Thursday, 27 October 2011

Small but perfectly formed

After my recent post about bobtail squid, I felt that I should give some airtime (if you're using WiFi) to the little ocean critters that I am actually involved with: the beautiful Emiliania huxleyi. It's not really a "critter" as such at all - it's a tiny marine phytoplankton, so it's more like a plant really.

Emiliania huxleyi (fondly known as "E hux") is a "Coccolithophore"; the funky appearance comes from the armoured "coccolith" plates that cover the outside of these tiny single-celled organisms. Nobody really knows what coccoliths are for but they are one of the primary reasons for the interest in species as the plates are made out of calcium carbonate. This makes E hux and its relatives a potentially potent carbon sink despite their minuscule size. (The scale bar in the image is 2μm, which is 1 million times shorter than Darth Vader.) This is because huge numbers of coccoliths sink to the sea floor and ultimately become the chalk of the future.

Although it would seem to make more sense to make these plates externally, they actually make them internally and then export them whole, as this video (of a different coccolithophore) shows. In the words of the experts:
"The coccoliths are rather large relative to the cell size; if scaled up to human size it would be like a person giving birth to a car wheel or a dustbin lid."
The project that I am involved with is primarily concerned with Ocean Acidification, which is one of the lesser-known aspects of climate change due to rising carbon dioxide (CO2). Approx a quarter of atmospheric CO2 is dissolved by the world's oceans. As CO2 levels continue to rise due human activity, the amount of dissolved CO2 therefore also increases. This, in turn, lowers the pH of the ocean, which makes calcium carbonate - the stuff of coccoliths, skeletons and shells - dissolve more easily. The prediction, therefore, is that this will be bad for calcifies, making calcification itself more difficult and reducing the effectiveness of the calcium carbonate structures that they make. (Although we don't yet know what E hux uses its coccoliths for, it's a fair bet that their important.)

The good news is that, as Dr Ian Malcolm would say, "Life finds a way" and so there is every expectation that E hux and friends could evolve and adapt to the elevated CO2 levels. The bad news, though, is that rate of man-made CO2 increase is so fast that they may not have the time and capacity to adapt before the oceans get too acidic for them. It is therefore important that we understand both how calcification is regulated and what the capacity of E hux for adaptation to high CO2 is. Until we get a handle on this, we also don't really know how E hux will respond. Will the increased solubility of the calcium carbonate release more carbon into the ocean, making things even worse? Or, will E hux respond by making thicker coccoliths, incorporating more carbon and help to offset some of the effects of human emissions? (At least, that's my understanding of the main questions.)

In a future post, I'll outline a bit of what we are doing. (I say "we" but my contribution is actually pretty small.) For now, though, just marvel at their coccospherical beauty:


  1. I just passed a link to this on to my brother and sister-in-law who are marine scientists. My brother even did his masters in Southampton.

  2. Your brother probably knows a lot more about E hux than me, then! :-)


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