Polarella: the rare algae from ice age.


Polarella is a small photosynthetic algae of dinoflagellates group, which is believed to contain lots of interesting information about the living organisms, ecosystem and biodiversity of about three millions years ago. And so far Polarella glacialis is the only known extant species from ice age that was first isolated in 1999 from the Ross Sea of Antarctica. Later it was also isolated in Arctic region, Canadian Arctic waters in 2003.

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Paleoceanographers and ecologists are very interested to study sea ice from polar region to know more about this ice age algae and then the time, living organisms, their diversity, trophic interaction etc.
Scientists and molecular ecologists at Uni Research are also eager to study the Arctic sea ice evolution to understand the variability of sea ice extent and to increase the knowledge about (the impact of) natural climate change on the Arctic cryosphere. For this reason, sediment samples from two cruises to the Greenland and Labrador Sea were collected.

Pictures are collected from google map and photo archive.

I was very inquisitive to see how environmental ancient DNA (aDNA) extracted from the sediments and microfossils (dinoflagellate cysts), can tell us the sea ice history over the last 100,000 years!

We wanted to see if the sediment contains the rare algae Polarella. We came up with the molecular technique to detect its presence. It was done by first, whole DNA extraction that ideally contains DNA from lots of organisms. To spot the presence of Polarella DNA in it, we did polymerase chain reaction (PCR) that purposely amplifies the tiny amount of DNA of our interest. We can see the amplicon (amplified product) under the UV light thru agarose gel electrophoresis. One important thing here is, we needed to develop specific primer for PCR that targets and thereby amplifies only our genes of interest. Again we needed to make sure thru specificity test that the primer did not target any unintended DNA.

We are also interested to see the DNA sequence of our PCR amplified product in order to be cent per cent sure about our claim to have Polarella detected in the sample. We did, but the DNA sequence result seemed to be too noisy to read the exact sequence. It may happen because of the presence of residual primers, and other ingredients present in PCR product though a cleaning step was followed beforehand. A good solution to this is to clone the desired DNA fragment. Cloning is similar to PCR that amplifies the DNA but in vivo whereas PCR is in vitro. Due to in vivo amplification process, cloning gives us fresh and clean DNA fragments that show noise-free sequence result. In the end, we successfully sequenced the DNA that confirmed the presence of ice age algae Polarella in our ancient DNA.

Now, we are in process of checking other dinoflagellates those have shown more than 96% sequence similarity with Polarella glacialis. We are striving to know even more and more…

I will talk about another interesting story of mackerel’s predation on herring fish in my next blog.
Ha det bra,…

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