How Many Species Live in the Ocean?

The number of species that live in the ocean is unknown.

Earth viewed from the surface of the moon

While scientists estimate that 91 percent of ocean species have yet to be classified, the global scientific community continues to amass as much knowledge as possible about ocean life. Shown here: Kelp forests within Monterey Bay National Marine Sanctuary.

Given the vast size of the ocean, it is impossible to know the exact number of species that live there. Research suggests, however, that the number of species in the ocean is decreasing. The continued decline in the health of many ecosystems, coupled with rising extinction rates, are likely outpacing species’ ability to evolve to tolerate the conditions of our rapidly changing planet. It is not all bad news, though. Researchers around the world continue to study marine life and habitats to help develop new strategies to preserve vital ocean ecosystems.

Scientists estimate that 91 percent of ocean species have yet to be classified, and that 95 percent of the ocean remains unexplored. While these statistics may sound daunting, they have not stopped the global scientific community from striving to amass as much knowledge as possible about ocean life.

One recent effort—the Census of Marine Life—was an international project spanning 10 years that recorded the diversity, distribution, and abundance of life in the ocean. More than 2,700 scientists from 80 nations contributed to the Census. The results of their research, which included 540 marine expeditions, were reported at The Royal Society of London in October 2010. The Ocean Biogeographic Information System contains the Census data. NOAA Fisheries is responsible for the protection, conservation, and recovery of endangered and threatened marine and estuarine species in the United States under the Endangered Species Act.

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Whether you’re dealing with humans or horseshoe crabs, it’s important to mind your manners. Being respectful of ocean life is vital to protecting endangered species, federally-protected species, and thousands of other species. Learn more about ocean etiquette.

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Last updated: 06/25/18
Author: NOAA
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