosynthesise; the major oxygen fall is caused by decomposer bacteria respiring.
True or false, and why? “Fertiliser poisons the fish.”
Reveal answer
False. Fish die because dissolved oxygen falls.
True or false, and why? “Eutrophication happens instantly.”
Reveal answer
False. It is a sequence of events over days or weeks.