TPO26 - Integrated TOEFL essay

In this set of material, the reading passage claims that distribution of the zebra mussel, a kind of shellfish, in other areas besides its original habitat is not controllable and brings up three reasons to support. However, the lecturer finds all the ideas dubious and provides some evidence to advocate the idea that mussels do not threaten the fish population in North America.

First of all, it is mentioned in the reading passage that zebra mussels can attach themselves to the ships bottom and be transferred to different places in the North America. In contrast, the lecturer states that controlling the mussel's population was not possible in the past due to lack of knowledge but now, the vessels can be required to empty their ballast water - a suitable water for mussel's survival - while they are in the ocean and fill the ship again with ocean water. As the ocean's water is salty, the mussels will die.

Moreover, the author of the reading passage declares that mussels are hardy species and can survive and dominate in new places, especially that there would not be any predators in the destination. On the contrary, the professor contends that mussels cannot dominate an area because lack of predators may happen at the beginning of the mussel's migration but the birds are potential predators and can eat many mussels if there is not any food available.

Finally, the reading passage states that mussels pose a decline in the number of fish in the destination and new habitat where they will dominate. Conversely, the lecturer argues that it might be true that mussels eat plankton and have negative impacts on the fish that feed from plankton. Nevertheless, they can positively affect the fish that get their food in the bottom of the lake since mussels generate nutrients that are available for the fishes near the bottom of the lake or river.