This paper discusses the ocean floor is home to many unique plants and animals. Some parts of the ocean floor are more livable than others, however. Most marine ecosystems exist near the water surface, such as the Great Barrier Reef, a large coral formation off the northeastern coast of Australia. Coral reefs, like most complex living communities, depend on solar energy, known as photosynthesis for growth. The sun's energy, however, penetrates at most only about 300 meters below the surface of the water. The relatively shallow penetration of solar energy and the sinking of cold, subpolar water combine to make most of the deep ocean floor a frigid environment, capable of supporting only a few life forms.
