Standing up for the little guys – Phytoplankton and Southern Ocean Ecology Laura Bretherton , January 24 , 2013
If you ’ ve been keeping up with the blog , you ’ ll by now be well acquainted with marine plankton . These little guys are the topic of my PhD , though more specifically , I look at the phytoplankton – the photosynthetic microalgae – and how they might be affected by ocean acidification . That means I ’ ve been particularly focussed on the bioassay experiments we ’ ve been conducting at sea , and today marked the end of our second one . With that comes an early start and many water samples to process …
My role on this cruise is to look at the physiology of phytoplankton populations , and how that changes over the course of the bioassays . I use an instrument called a fast-rate repetition fluorometer ( or FRRF for short ), which monitors photosynthesis by detecting fluorescence given off by the chlorophyll inside the microalgae . Because we understand how changes in this chlorophyll fluorescence are linked to photosynthesis , the fluorometer can tell us things like how efficiently the phytoplankton are photosynthesising , or if they ’ re changing the structures within their cells that catch sunlight .
The FRRF ( top left ), water bath ( middle right ) and my dark sample bottles ( bottom ). @ Laura Bretherton
My sample bottles are made of opaque dark plastic to keep the phytoplankton out of the light for a period of time , in preparation for being put in the FRRF . This process is called dark-acclimation , and sort of “ resets ” the algae ’ s photosynthetic apparatus to ensure all the models the FRRF uses fit correctly . Once they ’ ve been dark-acclimated , a small volume of sample gets put in the FRRF , surrounded by cold water supplied from a water bath that ’ s pumped into the instrument to keep the phytoplankton at a constant and appropriate temperature . Finally , I use a laptop to tell the FRRF to start a sequence of flashes of light , and about 20 seconds later , I get some data . The results are available instantaneously ( a bit of a luxury on a cruise !), and as phytoplankton
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