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Around 100 million years ago, grass from land adapted to live and reproduce while submerged in seawater—the modern-day seagrasses. This sea invasion by land plants happened four separate times,...
Bottom trawl treasures from the shallow Chukchi Seafloor near the Canada Basin: sea stars , brittle stars , clams, some snails and crabs. View the “Under Arctic Ice ” photo essay to learn more.
Nudibranchs are mollusks that have evolved from shelled ancestors. Like the reddish-orange Coryphella verrucosa shown here, they're often noted for their vibrant colors and striking forms. View other...
This photo of Kingman’s Reef in the Line Islands shows what a healthy coral reef should look like. The water is crystal clear. A variety of richly colored corals carpet the seabed. And a native...
The Papahānaumokuākea site in the United States was inscribed on the World Heritage List in 2010. The site is a vast isolated cluster of small low-lying islands and atolls with its surrounding ocean...
Climate and sea changes in the Southern Ocean create conditions that favor the growth of salps over krill , the latter of which are a vital food source for seals, whales, and penguins. Salps are...
This male giant squid is on display in the Sant Ocean Hall at the Smithsonian’s National Museum of Natural History . It measures about 2.7 meters (9 feet) long and weighs a little more than 45.5...
Fitting nine of anything on two fingers is impressive. These mollusks and echinoderms are a teeny-tiny sample of the ocean's biodiversity. The Census of Marine Life estimates that there are at least...
These star-shaped grains of sand, collected from southern Japan, look like miniature works of art -- but they were not sculpted by an artist. They are the shells of microscopic organisms called...
Squids, octopuses and cuttlefish, such as this Australian Giant Cuttlefish ( Sepia apama ), compose just one group of animals that call seagrass beds home. Clams and worms bury themselves in the mud...
Hermit crabs, like this one collected in Moorea, usually protect their soft, vulnerable abdomens from predators by reusing empty snail shells. They are picky home owners and they will trade shells...
Sea stars are important members of marine ecosystems, especially in the tropics. We may think of tropical coral reefs as being home mainly to fish and corals, but in fact these habitats are home to a...
Sharks come in all sizes. The largest is the whale shark , which has been known to get as large as 18 meters (60 feet). The smallest fits in your hand. And the great white shark is somewhere in the...
The Hanse Explorer crew used a remotely operated underwater vehicle, or ROV , capable of diving to depths greater than 300 feet (91 meters). The ROV helped the crew document life in the waters off...
Flattened against a leaf, a tree frog blends right in with the mangroves. More about mangroves can be found in our Mangroves featured story.
Like other sea snakes , the turtle-headed sea snake ( Emydocephalus annulatus ) has fangs and venom. But its venom is weak so, instead of defending with a bite, the species tends to react to danger...
The ocean covers more than 70 percent of the Earth and is essential to all life. But forces of change, from overfishing to climate change, are affecting the ocean and humanity's relationship with it...
Scientists on the tiny island of Moorea, in the Pacific, are gathering one of every life form large enough to pick up with tweezers. They're on a quest to build a detailed catalog of the entire...
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