After a 3.5-year voyage at sea, scientists have discovered more than 100,000 new eukaryotic organisms, many existing in symbiotic relationships with each other.

Credit: M. Ormestad/Kahikai/Tara Oceans

Scientists aboard the research schooner Tara collected some 35,000 ocean samples at 210 locations around the world, from as deep as 2,000 metres below the surface. The team, led by Eric Karsenti at the European Molecular Biology Laboratory in Heidelberg, Germany, made environmental measurements and sequenced and analysed DNA fragments from the samples, looking for new viruses and organisms as big as fish larvae. They found 150,000 genetically distinct kinds of eukaryote (a Phronima crustacean is pictured), many of them single-celled organisms — and many more than the 11,000 previously known species of marine eukaryotic plankton. They also discovered more than 5,000 genetic populations of viruses, only 39 of which are similar to known viruses.

Temperature seemed to be the environmental factor with the strongest effect on microbial community structure in the upper oceans. The data could be fed into ocean models to predict how these communities might respond to global warming, the authors say.

Science http://doi.org/4tq; http://doi.org/4tr; http://doi.org/4ts; http://doi.org/4tt; http://doi.org/4tv (2015)