In coral reefs, the symbiotic relationship between corals and zooxanthellae is essential for what reason?

The symbiotic relationship between corals and zooxanthellae is essential primarily because it enhances the coral's ability to photosynthesize. Zooxanthellae are photosynthetic algae that live within the tissues of corals. Through the process of photosynthesis, these algae convert sunlight into energy, which they share with the corals. This relationship allows corals to obtain a significant portion of their energy needs from the zooxanthellae, enabling them to build their calcium carbonate skeletons and grow.

This cooperation is critical for the health of coral reefs, as it directly impacts the energy efficiency and overall health of the coral polyps. When environmental conditions lead to the loss of zooxanthellae—such as increased water temperature or pollution—corals can suffer from bleaching, which threatens the entire reef ecosystem.

While providing shelter for marine organisms is an important aspect of what coral reefs do, it is not the primary reason for this particular symbiotic relationship. Similarly, while maintaining water temperature and preventing overfishing are relevant to reef ecology, they do not directly relate to the fundamental role of zooxanthellae in enhancing photosynthesis for the corals themselves.