BIOMAGNIFICATON

• Magnification= INCREASE

• Concentration of toxins are increased in the upper tropic levels

• Sometimes called bioaccumulation

TO

XIN

S

BIOMAGNIFICATION

PRODUCER

1ST ORDER

CONSUMER

2ND ORDER

CONSUMER

3RD

ORDER

CONSUMER

TERTIARY CONSUMER

DDT and BIOMAGNIFICATION

• 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.

1948 DDT SPRAYING

The numbers are representative values of the concentration in the tissues of DDT (in parts per million, ppm)

Polychlorinated Biphenyls (PCBs)

• The term polychlorinated biphenyls refers to a group of 209 different chemical compounds. PCBs were used primarily for lubrication and insulation in electrical equipment.

• For 30 years PCBs were used and released into the Hudson River until they were banned in 1977.

• Although they are no longer used, PCBs are still at a level of concern in certain areas.

• Most of the PCBs that were released sank to the bottom of the river where they have bound to the sediments.

• In the Hudson River, the sediments are constantly being mixed due to tides and currents so that the contaminants continue to be available to bottom dwelling organisms like insects and mussels.

• This mixing is also believed to cause PCBs from the sediments to be re-released into the water column where they are made available to fish.

MERCURY

CONCENTRATION

OPERATION CAT DROP

• In the early 1950s, the Dayak people in Borneo suffered from malaria.

• The World Health Organization had a solution: they sprayed large amounts of DDT to kill the mosquitoes which carried the malaria.

• The mosquitoes died the malaria declined; so far, so good. But there were side-effects.

• Among the first was that the roofs of people's houses began to fall down on their heads. It seemed that the DDT was also killing a parasitic wasp which had previously controlled thatch-eating caterpillars.

• Worse, the DDT-poisoned insects were eaten by geckoes, which were eaten by cats.

• The cats started to die, the rats flourished, and the people were threatened by outbreaks of sylvatic plague and typhus.

• To cope with these problems, which it had itself created, the World Health Organization was obliged to parachute live cats into Borneo. (McShaffrey, 1999)

Byproduct 1:Eliminated the natural predator for the thatch eating caterpillar

Byproduct 2:Biomagnification of DDT poisoning in cats caused an outbreak of sylvatic plague.