Bio-magnification and bio-accumulation are terms which often get confused and misused by the media (and IB students!). Try to understand the distinction between the two:
A few slides on a powerpoint: BIO-MAGNIFICATION
READ THIS!!!! BIO-MAGNIFICATION
BBC 28th January 2017
The link below is to an excellent, excellent article, describing Swedish research which appears to demonstrate how the bio-magnification of mercury is being brought about as one of the effects of global warming. Increased bacterial presence in the oceans is adding another level in the food chains on top of the phytoplankton producers. This elongating of the food chain enables accumulation of mercury to dangerous concentrations by the time it reaches the higher trophic levels, including the fish we eat.Mercury is known as one of the most toxic elements to which humans and other living things can be exposed, and affects the nervous system in higher organisms.
READ THIS!!! A SAD STORY ILLUSTRATING BIO-ACCUMULATION
BBC May 2nd 2017
This sad story is about the death in 2016 of one of the few remaining killer whales which live off the western coasts of Scotland. Lulu was estimated to be 20 years old and was washed up dead and entangled in fishing net, on a small Scottish island. The cause of her death is not clear but an autopsy discovered unimaginable levels of accumulated PCB chemicals in her body. Polychlorinated biphenyls have been banned since the 1970’s but are so stable that, although slowly reducing in quantities, they are still very present.
PCB’s are synthetic and were widely used in all sorts of ways mid 20th century, but after their toxicity and tendency to bio-accumulate in food chains was better understood, they were banned. Nevertheless PCB’s remain present in the environment and it will be a long time before they vanish.
PCB’s are known to affect reproduction and can damage the immune and nervous systems. The autopsy of Lulu revealed that she probably had never born calves, perhaps because of the high amount of PCB’s in her tissues. It is also quite likely that she suffered brain damage as a result of PCB toxicity.
8 killer whales remain in the pod (group of whales) off western Scotland and one wonders about the PCB levels in their bodies, and whether this bio-accumulation is sadly a major contributing factor to their slow disappearance and projected extinction.