Water Pollution and Eutrophication
Fertiliser runoff causes algal blooms that starve water of oxygen.
About this topic
Water pollutants include sewage, fertiliser runoff, pesticides, industrial waste, oil and plastics. In eutrophication, nitrates and phosphates from fertilisers or sewage promote algal blooms; the algae block light, plants below die, and bacteria decomposing the dead matter use up oxygen, so fish and other animals suffocate.
The sequence is important: excess nutrients, rapid algal growth, light blocked, submerged plants die, decomposers multiply and consume dissolved oxygen, and aerobic organisms die. Some algal blooms release toxins harmful to people and animals. Low oxygen creates dead zones, like the one in the Gulf of Mexico.
Invertebrates act as indicator species: mayfly larvae and stonefly nymphs need clean, oxygen-rich water, while bloodworms and sludge worms tolerate pollution. Finding which are present shows the water quality. Sewage is treated to remove solids and break down organic matter using bacteria before release.
Prevention includes using fertilisers carefully, planting buffer strips by streams, treating sewage and banning harmful chemicals. Plastics harm marine life through entanglement and ingestion, and microplastics enter the food chain. A misconception is that eutrophication is caused by too little oxygen at the start; the low oxygen is a result, not the cause.
Key ideas
- Nutrients feed algae
- Algae block light and die
- Decomposers use up oxygen
Quick check
Use cases: where Water Pollution and Eutrophication helps
- Homework: review the key idea behind Water Pollution and Eutrophication before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Water Pollution and Eutrophication without notes.
- Visual learning: play with the interactive lab to see how Water Pollution and Eutrophication changes when you adjust its inputs.
- Teaching a friend: explain Water Pollution and Eutrophication in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Water Pollution and Eutrophication?
Fertiliser runoff causes algal blooms that starve water of oxygen.
What will I learn in Water Pollution and Eutrophication?
Nutrients feed algae. Algae block light and die. Decomposers use up oxygen.
Is Water Pollution and Eutrophication part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Water Pollution and Eutrophication lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Water Pollution and Eutrophication?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.