Ediacaran Biota might have developed in a bacteria-rich environment

Spriggina flounensi
Spriggina flounensi

An article published in the journal “Nature Communications” describes a research on the environmental conditions in which the organisms known as Ediacaran Biota lived. A team of researchers from the University of California at Riverside (UCR) used biomarkers found in ancient rocks to obtain new information on the conditions and food sources of some of the most bizarre organisms in the history of life on Earth. They concluded that their habitats were rich in bacteria that contributed to the ecosystem.

Ediacaran fossils date back to between 635 and 542 million years ago and have always been at the center of controversy in the field of paleontology because they’re different from all the other known organisms with the consequent difficulty in classifying them. For example, Spriggina floundersi (photo ¬©Verisimilus) was classified into very different groups over time. The first organisms belonging to the Ediacaran Biota were found in 1868 but only after many years researchers started understanding their importance.

Among the various mysteries related to that remote era there’s the one concerning the causes of what was a great biological differentiation, what in jargon is called an evolutionary radiation. According to one of the theories, the growth of oxygen was the engine of the rise of the multicellular organisms as seen in connection with the Great Ordovician Biodiversification Event, tens of millions of years after the Ediacaran period. However, sources of nourishment could have had their importance.

A team of researchers led by Gordon Love, professor of biogeochemistry at UCR, tried to establish the causes of the Ediacaran radiation examining molecular fossils. These are biomarkers, fossil lipids produced by biological communities of that time and preserved inside sedimentary rocks together with the organism fossils. They lived in Baltica, an ancient continent that includes a part of current Eurasia, between 560 and 540 million years ago.

The biomarkers indicated a significant presence of compounds generated by bacteria. This suggests that in that environment bacteria were even more important than algae, a group of eukaryotic organisms that was emerging. Traces of compounds can help to understand which groups of organisms were more dominant and some changes in the ecosystem in a period that’s still not very well known in many ways. There was a complex relationship among the Ediacaran Biota, bacteria and other groups such as sponges and research will continue to accumulate more data.

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