BIOACCUMULATION

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BIOACCUMULATION

• DDT
• A persistent pollutant

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BIOACCUMULATION

• When a chemical pollutant enters an ecosystem
  through accidental or deliberate discharge to the
  soil, water or air, this chemical may enter the
  food chain.
• If it is not readily broken down by organisms, it
  will accumulate and become progressively
  concentrated as it enters organisms at higher
  trophic levels.
• This concentration is termed bioaccumulation or
  biological magnification
• Substances that cannot be excreted or broken down
  by metabolism are non-biodegradable or
  persistent.
• Examples DDT, PCBs and dieldrin

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DDT Background

• DDT is a pesticide used for mosquito control and
  pest control in agricultural crops.
• DDT accumulation in some bird species resulted in
  death, nervous system damage, and reproductive
  failure.
• As a result DDT was banned in the United States
  in 1972.

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What kind of damage can DDT cause to birds?
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In the body of an animal, DDT 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

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How does DDT move into lakes, streams and oceans?

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• After DDT is applied, some DDT volatizes, some
  remains on the plant, and some washes off the
  plant into the soil, eventually making its way to
  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). An
increase in the concentration of a chemical in a
biological organism over time, compared to the
chemical's concentration in the environment.
Compounds accumulate in living things any time
they are taken up and stored faster than they are
broken down (metabolized) or excreted.

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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 an 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
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
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Units of Measurement

• 1 gram 1000 milligrams (mg) 1,000,000
  micrograms (µg)
• microgram (µg) one millionth of a gram
• To describe concentrations µg/g number of
  micrograms
• (of toxin) per gram (of tissue)
• 2 µg/g DDE in egg content means there is 2 parts
  of DDE in 1,000,000 parts of an egg contents
• ww or wet weight refers to the fresh weight of
  animal tissue.
• dw or dry weight refers to the weight of animal
  tissue after it has been dried in an 65C oven to
  remove all the water.

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The Effects of DDE on Reproduction
Species Effect on Reproduction DDE Critical Concentration (measured in egg contents)
Bald Eagle None lt 3µg/g 1
Bald Eagle Failure 16 µg/g 1
Osprey Failure 17.6 µg/g 2

1. Wiemeyer, S.N. et al., 1984. Organochlorine
   pesticide, polychlorobiphenyl, and mercury
   residues in bald eagles, 1969-1979, and their
   relationship to shell thinning and reproduction.
   Arch. Environ. Contam. Toxicol., 13, 529.
2. Johnson, D.R. et al., 1975. DDT and PCB levels in
   Lake Coeur dAlene, Idaho osprey eggs, Bull.
   Environ. Contam. Toxicol., 13, 401.

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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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How is the impact of DDE on osprey and eagle
reproduction measured?

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One Method for Measuring the Impact of DDE on
Osprey Reproduction

• Collect eggs from abandoned osprey nests.
• Measure the thickness of the eggshells.
• Measure the amount of DDE in the egg.
• Determine the association between eggshell
  thickness and DDE residue.