Bioamplification, Bioaccumulation and Bioconcentration

By: Julie van der Hoop

The confusion between bioamplification, bioaccumulation and bioconcentration is understandable. Yesterday, delegates asked for a clarification and explanation as to how this happens. These terms are not interchangeable, though they are often used as if they were. This post should clarify the situation.

bioaccumulation_graphic

Bioamplification (or biomagnification, as the picture shows) refers to an increase in the concentration of a substance as you move up the food chain. This often occurs because the pollutant is persistent, meaning that it cannot be, or is very slowly, broken down by natural processes. These persistent pollutants are transferred up the food chain faster than they are broken down or excreted.

In contrast, bioaccumulation occurs within an organism, where a concentration of a substance builds up in the tissues and is absorbed faster than it is removed. Bioaccumulation often occurs in two ways, simultaneously: by eating contaminated food, and by absorption directly from water. This second case is specifically referred to as bioconcentration.

So, what have we learned? Bioconcentration and bioaccumulation happen within an organism, but biomagnification occurs across levels of the food chain. An example: phytoplankton and other microscopic organisms take up methylmercury and then retain it in their tissues. Here, mercury bioaccumulation is occurring: mercury concentrations are higher in the organisms than it is in the surrounding environment. As animals eat these smaller organisms, they receive their prey’s mercury burden. Because of this, animals that are higher in the food chain have higher levels of mercury than they would have due to regular exposure. With increasing trophic level, mercury levels are amplified.

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