Bermudian Biomagnification Pyramid
 

Nahant Biomagnification Pyramid

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Nahant

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Biomagnification occurs when a chemical increases in concentration as it moves along a food chain.  "In essence, the biomagnification results from a sequence of bioaccumulation steps that occur along the chain," (Baird 305).  We will use some of the organisms from the Nahant pyramid as an example of how this works.  Mitilus edulis (mussels) start out the chain because they are filter feeders.  Filter feeders actively filter the water for planktonic organisms which they will eat.  Since they take the food directly from the water column, they naturally absorb some of the chemicals that may be in the water.  The concentrations are still relatively low at this stage.  Asterias forbesi (sea stars) then eat the mussels, acquiring their concentrations of chemicals.  Since the sea stars are higher on the food chain, they naturally have to eat more than the mussels to sustain themselves.  By eating more, the sea stars accumulate more of the chemicals.  Thus is the beginning of the biomagnification effect.  It is then possible for some bird of prey to eat the sea stars, and accumulate all of the chemicals inside of them.  In summation, biomagnification is simply the accumulation of chemicals from one trophic level to another due to the increased ingestion needs of the animals higher on the food chain. 

Pictures located at the gates of the Northeastern University study site in Nahant, MA.  It is not a good idea to eat the filter feeders from this area because of the possible toxins they may be storing, which would be transferred to the one ingesting the food, propagating biomagnification.

Bermudian Biomagnification Pyramid:

Nahant Biomagnification Pyramid: