VCE Environmental Science

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What is the difference between bioaccumulation and biomagnification? Read an interesting article from the Scientific American – “Bald eagles succumb to poisin in rat eradication on Alaskan island” . Is this an example of bioaccumulation or biomagnification?

Local examples of bioaccumulation from the Australian government department of environment, water, heritage and the arts – uranium in freshwater mussles and fish in the Northern Territory. Bioaccumulation of copper and tungsten in northern Queensland. What types of toxins are most likely to bioaccumulate and biomagnify?

“Almost all mercury compounds are toxic and can be dangerous at very low levels in both aquatic and terrestrial ecosystems. Because mercury is a persistent substance, it can build up, or bioaccumulate, in living organisms, inflicting increasing levels of harm on higher order species such as predatory fish and fish eating birds and mammals through a process known as “biomagnification”. Although the long-term effects of mercury on whole ecosystems are unclear, the survival of some affected populations and overall biodiversity are at risk.” from Mercury and the Environment. Another resource about mercury in our environment here: “Methylmercury Contamination in Fish and Shellfish.” Health effects of mercury here: “Mercury in the body and health effects“.

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Mercury, dioxin, hexachlorobenzene and polycyclic aromatic hydrocarbons (PAH’s) are all persistent, bioaccumulative toxics (PBT’s) and therefore pose risks to human health and the environment. Hexachlorobenzene and PAH’s are probably carcinogens, according to the U.S. E.P.A. More information here.

This animation shows the chain of contamination in the human food supply.

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Mercury is a metal which bioaccumulates – which means it can build up in tissues. It is a potent toxin that affects the nervous system of mammals and is especially harmful to developing fetuses. It can cause sensory loss, tremors, loss of muscular coordination, speech, hearing, and visual problems, as well as increased risk of heart attack.

Mercury gets into the environment when toxic waste is burned and the mercury molecules fall from the smoke onto the ground and into water. It moves up the food chain when herbivores eat contaminated plants and drink contaminated water; these animals in turn are consumed by predators, which have a higher concentration of mercury in their flesh.

Californian scientists have found that the mercury in fish is found as a compound with carbon and sulphur, not as methyl-mercury chloride as previously assumed. Further research needs to be done, but it may mean that the mercury in fish is not as toxic as previously thought.

Find out more at: 

• Catalyst;
• National Pollutant Inventory
• Australian Government Food Standards on Mercury