2016 was another record-breaker in terms of global temperatures, and it’s part of a longer-term trend which has seen 15 of the hottest years on record since 2001. One victim of this warming is the Artic. The sea ice is steadily retreating, which means that the habitats for species that live there are also radically altering. So are these organisms equipped to cope with the change? Thomas Mock, from the University of East Anglia, has been studying one marine species which use a genetic trick to adapt, as he explains…
Thomas – With our study we have provided first isights into the evolution adaptation of phytoplankton which are little plants floating in the ocean and we selected to sequence one of their genomes. It was a diatome, they prefer to live in nutrient rich and cold water and therefore their natural home are the polar oceans like the Southern Ocean and the Arctic Ocean. In polar oceans they are the base of the entire food web, including fish, birds and mammals like the polar bears and whales. So if their diversity changes according to global warming, which is a significant concern, then the entire food web might change with consequences for human societies.
Tom – You said that you’d looked at the genome of these phytoplankton – is that DNA sequencing?
Thomas – Yes, what we did is we selected one keystone species and we sequenced its DNA. And what we found is that they are very very different to anything that was sequenced before, at least form the marine system.
Tom – And those differences, are they because of the cold and variable environment?
Thomas – Yes that’s what we think. The variability of the polar oceans has basically caused or shaped the genomes of these organisms. What we’ve found is that the adaptation basically boils down to how they use their alleles. Alleles are basically different versions of the same gene. So in our genome we have two versions of each gene. One is derived from the mother and the other is derived from the father. They can be different from each other which impacts how we look. So I can give you an example, for instance the gene for eye colour has an allele for brown and for blue eyes. People can have two for brown, two for blue or a mix of both alleles. And this mix of alleles is basically what we found in our polar diatome genome, but not only for a small number of genes, but for 25% of all genes in the genome. These different versions are used under different environmental conditions.
Tom – So the phytoplankton are in some sense switching on the genes that help them to survive given the current environment?
Thomas – Yes that’s right – they switch on different versions of the same genes in different ways and this makes them able to cope with changing environmental conditions.
Tom – Could you give an example of one of these particular alleles that you found specifically in the phytoplankton?
Thomas – One group of genes we found is the group of antifreeze proteins. And they are expressed, they are used whenever temperatures drop below the freezing point of seawater. These creatures live between the ice crystals – this very very extreme habitat with high salinities and very low temperatures and they can cope in these extreme conditions very well because they have very different types of these antifreeze proteins.
Tom – I’m putting myself in the shoes of one of these phytoplankton. If I’m happily floating about in the sea and then suddenly the sea freezes and I become trapped in sea ice, would I then suddenly switch on this particular version of this protein to allow me to survive.
Thomas – Yeah that’s correct and this is what we actually tested in the laboratory. We simulated sea ice formation and then we looked at how all of the different genes in the genome are expressed.
Tom – Now that we now this, ultimately how is this going to help us, what does this actually mean going forwards?
Thomas – We hope that we can make predictions better about polar organisms cope with global warming. We have global warming and the most threatened ecosystems are polar ecosystems because they are the most sensitive – we see a retreat of sea ice and so on. What we didn’t know so far is how these organisms cope. What are the mechanisms that underpin how they can cope? And with our study we can say that they have a very broad tool set. To me it doesn’t seem to be all doom and gloom, they are very resilient to be honest. With our study we can say that they are very well equipped to cope with global warming and potentially also loss of sea ice.
You can listen to the full interview for the Naked Scientists here.