Bioaccumulation

Chemical Pollutants Humans have been introducing synthetic (man-made) chemicals into the environment. Some examples are: PCBs (polychlorinated biphenyls) widely used in paints, plastics, lubricants up to 1977 DDT (an insecticide for mosquitos) now banned in many countries Dichloro-diphenyl trichloroethane

Persistent Pollutants! Both DDT and PCBs are called “persistent organic pollutants” (POPs) This is because they take a LONG time to break down HALF-LIFE = the time it takes for ½ the substance to break down Half-life (PCBs) = 8 -10 years Half-life (DDT) = 15 years

Bioaccumulation DDT and PCB are chemicals that can be eaten or absorbed organism slowly build up these chemicals in their bodies and this is called Bioaccumulation As we follow a food chain from the producers up to the highest consumers the pollutants become magnified or more concentrated. This is call Biomagnification. measured in ppm (parts per million) At even low levels (5 ppm), DDT in animals can cause nervous, immune and reproductive system disorders

Effect of Bioaccumulation on Ecosystems

Orca Whales highest PCB level in animals. PCBs concentrate in the blubber of the whale and when it is used for energy it is release into the bloodsteam Calves are born with the same PCB levels as mother PCB’s will affect the reproductive cycles of orcas until at least 2030

Heavy Metals Heavy metals are metallic elements that are toxic Lead Naturally present in soil but levels have increased due to human activities Lead is not considered safe at any level. Many electronics contain lead and must be recycled carefully Lead can cause anemia and nervous and reproductive system damage.

Heavy Metals (con’t) Cadmium is also found in low levels naturally (by weathering) used in plastics and nickel-cadmium batteries toxic to earthworms and causes many health problems in fish In humans, the main source of cadmium is exposure to cigarette smoke Cadmium causes lung diseases, cancer, and nervous and immune system damage

Heavy Metals Mercury is high in density and toxic at low levels also is found naturally. Mercury has entered ecosystems through: fossil fuels, mining, batteries… Coal burning accounts for 40 percent of the mercury released into the atmosphere. Mercury bioaccumulates in the brain, heart and kidneys of many animals. Mercury compounds bioaccumulate in fish easily,

How BIOACCUMULATION affects ecosystems: Salmon is an important food source for bears, wolves, eagles and otters, their decaying bodies are rich source of nutrients for plants As chemical build up, salmon reproductive system can be affected resulting in fewer numbers of salmon and/or passing on these chemicals to its predators Therefore the predators numbers are also affected and so on… If one species can greatly affect population and the health of an ecosystem then is is called a Keystone species

Reducing the effects of chemical pollution By trapping chemicals using plants The oil industry will often use bacteria to “eat” oil spills The process of using living things to clean-up naturally is called bioremediation

Rhodococcus bacteria can biodegrade PCBs