Mangroves sprouted in Arctic during Eocene

by Bethany Augliere
Friday, October 13, 2017

Evidence of ancient mangrove plants was found in lignite seams, such as in this outcrop on Faddeevsky Island. Credit: Guillaume Suan.

Mangrove trees, which today thrive in tropical and subtropical climates in the low and midlatitudes, grew in the high Russian Arctic about 56 million years ago, scientists reported in Geology. It’s the northernmost occurrence of mangrove trees ever documented.

Researchers traveled to the coastal plains of Belkovsky and Faddeevsky islands to study the paleoclimate of the Siberian Arctic during the Eocene. They dated and analyzed Eocene sedimentary samples for pollen grains and spores, cataloging grain shapes and sizes as well as botanical species. Pollen grains from the two islands were exceptionally well preserved, the authors reported, allowing them to identify members of 117 taxa on Belkovsky Island and 76 taxa on Faddeevsky Island. There were species from the cypress and palm families, as well as Avicennia, a genus of mangrove.

“It was the first time mangroves were found at such high latitude,” says Guillaume Suan, a sedimentologist from the University of Lyon in France and lead author of the new study. The team also found the clay mineral kaolinite in their sediment samples in similar abundances to those observed in the modern soils of subtropical environments with relatively high rainfall.

The floral assemblages from the islands suggest that conditions in the Siberian Arctic during the Eocene were warm, with temperatures averaging 16 to 21 degrees Celsius, Suan and colleagues reported, similar to what other paleoclimate proxies have indicated. However, current climate models cannot simulate these temperatures for the Eocene Arctic without including atmospheric carbon dioxide levels well above what’s estimated for the time, Suan says, suggesting problems in the models.

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