Census of marine life released
New species are continually emerging from the ocean depths, comprehensive record of biodiversity reveals.
A ten-year inventory of the world's sea creatures has revealed an astonishing level of diversity and a growing number of species, with no end in sight.
The latest collection of papers relating to the Census of Marine Life (CoML), posted on PloS ONE, contains the most comprehensive record of marine biodiversity ever, says senior project scientist Ron O'Dor, based at Dalhousie University in Halifax, Nova Scotia, Canada1.
The census has focused on the participating countries' 'exclusive economic zones', which stretch 200 nautical miles (370 kilometres) out from the coastline.
"One might have thought that these waters were well documented, but no," says O'Dor. "In fact, the papers' authors estimated that, on average, there are three or four more species to be discovered for every one documented."
Of the minuscule deep-water crustaceans known as copepods that were collected off the coast of Africa, 99.3% were previously undescribed species, says Thomas Shirley, endowed chair of biodiversity and conservation at Texas A&M University's Harte Research Institute in Corpus Christi. Furthermore, copepod samples taken just 30 kilometres apart in the area had only two species in common.
"One conclusion is that we have a lot more to learn about the ocean," says Sylvia Earle, explorer-in-residence at the National Geographic Society in Washington, DC. "A conservative estimate of ocean species is 10 million, and it may be 50 million or more. Less than 5% of the ocean has been seen, let alone explored."
Thirteen national and regional committees, involving more than 360 scientists worldwide on the committees but many more overall, assembled published and unpublished data on marine biodiversity. Some were recorded as long as 500 years ago. The committees were required to organize themselves.
Europe, for example, formed one committee covering its multiple bodies of water. Countries around the Indian Ocean also formed a single committee. This organizational approach will facilitate application for conservation and management, O'Dor says, as more nations adopt ecosystem-based management plans in preference to single-species efforts.
Highest species diversity turned up in the regions that scientists expected — in the tropics, where it was generally associated with coral reefs. Australian and Japanese waters were the most biodiverse — each with almost 33,000 forms of life deserving of species status — followed by the oceans off China, the Mediterranean Sea and the Gulf of Mexico.
However, committees covering highly diverse areas, including Indonesia, Madagascar and the Arabian Sea, have yet to report.
The census authors also rated the greatest threats to marine biodiversity around the world, which have been overfishing, habitat loss, invasive species and pollution, and emerging threats, including rising water temperatures and ocean acidification.
Another of the CoML's latest findings is that a high proportion of marine species around Antarctica, New Zealand, South Africa and Australia are endemic — or exclusive — to their region, says Mark Costello of Leigh Marine Laboratory in Warkworth, New Zealand, and lead author of summary paper "A Census of Marine Biodiversity Knowledge, Resources, and Future Challenges"2. He and other scientists expressed concern that decreasing taxonomic expertise means declining ability to identify new species.
The project is working closely with the Barcode of Life, O'Dor says, assigning a DNA barcode to each species. A code identifies an individual plant or animal as different from every known species, although the Barcode of Life project cannot allocate names to new species. CoML scientists estimate that it would take 200 years to describe all the currently undescribed specimens, O'Dor adds. "With the barcode, we at least have a machine name for a new species, even if it hasn't made it into the literature."
Identification remains an important issue because the rate at which undiscovered species are being found shows no signs of slowing. "The CoML represents a fraction of the species that are out there," Shirley says. "Since we don't know all the species, we don't know their ecological roles. Every species is a wheel or cog in a big, complex watch. Start removing those little pieces and you get a cascading effect and start losing function."
Eventually, it will be possible to search the CoML by ocean, as well as by country, as computers sort data from the various committees into locations. CoML data are being entered into the project's Ocean Biogeographic Information System.
"It could not be more timely to have this come out while we are looking at serious issues in the ocean," Earle says. "These are vital endeavors to size up the planet and give us information we need as we go forward with policies."