Summary
Oxygen-depleted ocean areas caused by nutrient runoff, fertiliser and decomposition of algal blooms.
In depth
Over 400 coastal hypoxic zones exist. The Gulf of Mexico zone reaches the size of a US state in summer. Cause: fertiliser from the Mississippi basin. Reducing nutrient loads is the only cure.
Hypoxic waters (below 2 mg/L oxygen) force mobile animals to flee and kill sessile ones. Stratification prevents re-oxygenation. Dead zones are expanding with warming.
Example: nutrient reduction in the Black Sea led to partial recovery.
Frequently asked questions
What is Dead Zones?
Oxygen-depleted ocean areas caused by nutrient runoff, fertiliser and decomposition of algal blooms.
Which area of biology covers Dead Zones, and how advanced is it?
Dead Zones is one of the 54 topics in Marine & Environmental Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Harmful Algal Blooms, Remote Sensing in Ecology, Marine Protected Areas.
Can you give an example of Dead Zones?
The Baltic Sea has large dead zones.
What should I learn before Dead Zones?
Work through the Beginner topics in Marine & Environmental Biology first, such as Oceans, Ocean Zones, Plankton, then return to Dead Zones. Advanced topics assume the Intermediate vocabulary.
What topics are related to Dead Zones?
The closest topics to Dead Zones are Harmful Algal Blooms, Remote Sensing in Ecology, Marine Protected Areas, Ecosystem Tipping Points. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Dead Zones?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Dead Zones. To practise the whole of Marine & Environmental Biology, use the Marine & Environmental Biology quiz.
How is Dead Zones different from Harmful Algal Blooms?
Dead Zones: Oxygen-depleted ocean areas caused by nutrient runoff, fertiliser and decomposition of algal blooms. Harmful Algal Blooms: Toxin-producing algae multiply in nutrient-rich water, poisoning shellfish and marine life. Read both side by side and note what each one explains.
How should I study Dead Zones step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Harmful Algal Blooms and explain the difference aloud. Finally, take the Marine & Environmental Biology quiz and come back to this page for any question you miss.