Marine life far less abundant than thought


Far fewer species are living in our oceans than assumed, an international study has revealed. Yet marine life forms represent a far richer source of biodiversity than life forms on land.

Details of the first substantial inventory of marine life, the World Register of Marine Species was published yesterday in the journal Current Biology. It included a significant contribution by NUI Galway’s Prof Mike Guiry, whose AlgaeBase database provided information on tens of thousands of the world’s algal forms.

The nearly complete world register has been built by 270 “taxonomists” – scientists involved in biological classification – and marine biologists from 146 institutions in 32 countries. Each contributed their own lists and collection details for the species that they hold.


The register therefore holds everything from sardines to whales and sea sponges to sea snails, any animal or plant living in the oceans that is made up of cells.

A key finding of the research paper, The Magnitude of Global Marine Species Diversity, was not the abundance but unexpected paucity of distinct marine species, said Prof Guiry. The paper comprises contributions from 220 authors.

In simple terms, the study attempted to assess how many species there were in the sea. “It is less than we would have assumed,” he said of the findings. It had been assumed there were about one million distinct species. “To date about 226,000 have been described,” said the emeritus professor of botany at NUI Galway.

The ultimate figure will be higher than this, increasing by, for example, up to 70,000 specimens held in collections that have yet to be described or added to the list of known species, he said.

The importance of knowing such a thing is the potential for making biodiscoveries.

Marine species have genes which produce unique substances that may have application as useful drugs for human ailments.

“This is the first time we have managed to get the species collections assembled. This is getting us close to the total number of species,” he said. “The only thing is we don’t know how many in the sea that have not been described.”


Despite the lower than expected total, there are many more distinct lineages of organisms in the marine environment compared to land dwellers, said Prof Guiry. The great majority of species on land are insects and beetles make up a large fraction of all of these. “They are all going to be pretty much the same.”

Taxonomists have found, however, that while there are fewer species in the seas they come from more varied lineages. This means there are fewer repetitive species and more uniqueness within their DNA. “The potential for biodiscoveries is much higher in the sea than . . . land,” said Prof Guiry.

Ireland shares in this rich resource. While our land mass accounts for just half a per cent of the world’s flowering land plants, our coastlines feature 7 to 8 per cent of the total number of sea weeds.

Galway’s main contribution was AlgaeBase, started by Prof Guiry. His research was supported by the Higher Education Authority’s Programme for Research in Third-Level Institutions.

What’s on

Science Week Movie Night:Back to the Future, family film, admission free, Church Cafe Bar Restaurant , at the Mary Street and Jervis Street intersection, Dublin, 7pm

Sligo’s Estuaries and their Wildlife, a lecture by Dr Don Cotton, general audience, admission free, 8pm, Institute of Technology Sligo, theatre A0005

Tomorrow:“Weather and Health – an Irish Perspective”, a free seminar open to the public, will feature discussions on heatwaves in Ireland, cancer risks and weather, coping with cold weather and fuel poverty, and related topics. 9.15am-3.45pm, visitor centre, National Botanic Gardens, Dublin.

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