The unicellular algae that inhabit the oceans and turn into limestone after their death, undergoing a phase of coccolith microfossil, undergo a cyclical evolution that a group of researchers from France has linked to the orbital variations of our planet.
A cycle of change in the pattern of rotation around the Sun lasts 405,000 years, during which the Earth’s orbit stretches or becomes more elliptical (orbital eccentricity phenomenon) and then is rounded again. Another 100,000-year cycle affects both the eccentricity and the position of the planetary axis, a phenomenon that several previous studies linked to periods of ice age.
According explains a statement from the French National Center for Scientific Research, their new study has revealed that when the Earth’s orbit is more circular or slightly eccentric, as in the present time, the equatorial regions of the planet experience little seasonal variation. Such a situation is advantageous for species such as algae called coccolithophores, which abound in the oceans without specializing, producing biodiversity.
On the contrary, as the eccentricity increases and more pronounced stations appear near the equator, the coccolithophores need a better adaptation to the extreme conditions and therefore diversify into many specialized speciesBut overall they end up producing less limestone.
The research focused on the analysis of samples of this sedimentary rock with numerous fossilized microorganisms inside. The scientists applied an automated method of microscopy and artificial intelligence to at least 9 million coccoliths ages up to 2.8 million years.
The measurements showed that the small algae were exposed to cycles of approximately 100,000 and 400,000 years and their diversity and number as a function of changes in the cosmic scale.
“A greater diversity of ecological niches when seasonality is high leads to a greater number of species,” the scientists explain in a published article on December 1, in which they relate this fact to the adaptation that shows “the coccolith size adjustment and the degree of calcification to thrive in new environments. “
The researchers also appreciate a relationship between the abundance cycles of microscopic algae and periodic climatic changes, but they reject that a more or less warm climate directly influences the proliferation of these unicellular organisms. On the contrary, they would be the ones who can alter the proportions of gases in the atmosphere and, therefore, set the pace of climatic variations, as they concluded.
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