An international team of scientists has found a remarkable form of fossilization that has hitherto been almost completely overlooked. The fossils are microscopic imprints, or “ghosts,” of single-celled plankton called coccolithophores that lived in the seas millions of years ago, and their discovery is changing our understanding of how plankton in the oceans is affected by climate change.
Declines in the abundance of coccolite fossils have been documented from multiple past global warming events, suggesting that these plankton were severely affected by climate change and ocean acidification. But one study found ( Science) new global records of abundant ghost fossils from three Jurassic and Cretaceous warming events (94, 120 and 183 million years ago), suggesting that coccolithophores were more resilient to past climate change than previously thought.
Despite their microscopic size, coccolithophores may be immensely abundant in today’s ocean, visible from space as cloud-like flowers. After death, their calcareous exoskeletons sink to the seafloor, where they accumulate in large numbers and form rocks like chalk.
As more mud was gradually deposited on top, the coccolite plates and other organic debris were compressed by the resulting pressure, and the hard coccolites were pressed into the surfaces of pollen, spores, and other soft organic matter. Later, acidic waters in spaces in the rock dissolved the coccolites, leaving behind only their impressions – the ghosts.
“The ghost fossils show that nannoplankton were abundant, diverse and thriving during previous warming events in the Jurassic and Cretaceous, where previous records have suggested plankton collapsed due to ocean acidification,” said Prof. Richard Twitchett of the Natural History Museum. , London in a let loose. “These fossils rewrite our understanding of how the calcareous nannoplankton respond to warming events.”
SOURCE – www.thehindu.com