Britannica
Sources used in this answer
How can fertilizer runoff harm aquatic ecosystems?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Biology
A researcher using a microscope to examine a specimen in the laboratory.
Fertilizer runoff harms aquatic ecosystems primarily by triggering eutrophication, a process where excess nutrients like nitrogen and phosphorus enter water bodies and stimulate the rapid, artificial growth of algae and phytoplankton.123
This process damages ecosystems in several ways:
- Oxygen Depletion: As these massive water blooms die and decompose, the process consumes vast amounts of dissolved oxygen. This leads to hypoxia, creating "dead zones" where fish, crustaceans, and other aquatic life suffocate and die.123
- Light Blockage: Dense algal mats block sunlight from reaching underwater plants, disrupting photosynthesis and degrading the habitat.24
- Toxin Production: Some blooms produce harmful toxins that can poison wildlife, contaminate shellfish, and cause health issues in humans.34
- Physical Interference: Excessive plant growth can clog the gills of fish and obstruct irrigation or drainage structures.54
Ultimately, this nutrient enrichment degrades water quality, reduces biodiversity, and can cause the collapse of local fisheries and food chains.23