Final answer:
The reduction in abundance of the top predator, larvae W. smithii, leads to an increase in rotifer H. rosa abundance, increase in protozoan abundance and diversity, and decrease in bacterial abundance and diversity; hence, all of the above.
Step-by-step explanation:
The top-down or "predatory-prey model" suggests that the reduction in abundance of the top predator, larvae W. smithii, leads to a series of ecological consequences. Specifically, when a top predator is no longer controlling the population of primary consumers, those consumer species will increase in abundance. This can lead to an increase in rotifer H. rosa abundance, an increase in protozoan abundance and diversity, and, paradoxically, a decrease in bacterial abundance and diversity due to overgrazing by the now-unchecked protozoan and rotifer populations. Therefore, the correct answer is d) All of the above.