Researchers who studied fossil fossils under a microscope discovered large numbers of imprints of unicellular organisms, specifically plankton. They are extremely small, five thousandths of a millimeter – but detailed.

“Ghost fossil” is a preserved imprint of an organism, unlike a fossil where the organism itself has been preserved petrified.

Implants of plankton have now been studied under powerful microscopes by researchers at The Swedish Museum of Natural Historyin collaboration with University College London, the University of Florence and the Natural History Museum in London.

The imprints are traces of coccolitophores, which are very small phytoplankton that still produce oxygen and carry carbon dioxide that is bound to the seabed.

The algae form plates of calcium carbonate, so-called coccolites. They are embedded in clay and other materials on the seabed, which form limestone, for example. When acidic water in the stone dissolves the fossilized plankton, a “ghost fossil” remains in the form of an imprint.

The ghost fossil shows: coccolitophores in abundance

The findings overturn previous research that noted a decrease in coccoliths in fossil form during three periods of Jurassic and Cretaceous, and then concluded that they could not cope with the acidification.

However, the new ghost fossils show that coccolitophores were in abundance during the warming periods 94 million, 120 million, and 183 million years ago. This means that they were more resilient than previously thought, which surprised the researchers.

– Usually paleontologists only look for the fossil itself of coccolites, and when they do not find them, they often assume that these ancient planktonic societies have collapsed. But the ghost fossil shows that the fossil substrate sometimes deceives us – and that there are other ways in which calcareous nanoplankton can be preserved, which must be taken into account when trying to understand the impact of previous climate change, says Vivi Vajda, paleontologist and professor at the Swedish Museum of Natural History. CNN.

She is the co-author of the study, which has been published in Science.

In Sweden, among other places, ghost fossils have been found linked to global warming 120 million years ago and 94 million years ago. According to Sam Slater at the Swedish Museum of Natural History, nanoplankton and other algae may have given rise to dead marine zones as a result of algal blooms during the warming period. But at the same time, the ghost fossil suggests that nanoplankton over time probably contributed to cooling the climate.