Given a strong dependence on fossil fuels, global warming will continue to proceed at an unprecedented rate and undoubtedly result in significant reorganizations of biological systems across the planet.  Higher latitudes will experience the largest increases in temperature relative to lower latitudes, a condition referred to as “Arctic amplification.”  How will ecosystems in the Arctic respond to a greenhouse world?  The most direct way to address this question would be to examine high latitude ecosystems under a warm climate, a condition not possible since we currently live in an icehouse world.  One answer lies in the fossil record. The Paleogene, especially the early to middle Eocene, represents the warmest period of the Cenozoic, during which time the Earth experienced greenhouse conditions that could be approached again within a few hundred years given current warming trends.  This time period in the geologic past is of significant interest since it is close to the point where polar ice started to form, especially in the Antarctic. In this study we examined the remains of an Arctic waterbody known as the Giraffe locality that existed 40 million years ago under a warm greenhouse planet.  The Giraffe core contains an unprecedented number of exquisitely preserved fossils and represents the most important deep-time freshwater analog known from an Arctic lake that existed under a warm greenhouse climate.

The primary objective of this project was to document the vast assemblages of aquatic freshwater microorganisms preserved in the 163 m long core, and position us to be able to use the fossils to reconstruct the history of the Giraffe waterbody and to better understand the climate of this region of the world during the Eocene.  To date, we have recorded over 270 aquatic microbes from Giraffe, including photosynthetic and heterotrophic species, planktonic and benthic forms, and numerous taxa that grow and thrive under specific environmental constraints.  Organisms that today are restricted to warm tropical and subtropical regions, including those belonging to sponges, diatoms, synurophytes and higher plants, were documented throughout the core.  Our findings underscore the premise that Arctic waterbodies will undergo significant shifts in community structure with continued warming, including the potential arrival of microorganisms from distant sub-tropical and tropical locations.  

In addition, fossil remains from the core were used to help understand the evolutionary history of important groups of aquatic microbes, including synurophytes, diatoms and testate amoebae. The specimens were further used to calibrate phylogenies for these organisms based on molecular data to geologic time.  In this manner we were able to estimate approximate ages for specific lineages of microscopic eukaryotes that are important components of freshwaters today.  Other fossil organisms were used to study evolutionary stasis, a process where morphological structure remains largely unchanged over long time periods.  In total, the project yielded 17 publications describing new species and addressing questions of biodiversity, evolutionary history, ecology and molecular phylogeny.  Lastly, a substantial on-line database containing over 4,500 records and images has been established, and archival splits of all samples have been sent to the Smithsonian Institution and the Canadian Museum of Nature.  Given the wealth of information gleaned thus far from the Giraffe locality, and the vast potential for understanding future impacts of global warming on climatically sensitive Arctic environments, further inquiry is warranted.

Last Modified: 03/22/2017
Modified by: Peter A Siver