Crustacean species outnumber all the fish in the seas
By Lewis Smith
August 02 2010 Lewis Smith
Dragonfish found in the seas off Australia
Dr Julian Finn, Museum Victoria
More species of crustaceans can be found in the world’s oceans than any other type of sealife, the Census of Marine Life has found.
Lobsters, crabs, krill and other crustaceans make up 19 per cent, almost a fifth, of the species that have been identified.
Mollusc species including squid, octopus and marine snails, boast the second-highest number of species while fish are third with 12 per cent of known species.
Many of the best known species, including whales, sea birds, turtles, seals, and walruses are comparatively few and make up just two per cent, being categorised merely as "other vertebrates".
Among fish the manylight viperfish, Chauliodus sloani, has been described as the most widely travelled species, being found in more than a quarter of marine waters. Many microscopic plants and animals are even more widespread but just how they spread so far is still a subject of debate and study.
The figures, which represent primarily a roll call rather than a calculation of total biomass, were released among the most recent results produced by the 10-year Census of Marine Life project.
The Census, which was designed to promote marine research and to establish the types and quantity of life living in the seas, comes to an end in October when the final results, including the total number of known marine species, will be announced. The figure is expected to exceed 230,000.
Much of the work over the last 10 years has been to bring together centuries of discoveries about sea life and to bring it together in an accessible form. Information yielded by the Census is regarded as baseline data which will enable scientists to recognise and understand how the marine ecosystem changes in the future.
Scientists from around the world have over the last decade discovered a host of marine animals which had never been seen before. They ranged from the extraordinary to the tiny but researchers believe they have only uncovered a fraction of the true numbers. For every known species there are thought to be at least four waiting to be discovered.
Dr Ron O’Dor, the senior scientist for the Census, said the biggest surprise was the number of bacteria which researchers can now estimate because of the development of genetic sequencing to identify them.
"The bacteria don’t actually have species. We call them operational taxonomic units. The estimate is there are a billion of them," he said.
"It wasn’t until 2004 that we found any scientists who thought they could so anything sensible to inventorise them. They’ve made amazing progress. I was staggered. I had no idea there was so much out there."
Dr Nancy Knowlton, of the Smithsonian Institution and head of the Census’ coral reef project, said: "At the end of the Census of Marine Life, most ocean organisms still remain nameless and their numbers unknown.
"This is not an admission of failure. The ocean is simply so vast that, after 10 years of hard work, we still have only snapshots, though sometimes detailed, of what the sea contains. But it is an important and impressive start."
She added: "The sea today is in trouble. Its citizens have no vote in any national or international body, but they are suffering and need to be heard."
Seas around Australia were found to have the most diverse range of life in total with 32,889 known species and Japan with 32,777. China’s seas, the Mediterranean and the Gulf of Mexico were the next most diverse of 25 regions assessed. The results for some regions, including diverse areas like Indonesia’s waters, have yet to be completed.
But South Korea was found to be the most diverse when measured in terms of species per square mile of seabed. It was followed by China, South Africa and the Baltic.
An average of 10,759 named species was counted for each of the 25 regions, with numbers ranging from 2,600 to almost 33,000.
Creatures and plants in the Gulf of Mexico, the Mediterranean, China’s shelves, the Baltic and the Caribbean are the most threatened. Among the problems in the Mediterranean is the number of invasive species which represent 4 per cent of all its species and mainly reached it from the Red Sea via the Suez Canal.
Overfishing, the spread of invasive species, pollution and the destruction of habitat have been the biggest threats to biodiversity in the seas, the researchers found, and they are likely to be joined by water temperature and acidity in the near future.
The papers published on PloS One, an open access online journal, follow a study in February which concluded there were 16,764 known species of marine fish.
Pictures:
Bottom, new species of sea cucumber. Photo Credit: Antonina Rogacheva, Shirshov Institute of Oceanology, Moscow
Second bottom, deep sea jellyfish from Japan. Photo credit: JAMSTEC
Second top, a type of Leptocheliidae crustacean. Photo Credit: Magda Blazewicz-Paszkowycz, University of Lodz
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