A group of researchers from the Department of Earth Sciences at the University of Pisa has identified a new climatic period on our planet, named the Ophiuroid Optimum, which spanned from 50 to 450 A.D.

The study, published in the journal Scientific Reports, was conducted in collaboration with Ca’ Foscari University of Venice and the National Museum of Natural History in Luxembourg.

The researchers analyzed a core of marine sediment collected at a depth of 462 meters below sea level in the Edisto Inlet, located in the western sector of the Ross Sea in Antarctica. The study of the core allowed them to reconstruct Earth’s climatic history over the past 3,600 years, highlighting known periods such as the Medieval Warm Period, between 950 and 1250 A.D., and the Little Ice Age, from 1300 to 1850 A.D.

Coring sites in the Edisto Inlet in the Antarctic.
Coring sites in the Edisto Inlet in the Antarctic.Credit: Galli et al.

During the time interval called the Ophiuroid Optimum, the Antarctic region of Edisto Inlet experienced austral summers characterized by the absence of sea ice and significant algal blooms.

The persistence of this environmental stability over time allowed the development of a rich benthic community abundant in ophiuroids (commonly known as brittle stars).

This sediment core has allowed us to conduct high-resolution paleoecological and paleoclimatic studies – explains Giacomo Galli, a graduate from Pisa and now a Ph.D. student jointly at the Universities of Pisa and Ca’ Foscari Venice – This is because it is largely composed of mud formed primarily by diatoms, which are small single-celled algae with a siliceous shell, along with foraminifera, which are single-celled organisms with shells that can fossilize, and remains of ophiuroids, animals known as brittle stars, which are echinoderms similar to starfish. In particular, the abundant fossil remains of brittle stars allowed us to identify and characterize this new climatic period.

Breviturma pica, an ophiuroid from Réunion Island
Breviturma pica, an ophiuroid from Réunion Island. Credit: Philippe Bourjon / Wikimedia Commons

During this climatic phase, which lasted about 400 years, the bay regularly opened during the austral summer, allowing the reproduction of algae (diatoms) that provided food for the organisms living on the bay’s floor. The ophiuroids benefited from this environmental situation, reproducing in large numbers.

The presence of ice sheets and sea ice on our planet has a very strong impact on the climate – adds Professor Caterina Morigi from the University of Pisa – Since our understanding of the present climate, as well as the ability to model the future, is only possible thanks to data obtained from information about past climates, every piece that helps us better understand the climatic history of our planet has enormous implications for helping us comprehend how it will evolve in the near future.

The research team from the Department of Earth Sciences at the University of Pisa included Giacomo Galli, Caterina Morigi, who is responsible for several research projects in Antarctica (National Antarctic Research Program, PNRA) and the Arctic (Arctic Research Program, PRA), and Karen Gariboldi, a researcher expert in diatoms. Among the other authors is Ben Thuy, a researcher from the National Museum of Natural History in Luxembourg, one of the world’s leading experts on fossil ophiuroids.


SOURCES

Università di Pisa

Galli, G., Morigi, C., Thuy, B. et al. Late Holocene echinoderm assemblages can serve as paleoenvironmental tracers in an Antarctic fjord. Sci Rep 14, 15300 (2024). doi.org/10.1038/s41598-024-66151-5


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