Defining Bioaccumulation
Bioaccumulation refers to the increase in concentration of a substance, such as a pesticide or heavy metal, in an organism over its lifetime. This occurs as the organism absorbs the substance faster than it excretes it, resulting in a buildup within a single individual from its immediate environment, including its diet.
Defining Biomagnification
Biomagnification, on the other hand, describes the increasing concentration of a substance in the tissues of organisms at successively higher trophic (food chain) levels. It happens when a bioaccumulated substance is transferred from prey to predator, becoming more concentrated as it moves up the food web because predators consume many contaminated prey.
A Practical Example
Consider mercury in an aquatic ecosystem: a small fish might bioaccumulate mercury in its body over time, even if the water concentration is low. When a larger predatory fish eats many of these smaller, mercury-laden fish, the mercury biomagnifies, resulting in significantly higher concentrations in the larger fish's tissues than in its prey or the water.
Ecological Importance and Applications
Understanding these processes is critical for assessing ecological and human health risks associated with persistent environmental pollutants. It helps explain why apex predators, including humans who consume contaminated seafood, can accumulate dangerously high levels of certain toxins, even when pollutant levels in the environment seem relatively low.