Climate crisis

Look: Hidden fossils reveal a microscopic creature that may be resilient to climate change

Robin Mejia. Image courtesy Dr. Alison Taylor via Wikimedia Commons

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Today’s climate crisis is unprecedented thanks to human activity.

But historical climate fluctuations help researchers gauge how rising greenhouse gas levels will have a domino effect on modern ecosystems.

Take the oceans, for example.

Oceans are absorbing extremely high levels of CO2 from the atmosphere. In turn, the water is becoming more acidic and making it difficult for sea creatures to form strong bones and shells from declining levels of calcium carbonate in the water.

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Similar cycles in Earth’s past show that as oceans acidify, vital organisms die off.

But a new report this week in Science shows that some may have been more resilient than we previously thought.

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During an ocean acidification event that took place 183 million years ago, the current fossil record shows very few remains of phytoplankton called coccolithophores.

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Coccolithophores may be at the bottom of the food chain, but they play a vital role in regulating ocean CO2 levels.

Robin Mejia. Image courtesy Dr. Alison Taylor via Wikimedia Commons

They make up algal blooms and they form calcified shells called coccoliths.

When less coccolithophore fossils are present at a certain past time period, that indicates to researchers that less calcium carbonate was present in the ocean.

But for the Science report, researchers looked at hidden fossils that reveal more to the phytoplanktons’ story.

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They analyzed samples of black shale from across the world that dated back to several ancient ocean acidification events.

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Dr. Sam Slater, Swedish Museum of Natural History

Instead of finding fossilized remains of coccolithophores themselves, the researchers unearthed plentiful imprints of their tiny, shelled bodies.

Like a miniature footprint, this ancient coccolithophore left behind an imprint of its body in a piece of fossil pollen.

Dr. Sam Slater, Swedish Museum of Natural History

The microscopic imprints represent creatures that only reach 2 to 75 micrometers in size.

Dr. Sam Slater, Swedish Museum of Natural History

These newly discovered fossils reveal that there may not have been a period of time when populations of coccoliths dramatically dropped due to inhospitable ocean conditions.

Instead, these phytoplanktons were likely more resilient to changing ocean conditions than we give them credit for.

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However, that doesn’t mean the coccolithophores’ CO2-regulating properties will save the entire ocean ecosystem from acidification today.

In fact, an excess of phytoplankton could mean larger algal blooms on the surface of the ocean, which block out sunlight and make it harder for organisms living at deeper levels of the ocean to survive.

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Fossil records show that the habitats for larger organisms were depleted during acidification events, writes Uppsala University paleobiology professor Jorijntje Henderiks in a related Science commentary.

That may have had to do with the resilience of phytoplankton.

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So while the past indicates that coccolithophores have a competitive advantage during climate change events, it might not be the best news for other creatures.