IB ESS - Impacts of water pollution | Free Notes

Impacts of water pollution

Big idea: Water pollution affects ecosystems through bioaccumulation (toxins build up in organisms) and biomagnification (toxins concentrate up food chains). Top predators — including humans — receive the highest doses.

Bioaccumulation vs biomagnification

Bioaccumulation

Toxins build up in ONE organism over time
Organism absorbs toxins faster than it excretes them
Example: mercury accumulating in a single fish
Influenced by fat solubility, persistence, and exposure time

Biomagnification

Toxin concentration increases at higher trophic levels
Each level contains a higher concentration than the one below
Example: plankton → fish → seals → top predators
Top predators have the highest concentrations

Substances that biomagnify

Heavy metals — mercury, lead, cadmium
Persistent organic pollutants (POPs) — DDT, PCBs, dioxins
Microplastics — absorb other toxins and enter food chains
These substances are fat-soluble, persistent, and not easily excreted

Be able to clearly distinguish between bioaccumulation and biomagnification, and explain why toxin concentrations are highest in top predators using simple food-chain examples.

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Impacts of water pollution

Practice the questions examiners actually ask

Impacts of water pollution

Bioaccumulation vs biomagnification

Substances that biomagnify

Related ESS Topics

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