What's polluting the whales?

Things to think about

1. Before viewing

How would you describe the environment of Antarctica?

Large numbers of whales are often found in the waters of Antarctica, why might they be found there?

How might chemical pollutants get into a whale's body?

2. As you view

The scientists are collecting krill. What are they trying to find out?

Watch the examples of chemical use in the past. What properties of these chemicals 'POPs' resulted in them being banned?

The presenter uses a model of the Earth to describe the movement of chemicals in the atmosphere. How do the chemicals travel to Antarctica?

3. After viewing

Draw a food web illustrating how the chemicals accumulate in Antarctic species, starting with how they enter the food chain through algae.

On a diagram of the planet, illustrate the processes involved, such as evaporation and condensation, that result in chemical pollutants being concentrated at Earth's polar regions.

4. Next steps

How can other substances accumulate in food webs, for example heavy metals in fish populations?

List other examples of where polluting activities in one part of the world can affect other regions far away, for example fertiliser run-off into the oceans.

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3 mins 32 secs

Source: Catalyst | Learning area: Science | Secondary: Years 7, 10




00:00:11:18MARK HORSTMAN:Of all the continents, Antarctica is the coldest, the driest, the highest, the windiest and the brightest. And as the only landmass with hardly any people, you'd expect that it's also the cleanest. For the Southern Hemisphere's population of humpback whales to remain healthy, Antarctica needs to be free of chemical pollution.

...Read more >

00:00:41:09DR SUSAN BENGSTON NASH:The main concern is that the diffused toxic effect it has in just compromising the immune system and, therefore, making the humpback whales more vulnerable to fighting disease.00:00:54:18MARK HORSTMAN:But new research is revealing that humpback whales are contaminated by toxins that can only come from their staple diet of krill. A few years ago, Susan Bengston Nash analysed several thousand of them to see what they might contain.00:01:16:05DR SUSAN BENGSTON NASH:We started with krill, krill being the keystone species of the Antarctic, meaning that if you remove the krill you're also effectively removing other species. So it made sense to really start with krill. Find out what's in krill and thereby you can see what predators are exposed to as well.00:01:35:23MARK HORSTMAN:She found more than 100 different forms of chemicals, known as persistent organic pollutants or 'POPs' for short. They're organochlorine pesticides like DDT... or industrial chemicals like PCBs and dioxins. Many were banned decades ago, but are so long-lived they continue to persist today. The problem is that persistent organic pollutants aren't broken down by water. Instead, they dissolve in the body fat of animals.00:02:13:05DR SUSAN BENGSTON NASH:They're very lipophilic, so fat-loving. So if they do make it into the food web they can accumulate in our bodies.00:02:22:04MARK HORSTMAN:But how do these synthetic chemicals end up in remote Antarctica, far away from agriculture and industry? Let's say we dump a load of DDT onto our imaginary planet here. Now, it's long-lived and a volatile chemical. So over decades it evaporates out into the atmosphere. And it only comes back down again when it hits a colder temperature and condenses out of the air. That's how these chemicals move around the world, bouncing from a warm climate down to a colder climate. But, of course, once they're down here it's a one-way trip. There's no going back. That's why persistent organic pollutants end up concentrating at the poles.00:03:07:13DR SUSAN BENGSTON NASH:Assuming that an air mass has deposited some DDT out of the atmosphere onto the ice, perhaps, then in the summer, when the ice melts, it would either be taken up by herbivores, such as the krill, or else deposited to the sea bed.00:03:23:03MARK HORSTMAN:And after krill?00:03:24:15DR SUSAN BENGSTON NASH:After krill you've got everything else in the Antarctic.

For teachers

  • Science: Year 7
  • Strand: Science Understanding
  • Substrand: Biological sciences
  • Content code: ACSSU112
  • Content description: Interactions between organisms can be described in terms of food chains and food webs; human activity can affect these interactions
  • Science: Year 10
  • Strand: Science Understanding
  • Substrand: Earth and space sciences
  • Content code: ACSSU189
  • Content description: Global systems, including the carbon cycle, rely on interactions involving the biosphere, lithosphere, hydrosphere and atmosphere

About this resource



Date first broadcast:

16 October 2008

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What's polluting the whales?