Between one- and two-thirds of marine species remain to be discovered, researchers estimate.

Ward Appeltans of UNESCO's Intergovernmental Oceanographic Commission in Oostende, Belgium, headed up a group of 270 taxonomists from around the world to build the World Register of Marine Species. The researchers report between 222,000 and 230,000 known marine eukaryotes — species with complex cells containing membrane-bound organelles. On the basis of past rates of species discovery, statistical modelling suggests that the total number of eukaryotic species in the world's oceans comes to between 320,000 and 760,000.

The team also asked 120 of the taxonomists to estimate how many species were likely to be discovered in their areas of expertise. This yielded totals of 704,000 to 972,000.

Curr. Biol. (2012)