TPO26 Integrated Task

The reading and the lecture are both about a freshwater shellfish named zebra mussels and its ways of spreading out. Whereas the author of the reading states that an increase in the zebra mussels’ population is continuous and they are a threat to the freshwater fish population, the lecturer suggests that the reasons are not convincing. The lecturer casts doubt on the main points made in the reading by providing three reasons.
First of all, according to the reading, ships that transfer cargo in the canals can spread out the zebra mussels which attached to the ship and can be alive in the ballast water. However, the lecturer disputes this point. He says that it depends on the previous knowledge of the people. Furthermore, he mentions that the ships can be forced to deplete the ballast water, which contains zebra mussels before they arrive at the destination and this can control the increase in zebra mussels’ population.
Secondly, the reading states that the zebra mussels have no predators in new habitats and they are resistant to various difficult conditions and can dominate the new habitat. Nevertheless, the lecturer refutes this argument. He argues that the lack of new predators just occurs in the beginning. For example, he points out birds after some times understand that there is new food in their habitats, so they prevent the domination of zebra mussels’ population.
Finally, the reading claims that while zebra mussels eat plankton, they can cause a lack of food for freshwater fish and a decrease in their population. On the other hand, the lecturer believes that although the presence of zebra mussels may decrease in the overall freshwater fish population due to eating plankton, there are some bottom fish that eat the nutrients made by zebra mussels and thus their population may increase as well.