8.8 Bioaccumulation and Biomagnification
Biomagnification (methylmercury)
- 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
Bioaccumulation - Define - How build up?
- Selective Absorption and concentration of compounds (especially fat-soluble ones like POPs) in the cells & fat tissues of organisms; DDT, PCBS, & Methylmercury ●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
Biomagnification
Biomagnification is the increase in concentration of substances per unit of body tissue that occurs in successively higher trophic levels of a food chain or in a food web
Identify a toxic metal other than mercury that has a negative impact on human health and describe how it is introduced into the environment. Describe an acute sublethal effect on humans that results from exposure on this metal.
Lead is another toxic mineral introduced into the environment from the dumping of toxic waste into rivers and streams. Lead enters the body either by being breathed in or by gastric consumption (eating or drinking) and can cause lead poisoning, severe brain damage, and death.
Describe the effects of bioaccumulation and biomagnification.
Some effects that can occur in an ecosystem when a persistent substance is biomagnified in a food chain include eggshell thinning and developmental deformities in top carnivores of the higher trophic levels. Humans also experience harmful effects from biomagnification, including issues with the reproductive, nervous, and circulatory systems. DDT, mercury, and PCBs are substances that bioaccumulate and have significant environmental impacts
Explain why there are greater health risks associated with eating large predatory fish, such as tuna and sea bass, than from eating small nonpredatory fish.
c) There is a greater risk with eating larger fish than smaller ones, because of biomagnification and bioaccumulation. The concentration of bad substances increases with each trophic level.
How Biomagnification occurs - Describe at different trophic levels - At what level is highest
●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 levels
Biomagnification (DDT)
●Taken in by bottom feeders/zooplankton & biomagnified at higher trophic levels ●Reach highest levels in top predators, esp. predatory birds like eagles & osprey ○Causes thinning of the eggshells in these birds ○Linked to massive pop. decline of bald eagle in US, which prompted passage of Endangered Species Act (73')
