Chemosynthetic Oases
Video courtesy of NOAA Ocean Exploration, Gulf of Mexico 2017. Download larger version (mp4, 108.2 MB).

The majority of life on the planet is based in a food chain which revolves around sunlight, as plants make food via photosynthesis. In the deep ocean, however, there is no light and thus there are no plants; so instead of sunlight being the primary form of energy, chemical energy is produced via chemosynthesis. Places with chemosynthetic organisms can become oases of life in an environment often otherwise depleted of food.