Вы услышите интервью. В следующих заданиях выберите правильный ответ.
1. Algae is
1) out of control.
2) highly concentrated.
3) a plant-like creature.
2. Red tides are
1) always the same colour.
2) many different colours.
3) never colourless.
3. Water pollution is
1) a natural phenomenon.
2) caused by humans.
3) increased by algae.
4. High levels of nitrates and phosphates in the ocean
1) kill algae.
2) encourage the growth of algae.
3) are common in unpolluted waters.
5. Red tides that produce toxins
1) kill off fish.
2) must not be fished in.
3) can cause death in humans.
6. The term ‘algal bloom’
1) is unpopular with scientists.
2) is popular with the public.
3) refers to red tides.
7. When asked where red tides occur, Dr Samuel says they are
1) rare in freshwater bodies.
2) common near shorelines.
3) an exclusively marine phenomenon.
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2 – 2
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5 – 2
6 – 3
7 – 2
A: Welcome back, listeners. Now, many of you will have heard the reports in recent days about red tides along our coastline but, like me, still not know what red tides actually are. So I’m delighted to welcome Dr Alice Samuels to the studio. So, Dr Samuels, what are red tides?
В: Well, the ocean is full of tiny plant-like creatures called algae. Sometimes, conditions cause these algae to grow out of control. Higher-than-normal concentrations of algae in the ocean can discolour the water and cause the phenomenon known as red tides.
A: So red tides are simply an overgrowth of algae in the ocean?
A: And this turns the ocean red?
B: Sometimes. Although the name implies otherwise, red tides aren’t always red. They can be green, brown, pink, or even purple in colour. Or, the water can remain its normal colour.
A: I see. And are red tides a natural phenomenon?
B: They can be. But they are also caused by human activities. For example, water pollution can cause red tides. When human sewage is dumped into the ocean or when fertiliser from farmland washes into the ocean, nitrate and phosphate levels in the water increase. The growth of algae depends on the nutrients nitrate and phosphate. The algae feed on these nutrients; the population explodes; and a red tide forms.
A: I’ve heard red tides can produce toxins.
B: Yes. Most red tides are harmless. But occasionally they are caused by species of algae that produce toxins. The toxins aren’t fatal to humans – they only cause irritation. However, humans still need to be careful because the toxins can build up in the tissues of fish. So fishermen need to avoid catching fish near red tides, because eating these fish can cause food poisoning.
A: I’ve heard red tides being called ‘algal blooms’…
B: Yes. The term ‘red tide’ is actually being phased out among scientists and being replaced with ‘algal bloom’. This is because, as I mentioned, red tides are not always red and also because they are completely unrelated to the movements of tides. Scientists use the term ‘algal bloom’ as it’s more accurate. But the public will probably go on calling algal blooms red tides.
A: Where are red tides usually found?
B: Red tides occur in every ocean and sea in the world. They usually occur in coastal areas, not out at sea, so you might have seen one when you were walking along a beach. Red tides are not just a marine phenomenon though. Estuaries, lakes and rivers also experience them.