What do you think would happen to reef dwellers (e. g., coral, parrot fish, sea cucumbers) if the algae were not able to photosynthesize? explain in terms of photosynthesis and cellular respiration.

Photosynthesis is the process wherein energy from sunlight is used to catalyze the reaction converting carbon dioxide and water to glucose. If the algae were deprived of the capability to photosynthesize then they will not be able to derive the energy from the sun into usable energy in the form of glucose and eventually will lead to death of the algae. Algae, being in the bottom of the food chain, is the primary source of food, therefore energy (in the form of sugars) of reef dwellers. Cellular respiration is the process where energy stored in sugars such as glucose is converted into usable energy in the form of adenosine triphosphate and waste products such as carbon dioxide and water is produced. Without the source of energy (algae), the reef dwellers will eventually starve and die. 

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Sorry i dont understand the question can you rephase it?