← All questionsGS1 · 2018 · Geography ·Spread of Ocean Dead Zones
QUESTION 7
GS1
10 marks

What are the consequences of spreading of ‘Dead Zones’ on marine ecosystem?

WRITE IN
7 min
150 words
☆ Save✎ Write this answer

What the examiner wants

Explain how spreading low-oxygen 'dead zones' affect marine ecosystems.

ExplainMake clear how and why it happens: causes, process, and an example for each point.

Demand-wise check

  1. 1Cause: nutrient runoff (fertiliser, sewage) → algal blooms → decomposition uses oxygen (hypoxia); warming worsens it≈30 words
  2. 2Consequences: fish kills and migration, loss of biodiversity, collapse of fisheries, shift to jellyfish and microbes, greenhouse gas release (nitrous oxide)≈30 words
  3. 3Examples: Gulf of Mexico, Baltic Sea, Arabian Sea oxygen minimum zone≈30 words
  4. 4Effects on livelihoods; measures≈30 words

Open in about 20 words and close in about 20.

Answer plan

What dead zones areConsequencesExamplesMeasuresConclusion

Where marks usually go

  • Only causes, the question asks consequences
  • No named zone like Gulf of Mexico, Baltic Sea or Arabian Sea

Draw this

  • Flow: runoff → bloom → decay → hypoxia

Value addition

  • DataOver 400 coastal dead zones have been identified worldwide (Diaz and Rosenberg, 2008), and the number keeps rising.Science, 2008
  • ExampleThe Arabian Sea has one of the world's largest oxygen minimum zones, affecting Indian fisheries.NIO / scientific studies