Answer:
A: The marsh will become less productive
Explanation:
Option A is the correct answer because, if the water flow changes to the point where no water is able to enter a certain area, most plant life will die out.
There are a few plants that can survive with very little water, but not enough to sustain a whole ecosystem.
The marsh will not have more oxygen, because underwater plants acquire oxygen through the water surrounding it (oxygen diffuses into the water).
The marsh will not grow more plants, because water is the key factor needed in order for plants to grow, and due to no plants being able to sustain themselves, the rate of photosynthesis will also decrease.
