Vicky Peck, British Antarctic Survey, Cambridge, Tuesday, 26 June 2012
Today has been much like every other day so far this cruise, except for the ones with the polar bears or islands. As mentioned elsewhere on the blog we do a major sampling station every morning where a range of different techniques are used to collect samples. Unfortunately the zooplankton nets which my colleague Geraint and I use are the first things to be deployed – at 5 am in the morning. We have a pair of ‘bongo’ nets formed of a fine plastic mesh.
These are lowered to 200m below the ship then slowly pulled back up filtering the seawater and collecting any plankton unlucky enough to enter them into a jar at the bottom. Well actually not all plankton, the really small plant plankton which most people on this cruise are studying pass straight through our mesh leaving the larger and more interesting zooplankton. Zooplankton are minute animals which float and swim in the water eating the phytoplankton and in turn forming the basic foodstuff for a wide range of other creatures from herring to blue whales.
After preserving our first ‘catch’ which will be analysed back on shore to characterise the plankton community as a whole, we search through the second and third catches for animals we’d like to incubate in bottles of seawater which have had acid and bicarbonate added in carefully calculated quantities to simulate a range of future pCO2 scenarios. The objective of these incubations, which last between 2 and 8 days, is to study the effects of ocean acidification on respiration rates and other bodily functions. We are studying three groups – copepods, planktonic foraminifera and pteropods. Copepods are minute crustaceae a bit like shrimps with very long antennae, and have been collected in our morning catches throughout the cruise. In fact in some samples they are the only thing there, having eaten everything else. Pteropods and forams are less abundant but as they have calcareous shells they are of special interest for ocean acidification studies and we are carrying out experiments to test their ability to grow and maintain their shells in more acidic waters. The effect that the different treatments had on the shells will be analysed back in Cambridge using electron microscopy. That is not practical onboard the ship, however the microscopes we do have on the ship really do show the beauty of the living animals. I usually work with fossil plankton and this cruise has been an inspiring change for me.