Numbers tell the tale during the Expedition to the Antarctic

Gepubliceerd op
25 augustus 2013

The researchers who are on an expedition to Antarctica would like to do some fishing under the ice, but they are not there yet. Measurements are now being done in the ‘iceless’ waters of the Southern Ocean.

Photo: During the collection of the sediment trap, high waves wash over the back of the ship. Although the crew and researchers are nowhere near, the rolling of the ship creates a water flow over the deck, leaving some people with wet feet.

Taking water samples

Despite of our own desire to fish with the SUIT net underneath the ice, a lot of measurements are also being done in the ‘iceless’ waters of the Southern Ocean. For example, between the Falkland islands, South Georgia and the ice edge regular measurements are done with the CTD. This device is lowered into the water and measures Conductivity, Temperature and Depth. Around the CTD there is a rosette of 24 bottles which can all be closed  at a certain time. This way, a water sample can be taken at any desirable depth. These water samples can then, for instance, be used to measure the amount of nitrate, ammonium and silicate at a certain depth and which organisms can be found there.

Collecting deposit in a sediment trap

Nearby South Georgia a sediment trap was retrieved which has rested on the bottom of the ocean for a year. This sediment trap caught what has been sinking down from the surface. Dead organisms, poo or sloppy eaten food sinks to the bottom where is provides an important carbon source for deep sea and bottom organisms. At the surface, algae form the bottom of the food chain. These algae obtain their energy for growth and reproduction from sunlight. As there is no sunlight in the deeper waters the algae cannot grow here and the deposit becomes important. By collecting the deposit, researchers can investigate what and how much is sinking to the bottom and how organisms use this.

Various fishing nets

Apart from the SUIT, several different nets are being used with several different goals. One of these is the Rectangular Midwater Trawl or RMT. This net is towed behind the ship and fishes from 0 to, for example, 500 meters deep. Amongst other things, the catch is being used to investigate diets and for genetic research.

Fokje Schaafsma