Aquatic Pollution and Coastal Management

Unit 4 : Pesticide pollution

4.11.Bioaccumulation
Biodegradable substances are those which can be broken down by microbes into harmless compounds. Conservative pollutants are unable to be broken down and will build up in the soil or marine environment. Conservative pollutants include some pesticides, industrial chemicals such as PCBs and heavy metals such as tin, lead and mercury.

Bioaccumulation
Conservative pollutants can enter living organisms at any time and accumulate in their tissues. Such organisms are able to build up very high levels of such pollutants - eg oysters can concentrate DDT from 0.001 ppm in sea-water to 700ppm in their bodies. This is known as bioaccumulation.
Bioaccumulation occurs within a trophic level.

The rate at which pollutants are accumulated in the tissues of an organism may be influenced by the following:

• The concentration of pollution in the water
• The water temperature - if the metabolism of the organism increases, so too may its rate of uptake.
• The age and sex of the organism.