TPO 26 integrated writing

Both the reading and the listening sections are about zebra mussel. The author of the reading passage argues that intrusion cannot be interrupted and it is serious anxiety to freshwater fish population in all of the Northern America. The lecturer, however, challenges the claim made by the author. He is of the opinion that there are ways to control the zebra mussel spread. Furthermore, it is not so clear that zebra mussel is a serious threat to fish population.

To begin with, the author notes that zebra mussel's spread provided by human transportation and cannot be controlled at all. The mussel can attach itself to ship's bottom or can be hold in the ballast water. This argument is challenged by the professor. More specifically he claims that in the past spread of the mussel could not be controlled because people did not have enough knowledge at that time. In addition to this he mentions that there are effective ways to stop ships from carrying mussels to the other location. Ships take on fresh ballast water then empties that water into North American waterways once it arrives full of zebra mussels, but ship can be required to empty out the freshwater and can be refiled by ocean water so salt water will kill mussels.

Secondly, the text suggests certain statistics that zebra mussel can become dominate in a new habitat due to lack of predators and high level of reproduction. The lecturer, by contrast, rebuts this argument by pointing out that it is true that they do not have predators in the new habitat but there are local bird spices that have no food so sooner or later they can start eating mussels.

Finally, the reading passage contends that zebra mussels are plankton eaters, which means that they can led to decrease many freshwater fish species. The lecturer, rebuts this by mentioning that they may have negative impact on fishes that eat plankton but also they can have positive impact on other fish species. He elaborates on this by bringing up the point that mussels generate nutrients that are eaten by fishes which feed near the bottom of the lake or river. So bottom feeding fish population may increase even if plankton eating fish population decreases.