Integrated tpo 26

The reading and the lecture are both about stopping zebra mussels' spread. The author of the reading feels that invasion by zebra mussels can not be stopped, and it makes freshwater fish populations to face threats. The lecturer challenges the claims made by the author. He is of the opinion that there are some means to control spread of zebra mussels, and it is not necessary threat against freshwater fish populations.

To begin with, the author mentions that because human transportation is one of the most important reason of zebra mussels' spread, he thinks that it is unstoppable. The author clarifies this process by mentioning the waterways between Europe and North America and how zebra mussels attach themselves to the ship's bottom and survive in the ballast water during this transportation. This specific argument is challenged by the lecturer. He claims that ships can remove the freshwater and switch it with ocean water. He says that by this way they can prevent the transportation of zebra mussels through the waterways between Europe and North America.

Secondly, the writer says that zebra mussels are dominant species in the habitat. In the article, it is said that they are enduring species, and they have high rate of reproduction. The lecturer, however, rebuts this by mentioning that mussels are dominant only in the beginning. He elaborates on this by bringing up the point that some species of birds can easily eat them.

Finally, the author posits that zebra mussels are likely to decrease the overall fish population if they become dominant in the habitat. Moreover, it is stated that the mussels are also plankton eaters like many freshwater fish species, and it means that there will be high competition between them. In contrast, the lecturer says that mussels may have negative impact on some fish species, but they also have positive impact on other fish species. He notes that mussels generate nutrients for some of them, and they take advantage of these nutrients.