雅思阅读第084套P2-The cells from hell

The cells from hell

Recently, an international team of biologists met to discuss what they believe is a global crisis in the sudden appearance of strange marine microorganisms capable of poisoning not just fish but people too.

In the mid-1980s, fishermen in North Carolina, on the eastern coast of the United States, began complaining about mysterious fish kills. They were convinced that pollution was responsible but nobody would listen. That changed in 1988 after an accident at. a research center. Tank after tank of fish suddenly died. Researchers spotted an unknown microorganism in the water. It was later named pfiesteria.

Pfiesteria belongs to a prehistoric group of algae that are part plant, part animal. They are called dinoflagellates after the liny whips or flagella that propel them through the wafer. Magnified a thousand limes they are some of the strangest and most beautiful creatures in the sea. They are at the bottom of the food chain but, to deter fish from swallowing them, some have evolved powerful toxins.

As the researchers were to discover, pfiesteria doesn’t just discourage fish. It actively hunts them, then eats them. Fish are one of its preferred foods but one of the intriguing things about pfiesteria is that it will eat everything from bacteria to dead plant and animal remains all the way up to mammalian tissues. So its food spans the entire food web of an estuary. Gradually the researchers realised that nothing in the water was safe from pfiesteria. It could harm humans too. A mis-directed air-conditioning duct from a room containing the toxins nearly killed one of the researchers. He suffered a host of symptoms ranging from profuse sweating, tingling hands and feet, to liver and kidney problems, as well as memory

As the research intensified, some startling discoveries were made. In tanks, pfiesteria was quite content to behave like a plant and photosynthesize. However, when fish were added, a dramatic transformation occurred, pfiesteria switched to attack mode. In a matter of minutes it changed shape and secreted a toxin. The fish quickly became disorientated and within five minutes all were dead. Pfiesteria changed shape again and devoured them. When it had had its fill, it vanished. No one had ever seen an organism do this.

Initially scientists believed this was part of a natural cycle, but on closer examination, it seemed pollution was to blame. When the water containing the biggest fish kills was analysed, scientists found high levels of pollution. But this is just one of the factors that can boost the transformation in pfiesteria. Others include large numbers of fish travelling together which feed in poorly flushed places with a lot of algae to eat and other rich food sources. That is the perfect habitat for pfiesteria.

But pfiesteria is not the only concern. In the oceans all around the world similar kinds of algae are now materialising and turning toxic. In the last decade these algal blooms¹ have poisoned sea-lions in California, caused catastrophic fish kills in the Pacific, the Mediterranean and the North Sea, and devastated the shellfish industry in New Zealand. Researchers from forty-seven nations met recently to share the latest information about harmful algal blooms. They heard about new kinds of toxins and discussed possible links between algae and whale standings. But what dominated the proceedings was news that toxic algae are spreading to new shores in ballast water carried by ships.

That may have already happened in Australian waters. A tuna kill in 1996 cost fish farmers an estimated $45 million. The official explanation was that a storm was to blame. But there were also reports of orange-brown streaks in the water. When a water sample was examined, it was found to be teeming with an alga never before seen in Australia, called chattonella. The same chattonella killed half a billion dollars’ worth of fish in Japan in 1972.

This toxin was also present in the livers of the dead tuna. Despite this powerful evidence, the official explanation remains that a storm was the killer. However, in Japan this was a prime example of an algal bloom induced by the waste products of the aquaculture industry itself, and of course that is not something that the tuna industry wants to hear.

It is clear that chattonella is present in Australian waters. But there is little knowledge of what else may surface or where it may have come from. What is of greater concern is that, in Australia and around the world, there is a reluctance to acknowledge that it is human activity which is triggering the transformation of normally benign organisms into increasingly dangerous forms. If we continue to mismanage the way nutrients and pollutants are released into the environment, we will have to confront new versions of the cells from hell.

Glossary

¹ algal bloom: The rapid growth under specific conditions, of minute aquatic plants

SECTION 2: QUESTIONS 14-26

Questions 14-17

Complete the summary below.

Choose your answers from the box below the summary.

There are more words than you need so you will not use all of them.

List of Words

Questions 18-21

Fill in the blanks with NO MORE THAN THREE WORDS from the passage.

Questions 22-26

Classify the following as:

Example

Serious illness of researcher A

22 _________ death of sea-lions off the coast of California (1990s)

23 _________ fish kill in Japan (1972)

24 _________ shellfish industry losses in New Zealand (1990s)

25 _________ tuna industry losses in Australia (1990s)

26 _________ fish kill in North Carolina (1980s)