Toxic Chemicals May Kill Half of Killer Whales in a Few Decades, Research Finds

Category: Science/Environment

Listening

Unlocking Word Meanings

Read the following words/expressions found in today’s article.

  1. annihilate / əˈnajəˌleɪt / (v) – to completely destroy something
    Example:

    Climate change has annihilated some species of animals.


  2. diminish / dɪˈmɪnɪʃ / (v) – to lessen or reduce something
    Example:

    Cutting down trees greatly diminished the number of animals in the forest.


  3. equilibrium / ˌiːkwəˈlɪbrijəm / (n) – a state of equality in balance
    Example:

    It was difficult to maintain equilibrium between my spending costs and savings.


  4. hemisphere / ˈhɛməˌsfiɚ / (n) – one half of the Earth
    Example:

    Australia is one of the countries I would like to visit in the Southern Hemisphere.


  5. leach / liːtʃ / (v) – to cause a substance to be washed off from something
    Example:

    When it rains, harmful chemicals that are leached from the soil can flow into rivers and oceans.


Article

Read the text below.

Pollution from toxic chemicals threatens to annihilate half of the entire killer whale population, a new study has found.


An international research team observed 351 killer whales, also commonly called orcas. The team studied how polychlorinated biphenyls (PCBs) and other toxins affected the orca population.


PCBs were used in plastics, dyes, and oils for motors until the chemicals were banned in the 1970s and 1980s due to their harmful effects. Although many years have passed since the ban, one million metric tons of PCBs have not yet been disposed of properly. Thus, the chemicals still continue to leak into oceans from landfills.


The study found that concentration of PCBs is highest among orcas, who are at the top of the aquatic food chain. This is because chemicals accumulate in the blood of predators as they eat smaller contaminated animals.


In addition, the research also revealed that orca populations in Brazil, Japan, Northeast Pacific, Strait of Gibraltar, and the United Kingdom are diminishing fast. Scientists predict that half of orcas would be extinct within a few decades due to PCB contamination. This poses a threat to the equilibrium in ocean ecosystems, as other animals may increase uncontrollably when the population of the top predator drops significantly.


Marine Biologist Ingrid Visser, who was not part of the study, expressed concern about the findings. Based on her own research on New Zealand Orcas, she said that the species is the most PCB-contaminated animal in the Southern Hemisphere. In line with this, she asserted that research on orcas must be taken seriously and that further leaching of PCBs into the ocean must be prevented.


Viewpoint Discussion

Enjoy a discussion with your tutor.

Discussion A

• Do you think the further decline of orcas can still be prevented? Why or why not?
• Why do you think it is important to monitor the population of animals? Explain.

Discussion B

• What do you think manufacturers should do before using new chemicals on their products? Discuss.
• How do you think chemical contamination of oceans can be prevented? Discuss.