Bioaccumulation & Biomagnification (College Board AP® Environmental Science): Study Guide
What is bioaccumulation?
Bioaccumulation is the build-up of persistent or non-biodegradable pollutants within a particular organism or trophic level because the toxins cannot be easily broken down
This means that organisms at higher trophic levels (such as top predators) may accumulate higher concentrations of pollutants than those in the lower trophic levels
Some bioaccumulating pollutants:
Persistent organic pollutants (POPs) such as DDT and PCBs
Heavy metals such as mercury, lead, and cadmium can be consumed from contaminated fish and shellfish
What is biomagnification?
Biomagnification is the increase in the concentration of persistent or non-biodegradable pollutants along a food chain
As pollutants are passed up the food chain from one trophic level to the next, they can become more concentrated due to the decrease in total biomass of organisms at higher trophic levels
Biomagnified effects on ecosystems
Biomagnification affects the food-chain stability by altering the number and spread of species within different trophic levels
It also disrupts an ecosystem's equilibrium by disproportionately affecting top predators and causes:
population declines
reproductive issues
developmental problems
health issues
Case Study
DDT, a popular insecticide in the mid-20th century, had a detrimental effect the bald eagle population
DDT from crop spraying leached into freshwater and marine habitats
DDT then entered the food chain via plankton and accumulated in fish feeding on the plankton
Birds would eat the fish and higher concentrations of DDT would accumulate in the birds
This caused eggshell thinning and reproductive failure in the birds and eventually a severe decline in bald eagle populations
By 1963, only 417 nesting pairs of bald eagles known to exist in the US
As a result of pressure from the American public in the early 1970s and the 1962 publication of Rachel Carson’s book Silent Spring, the US and Canadian governments banned the use of DDT and related pesticides
The bald eagle was placed on the endangered species list and a conservation program was established, which included:
captive breeding programs
working with landowners, tribes and agencies to reintroduce them into the wild
law enforcement
nest site protection during the breeding season
By 1995, bald eagles had recovered enough to be re-classified as threatened
According to the U.S. Fish and Wildlife Service, as of 2020, there were an estimated 316,700 bald eagles in the lower 48 states, which included 71,467 nesting pairs
Biomagnified effects on humans
Biomagnification can cause serious health problems in humans, including
Certain cancers
Liver and kidney failure
Birth abnormalities
Brain damage and degeneration
Neurological diseases like Alzheimer's are increasingly linked to biomagnification
Increased risk of heart disease
Development in babies and children
Effects of bioaccumulation on ecosystems and humans
Toxin accumulation can cause reproductive failure, developmental defects, and population loss, particularly in predators like birds of prey and marine animals
Contaminants at higher trophic levels can disturb predator-prey relationships, influencing ecosystem balance and stability across the food chain
This can lead to a trophic cascade of extinction, as keystone species play a critical role in the structure and function of ecosystems
In the Pacific Northwest's nearshore marine ecosystem, sea otters are a keystone species
They consume the sea urchins, which consume the kelp that other species in the system rely on
Without the sea otters, the urchins can easily overpopulate and eat all the kelp
This impacts other species that depend on the kelp forest
Species with slower metabolisms or longer lifespans store more poisons, making them more vulnerable to bioaccumulation
Microplastics can be absorbed through the intestinal wall of animals and become lodged in their bodies, leaching chemicals and accumulating over time
Bioaccumulated toxins can harm the environment, plants and other organisms in the ecosystem, leading to habitat deterioration
Key bioaccumulation effects in humans
Exposure to bioaccumulated poisons, such as mercury, can cause neurological damage, compromising cognitive processes, memory, and motor skills
Microplastics are selectively accumulated in the brain, liver, and kidneys, and concentrations are rising, leading to
cancer from changes in DNA
endocrine disruption
decrease in reproductive health
increased risk of cardiovascular diseases
neurotoxicity of the brain and nervous system
inflammation of the heart, liver, brain and kidneys
Exposure to certain pollutants can disturb hormone balance, causing reproductive disorders such as infertility and birth abnormalities
Lead buildup from drinking water is the major cause in humans
Lead comes from landfills, electroplating, mining, and pipework
Lead exposure causes deterioration in cognitive function
Exposure to chemicals at important developmental periods can cause delays and deformities in children
Known carcinogens in bioaccumulated substances may increase the incidence of some cancers in humans
In 1956, a chemical factory released toxic methylmercury into wastewater entering Minamata Bay in Japan
Mercury accumulation in fish and shellfish caused mercury poisoning in local people (who ate the fish and shellfish) and resulted in severe symptoms (paralysis, death, or birth defects in newborns)
You've read 0 of your 5 free study guides this week
Unlock more, it's free!
Did this page help you?
