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80% of living space is dark
Life runs on a star
Nearly all the life people know runs on a star. Sunlight hits Earth, and algae, microbes, and plants harness that energy to create the organic matter that animals eat. The science word for it is primary production.
The dark majority
Below 1,000 meters, the water is beyond that light, and by volume it makes up about 80% of the planet's living space. The coral reefs, the Amazon rainforest, the tundra, the Great Plains, the Serengeti, Boston, and Los Angeles all fit in the other 20%.
Food from above
Many, though not all, of the animals and microbes down there live on food that comes down from the surface. A lot of the research asks how much of that food rains down, how much animals eat, and how much gets buried and tucked away for all time.
Why does the deep ocean dominate living space?
The ocean covers about 71 percent of Earth's surface and averages roughly 3,700 meters deep. Light supports photosynthesis only in the top couple of hundred meters. That makes the sunlit layer a thin skin on top of a very large volume. Most of the room for life lies in the water below it.
How do algae turn sunlight into food?
Algae use chlorophyll to capture light and use that energy to convert carbon dioxide and water into sugars. The process is photosynthesis, and the sugars it makes are what scientists call primary production. Tiny floating algae called phytoplankton do roughly half of all the photosynthesis on Earth. They are eaten by small animals, which are eaten by larger ones, and the leftovers sink.
What happens to food that gets buried?
Organic matter that reaches the sea floor can be buried by more sediment and stay out of reach of animals and microbes. Buried carbon can stay locked in rock for millions of years. This slow burial is part of the long-term carbon cycle, which helps set the carbon dioxide level in the air. Some of the oil and gas people burn today formed from marine organic matter buried in this way.
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