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CELPIP Practice Reading: Reading for Information ID: #63081 Medium Zebra mussels in the Great Lakes

Read the following passage.

A. Zebra mussels are small freshwater mollusks, usually 2 to 2.5 centimetres long, with zigzag patterns of black or brown on white and yellow. They come from the region around the Black and Caspian seas in southeastern Europe. In the late 1980s they entered the Great Lakes in ballast water discharged from ships, and the first established population was discovered in 1988 in Lake St. Clair, which connects to Lake Erie and Lake Huron. Scientists have deduced that the likely source was a single cargo ship travelling from the north shore of the Black Sea, which released larvae during its ballast exchange.

B. From there the mussels spread quickly across the Great Lakes and later through much of eastern Canada and the United States. They breed fast, since a female can release up to one million eggs in each breeding season. The larvae, called veligers, are microscopic and swim freely for up to a month, carried by currents until they settle on a solid surface. Adults then fix themselves to rocks, docks, boats and plants with strong threads, sometimes at densities of more than 700,000 per square metre. Out of water they can live for up to 18 days in high humidity, which lets them be carried over land on boats.

C. Each mussel feeds by filtering water, and a large population can quickly clear the water of almost all floating particles. In Lake Erie, transparency increased by 100 per cent during the first years of the invasion. The filtering removes plankton that native species feed on, which can shift local food webs. Zebra mussels also attach to native mussels, many of which are species at risk, and can suffocate them. In Canada they do millions of dollars in damage each year by clogging the intakes of power stations and water treatment plants.

D. Once established, a population is very hard to remove, so management focuses on prevention. Zebra mussels are one of six species prohibited under the federal Aquatic Invasive Species Regulations, so they cannot legally be imported into Canada. Since January 1, 2022, Ontario's Invasive Species Act has required boaters to clean plants and animals off their boats and to drain standing water before launching. Ships coming into the St. Lawrence Seaway from beyond the sea zone Canada controls are inspected before they enter the Great Lakes, to check that they have exchanged their ballast. Since these inspections began in 2006, no new non-native species attributed to ballast water has been reported in the Great Lakes.

E. Not given in any of the above paragraphs.

Decide which paragraph, A to D, has the information given in each statement below. Select E if the information is not given in any of the paragraphs.

- 1.
These invaders can kill other mussels by fastening themselves onto them.

- 2.
The earliest lasting group of these mussels was found in a lake linked with both Lake Huron and Lake Erie.

- 3.
In one lake, the water became twice as clear soon after the mussels arrived.

- 4.
University divers were the first people to notice the mussels in North American waters.

- 5.
Anyone taking a boat out in Ontario must now, by law, let the water inside it run out.

- 6.
These mussels cause more damage in Canada than any other invading species.

- 7.
Ships arriving from outside the waters Canada controls are examined before they may continue into the lakes.

- 8.
The young mussels can drift about in the water for weeks before they cling to something.

- 9.
It is against the law to bring these mussels into Canada.

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