Bioaccumulation Facts for Kids

Bioaccumulation is when substances, like pesticides or other chemicals, slowly build up inside a living thing. This happens when an organism takes in a substance faster than it can get rid of it. So, if a harmful substance stays in the body for a long time, there's a bigger risk of getting sick, even if there isn't much of it in the environment. For example, scientists can predict bioaccumulation in fish.

When metals build up in the body, it can cause harm. If an organism takes in a metal faster than it can use or get rid of it, the metal will accumulate. Understanding bioaccumulation helps us check for harmful chemicals in the environment and control their use.

Living things can take in chemicals by breathing, absorbing them through their skin, or swallowing them. When a chemical's concentration is higher inside an organism than in its surroundings (like air or water), it's called bioconcentration. Another related process is biomagnification. This is when the amount of a chemical or metal increases as it moves up the food chain from one animal to another. Bioaccumulation is a natural process needed for growth. However, harmful substances can also build up this way.

How Chemicals Build Up
Real-Life Examples
- On Land
- In Water
Studying Turtles
- Effects on Turtle Development
See also

How Chemicals Build Up

Chemicals can enter an animal's body in different ways. They might breathe in polluted air or water. They could also absorb chemicals through their skin. Eating food or drinking water that contains chemicals is another common way. Once inside, these substances can get stored in different parts of the body. For example, some chemicals like DDT or methylmercury are "fat-soluble." This means they can dissolve in fats and oils. So, they often get stored in an animal's body fat.

When an animal uses its fat for energy, these stored chemicals can be released. This can cause sudden sickness or poisoning. The longer a harmful substance stays in an animal's body, the more it can build up. This is why even small amounts of a chemical in the environment can become dangerous over time.

Real-Life Examples

On Land

Have you ever heard the phrase "mad as a hatter"? This saying came from the 18th and 19th centuries in England. Hat makers used mercury to stiffen the felt for hats. The mercury would build up in their bodies, especially in their brains. This caused mercury poisoning, making them act strangely.

Another example is Strontium-90. This substance comes from nuclear fallout (dust from atomic bombs). Strontium-90 is very similar to calcium. Because of this, it gets taken up by the body and builds up in bones. Once in the bones, its radiation can cause damage for a long time.

Some animals use bioaccumulation to protect themselves. They eat toxic plants or animals and then store the toxins in their own bodies. This makes them poisonous to predators. For instance, the tobacco hornworm caterpillar eats tobacco plants. It builds up nicotine (a toxic chemical in tobacco) to a level that harms predators. If small animals eat these toxic creatures, the poison can move up the food chain.

Even substances that aren't usually considered toxic can build up to dangerous levels. A classic example is vitamin A. This vitamin becomes highly concentrated in the livers of carnivores, like polar bears. Polar bears eat seals, which also eat other animals. So, polar bears accumulate huge amounts of vitamin A in their livers. Native people in the Arctic knew not to eat the livers of carnivores. But some Arctic explorers got sick from eating bear livers. There was even a case of Antarctic explorers getting sick from eating husky dog livers.

In Water

Coastal fish (like the smooth toadfish) and seabirds (like the Atlantic puffin) are often checked for heavy metal bioaccumulation. Methylmercury enters freshwater systems from factories and rain. As it moves up the food web, its concentration increases. This can reach dangerous levels for fish and for humans who eat fish.

Scientists often study fish to see how chemicals build up in them. Common fish species used for this include the common carp, rainbow trout, and bluegill sunfish. Fish usually take in chemicals from the water through their skin. They can also get harmful chemicals by eating other organisms or substances in the water that contain them.

Natural toxins can also bioaccumulate. For example, marine algal blooms, known as "red tides," can make filter-feeding organisms like mussels and oysters toxic. Fish on coral reefs can cause ciguatera poisoning. This happens when they accumulate a toxin called ciguatoxin from reef algae.

Studying Turtles

Scientists study bioaccumulation in turtles. This happens when synthetic organic contaminants (like certain chemicals) or heavy metals enter a single turtle. These substances can harm the turtle's health. Researchers are studying how pollution, climate change, and changes in habitats affect the amount of these toxins in the ecosystem.

The most common elements studied in turtles are mercury, cadmium, and selenium. Heavy metals get into rivers, streams, lakes, and oceans. Plants living in these places absorb the metals. Turtles naturally eat these plants and sediments, so they take in various trace elements. Once these substances enter the turtle's bloodstream and muscles, their concentration increases. They can become toxic, possibly causing problems with the turtle's body processes, hormones, and ability to reproduce.

Some marine turtles are used for studies because they live near shorelines. This makes it easier for scientists to collect blood samples and other data. Freshwater turtles are also good for studying bioaccumulation. Since they usually stay in a small area, scientists can link the chemicals found in the turtles to the specific water body they live in.

Effects on Turtle Development

High levels of toxins in turtle eggs can harm the baby turtle's development. For example, in the Australian freshwater short-neck turtle (Emydura macquarii macquarii), mother turtles accumulated certain chemicals. They then passed these chemicals into their eggs. This affected how the baby turtles developed and how they stored fat.

Also, high levels of heavy metals were seen to lower the egg-hatching rates in the Amazon River turtle, Podocnemis expansa. In these eggs, heavy metals reduced the fat and changed how water was filtered. This can affect how many turtle eggs survive and hatch.

Bioaccumulation facts for kids

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