Healthy coral is brown, green, red, blue, or yellow, depending on the type of algae residing in the transparent coral-polyp host. The algal microscopic plants use the sunlight shining through their animal symbionts and absorb the polyp’s waste products, including carbon dioxide, for their nutrition. In turn, through photosynthesis the algae provide oxygen, food, and energy for the coral tissues. This partnership with algae allows coral to grow faster and survive in the nutrient-poor tropical waters. Both have the best of plant and animal worlds. What a masterly and wise design!

Nutrition for the coral is supplied by algae (scientifically called zooxanthellae), which live in the polyp’s transparent body, and also by microscopic animals that are captured in the coral’s tentacles. The end result is a coral reef that is home to thousands of marine species in otherwise shelterless oceans.