Two thirds of marine plants and animals may be undescribed according to new research: oceans may be home to almost a million species.

Experts have calculated the number of existing species within their specialty and estimated the number that remain to be discovered. The estimate of number of species ranges from 708,000 to 967,000.

All the information pooled by the experts show that just 226,000 species are correctly described. In fact, researchers found about 170,000 cases of synonymy among previously known species. That is, one single species described under two (or more) different names.

“Building this [inventory] was not as simple as it should be, because there has not been any formal way to register species,” says Mark Costello from the University of Auckland. A particular problem is the occurrence of multiple descriptions and names for the same species—so called “synonyms,” Costello continued. “For instance, each whale or dolphin has on average 14 different scientific names.”

As those synonyms are discovered through careful examination of records and specimens, the researchers expect perhaps 40,000 “species” to be struck from the list. But such losses will probably be made up as DNA evidence reveals overlooked “cryptic” species.

“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,” says Ward Appeltans of the Intergovernmental Oceanographic Commission (IOC) of UNESCO.

The findings provide a reference point for conservation efforts and estimates of extinction rates, the researchers say. They expect that most of marine life will be discovered this century. The vast majority of unknown species are composed disproportionately of smaller crustaceans, molluscs, worms and sponges.

You can read the inventory of marine species at The World Register of Marine Species (WoRMS). It is now 95% complete and is continually being updated as new species are discovered.

Further Reading
The World Register of Marine Species
Appeltans et al., The Magnitude of Global Marine Species Diversity, Current Biology (2012),

Pictures: WoRMS Photo Gallery / Paulay, Gustav, 2010 / Collins, Allen G., 2012 / Paulay, Gustav, 2010