Science 10: 2.3 Bioaccumulation in Ecosystems Page 1

Science 10: 2.3 Effects of Bioaccumulation on Ecosystems

Text: Chapter 2, pages 92-103

Part A: Synthetic Chemicals in the Ecosystem and

Amphibians

-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

animals.

-Amphibians are often good indicators of ecosystem

health as they live on both water and land during their

lifecycle.

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 2

1. Bioaccumulation and Biomagnification

a) Bioaccumulation:

Accumulation of chemicals in organisms’

bodies.

How do synthetics enter an organism’s body and

how do they accumulate/are stored?

Enter through food, skin contact or

respiration.

Accumulate if taken up faster than broken

down.

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 3

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

populations?

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: https://www.youtube.com/watch?v=gtcXXbuR244

b) Rachel Carson and Silent Spring: https://www.youtube.com/watch?v=Ipbc-6IvMQI

-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 4

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

whales.

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 5

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 6

Mercury

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

http://www.bbc.com/news/magazine-29631332

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