Researchers writing in the journal Current Biology estimate the ocean may be home to as many as 1 million species in total, and about 226,000 of those species have so far been described, with another 65,000 unidentified species waiting in specimen collections around the world.
A massive collaborative undertaking by hundreds of experts around the globe has resulted in the first comprehensive register of marine species of the world.
"For the first time, we can provide a very detailed overview of species richness, partitioned among all major marine groups. It is the state of the art of what we know -- and perhaps do not know -- about life in the ocean," Ward Appeltans of the U.N. Educational, Scientific and Cultural Organization's Intergovernmental Oceanographic Commission said.
The researchers say they expect the vast majority of unknown species -- mostly smaller crustaceans, mollusks, worms and sponges -- will be found this century.
The World Register of Marine Species is an open-access, online database at marinespecies.org created by 270 experts representing 146 institutions and 32 countries.
It is now 95 percent complete and is continually being updated as new species are discovered, researchers said.
While fewer species live in the ocean than on land, marine life represents much older evolutionary lineages that are fundamental to our understanding of life on Earth, Appeltans said.