The first analyses of plankton collected by Tara, a research schooner that sailed across the globe collecting water samples, suggest that the world's oceans harbor some 1.5 million different plankton taxa, many of which are currently unknown to science, ScienceNOW reported. Planktonic diversity is an "almost virgin field," Eric Karsenti, a molecular biologist at European Molecular Biology Laboratory and the project’s co-director, said last week (July 12) at the Euroscience Open Forum, a biennial science and policy meeting.
Known as the Tara Oceans, the year-long expedition returned to port in Lorient, France, at the end of March, and already, preliminary analyses of the samples collected has turned up hundreds of thousands of organisms, including bacteria, archaea, protists, metazoans, viruses, and fish larvae. In total, the team collected samples from 153 different locations, from the water surface to depths of nearly 1 kilometer. The preliminary results focus on 27,000 samples from just 35 of those spots, but even from this subset of samples, it’s becoming clear that smaller organisms are more abundant and diverse, Karsenti said, and that there is “an almost entirely unknown viral diversity.” Other findings include the fact that archaea tend to live with bacteria, but not protists or viruses; there is large geographical variation in diversity; and many plankton species appear to be very sensitive to temperature changes and other factors, including ocean streams and acidity. Metagenomic analyses of the samples have also revealed an abundance of unknown protein sequence codes, as well as complex interactions between species of different kingdoms.
Samples from the other 118 locations are likely to bring even more insight into the oceans’ smallest creatures, and Karsenti says he hopes that the expedition will raise awareness about ocean science in general.