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Bioaccumulation and Biomagnification

Chemicals can enter the environment from many different sources, but nearly all of them originate from human actions. Once they are in the environment, they can cause serious damage to individual organisms and entire ecosystems. Two of the ways this damage can happen is by bioaccumulation and biomagnification.


What is bioaccumulation?

Comic strip showing how bioaccumulation works, with one fish accumulating more and more pollutants as it eats
The Bioaccumulation Process

Bioaccumulation is when chemicals build up inside an animal over time. For example, if a lake is polluted with chemicals, the chemicals can be absorbed by the plants growing in the lake. The fish that feed on those plants will then be ingesting the chemicals as they eat. If they cannot digest, process or excrete the chemical, it will stay in the fish’s body tissues.  Over time, as the fish continue to eat the contaminated plants, more and more of the chemical is ingested by the fish, accumulating in its body tissues. This process is called bioaccumulation.


What is biomagnification?


Comic strip showing how a top predator absorbs more and more pollutants as it eats polluted prey.
The Biomagnification Process

Animals lower in the food chain can accumulate harmful chemicals in their tissues through bioaccumulation. When predators further up in the food chain eat prey lower down, they absorb all the chemicals stored in the prey. If an animal eats something that contains a chemical it cannot digest, process or excrete, the chemical will stay in the animal’s tissues. Over time, as the predators further up the food chain eat more and more contaminated prey lower down, the level of chemicals in the predator is magnified. This is biomagnification.

Bioaccumulation and biomagnification are not natural processes. The chemicals involved can be toxic or dangerous to the animal eating them. For example, tiny pieces of plastic can be bioaccumulated or biomagnified. These are particularly problematic in aquatic ecosystems and can come from washing machines cleaning man-made fibres in clothes, the breaking down of larger plastics and micro-beads.


So what's the problem?

One of the major pollutants that has been found in animals studies by scientists researching bioaccumulation and biomagnification is microbeads.


Microbeads are tiny pieces of plastic that were used extensively within industry, especially in the manufacturing of beauty products such as skin exfoliants and toothpastes. Scientists and environmental charities raised concerns about the affect of micro-beads on animals in the ecosystem. Studies showed that the beads bioaccumulated in predators, negatively affecting their health. Microbeads were banned in the UK in 2019, but there are literally millions already in circulation in our oceans.