TPO26

The article states one of the fresh water shellfish species named zebra mussel has been spreading out from its original habitats, Eastern Europe, to other parts of the Europe and now this spicy reaches the North America. The author states that this population increase threatens other species' population and provide three reasons to prove this. However, the professor explains that the author's statements are not true and now there are some ways to control their population and they would not be a threat for other species because their population is controllable now. The professor refutes each of the author's reasons.
First of all, the reading claims that some evidence show that the zebra mussel's population increase is unstoppable. The author says that the zebra mussels can attach themselves to the ship's body and move to other habitats. Also, they can live in the water in the ship which make to balance for the ship, named ballast water. This ability causes their movement to another habitats and spread fast and easy. The professor refutes this opinion by saying that this claim cannot be true because the ships have to extract the fresh ballast water while they tend to settle, then they hold this water into the ocean salty water. So, the zebra mussel cannot survive in salty water and being killed easily.
Secondly, the article posits that the zebra mussels have strong ability to be dominate spicy in a new habitat. As this spicy does not have a specific predator its population can be growth easily. However, the professor says that this allege could be true at the beginning but after a while by reducing the food resources, a type of bird had to change its food resources into the zebra mussels. Therefore, the zebra mussel's population is being controlled.
Third, the reading says that the zebra mussels are able to decrease the fish populations in their new habitats. The author says that while the zebra mussels being a dominant spicy in a habitat, they would became a rival for other fishes in eating planktons. The professor opposes this point by saying that this issue is true merely for fish spices which eat planktons, but the zebra mussels themselves are a good food resources for the fishes on the bottom of the lake which do not eat planktons.