Nitrogen is an essential element in the biosphere, as it is essential for the growth of plants in both terrestrial and aquatic ecosystems. Tropical rainforests, seagrass meadows and microscopic algae, through the process of photosynthesis, feed food chains and remove carbon dioxide from the atmosphere. “Despite the fact that molecular nitrogen (N2) exists in large quantities in the atmosphere, only a few specialized microorganisms are able to use it,” explains Beatriz Mouriño, professor in the Biological Oceanography Group of the Marine Research Center of the University of Vigo. “The rest have to make do with forms of nitrogen that are less abundant but cheaper in terms of energy when it comes to assimilating them, such as nitrate or ammonium,” points out Mouriño.
Until recently, it was believed that in the ocean, the incorporation of atmospheric nitrogen by microorganisms was a process of little importance, and restricted to the surface layers of tropical regions where there is very little nitrate and ammonium. In fact, traditionally, biological nitrogen fixation has always been linked to tropical and subtropical regions, but in recent years many publications have shown that the range of environments in which nitrogen fixation is an important process is much greater, since there are fixing organisms spread throughout all the waters of the entire planet. One of these studies, carried out by researchers from the University of Vigo, the Spanish Institute of Oceanography (IEO) and the University of California at Santa Cruz (USA), has just been published this Wednesday by the journal Scientific Reports, of the Nature group, and it shows that these microorganisms are also present in the Galician estuaries. “Our data reveal the existence of a great diversity of specialized microorganisms, whose presence and activity throughout the year varies depending on environmental conditions,” says Víctor Moreira, first author of this work, who has just defended his doctoral thesis at the University of Vigo.
20 months of study in the A Coruña estuary
The research was carried out over 20 months in the Ría de A Coruña within the framework of the Nicanor project, funded by the Xunta de Galicia, which studies nitrogen fixation and diffusive flux in the northwest of the Iberian Peninsula. During this time, experiments were carried out to measure the use of atmospheric nitrogen, while DNA samples were obtained to identify and quantify the microorganisms responsible. At the same time, instruments were launched that assessed the level of turbulence and the rise of nitrogen from the deep layers. According to Emilio Marañón, professor at the Department of Ecology and Animal Biology at the University of Vigo and researcher in the Biological Oceanography group at CIM-UVigo, who is also participating in this research, “the amount of nitrogen that is incorporated into the Galician Rías by this mechanism is small compared to the fertilization by the rise of deep waters associated with upwelling; however, due to global change processes such as ocean warming, these microbes may see their relevance increase in the future”. That is, this study will serve as a basis for determining changes in the relative importance of the different mechanisms that control the entry of new nitrogen into ecosystems, a process that ultimately determines the productivity of exploitable resources in this region.
Part of the doctoral thesis
The study is part of Víctor Moreira’s doctoral thesis, defended in December 2018, within the framework of the Marine Sciences, Technology and Management program. The research was coordinated by Professor Beatriz Mouriño and includes the participation of Emilio Marañón and Ana Fernández, all from the Biological Oceanography group of the Department of Ecology and Animal Biology, together with Marta Varela, Antonio Bode and Eva Sintes, researchers from the Spanish Institute of Oceanography and Jonathan Zehr and Kendra Turk-Kubo, from the University of California at Santa Cruz (USA).
Source: DUVI
