As man-made toxicants make their way
up the food chain, they accumulate and become concentrated
in the fats of top order predators, a process known as 'biomagnification.'
Drawings: Judith Scott.
November 2, 2001
Ocean or 'Toxic Soup?'
This is Genevieve Johnson speaking to you from the Odyssey in Darwin, Australia.
"Chemicals that were developed to control disease, increase food production, and improve our standard of living are a threat to biodiversity and human health"-according to a January 1999 World Wildlife Fund (WWF) Issue brief - "Persistent Organic Pollutants".
Because the risk from these originally well-intentioned chemicals now outweighs their benefits, their continued use is no longer warranted in modern society.
Today, the contamination from persistent man-made chemicals is a pervasive global problem that urgently demands a global solution.
These contaminants are found in all of the world's oceans. They include pesticides such as Dichlorodiphenyltrichloroethane (DDT), and many industrial chemicals including Polychlorinated Biphenyls (PCBs) which are used in the production of plastics, carbonless paper and paint.
Given enough time, most contaminants end up in the oceans and there are strong indications that this toxic soup is killing the Earth's marine life. They have the potential to interfere with an individuals' ability to develop and behave normally, to breed and to cope with stress and infectious disease. These pollutants are generally non-biodegradable, meaning they are resistant to the normal processes of degradation. They have a special affinity for fat, accumulating in the bodies of most fish and marine mammals. These compounds accumulate in greater concentration as they move up the food chain from one creature to another - a process called 'biomagnification'. In this way, small levels of contaminants in water or soil can magnify into a significant hazard to predators feeding at the top level. No level of the marine food chain is exempt.
As a result, apex predators such as birds, fish and marine mammals possess the highest concentrations of these compounds in their fatty tissue and are thus most vulnerable.
Not only do these chemicals build up as a result of biomagnification, but they also move across generations in a process called 'bioaccumulation'. It has been suggested that synthetic chemicals that accumulate in the tissues of female mammals over an entire lifetime, are transferred to their offspring during gestation and lactation. The effects on the young can be insidious and grow exponentially with each generation. The young animal does not begin its life as a pristine creature, it now carries contaminants passed on from it's mother as well as accruing a continuous load of chemicals as it feeds throughout it's life.
It is a disturbing and perhaps more urgent issue considering the fact that humans are long-lived, top order predators, situated at the apex of food pyramids. In just the same way that toxicants are building up in the tissues of the great whales, humans are equally susceptible. Especially when we consider that the oceans are one of our main sources of food.
Already these poisons have been linked to hearing loss, learning disabilities, suppressed immune systems, cancers, it is believed they may act as hormone mimics and endocrine disrupters. Alarming results of this global experiment are already showing that the native Inuit's of the Arctic, whose diet is dependant to a large extent on marine mammals, are accumulating the highest levels of contamination from man-made toxicants in the world - the effects of which are now noticeable in their children.
Living in a dramatically altered, manmade landscape, we easily forget that our well being is rooted, in fact utterly dependent on, healthy functioning natural systems, such as clean air, clean soil and clean fresh water.
As stated by early twentieth century environmental philosopher, John Muir, "When we try to pick out something by itself, we find that it is bound by a thousand invisible cords…to everything in the universe."
The Voyage of the Odyssey and its goals are a vital first step in this process of understanding human impacts on the marine environment. By establishing baseline levels of toxicants in the oceans, we hope to inspire awareness and change.
Log by Genevieve Johnson
- In the Company of Whales - Status report on the world's oceans 1992.
Center for Marine Conservation for The Discovery Channel.
- Persistent Organic Pollutants - Issue brief, Jan 1999.
World Wildlife Fund.
- Our Stolen Future - Colborn, Dumanoski, Myers.
Penguin Books, 1997.