Food Webs and Bioaccumulation

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Food Webs and Bioaccumulation

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What kind of damage can DDT cause to birds?
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In the body of an animal, DDT (Dichloro-Diphenyl-T
richloroethane) one of the best known synthetic
pesticides, is changed (metabolized) to DDE.
DDE dissolves in fat, not in water, and is
stored in fatty tissues. Thus, DDE tends to
remain in the body and can cause several problems.

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DDE Kinds of Damage

• Reproductive failure (in birds- eggshell
  thinning)
• Immune system problems
• Nervous system damage
• Death
• Breast cancer in humans

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How does DDT move into lakes, streams and oceans?

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• After DDT is applied, some washes off the plant
  into the soil, eventually making its way to a a
  stream, river, or lake.
• The DDT that remains on the leaves of plants may
  be ingested by primary consumers such as insects
  and rodents.
• DDT that has washed into a waterbody, remains in
  the sediment or is consumed by bottom-feeding
  organisms or absorbed by fish gills and skin.

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Is DDT still used today?

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• YES
• DDT is still used in some countries for insect
  control on crops.
• In countries where mosquitoes carry malaria, DDT
  is currently used for mosquito control.

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What is a Food Web?

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Food Web A summary of the feeding relationships
within an ecological community.
Osprey
Sucker
Trout
Silverside
Bay Shrimp
Water Plants
ORGANIC DEBRIS
Plankton
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Food Chain One thread of the food web
Osprey
Large Mouth Bass
Crayfish
ORGANIC DEBRIS
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Cast of Food Web Characters

• Tertiary Consumers Animals that eat animals
  that eat animals
• Secondary Consumers Animals that eat animals
  that eat plants
• Primary Consumers Animals that eat plants
• Primary Producers Plants and Phytoplankton
  organisms using the sun for energy

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Why is food web knowledge important for
understanding the impact of DDT on ospreys and
eagles?

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Ospreys and eagles are tertiary consumers and
this makes them particularly vulnerable to DDT
because of bioaccumulation and
biomagnification.
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What is bioaccumulation?

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Bioaccumulation the accumulation of a
contaminant or toxin in or on an organism from
all sources (e.g., food, water, air).

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What is biomagnification?

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Biomagnification the increase in concentration
of toxin as it passes through successive levels
of the food webDDE accumulates at higher levels
in organisms that are higher in the food chain

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Biomagnification of a DDE in Aquatic Environment
Amount of DDE in Tissue
Level
Tertiary Consumer 3-76 µg/g
ww (fish-eating birds)
Secondary Consumers 1-2 µg/g ww (large
fish)
Primary Consumers (small fish)
0.2-1.2 µg/g ww
Primary Producers (algae and aquatic plants)
0.04 µg/g ww
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Considering biomagnification, how could DDE harm
an osprey?

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Osprey Food Web
DDE Concentration
3-76 µg/g ww (enough to cause death)
Osprey
Large Mouth Bass
1-2 µg/g ww
0.2- 1.2 µg/g ww
Crayfish
Plant material and algae
0.04 µg/g ww (not enough to cause harm)
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High levels of DDE cause the female ospreys to
lay eggs with thin eggshells.Thin eggshells
have a greater chance of breaking, leading to
embryo death.With high levels of DDE, female
ospreys can also lay eggs that contain high
enough concentration of DDE to prevent embryo
development.

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Biomagnification

• means even small amounts of toxins in the food
  chain cause increasing problems for higher order
  consumers