2. Coral and Zooxanthellae: The Foundation of Reef Ecosystems
Every coral reef is based on a vital symbiotic interaction between coral polyps and small algae known as zooxanthellae, which forms the basic basis of these varied ecosystems. This link is so basic that coral reefs as we know them would not survive without it. Actually, coral are small organisms closely linked to marine anemones and jellyfish. Comprising thousands of individual polyps, they excrete calcium carbonate to form the framework of the reef. But the vivid colours of reefs and, more crucially, provide the coral with vital nutrients are derived from the zooxanthellae dwelling within its tissues. Using sunlight to generate food not only for themselves but also for their coral hosts, these minuscule algae photosynthesise. Actually, the coral polyps absorb up to 90% of the organic content generated by zooxanthellae. The coral gives the algae a sheltered environment the compounds they need for photosynthesis in return. In tropical environments lacking nutrients, this mutually beneficial connection helps corals to flourish. Environmental stresses like pollution or rising water temperatures, however, can upset this delicate equilibrium and cause coral bleaching—a phenomena whereby coral colonies die if prolonged or expel their zooxanthellae. Since it underpins the whole ecosystem and maintains the amazing biodiversity seen in these undersea marvels, the preservation of coral reefs globally depends on an awareness and protection of this essential symbiosis.