Final answer:
The flow of acid rainwater into a river makes survival difficult for aquatic life due to the decrease in dissolved oxygen levels and the increased toxicity of the water.
Step-by-step explanation:
The flow of acid rainwater into a river makes survival difficult for aquatic life. Acid rain primarily affects sensitive bodies of water, decreasing their pH levels. In areas where the buffering capacity is low, acid rain releases aluminum from soils into lakes and streams, which is highly toxic to many species of aquatic organisms. Decreased levels of dissolved oxygen in the water due to acid rain can also have serious consequences for the health of the water's ecosystems and result in large-scale fish kills.