Question

Zebra mussels were first discovered in North America in the Great Lakes in 1988. This invasive species eats phytoplankton and other microscopic organisms in fresh water. What would be the most likely effect if zebra mussels are introduced into a local fresh water lake?

Answer 1

Zebra mussels are known for being particularly invasive. Once in a lake, the population can explode in numbers. Each mussel can filters about a quart of water in a day, so if the population gets large enough, an all of the water in a lake might be filtered in one day.

Such a huge change in the filtering of that ecosystem can decimate the native populations. With this new competition for microscopic organisms and phytoplankton, many of the other species cannot survive.

There is more that could be said, but with the information given in the question, I'm guessing this is the main thing that it is looking for.