25.06.2012 change 25.06.2012

Paleontologists from the UW: corals may be unreliable in climate reconstruction

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Polish and French paleontologists led by Dr. Mikołaj Zapalski from the Faculty of Geology, the University of Warsaw, challenged the widespread view that for palaeontologists corals are a reliable tool for reconstructing climatic and environmental changes.

Article by Dr. Zapalski, Jerzy Trammer from the UW, and Prof. Bruno Mistiaen from the French CNRS was published in the May issue of the prestigious British magazine Palaeontology.

Study of the Polish-French team challenges many climate reconstructions based on previous studies of coral.

The UW representatives explained in a release sent to PAP that corals are animals that build massive skeletons of calcium carbonate. With the ability to accumulate this compound, corals form the largest biological structures on Earth: the reef. At the same time, these animals are very sensitive to environmental changes. Fluctuations in temperature, salinity, or food availability can cause that the skeleton to accumulate faster in certain periods, slower in others.

Until now it was thought that the growth of these corals, stored in the skeleton, resembles a record of seasons in the wood grain, and the analysis of how the coral growth allows the reconstruction of climatic and environmental changes.

This widely accepted view has been challenged by the team of Dr. Zapalski. Tests on Devonian (about 380 million years old) coral from Świętokrzyskie Mountains show that the growth of particular polyps (that is, individual animals in the colony) had different dynamics.

Polyps reproduce by budding, so they have the same genetic information, they are clones. "Changes in the environment should equally affect the growth of all individuals. The existence of differences in the growth of individual polyps contradicts that" - explained the release of the Faculty of Geology. Thus,, skeletons of some corals do not allow to draw clear conclusions about changes in their environment. This may mean that many climate change reconstructions based on coral studies are erroneous.

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