A Genetic View into Past Sea Ice Variability in the Arctic

Informations projet

AGENSI

N° de convention de subvention: 818449

DOI

10.3030/818449

Projet clôturé

Date de signature de la CE 21 Janvier 2019

Date de début 1 Août 2019

Date de fin 31 Octobre 2024

Financé au titre de

• EXCELLENT SCIENCE - European Research Council (ERC)

Coût total

€ 2 615 858,00

Contribution de l’UE

€ 2 615 858,00

Coordonné par

NORCE RESEARCH AS
Norway

Periodic Reporting for period 4 - AGENSI (A Genetic View into Past Sea Ice Variability in the Arctic)

Période du rapport: 2024-02-01 au 2024-10-31

Résumé du contexte et des objectifs généraux du projet

The Arctic Ocean is turning blue. Sea ice extent is decreasing at an unprecedented rate. It is projected that the Arctic will be sea ice free during summer within a few decades. An Arctic without sea ice will drastically transform the pristine Arctic environment, impact the regional and global climate, arctic ecosystems and create new economic opportunities. But it is uncertain how the Arctic will look like, and how it will impact climate and biosphere. To better assess, predict and possibly adapt to the impact of Arctic sea ice retreat, we can investigate, document and understand an Arctic with less or even without sea ice looked by looking into the geological past. Information about a sea-ice free Arctic Ocean is stored in the geological record of the Arctic, where we use indirect evidence from so-called proxies to investigate past climate conditions. However, there are only few sea ice proxies available, which often have limitations to their applicability and thus limit our understanding of sea ice in the climate system.
AGENSI has explored using sedimentary ancient DNA (sedaDNA), i.e. genetic information stored in marine sediments, for reconstructing past sea ice conditions in the Arctic. Recent technological and bioinformatical advances allow the analyses of the genetic signatures of the phytoplankton and benthic ecosystem that get incorporated in sea floor sediments over time. This wealth of information in ocean sediments is underexplored to understand past sea ice extent and ocean conditions during climate transitions. This project was designed to access that information, and the main objective was to establish sedimentary ancient DNA as a novel proxy for sea ice reconstructions.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

We have built a dedicated ancient DNA clean laboratory and established a contamination-free sampling workflow. We organized a 12-day, project-dedicated Arctic Ocean cruise with the Norwegian sea ice going vessel RV Kronprins Håkon during which we sampled sea ice, the water column and bottom sediments at 50+ stations. In addition, we participated in (inter)national research cruises to Svalbard, the Fram Strait, NE Greenland and the Arctic Ocean to collect sediment records from key locations in sea ice free, seasonal and permanent sea ice environments.
We explored sedimentary ancient DNA as a new tool for sea ice reconstructions following different approaches. In a first approach, we built the first comprehensive Arctic sedimentary ancient DNA (sedaDNA) database (metabarcodes) through the collection of Arctic sea floor sediment samples from different sea ice environments. Comparing that dataset with modern sea ice observations, as well as other sea ice proxies (palynology, biomarkers), allows a qualitative assessment of how sedaDNA metabarcoding signatures document the different sea ice environments and marine biodiversity. In a next step, the relationships between DNA metabarcodes and the modern environment, can be applied to the geological record to estimate past sea ice cover either directly or via a transfer function.
We also explored the sedaDNA (metabarcode) database for sea ice bioindicators, that could eventually be developed into proxies. The genetic signature of several organisms were identified as potential markers for sea ice free, seasonal or permanent sea ice conditions. For a selection of key taxa, i.e. sea ice dinoflagellates and diatoms, we developed a genetic fingerprinting tool (ddPCR assay) and tested it on our sedaDNA database and on Arctic sediment records dating back several thousands of years.
We analyzed several short (multicore) and longer (gravity core) sediment records that cover different time intervals over the last ca. 150,000 years in the Greenland Sea, Labrador Sea, Fram Strait and Arctic Ocean. We described the lithology, measured geophysical parameters, established age models and analysed palynology, biomarkers and sedaDNA with the aim to reconstruct oceanography, sea ice conditions and marine biodiversity. Generally, we observed that DNA stored in sea floor sediments reveals information on ecosystems and biodiversity beyond what is known from the “traditional fossil record, sedaDNA can be used to extract climate information from sediments dating back to >150,000 years, and substantial marine biodiversity shifts occurred in relation to climate shifts and changes in sea ice cover.
Finally, we contributed to studies, position and review papers that highlighted the importance of sedimentary ancient DNA as a tool for past environmental studies as well as methodological studies.
All our published scientific work and data is available in open access. Future publications and data will also be accessible in open access. Our results have been disseminated at (inter-)national conference, workshops, seminars. Team members have been key in the organization of the International Conference on Paleoceanography in Bergen, Norway (2022) and the ECOP/ISOP meeting in Vienna, Austria (2023). Several team members were involved in public outreach related to STEM and specifically the AGENSI project: talks at Pint of Science Festival, outreach to school kids during the OneOcean expedition, Passion For Ocean Summer school and FIRST Lego League, podcasts and the AGENSI website (www.agensi.eu).

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

At the onset of the project, few proxies were available for sea ice reconstructions, each of which with their limitations to their applicability. We explored sedimentary ancient DNA as a new tool for sea ice reconstructions and can conclude that sedaDNA metabarcoding and targeted ddPCR work can be used for sea ice reconstructions. In the process, we also realized that sedaDNA will be an essential tool to investigate past biodiversity and ecosystems.
Prior to starting this project, sedimentary ancient DNA in marine sediments was only documented in a handful of studies. We have now demonstrated that it is a useful tool for paleoceanographic reconstructions on timescales exceeding ca. 150,000 years. It is also clear that the DNA stored in sea floor sediments reveals information on ecosystems and biodiversity beyond what is known from the “traditional” fossil record. Previously unknown organisms, of which many likely do not fossilize, have been discovered in our seafloor sediment DNA database as well as in longer geological records. This opens an entirely new window on paleodiversity and ecosystems, and some of these organisms can be exploited as bioindicators for sea ice and other oceanographic parameters (e.g. Atlantification of the Arctic, productivity, invasive taxa).
Our Arctic sedaDNA database is unique in its kind as a state-of-the-art census of the Arctic Ocean where summer and winter sea ice still occurs. This unique dataset can be used for testing and developing new paleoclimate proxies, but also serve as a baseline for the state of marine biodiversity, both planktic and benthic, in a region that is rapidly changing and gradually turning blue.
The project represents also a major step forward in bringing together the sedimentary DNA techniques into the marine realm, and into the field of paleoceanography. Focused mostly on lacustrine environments previously, there is now an increasing interest from the sedaDNA community to focus on paleoceanography and paleoclimate questions, which was one of the main goals and achievements of the project.

See ice conditions in the Arctic Ocean at 82N on 6 July 2021