Answer: Water Quality.
Explanation:
The figure of the unhealthy ecosystem shows the industrial runoff into the water. This run off contains nitrogen and phosphorous in excess amount.
This excess nutrients leads to the growth of the algal bloom in water which in turn reduces the amount of oxygen which is easily seen in the the water.
This growth is caused due to poor water quality, and if the industrial run off will be reduced the quality of water will improve.
