Ice Age algae bloom on Andøya

Algae blooms are not only due to modern pollution. When most of Fennoscandia was covered by ice, a large algae population thrived in a small ice-free refugia just north of the Lofoten Islands.

mann som ror en båt
Researcher Youri Lammers exploring the site on Andøya. Foto: Inger Greve Alsos

A remarkably high amount of algal material was detected in sediment cores from Lake Øvre Æråsvatnet located on Andøya, north of the Lofoten Islands. The sediment material was dated to 20,000 before present, which places it in the middle of the last ice age.

The presence of the algae was detected with a new ancient DNA method that aims to identify all material present in a sediment sample, rather than a particular group of organisms.

Remained ice free

Andøya is unique in Fennoscandia as the northern part of the island remained ice free during the last ice age. By investigating the life on the island during this period, we can learn more about what species survived there and how they spread after the ice retreated. This is done by studying the DNA remains captured in lake sediments from the island.

alger sett i mikroskop
The algae species Nannochloropsisa, a small green algae that survived the last Ice Age. Foto: Public domain image of the algal genus Nannochloropsis.

The high abundance of algal DNA in the sediment allowed us to puzzle together the genome of the species present, a first for the method used.

The reconstructed genomes enabled us to accurately tell which algal species was present, namely Nannochloropsis limnetica.

Reconstruction from DNA

Normally genomic reconstruction requires the presence of fossil remains, which are not always available for smaller organisms, or those that don’t leave clear remains, like the algae we detected on Andøya.

This demonstrates the importance of our method as it still allows for reconstructions based on the DNA that the organisms leave behind in the sediment.

Furthermore, the abundance of DNA made it possible to dive deeper into the species present. The genomic data indicated that at least two distinct populations were present in Andøya during the last ice age. This is a new discovery that could not have been made with previous DNA methods.

Mann som holder en sedimentprøve
Youri Lammers holding a section from the sediment core in the storage at the Tromsø University Museum. Foto: Sandra Garcés Pastor

Large algal blooms

The presence of algae on Andøya 20,000 years ago is interesting, as it shows that even during adverse conditions, some species were able to thrive in the cold climate.

Our species in particular was present in high quantities to generate the amount of DNA detected, which could have been in the form of larger algal blooms.

Ancient DNA from sediments has been used before to identify which species were present in the past, but the ability to identify distinct populations allows us to investigate how species and populations moved across the time and space.

This is of particular interest for Scandinavia, as it allows us to track how species and populations recolonized the land after the last ice age and is of importance to understand how species might respond during the ongoing change in climate.

Les også: Verdens eldste DNA gir ny innsikt i mammutens evolusjon

Portrettbilde av Alsos, Inger Greve
Alsos, Inger Greve Professor i biologi
Portrettbilde av Heintzman, Peter
Heintzman, Peter Førsteamanuensis
Portrettbilde av Lammers, Youri
Lammers, Youri
Publisert: 23.02.21 14:15 Oppdatert: 24.02.21 12:44
Innlegget er en del av UiT sitt Forskerhjørne, hvor forskere ved UiT formidler sin egen forskning.
Forskerhjørnet Arktis Klima Naturvitenskap
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