Final answer:
Increasing stress to the ocean can disrupt the coral's ability to host zooxanthellae, affecting the entire food chain.
Step-by-step explanation:
Increasing stress to the ocean can have significant impacts on the food chain containing zooxanthellae, corals, parrotfish, and sharks. The correct statement is a) It disrupts the coral's ability to host zooxanthellae, affecting the entire food chain. Coral reefs rely on zooxanthellae for food and energy through photosynthesis. When stressed, corals expel zooxanthellae, leading to coral bleaching and a decline in coral health. This can have cascading effects on the rest of the food chain, as many organisms depend on corals for shelter and food.