Shark Meat, What is Bioaccumulation?

 
 

Aside from the slow reproductive rate of sharks (which makes populations very slow to bounce back from overfishing), we should not be consuming these animals due to the toxic metal levels found in their tissues. Sharks have a much higher concentration of metal toxins because of their high status on the food chain, a process that can be explained by “bioaccumulation”.

Heavy metals naturally occur on our planet because they are a part of our Earth’s crust. These elements cannot be broken down into simpler forms. Such metals can be toxic when consumed, for example mercury, arsenic and lead. So why are these toxic elements found in our water? The simple answer is that when the elements are worn off of rocks, they seep into the groundwater and enter bodies of water eventually via waste dumps, sewage, rain, runoff, etc. It goes without saying that a lot of this is due to the burning of fossil fuels, all kicking off with the Industrial Revolution.

When mercury is converted by microorganisms it turns into Methylmercury. Methylmercury, according to the World Health Organization, is the most toxic of all mercury compounds. Unfortunately for us humans, this compound is extremely common in the ocean, and therefore our seafood. It messes with our nervous system to potentially cause memory loss, insomnia, motor and cognitive disfunction and strongly affect child development in pregnancies.

Okay, so what is bioaccumulation? Bioaccumulation is a process by which heavy metal compounds are consumed by the lower trophic levels (bottom of the food chain) and builds up in the high trophic levels when consumption. In other words, the metals are “biomagnified” as you move up the food chain. Concentrations of these metals accumulate in larger fish (such as sharks) faster than they can naturally eliminate it. No only are sharks filled with these toxins, but they also offloaded them into their pups. So when a pup is born they already have a high threshold of metals in their bodies. It has been found that juvenile Great White Sharks actually have some of the highest levels of DDT measured.

 
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Laurel Irvine