On the hunt for elusive calcifying zooplankton … Victoria Peck, January 14, 2013
Today’ s plankton catch – on some days the bucket is swarming with krill and other plankton but today it was almost empty. @ Vicky Peck
On a non-bioassay day onboard the cruise, scientific deployments begin at 05.15 with the bongo nets. These twin nets, made of a fine nylon mesh are lowered down to 200 m beneath the sea surface and hauled vertically through the upper ocean catching anything that doesn’ t have the ability or foresight to swim out of its way … i. e. plankton and the odd hapless fish. To investigate the potential consequences of ocean acidification on zooplankton, we are primarily interested in the calcifiers, the plankton that make their shells from calcium carbonate, namely foraminifera and pteropods – see images. As well as observing the condition of their shells in the their natural environment, we will also incubate certain species in water manipulated to simulate water chemistry under future pCO2.
As Toby reported of our‘ catch’ at Station 1, we recovered more pteropods than I could have ever dreamt for, unfortunately, since we were fresh out of the Falkland’ s and north of the polar front with temperatures in the heady heights of 6 C, they were not the polar species we were looking for. Since passing the polar front and the notable drop in sea and air temperature the pteropods have become somewhat elusive. A handful, well, a micropipetteful, of the polar species Helicina limacina were caught yesterday morning, but were too few to be added to the bioassay experiment. Foraminifera on the other hand were massively abundant, apparently feeding on the abundant phytoplankton community dominated by siliceous diatoms.
19