1. An Epic Exploration After a decade of study, during which 2,700 researchers spent over 9,000 days at sea on more than 540 expeditions, the Census of Marine Life (CoML) unveiled its final findings with the release of three books and a series of maps at a press conference in London today. The brainchild of Fred Grassle of Rutgers University and Jesse Ausubel of the Alfred P. Sloan Foundation, CoML resulted in the publication of more than 2,600 scientific papers – almost one every 1.5 days. It also produced an array of startlingly beautiful images of marine life, including this cirrate octopod, Stauroteuthis syrtensis, one of the few bioluminescent octopuses, photographed 800 meters (2,600 feet) below the surface of the Gulf of Maine.

2. In Plain Sight Since the Census began in 2000, researchers have added an average of 1,650 species annually to the list of known marine species. Some of these species have apparently been hiding in plain sight: For example, this copepod, Ceratonotus steiningeri, was first discovered 5,400 meters (18,000 feet) deep in the Angola Basin in 2006, but within a year had also been collected in the southeastern Atlantic, as well as some 13,000 kilometers (8,000 miles) away in the central Pacific Ocean. Scientists are puzzled about how this animal achieved such widespread distribution, and how it avoided detection for so long. One clue to the latter may be its size: It measures only half a millimeter in length.

3. Ocean Snow Census maps of the seafloor showed that the abundance and distribution of life at the bottom of the ocean is controlled by the delivery of food in the form of “snow” from water above. The remnants of dead animals and plants fall as detritus, ultimately consumed by “deposit feeders” such as this sea cucumber, Psychropotes longicauda, here ingesting sediments from around a field of manganese nodules. Its upright “sail” allows it to use deep ocean currents to transport it along the seafloor.

4. Feast on the Sea Floor In the dark ocean depths, animals have evolved to feast specifically on the fallen carcasses of whales. Among the species to dine on these so-called whale falls is this newly-discovered polychaete worm, found at a whale fall in Japan's Sagami Bay. “The Census enlarged the known world. Life astonished us everywhere we looked,” observes Miriam Sybuet, vice-chair of CoML's scientific steering committee. “In the deep sea we found luxuriant communities despite extreme conditions. The discoveries of new species and habitats both advanced science and inspired artists with their extraordinary beauty.”

5. Links in the Food Chain “Setting out to draw baselines of the diversity, distribution, and abundance of species, the first Census of Marine Life documented a changing ocean, richer in diversity, more connected through distribution and movements, more impacted by humans, and yet less explored than we had known,” said Jesse Ausubel of the Alfred P. Sloan Foundation, one of the co-founders of the Census. Here, small amphipod crustaceans gather under near-shore ice in the Beaufort Sea. Feeding on algae on the underside of floes, ice-associated amphipods are a major food source for Arctic cod, which in turn are the main prey for species such as ringed and ribbon seals. As sea ice declines due to climate change, so too do the algae and thus the crustaceans, with cascading effects throughout the Arctic marine ecosystem.

6. Keep Exploring The Census of Marine Life expanded the list of known marine species from approximately 230,000 to almost 250,000. Thirty million observations of marine life have been filed in an online database called the Ocean Biogeographic Information System (OBIS). Even so, much remains to be learned: Researchers estimate, for example, that the known species constitute only a quarter of the organisms that exist in the ocean today. As a result, there is already talk of a second census to shine yet more light on marine life. “All surface life depends on life inside and beneath the oceans,” says Ian Poiner, chair of the CoML's steering committee. “Sea life provides half of our oxygen and a lot of our food and regulates climate. We are all citizens of the sea. And while much remains unknown, including at least 750,000 undiscovered species and their roles, we are better acquainted now with our fellow travelers and their vast habitat on this globe.”