Notes on Bioaccumulation and Biomagnification

Learning Objectives

  • Describe bioaccumulation and biomagnification and their effects.

Bioaccumulation

  • Definition: Bioaccumulation refers to the accumulation of substances, such as pesticides, or other chemicals in an organism.
  • Process: Occurs in individual organisms over extended periods as they continue to consume contaminants.
    • Key Points:
    • Contaminants are taken up in small amounts by organisms (e.g., phytoplankton) over time.
    • Phytoplankton filter large quantities of water to obtain nutrients like nitrogen and phosphorus.
    • If the water contains harmful chemicals (e.g., DDT, PCBs), these are absorbed along with nutrients.
    • Since phytoplankton cannot metabolize these chemicals, they accumulate in their body, particularly in fat cells.

Biomagnification

  • Definition: Biomagnification is the increase in concentration of substances, like contaminants, as one moves up the food chain.
  • Process: As higher trophic level organisms consume lower trophic level organisms, the contaminant concentration increases.
    • Example:
    • If mercury is introduced into a water body, low levels are absorbed by plankton.
    • When these plankton are consumed by small fish, the mercury accumulates in the small fish due to their consumption of many plankton.
    • Larger fish that eat these small fish will accumulate even more mercury as they consume multiple small fish.
    • This process continues up the food chain, leading to apex predators (e.g., larger fish or birds) having the highest contaminant levels.

Essential Knowledge

  • Bioaccumulation:
    • Involves selective absorption and concentration of compounds, mainly fat-soluble ones, in living organisms.
  • Biomagnification:
    • Results when bioaccumulation effects are magnified through food chains, often associated with metal pollution (mercury, lead).

Important Concepts

  • Contaminant Levels:
    • Both bioaccumulation and biomagnification highlight how persistent environmental pollutants can pose risks to ecosystems and human health, particularly through food webs.