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All 10 Flashcards — Eutrophication
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Question
Define eutrophication.
Answer
Eutrophication is the process where excess nutrients (especially nitrogen and phosphorus) cause rapid algal growth, leading to oxygen depletion and ecosystem damage.
💡 Hint
Nutrients → algae → low oxygen.
Question
Eutrophication in one chain (cause → effect).
Answer
Excess nutrients → algal bloom → light blocked → plant death → decomposition → oxygen depletion (hypoxia) → fish kills/dead zone.
💡 Hint
Learn the chain.
Question
Name the two key nutrients most linked to eutrophication.
Answer
Nitrogen (often nitrates) and phosphorus (often phosphates).
💡 Hint
N and P.
Question
What are the main nutrients responsible for eutrophication?
Answer
Nitrogen and phosphorus.
💡 Hint
N and P.
Question
Eutrophication sequence: after an algal bloom, why does oxygen decrease?
Answer
When algae and plants die, decomposers break them down and use up dissolved oxygen during respiration, causing hypoxia.
💡 Hint
Decomposition consumes oxygen.
Question
Name two well-known locations that experience dead zones from eutrophication.
Answer
Examples include the Gulf of Mexico and the Baltic Sea (also Lake Erie and Chesapeake Bay).
💡 Hint
Gulf + Baltic.
Question
Why can eutrophication reduce aquatic food production?
Answer
Hypoxia and dead zones reduce fish and shellfish survival, forcing fish to migrate or die, lowering catches and damaging fisheries.
💡 Hint
Dead zones reduce fisheries.
Question
What is a “dead zone”?
Answer
A dead zone is an area of water with oxygen levels too low to support most aquatic life, often caused by eutrophication.
💡 Hint
Very low dissolved oxygen.
Question
Give three common sources of nutrient pollution.
Answer
Agricultural fertilizers, sewage/wastewater, and animal waste (also urban runoff and atmospheric deposition).
💡 Hint
Farms + sewage + manure.
Question
Exam tip: what do examiners want most in eutrophication questions?
Answer
A clear cause-and-effect sequence linked to the question context (for example fisheries, ecosystem services, or biodiversity).
💡 Hint
Sequence + context.
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Topic 4.4 hub
Water pollution
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