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Insights into the formation of chalk in algae by electron microscopy


Calcareous algae save important environmental information within their solid cover. An international team of scientists, including GFZ scientists, now gained new insights into the chalk formation of Emiliania huxleyi - the globally most common species of calcareous algae. Via the chemical composition of its chalk cover this species provides information on the climate and environmental conditions of the past.

Based on spectroscopic and microscopic techniques the team was able to identify a to date unknown intracellular reservoir of calcium within this single-celled alga, covered in calcareous disks. This investigation allows for new insights into the process of chalk formation within this organism. The study is published in Nature Communications. An important part of the electron-microscopical investigations was done at the GFZ, led by Dr. Richard Wirth, section Chemistry and Physics of Earth Materials. With the help of these investigations it was possible to figure out that calcium is stored in the form of polyphosphates in the reservoir.

Emiliania huxleyi responsible for a third of all biologically precipitated chalk in the oceans. Its fossil record goes back into the past for more than 200 million years. Calcareous marine sediments mainly consist of the remains of this species of algae. For this reason this species is widely used by means of reconstructing environmental conditions of the past. Despite its popularity, to date not much is known about the exact conditions of its chalk assembling.

But it is not just about information of the past: Due to its widespread occurrence this alga is a key species of the oceans. Since it is doing photosynthesis it is of immense importance for the marine contribution to the global carbon cycle. The process of calcification stores vast amounts of carbon in marine sediments. After its death the chalk sinks to the ocean floor, forming sediments, and by this extracts carbon from the oceans. To know more about the chalk formation of this alga also means to better understand the future of how ocean acidification impacts calcification under global warming.

» Original publication

Source: Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences