Emptying a full net
Received from Daniella Gredin, The Swedish Polar Research Secretariat and Kajsa Tönnesson, Institute of Marine Ecology at the University of Gothenburg.
Edited by Jane Holst, GEUS
The icebreaker Oden
Position: 88°N 179°W
Weather: Cloudy, temperature -0.5°C, wind 4 m/s
Calanus hyperboreus, Calanus glacialis and Metridia are not likely to be household names for most people. But to one of the research groups on board, these are three well-known names of dominant species of copepods here in the Arctic. In these cold waters 90% of all zooplankton are copepods.
In the oceans plants and animal are interconnected in a long food chain, the basis of which is plankton. Phytoplankton are eaten by small zooplankton, which again larger zooplankton, bottom-living animals and fish feed on. In this way a long food chain is built. Zooplankton together with bottom-living algae make up the basis of almost all life in the oceans. By photosynthesis they transform solar energy, carbon dioxide, water and nutrients into carbohydrates and other building blocks of life. Herbivorous zooplankton are the next, important link in the food chain of the oceans. When an animal eats a plant or another animal this means that energy and material are transferred to this animal. To be able to study the various links in the food chain it is important to measure these intakes.
In the large laboratory, placed at the stem of Oden, bottles and water cans are lined up. They will soon be filled with ocean water from the water pump which has given us problems up till now. Behind books, bowls and a crumpled paper towel, pipettes of various sized are lying on a workbench. Right now the number of excrements in a water sample is counted in a microscope.
By means of a net, which is lowered to a depth of 100 m, four of the most common species of copepods in the Arctic are caught. In the laboratory, the individual copepods are placed in bottles, and after 24 hours the number of eggs and excrements the animal has left are counted, giving evidence of how much it has eaten in 24 hours. A selection of copepods in this way represents the entire zooplankton community, in that by measuring how much they eat, the amount of energy transported up the food chain can be determined. This can be used for instance to estimate how large an amount of fish the zooplankton community can sustain. Also, by counting the number of excrements the amount of material which is sedimented down to become food for bottom-living animal can be found. Excrements from copepods also constitute a major food source for many animals in the oceans.
When work is done on the ice, the multinets are used to determine species and count the animals. The net is lowered to a depth of 250 m and is opened and closed at five different depths. The research group also used water from the sampler on the CTD to determine the amount of chlorophyll, which reflects the amount of phytoplankton. Furthermore, samples are taken to estimate the distribution of phyto- and microzooplankton.
We have celebrated another two birthdays on board, on one of which a round number was reached. So on Sunday 16 August we all got together in the bar for a drink before we settled in the mess to enjoy a banquet with starter as well as cheese. The clouds are hanging low and have done so for several days.
Received from Daniella Gredin, The Swedish Polar Research Secretariat
Edited by Jane Holst, GEUS
20 August 2009
The icebreaker Oden
Position: 89°N 135°W
Weather: Cloudy, temperature -0.5°C, wind 6 m/s
We are now in our third week of the expedition and again it is time for the traditional pea soup with pancakes and hot punch. And how we have looked forward to it! The purpose of this menu is not only to fill our stomachs; it also helps us to tell which day of the week it is. Everybody has his or her own habits and routines, according to which he or she sleeps, works and works out. But the meals are fixed slots in everybody’s schedule. We are served three meals a day as well as elevenses and afternoon coffee. For those that are still hungry for at midnight snack there are left-overs in the mess’ fridge. The meals help us to keep track of time of day, since the light does not change from day to night. The weekdays are much more difficult to keep track of – and this is where the pea soup comes in handy as a reference point.
Yesterday the grey cover of clouds, which has been hanging over us for several days, was substituted by glittering sunshine. The otherwise rather cold bridge warmed and actually became a comfortable place to work. After dinner we saw polar bear tracks, perfectly frozen into the ice, for quite a bit along the ship. Several of us found our way to the bridge ready with our cameras and everybody was in high spirits. Perhaps we were hoping to see a white-furred figure approaching on the sea ice?
In the fine weather on Wednesday 19 August, taking advantage of the excellent visibility, several helicopter flights were made to the ice to take measurements. The helicopter is an important tool for the research and an invaluable help in navigating Oden in the unpredictable ice.
The main planning of the course takes place on board Oden, where ice concentration maps from satellite are studied to find the most appropriate route to take and to be able to calculate the how long it takes. The immediate navigation is done by means of radar, the officer on the bridge looking at the ice conditions approximately three nautical miles ahead. By doing ice reconnaissance from helicopter it is possible to plan the route better, helping to find open stretches in the ice. This makes the ice breaking easier and saves time. The helicopter, which is an AS350 Ecureuil model, is equipped with an AIS-transponder that registers the air route making it possible for the officer to follow it and compare it with his radar image. Since the sea ice drifts approximately 0.25 knots, the ice conditions change relatively fast and ice reconnaissance never covers more than 20 nautical miles ahead. Two helicopter pilots and an air mechanic are on board.