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Science 10: 2.3 Effects of Bioaccumulation on Ecosystems
Text: Chapter 2, pages 92-103
Part A: Synthetic Chemicals in the Ecosystem and
-Synthetic chemicals enter ecosystems by air, water and
soil and are incorporated into the food chain when they
are taken up by producers.
are dangerous chemicals as they can affect the
nervous, immune and reproductive systems of
-Amphibians are often good indicators of ecosystem
health as they live on both water and land during their
1. Brainstorm why frogs are sensitive to synthetic
chemicals in their environment.
Water: Egg membranes are permeable; Breathe through
skin = permeable skin.
-For these reasons, amphibian species have declined
significantly since the 1980s (other factors are also
involved in this trend, such as deaths related to fungi).
*Pesticides kill pests and can be classified as
Insecticides (kill insects)
Herbicides (kill weeds)
Part B: How Pollutants Climb the Food Chain
The introduction of synthetic chemicals has been one of
the most damaging and presented the biggest challenge
to clean up.
Synthetic chemicals often cannot be broken
down by decomposers and simply build up in
the environment.
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 1
1. Bioaccumulation and Biomagnification
a) Bioaccumulation:
Accumulation of chemicals in organisms’
How do synthetics enter an organism’s body and
how do they accumulate/are stored?
Enter through food, skin contact or
Accumulate if taken up faster than broken
Stored in fat tissue.
b) Biomagnification:
Accumulation of chemicals in increasing
concentrations in organisms’ bodies.
How are chemicals transferred from one trophic
level to the next?
Consumed with plant or animal tissue.
How does this scenario lead to an increase in the
concentration of synthetics in each successive
trophic level?
Consumers must eat many times their body
weight to survive
o small amounts of synthetics in
producers/prey being concentrated in
their bodies.
What are the implications for an ecosystem if a
Keystone Species (such as salmon) have significant
concentration of synthetics in their bodies?
Species rely on salmon for nutrients, either through predation, scavenging or decomposition.
Synthetics in their tissues would be transferred to a significant portion of the ecosystem.
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 2
1. PCB’s (and Killer Whales)
What are they?
PCBs (polychlorinated biphenyls) are synthetic chemicals
produced between the 1930s and 1970in industrial
products (paints, plastics, electrical fluids etc.).
PCBs were banned in 1977 over concerns about their
very long half-lives and the potential impacts this could
have on ecosystems.
What is a half-life?
Time it takes for half of a substance to decay.
The diagram right illustrates how PCBs have been concentrated
in Orca blubber.
In Orca’s PCBs suppress the immune system and
interfere with reproductive success. Because of PCBs’
long half-life, this synthetic will continue to be an issue
beyond 2030!
Do PCBs in aquatic ecosystems pose a threat to human
Yes, some populations rely heavily on fish, seal and whale meat
in their diet. PCBs likely cause cancer in humans.
*Watch 53:40 to 101:10 of PBS Frontline: Poisoned Waters
2. Persistent Organic Pollutants: DDT
PCBs and DDT (dichlorodiphel trichloroethane) are classified as Persistent Organic Pollutants (POPs),
which contain carbon and remain in the soil and water for long periods of time.
-Watch the following videos on DDT:
a) 1947 advertisement for DDT:
b) Rachel Carson and Silent Spring:
-Take your own notes on DDT from text page 96.
An insecticide, introduced (1941), to control disease carrying mosquitos
Like PCBs, bio-magnify, long half-life and persists in the environment
Cause nervous damage, immune a reproductive disorders
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 3
Why do cormorants have the highest bioaccumulation of DDT?
Eat many times their body weight of fish, this increases the
concentration of DDT.
In animals DDT is changed into a bioaccumulating chemical form that
causes nervous and immune system and reproductive disorders.
*Complete Concept Check page 103, #1-11
1. Provide several reasons to explain why amphibians are disappearing.
2. Describe how synthetic chemicals become biomagnified in organisms.
3. What factors determine whether or not a chemical will bioaccumulate?
4. What are PCBs?
6. Give an example of a persistent organic pollutant (POP).
7. How does DDT bioaccumulate?
9. Which is more toxic—a chemical with a toxic level of 3 ppm or a chemical with a toxic level of 0.03
ppm? Explain.
10. What effect does DDT have on humans?
11. Explain why the effect of biomagnification is so great in killer
3. Heavy Metals
-Heavy metals are metallic elements with a high density and are very
toxic in low concentrations. Additionally, they cannot be degraded or
destroyed and can bioaccumulate.
-However, some heavy metals are important to humans in low
quantities (copper, zinc).
-Take your own notes on the following heavy metals from text pages
97 through 98:
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 4
a) Lead:
Environmental sources:
Effect on organisms:
Effect on humans:
b) Cadmium:
Environmental sources:
Effect on organisms:
Effect on humans:
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 5
Environmental sources:
Effect on organisms:
Effect on humans:
Part C: Reducing the Effects of Chemical Pollution
-Scientists are continually exploring new ways to clean up synthetic chemicals in ecosystems. Some of
the ideas we have so far are:
1. Trapping contaminants in soil so that they cannot leach into water bodies and enter the food chain.
2. Bioremediation:
-Use of living organisms (bacteria or plants) to break down synthetics into non-toxic compounds.
*Watch Can Microbes Clean Up Our Oily Mess? from Scientific American.
3. Read the BBC article “The Dutch Boy Mopping up a Sea of Plastic” from
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 6
Science 10: 2.3 Bioaccumulation in Ecosystems
Page 7