integrated task

The passage states that the zebra mussel, a fresh water fish of Eastern Europe has been spread out to Native America, it believes that this invasion cannot be stopped and it poses threat to freshwater fish population in all of North America. It provides three reasons to support the claim. However, the lecture says the invasion can be stooped and it’s not clear yet that the zebra mussel is a serious threat. It opposes each reason mentioned in the reading.

First, the author posits that the history of the zebra mussel’s spread suggests that the invasion might be unstoppable. In contrast, the professor argues that its true that in the past people would not stopped it due to lack of knowledge. Now they can stop ship that carried ballast water from Europe to North America and replace the ballast water with ocean salt water, the zebra mussel cannot survive in the salt water.

Second, the article states that one the zebra mussels are carried to a new habitat, they can dominate it due to lack of a predator. On the other hand, the lecture refutes by stating that they do not have predator in the beginning, one aqua bird learns about them, they switch from their old prey to the zebra mussels. These birds eat many fishes, so the zebra mussel cannot become dominant.

Third, the author asserts that the zebra mussels are likely to cause a decline in the overall fish population in habitats, where they become dominant. However, the professor says they won’t decline overall fish population. It’s a true they have negative impacts on plankton fish but they have positive impact on the other species. The zebra mussels release nutrient in the water that reach to the fish at the lake bottom and their population will increase.
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