Fossil algae reveal 500 million years of climate change

For her research Witkowski gathered seawater with fresh, modern algae to test the potential indicators of the past. Credit: Caitlyn Witkowski

Scientists on Earth are able to travel far in time to reconstruct the geological past and paleoclimate to better predict future climatic conditions. By using the organic phytate molecule, a residual chlorophyll product, scientists from the Netherlands Institute for Sea Research (NIOZ) and Utrecht University have succeeded in developing a new indicator (proxy) of ancient CO2 levels. This new organic proxy provides not only the most watched CO record2 the concentration at all, covers a record half billions of years. Data confirm the idea of ​​increasing CO2 levels that have been used for millions of years are happening in the century. These findings are published in 2006 Scientific advances November 28.

Like what2 is increasing today, it is important to understand what impact these changes will have. In order to better predict the future, we need to understand long-term changes in CO2 through geological history. Direct measurement of past CO emissions2 there are, for example, bubbles in ice cores containing old gases. Ice cores, however, have a limited duration of 1 million years. To go further in time, Earth scientists have developed various indirect CO measurements2 from proxies such as algae, leaves, old soils, and chemicals stored in old sediments to rebuild past environmental conditions.

Phytane, a new way of traveling in time

A new representative using a chlorophyll degradation product allows geochemists to derive a permanent record of historical CO2 levels in deep time. Scientists from NIOS have recently developed phytans as a promising new organic proxy that reveals half a billion years of CO2 levels in the oceans, from the Cambrian to the recent times.

Thanks to the new representative, they were able to record the most uninterrupted records of the old levels of carbon dioxide. "We have developed and verified a new way of commuting on time to travel further in time and beyond," says Caitlyn Witkowski, NIOZ chief. "We have the longest CO with the phytane now2– Recording with a single marine representative. This new data is invaluable for modelers who can now predict the future more precisely. "

Witkowski and colleagues selected more than 300 samples of marine sediments from deep sea kernels and oils from around the world, reflecting most of the geological periods of the last 500 million years.

Fossil molecules

Past chemical reactions can be "stored" in fossil molecules, thus reflecting various ancient environmental conditions. Geochemists can infer these conditions, such as sea water temperature, pH, salinity, and CO2 levels. Organic substances such as phytate reflect CO pressure2 in seawater or in the atmosphere (pCO2).

Although all organic matter has the potential to reflect CO2, the phytane is odd. Fytan is the pigment responsible for our green world. Whatever uses photosynthesis to absorb sunlight, including plants, algae, and some types of bacteria, has chlorophyll, which is a phyton. Plants and algae in CO2 and produce oxygen.

Because chlorophyll is found all over the world, phytan is also everywhere and is the main element of decaying and fossilized biomass. "Fytan will not change chemically over time, even if it's millions of years," says Witkowski.

Isotope fractionation of carbon

WHAT2 the past is estimated from organic matter such as phytane, through the phenomenon of carbon isotope fractionation during photosynthesis. When boarding CO2, plants and algae prefer a light carbon isotope (12C) over a heavy carbon isotope (13C). They use only a heavy carbon isotope with respect to CO2 levels in the surrounding water or atmosphere are low. The ratio between these two isotopes therefore reflects the level of carbon dioxide in the environment at the time of growth.

It also explains why Witkowski did not use terrestrial plants as a resource for his research, exclusively using phytana from (fossilized) marine resources. The plant world is divided into so-called C3 and C4 plants, each with its own ratio of light to heavy carbon. Phytoplankton all have very similar ratios compared to their plant counterparts. Witkowski: "In selecting marine resources only, we could limit the uncertainty of the source of the pile in the dataset."

"In our data, we see high levels of carbon dioxide that reach 1000 ppm compared to today's 410 ppm." From this point of view, current levels are not unique, but the speed of these changes has never been seen before.2-Data can help us understand the future of our planet. "In future research, the phytan may use even more time back than Phanerozoic, first found in two billion years old patterns.

Explore the following:
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More information:
"Molecular fossils from phytoplankton reveal the worldly trend of PCO2 over Phanerozoic" Scientific advances (2018).

Magazine links:
Scientific advances

Royal Dutch Institute for Sea Research

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