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Dolphin
Watch
Nature Tours
Port Aransas
Texas 78373
Local:
(361) 749-6969
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Dolphin
Watch and Nature Tours
Educational
Resources for Teachers and Schools
Brown
Pelican
Pelicanus occidentalis
and
Biomagnification
and DDT
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This
section is designed to aid the teachers
in fulfilling the following TEKS knowledge
and skills requirements.
Grade K-2
(9)(B)
Grade 3-8 (3)(A)(D)
Grade 4 - 112.6 (5)(A)
Grade 5 - 112.7 (5)(A)(B)
Grade 6 - 112.22 (9)(A)(B)(C)
Grade
8 - 112.24 (6)(C) & (11)(A)
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“Pelicans almost disappeared from Texas
because they were poisoned by the pesticide DDT,
which caused them to lay thin-shelled eggs which
broke during incubation. Because they were not able
to produce young, the number of Pelicans dropped
to less than 100 birds during the years 1967-1974.
Since DDT was banned in 1972, Pelicans have made
a steady comeback.” (TPWD) |
- The American Brown Pelican is common along
the coastlines of North and South America.
- There length is around 40 inches long and
have a 90 inch wingspan.
- They live in social group and congregate
in large flocks.
- They nest in trees or on the ground in shallow
bays.
- Brown pelicans are primarily fish eaters.
They have extremely sharp eyesight.
- Once they locate a fish, they dive straight
down into the water sometimes from 50-60 feet.
- As they enter the water, they completely submerge
and come up with a bill full of fish.
- Other bird like terns, gulls and cormorants
constantly hassle them and steal their food.
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Biomagnification
and DDT
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Biomagnification:
An increase in the concentration of a pollutant
from one trophic level to the next in the food
chain
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Three conditions must be present for Biomagnification
to occur (Mader, 1996)
1. The pollutant must be long-lived.
2. The pollutant must be concentrated by the producers
3. The pollutant must be fat soluble |
| Stage 1:
Producers will for to great lengths to obtain nutrients,
sometimes even taking in more then they need and
storing it. Chemically pollutants such as DDT resemble
inorganic nutrients and are stored in the producer’s
body, making the pollutant at a higher concentration
in the producer than in the environment.
Stage 2:
Consumers eat the producers, and since not much
energy passes from one trophic level to the next
the producers consume large quantities of the
producer and in turn large quantities of the pollutant
and moves in to the fat storage of the consumers.
The best example is DDT; a long lived pesticide
(half life of 15 years) developed to improve human
health by killing mosquitoes. It was extremely
effective because it did not break down in the
environment, but it causes some severe long term
effects on birds. DDT interfered with the deposit
of calcium into the egg shells. As the eggs were
laid their shells were extremely soft and would
often break and the number of birds started to
decline. The brown pelican and Bald eagle have
made comebacks due to the ban of DDT pesticide.
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Proceed
to
Coastal Birds
Site Links:
Home
| Our Boats | The Island Queen
| The Mustang
| The Duke
Boat Trips | Bay Fishing
| Dolphin Watch
| Private Charters
For Teachers
| Virtual
Trip
Educational
Resources | Dolphins
| Practice
Classification Exercise | Dolphin Anatomy Handout
Plankton
| Phytoplankton
| Zooplankton
Coastal Birds
| Brown Pelicans
| Whooping Cranes
| In The Net
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