Bioaccumulation & Biomagnification

• Bioaccumulation


  The gradual build-up of synthetic and organic chemicals in living organisms
• Synthetic and organic chemicals build up in the environment when decomposers cannot break them down through the biodegradation process
• Bioaccumulation & Ecosystems

  • Human activity creates many harmful pollutants
  • These build up in the environment when decomposers are unable to break them down
  • Plants take up these pollutants
  • The pollutants are then transferred along the food chain until they reach the highest trophic level
• Biomagnification


  The process in which pollutants not only accumulate but also become more concentrated at each trophic level
• Organisms at lower trophic levels may be affected by the pollutant, but primary, secondary, and tertiary consumers will be more affected because levels will build up in their tissues as they consume contaminated food
• Biomagnification: Orcas


  • When orcas consume food contaminated with PCBs, they store some of the PCBs in their blubber
  • When salmon (their primary food) is not available, orcas use their blubber for energy, which releases PCBs into their system
• PCBs (Polychlorinated biphenyls)

  • Used in various things like paints, lubricants, plastics, etc. - They are banned since 1977 in North America
  • They interfere with the normal functioning of the body's immune system and cause problems with reproduction
• • PCBs have a long half-life (the time it takes for a substance to decrease by half)
  • They stay in the environment for a long time
  • Aquatic ecosystems are most sensitive to PCBs
  • Organisms at high trophic levels, like the orca, retain high levels of the pollutant
• POPs (Persistent Organic Pollutants)


  • Harmful, carbon-containing compounds that remain in water and soil for many years
  • Can cause reproductive failure, birth defects, immune system disorders (cancers, weakness to disease), behaviour and learning disorders, and death
• Examples of POPs: DDT


  • DDT (dichloro-diphenyl-trichloroethane) is a toxic POP that was used as a pesticide in the past to control disease-carrying mosquitoes
  • Accumulation is measured in parts per million (ppm)
  • This refers to one particle of a given substance mixed with 999 999 other particles
  • DDT is harmful at 5 ppm
• Heavy Metals


  • Metallic elements with a high density that are toxic to organisms at low concentrations
  • Within the biosphere, they do not degrade and cannot be destroyed
  • Some heavy metals such as copper, selenium, and zinc are essential to human health in very small quantities
• • Heavy metals can be found in water and air and are taken in through the food chain
  • They can bioaccumulate within organisms and biomagnify, moving up the food chain like POPs
  • The three most polluting heavy metals are lead (Pb), cadmium (Cd), and mercury (Hg)
• Bioremediation


  • The use of living organisms— usually micro-organisms or plants — to do the clean-up naturally, only faster through biodegradation
  • Micro-organisms that naturally feed on chemicals and reduce them to non-toxic compounds can be added to contaminated soil
  • Working at the molecular level, scientists have extracted enzymes from chemical-eating bacteria or pesticide-resistant insects and used these to create new environmental clean-up technologies