Dirty water and biomagnification
When thinking about the unfathomable depth and breadth of the world’s oceans, it can feel like any pollutants from humans that wind up there must be diluted beyond carrying any risks. And while in some ways this is true, it’s also not the reality when considering the way a food web and its environment interact.
Organochlorines
One particularly worrisome class of chemical pollutants are organochlorines, such as PCBs. These have been widely used as insecticides; as a sheep dip, for treating timber, and within the home, among other uses. Many of these substances do not break down easily and persist in the environment.
Substances like these find their way into all levels of the food chain and persist in the body. Every time a predator eats its prey, it accumulates all the toxin load its prey has accumulated (and the load of its prey’s prey before it). Whales (and humans) are at the top of their respective food chains, meaning they wind up with the highest toxin level.
Though these compounds were restricted in the 1970s and banned in Aotearoa New Zealand in 2004, 20% of PCBs ever made have found their way into the ocean, and into the systems of the creatures that live there. According to the Department of Conservation:
The World Health Organisation standard classifies any material with a PCB level of 50 parts per million (ppm) as highly toxic waste. Levels of organochlorines found in marine mammals in some parts of the world far exceed this level.
Biomagnification
This is an additional video, hosted on YouTube.
Climate changes
Plastic ocean
Currently, more than 11 million metric tons of plastic are flowing into the ocean each year. By 2050, there could be more plastic in the sea by weight than fish.
Cetaceans are far from the only animals dying in droves from plastic pollution. As consumers, it’s on each one of us to become more conscious of how we buy, use, and dispose of plastic packaging.
Further resources
Toxic tides, troubled whales: the toll of chemical pollution, Whale and Dolphin Conservation UK
Organochlorines, Science Learning Hub
Threats to whales, NZ Department of Conservation
Whales and the plastics problem, WWF
This young whale died with 88 pounds of plastic in its stomach, National Geographic
Plastic pollution likely killed whale found with nearly 30 kg of rubbish in its stomach, ABC News
The Significance of Whales to Aotearoa New Zealand
The Significance of Whales to Aotearoa New Zealand
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