8.8 - Biomagnification

Question 1

Bioaccumulation

Answer 1

• Absorption and concentration of compounds (especially fat-soluble ones like POPs) in the cells & fat tissues of organisms
• B/c fat-soluble compounds like POPs and methylmercury don’t dissolve easily in water, they don’t enter blood easily & don’t leave body in urine easily
  - Instead they build up in fat tissue
  - This leads to them building up to reach higher and higher concentrations in the organism over time

Question 2

Biomagnification

Answer 2

• Increasing concentrations of fat-soluble compounds like methylmercury and POPs in each level up the trophic pyramid or food web/chain
• Biomagnification begins with POPs or methylmercury in sediments or plants in an ecosystem (phytoplankton, grass)
• Primary consumers (zooplankton, bottom feeding fish, insects) take in POPs by eating producers, causing bioaccumulation of POPs in their tissues
• Secondary consumers eat primary consumers and take in the POPs in their tissues
  - Because of the 10% rule, organisms at each successive trophic level need to eat more and more biomass to receive enough energy, leading to higher and higher POP levels over their lifetimes
  - Large predators like salmon, dolphins, and whales have highest POP/methylmercury level

Question 3

Biomagnification (DDT)

Answer 3

• DDT was banned in many developed nations, but still persists in sediments of many bodies of water
• Taken in by bottom feeders/zooplankton and biomagnified art higher tropic levels
• Reach highest levels in top predators, especially predatory birds like eagles and osprey
  - causes thining of the eggshells in these birds
  - linked to massive population decline of bald eagle in US which prompted passage of endangered species act

Question 4

Biomagnification (methylmercury)

Answer 4

• Mercury is emitted from burning coal & by volcanoes, carried by wind, and deposited in water where bacteria convert it into toxic methylmercury
• Taken in by phytoplankton & biomagnified at higher trophic levels
• Reach highest levels in top predators, tuna, sharks, whales
• Neurotoxicant: damages the central nervous system of animals
• Human exposure to methylmercury & POPs comes from eating large predatory fish like tuna & salmon (and other seafood)
• Damage to human nervous system (esp. developing fetus) and disrupt reproductive system

Question 5

Biomagnification and Bioaccumulation

Answer 5

How can pollutants have long-term effects on organisms?
- Even when pollutants are not dangerous enough to kill animals, their presence can have lasting effects on food webs through Bioaccumulation and Biomagnification

• Toxins may increase in concentration as they pass up the food chain, in a process called Biomagnification
• Bioaccumulation occurs when pollutants build in a single organisms body over tim