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  CommunicationNewsGhost fossils rewrite the history of the oceans


Ghost fossils rewrite the history of the oceans

The cover of Science magazine for this study by an international team that included the Department of Earth Science

Microscopic footprints left by plankton millions of years ago in the seafloor are resurfacing. An international team of paleontologists has used a new technique to document the presence of fossils even after their shells have been gone for millions of years. From this discovery, to which the journal Science dedicates the cover of its latest issue, comes previously unpublished information about the resilience of these organisms—crucial to ocean health—to past climate changes on our planet. The study, online since May 20, was coordinated by researchers at the Swedish Museum of Natural History and is also authored by Silvia Danise, a professor in the Department of Earth Sciences, and colleagues from the Museum of Natural History and University College London. (Go to the article)

“Coccolithophores are unicellular planktonic organisms of microscopic size (15 times smaller than the thickness of a hair) that abound in the oceans,” says Silvia Danise, associate professor of paleontology and paleoecology. They play an essential role in marine ecosystems: they provide much of the oxygen we breathe, underpin marine food chains, and help store carbon in ocean floor sediments. After coccolithophorids die, the exoskeleton formed by calcium carbonate plates is deposited in large quantities in the seabed, fossilizing. So, paleontologists can study their characteristics and evolution by extracting them from rocks.”  the researcher continues.

The evidence available to the scientific community to date documented a decline in the presence of fossil coccolithophores at past global warming events. These data suggested that climate change and subsequent ocean acidification had severely affected the development of this plankton in the geological intervals considered.

"Despite the absence of coccolithophores plates in the rocks studied, we found that their presence is evidenced by the imprints they left on the surface of pollen and other organic matter fossilized in the seabed. Such footprints, similar to those we leave when we walk on the shoreline, testify that even during intervals of global warming in the past, coccolithophorids proliferated in the oceans,” Danise explains.

The discovery of the "ghost" imprint was the unexpected result of an analysis conducted with powerful scanning electron microscopes on rock samples from the United Kingdom, Germany, Japan and New Zealand that allowed researchers to document a consistent presence of coccolithophores even at three global warming events on the planet that took place millions of years ago, in the Jurassic and Cretaceous periods.

"Our study on the one hand makes available to paleontologists the description of a peculiar form of fossilization that will be useful in the future to study those geological intervals where original finds are missingon the other hand, it helps us to understand the reaction to past climate changes of nanoplankton, which may be more resistant to warming phases than previously assumed,” the researcher concludes.



31 May 2022
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