1. Mercury enters the ecosystem: Mercury is released into the environment through natural sources like volcanic eruptions and human activities like burning fossil fuels. It then transforms into methylmercury, a highly toxic organic form of mercury.
2. Small organisms absorb methylmercury: Methylmercury is taken up by small organisms like phytoplankton and zooplankton at the bottom of the food chain. They accumulate small amounts, but it's not harmful to them.
3. Biomagnification: As larger fish eat smaller fish, the methylmercury that's been accumulated in each prey fish gets passed up the food chain. Because each predator eats many prey, the methylmercury concentration increases at each trophic level.
4. Top Predators: Top predators like tuna, swordfish, and sharks are at the top of the food chain and have eaten many fish throughout their lives. This means they have accumulated high concentrations of methylmercury.
Here are some key factors contributing to biomagnification:
* Methylmercury is fat-soluble: This means it's stored in fatty tissues of organisms, making it difficult to break down and excrete.
* Long lifespan: Top predators often live longer, giving them more time to accumulate methylmercury.
* High trophic level: Top predators eat many prey, concentrating the methylmercury from all those individuals.
Consequences of high methylmercury levels:
* Methylmercury is toxic to the nervous system, especially in developing brains.
* It can lead to neurological disorders, developmental problems, and reproductive issues.
* High levels of methylmercury in fish can pose a risk to human health, especially for pregnant women, young children, and those who eat fish frequently.
Important Note: While methylmercury is a serious concern, it's important to remember that fish are a valuable source of nutrients. To minimize exposure, the Food and Drug Administration (FDA) provides recommendations for limiting consumption of certain types of fish.