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FortHjort: Microbes in the Arctic winter - Strategies for survival in the dark

Time: 16.12.2016 13:00 - 15:00
Location: The cinema – NERSC

A FortHjort Seminar will be given on the topic of microbes in the Arctic. The following presentations will be given:

Aud Larsen (Uni): Status microPolar

When the research project MicroPolar started we had some clear expectations: We wanted to describe the structure , function and diversity of the microbial community north of Svalbard during a full annual cycle, quantify carbon flow  in Arctic microbial food web, refine microbial food web models with the ultimate aim of providing data for parameterization of biogeochemical models.  The examples I will briefly present in this talk will tell how well we succeeded and comprise 1) new knowledge on the single celled cyanobacterium Synechocoocus north and west of Svalbard, 2) a look into organic carbon and nitrogen accumulation in the Atlantic gateway to the Arctic Ocean, and 3) a first attempt to evaluate how well  our food web model captured the dynamics during a mesocosm experiment in Ny Ålesund.

 

Bente Edvardsen (University of Oslo): Protist community structure in Atlantic Arctic through the year as revealed by high throughput sequencing

Unicellular protists, including microalgae are main suppliers of photosynthetic products that higher trophic levels depend upon in the Arctic. Yet, the Arctic protist community contains a vast unknown diversity and many of the described species are poorly known. Diversity and dynamics throughout the polar night and at great depths remains particularly understudied due to limited access. In the MicroPolar project we asked “Who are present and when during the year?”, “How is the community structured by depth and geography?” and “What are the environmental driving forces for the observed distribution?”

Sampling cruises to North and West of Svalbard were carried out five times during 2014 (January, March, May, August and November). Samples were collected at 3-6 stations and four depths (1-1000m). Fifty litres were divided into four size fractions from micro- to picoplankton. The 18S V4 region of the rRNA gene was high-throughput sequenced with Illumina.

We obtained c. 35 000 Operational Taxonomic Units (OTUs) clustered at 98% similarity. The protist community composition differed significantly between the dark and light seasons, and between surface water and beyond the photic zone. Also OTU richness varied significantly with depth and season. It was higher in the upper layers all months except March, and the January samples had lowest richness and August had highest. During my talk you will hear more about who were there, their distribution in space and time and main driving forces.

 

Lise Øvreås (UiB): The microbiome of the dark Arctic ocean

During polar winter nights the microbes are still thriving in the dark cold ocean.  The microbiome below the surface is definitely not sleeping, but is characterized by a number of processes and interactions yet to be fully described and understood. The dark polar night is actually a period facilitating quite some important biological activity. The majority of life on Earth—notably, microbial life—occurs in places that do not receive sunlight, with the habitats of the oceans being the largest of these reservoirs. Sunlight penetrates only a few tens to hundreds of meters into the ocean, resulting in large-scale microbial ecosystems that function in the dark. Our knowledge of microbial processes in the dark ocean increased substantially in recent decades. Studies that try to untangle the activity of microorganisms in the dark ocean, where we cannot easily observe them, are bringing new knowledge that are fundamentally changing our understanding of the role of the dark ocean in the global Earth system and its biogeochemical cycles.

In this talk I will focus on our current understanding of microbiology in the dark ocean, outlining relevant features of seasonal variations of microbial communities in the deep water column in the water around Svalbard throughout the annual cycling encompassing both the polar night and day. During the Micro Polar project we have collected samples throughout the polar year from the surface and down to 1000 meters depth. The samples have been analyzed using high throughput tag sequencing analyses of DNA and RNA extracted from the various water depths to compare the cold, deep and dark mesopelagic ocean with the cold, shallow and dark surface waters during the polar night to gain insight to the driving mechanisms of microbial community composition.

 

This event also marks the closing of Hjortcentre´ activities in the fall and after the talks refreshments will be provided.

After the talks refreshments will be provided.