Eutrophication is the process by which a body of water becomes overly enriched with nutrients, leading to excessive plant and algal growth. While it can occur naturally over long periods, most modern eutrophication is caused by human activity, particularly agricultural runoff, sewage discharge, and industrial waste. In IB ESS, eutrophication is a major topic in understanding how human actions disrupt natural systems and alter aquatic environments.
Quick Start Checklist for IB ESS Students
- Define eutrophication clearly for short-response questions
- Learn the steps of the eutrophication process
- Understand human and natural causes
- Study ecosystem impacts and mitigation strategies
- Review diagrams and case studies using RevisionDojo’s IB ESS resources
The Eutrophication Process
Eutrophication begins when excess nutrients — mainly nitrates and phosphates — enter water bodies such as lakes, rivers, and coastal zones. These nutrients come from:
- Agricultural fertilizers washed off farmland
- Untreated sewage and animal waste
- Detergents rich in phosphates
- Industrial discharges containing nutrient compounds
These nutrients fuel rapid algal blooms, often dominated by cyanobacteria. While initially increasing photosynthesis, these blooms block sunlight from reaching deeper water, reducing oxygen production by submerged plants.
When algae die, they become a food source for decomposers, whose respiration consumes dissolved oxygen. This creates hypoxic (low oxygen) conditions, leading to the death of fish and other aquatic organisms — a process known as a dead zone.
Key Stages of Eutrophication
- Nutrient enrichment (mainly nitrogen and phosphorus).
- Algal bloom development.
- Light penetration reduction.
- Plant and algal death.
- Increased decomposition and oxygen depletion.
- Aquatic organism die-off and biodiversity loss.
Ecological Impacts
- Loss of biodiversity: Oxygen depletion kills sensitive species and disrupts food webs.
- Toxic algae: Some blooms release toxins harmful to fish, animals, and humans.
- Reduced water quality: Eutrophic waters often appear murky and smell unpleasant.
- Economic impacts: Fisheries, tourism, and water treatment become more costly.
Human Influence and Management
Eutrophication is a clear example of anthropogenic impact on ecosystems, aligning directly with IB ESS topics on systems and sustainability.
Key management strategies include:
- Reducing fertilizer use and improving agricultural efficiency.
- Constructing wetlands to filter runoff.
- Improving wastewater treatment systems.
- Restoring ecosystems through aeration and nutrient removal.
These solutions demonstrate how environmental systems can recover when managed sustainably — a recurring theme in the IB ESS curriculum.
The ESS and IB Connection
Eutrophication links multiple IB ESS concepts: nutrient cycles, human impacts, and sustainable management. Students must analyze data, evaluate case studies (like the Baltic Sea or Lake Erie), and propose realistic mitigation strategies.
Using RevisionDojo’s IB ESS course, students can explore diagrams, practice structured essays, and strengthen understanding of eutrophication and other ecological processes through interactive revision tools.
FAQs
What causes eutrophication?
Mainly nutrient pollution from fertilizers, sewage, and industrial waste containing nitrogen and phosphorus.
Why is eutrophication harmful?
It leads to oxygen depletion, mass fish deaths, and long-term ecosystem damage.
How can eutrophication be prevented?
By controlling agricultural runoff, improving wastewater treatment, and promoting sustainable land management.
