Summary
Nutrient enrichment of water bodies causing algal blooms, oxygen depletion and fish kills.
In depth
Fertiliser runoff and sewage add nitrate and phosphate. Algal blooms block light, then die and are decomposed by bacteria using oxygen (high BOD), causing hypoxia and fish kills. Some blooms produce toxins.
Solutions: reduce fertiliser use, buffer strips, treat sewage and restore wetlands.
Natural eutrophication occurs slowly; cultural eutrophication is rapid and caused by humans. Effects cascade to oxygen loss, fish death and drinking water issues.
Example: phosphate bans in detergents reduced algal blooms.
Phosphorus is generally limiting in freshwater and nitrogen in marine water. Cultural eutrophication from human activity includes sewage, farm run-off and detergents (now phosphate-limited). Cyanobacterial blooms can produce toxins (microcystin) that harm livestock and drinking water. Dead zones, such as the one in the Gulf of Mexico, extend to over 15,000 square kilometres each summer from Mississippi River nutrients.
Control involves reducing sources: sewage treatment, buffer strips along streams, wetland restoration, and careful fertiliser use. In lakes, biomanipulation by stocking predatory fish can increase grazing zooplankton. Recovery can be slow because nutrients stored in sediments are released again.
Remember: oxygen depletion is caused by decomposition of dead algae, not by algae using oxygen in photosynthesis.
Frequently asked questions
What is Eutrophication?
Nutrient enrichment of water bodies causing algal blooms, oxygen depletion and fish kills.
Which area of biology covers Eutrophication, and how advanced is it?
Eutrophication is one of the 54 topics in Ecology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Trophic Cascade, Primary Productivity, Decomposers.
Can you give an example of Eutrophication?
Lake Erie blooms and the Gulf of Mexico dead zone.
What should I learn before Eutrophication?
Work through the Beginner topics in Ecology first, such as Ecology, Ecosystem, Biotic and Abiotic Factors, then return to Eutrophication. Intermediate topics assume the Beginner vocabulary.
What topics are related to Eutrophication?
The closest topics to Eutrophication are Trophic Cascade, Primary Productivity, Decomposers, Producers. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Eutrophication?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Eutrophication. To practise the whole of Ecology, use the Ecology quiz.
How is Eutrophication different from Trophic Cascade?
Eutrophication: Nutrient enrichment of water bodies causing algal blooms, oxygen depletion and fish kills. Trophic Cascade: Top predator effects ripple down through lower trophic levels, as in wolves reintroduced to Yellowstone. Read both side by side and note what each one explains.
How should I study Eutrophication 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 Trophic Cascade and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.