Billions of years ago the oceans of our planet would not have been blue, but green. This is the hypothesis supported by a new conducted by an international team led by researchers from the Physics Department of the University of Nagoya, Japan, and published in the magazine Nature Ecology & Evolution. This conclusion was achieved through the analysis of the photosynthetic characteristics of cyanobacteria dell’Archaneandeemed among the first unicellular organisms to populate the terrestrial oceans. These microorganisms are also considered the main managers of the great oxidative event, which occurred 2.4 billion years agowhich would radically upset the chemical composition of the atmosphere and oceans, significantly increasing the content of oxygen.
THE cyanobacteria I am photosyntheticsthat is, capable of carrying out photosynthesis. Like plants, they use the pigments of the chlorophyll To absorb sunlight, in particular the wavelengths of blue and red. However, the first cyanobacteria would have developed accessory pigments, organized in called protein structures Ficobilisomescontaining molecules like the pricklyable to absorb light in complementary wavelengths to chlorophyll.
At this point, scientists asked themselves a fundamental question: because the cyanobacteria should have equipped themselves with Other pigments In addition to chlorophyll? To find a satisfactory response, the authors of the study have integrated numerical modelsable to simulate the oceanic chemical composition and the underwater luminous spectrum during the Archean and the great oxidation crisis, with genetic engineering techniques aimed at identifying the environmental conditions favorable to the development of the prient -being. They also conducted phylogenetic analysis To reconstruct the evolutionary characteristics of the first cyanobacteria. The results revealed that the development of additional pigments it took place as a adaptive response to specific environmental changes, specifically, to life in oceans dominated by shades of green.
During the great oxidative event, the oxygen produced by the cyanobacteria reacted with the Ferroso iron (FE (II)) abundant in the oceans of the time, forming particles of Ferric hydroxide (FE (Oh) ₃). These insoluble particles radically modified the bright spectrum penetrating the waters, preferably absorbing the red and blue wavelengths, and leaving mainly green light (wavelength between 500 and 660 nanometers). Consequently, the oceans took on a greenish appearance.
In response to the change of the underwater bright spectrum, cyanobacteria would have specialized the protein prickly To effectively absorb green light, thus adapting to the new rich iron environment and allowing its diffusion and continuous evolution.
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