There may not be as many fish in the sea as was thought, to say nothing of all the other organisms.
In the past researchers have produced wildly differing estimates of how many eukaryotes – and other organisms – remain undiscovered in our oceans. Now a new analysis tied to the first comprehensive register of marine species has come up with a figure somewhere under one million.
While the number of 700,000 to 1 million reported this week in Current Biology is not as high as some previous estimates – which have ranged as high as 10 million – there is some positive news for lovers of all things sea: between one and two thirds of all species in the seas may remain to be discovered.
The new estimate stems from an online database called the World Register of Marine Species (WoRMS), set up to provide a central place for scientists to access information.
“Scientists have been describing species in the ocean – and on land – for more than 250 years but there has never been a central place where everything gets recorded. The only thing a scientist needs to do is publish a paper,” says Ward Appeltans, a taxonomist at the Intergovernmental Oceanographic Commission of UNESCO. “The result is a lot of species have been described more than once and a lot have been described with the same name. There was becoming a lot of confusion over the names.”
The team behind WoRMS found, for example, that for cetaceans (whales and dolphins) there are 1,271 names for only 87 actual species. WoRMS is now up and running and contains around 214,000 of the estimated 222,000 and 230,000 marine eukaryotes that have been described by researchers across the globe (examples pictured).
Once they had the database set up the team went about working out how many animals had yet to be discovered. They asked a subset of their taxonomy team to estimate how many animals they thought were undiscovered in their areas of expertise. This yielded a likely total of 704,000 to 972,000. In their paper they also note that past estimates have ranged from under 500,000 to over 10 million.
“Often these estimates are based just on the opinion of one person,” says Appeltans. “We thought if we had this core group of experts together, if we cut everything into small pieces and glue them together we probably have a less biased view.”
To check their estimates the researchers also constructed a statistical model based on the rate of species discovery. This suggested that the total number of species in the seas is likely 320,000 to 760,000. This means somewhere between one and two thirds of all marine species remain to be discovered. If marine scientists keep up the current rate of discovery, all these should be in the bag by the end of the century.