TPO 26 ZEBRA MUSSELSReading:The zebra mussel, a freshwater shellfish native to Eastern Europe, has long been spreading out from its original habitats and has now reached parts of North America. There are reasons to believe that this invasion cannot be sto

In this set of materials the reading part is about the ways which zebra mussels threat the ocean environment, and the listening section casts doubt on the information presented in the article, and argues that there is a ways to control the zebra mussels and it is not a threat nowadays maybe in the past because lack of the knowledge it was a threat for fishes.

First the passage posits that the zebra mussels spread with the ships, they come from Europe to north America in the ballast water of the ships. However, the talk makes the point that it is true but they can stop the ships from spreading mussels by force them to empty of the fresh water and refill with the ocean water.

Second, the text asserts that there is not any predator for zebra mussels in their new habitat and they can live in any condition. On the contrary, the lecturer believes that local birds can change their habit and use zebra mussels as their food source and this cause to not allow mussels to dominate their habitats.

Third, according to the article, zebra mussels by being dominant, decrease the population of the fishes, they food source which is plankton are same with the other fish species. The professor disagrees with this point, and postulates that however its true that they have negative impact on fish that eat plankton but on the other hand they can generate nutrition that are eaten by other fishes in the bottom of the lake or river.