Scientists discover new group of marine algae
Researchers have identified a previously unknown group of minute marine algae by analysing DNA found in samples of sea water taken from the northern Atlantic and Mediterranean. The results of the study, which was partly funded by the EU under its Fifth Framework Programme (FP5), are published in the latest edition of the journal Science. Around half of global photosynthesis takes place in the world's oceans where it is dominated by microscopic algae called phytoplankton. Scientists estimate that up to 90% of phytoplankton species remain unidentified. In this study, the researchers focused on the smallest phytoplankton, the so-called picoplankton, which are just a few thousandths of a millimetre long. Due to their small size, it is almost impossible to study the picoplankton using microscopy, so the research team studied differences in genetic material isolated from the sea water samples. By comparing familiar and unfamiliar gene sequences, the scientists discovered that they were looking at a completely new group of algae that did not appear to be closely related to any known groups. 'There was one group of sequences that just didn't line up with any of the known groups,' explained Dr Connie Lovejoy of the Laval University in Canada, one of the authors of the paper. 'In fact, the divergence of this group from known organisms is as great as the difference between land plants and animals.' 'This is a good indication for how much there is still to discover in the oceans, especially using molecular tools,' commented Dr Klaus Valentin of the Alfred Wegener Institute of Polar and Marine Research in Germany. The genetic studies also revealed that the new group of algae consists of three distinct subgroups. The scientists also detected the presence in the new algae of pigment proteins called phycobilins. While these have been found in other species of algae, in this new group the phycobilins were restricted to the plastids, the part of the cell where photosynthesis takes place. The authors of the paper have tentatively named the new group of algae 'picobiliphytes'; 'pico' because they are very small, 'bili' because they contain biliproteins and 'phyte' because they are plants. In the last 15 years, four other new classes of picoplankton algae have been identified, and the authors of the paper speculate that this diverse group of organisms could act as reservoirs of genetic capacity that are activated under specific conditions. 'The discovery of picobiliphytes and their apparent widespread distribution and contribution to marine protist assemblages highlight the imperative of understanding biodiversity before its loss on a global scale,' the scientists conclude.
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