Marine pollution – chemicals in the ocean.

What is bioaccumulation?

A major issue with marine pollution is bioaccumulation. Bioaccumulation is when chemicals build up in an organism in the natural world. These chemicals are often toxic. This is caused by marine pollution.

In the ocean, chemicals get into the food chain at the base. The smallest organisms absorb them faster than they can eliminate them from their system. This gradual build up in the individual is bioaccumulation. When these smaller organisms are then eaten by the next trophic level animal in the food chain, this is biomagnification. A lot of these chemicals are man made and don’t break down easily in the natural environment. Marine pollution builds up with each layer in the food web, the toxins magnify.

Where does marine pollution come from?

Some of these man made chemicals which are still prevalent in the oceans today are DDT, an insecticide used extensively after WW2; and PCB’s, a flame retardant. These chemicals were banned from production in the 70’s and 80’s, but can still be found in the living tissues of large marine animals, including sharks and marine mammals – those animals at the top of the food chain.

Another example of this is natural, but still highly dangerous to humans. Ciguatera is a food borne illness, from eating fish contaminated with the toxin. The toxin is produced around coral reefs by tiny organisms called dinoflagellates. The fish then eat these small zooplankton. Commonly affected fish include barracuda, grouper, snapper and many of the other large reef fish towards the top of the food chain. This toxin is harmless to the fish, but potentially deadly to humans. Symptoms include nausea and pain, as well as neurological and cardiac affects. Cooking the fish does not destroy the toxin, and it is odourless and tasteless, so you will not be able to tell if the fish you’re eating is contaminated.

In the Caribbean, the locals have a couple of ways they ‘test’ whether the fish is contaminated. One I was told is if you take the guts from the fish and put them on the beach, if the ants eat the guts then the fish is safe to eat. Can you believe this old wives tale?

So, is it worth eating some if these higher food chain animals?

Marine pollution makes this worth thinking about at least.