The Arctic Pelagic Environment
Arctic Pelagic System & Vertical Particle Flux
Unicellular protists from the Arctic Ocean. From left to right: Thalassiosira antarctica, Chaetoceros atlanticus (both diatoms, autotrophic unicellular plankton organisms), radiolarian & 2 tintinnids (both heterotrophic unicellular plankton organisms), Phaeocystis pouchetii (colony forming prymnesiophyte, autotrophic unicellular plankton organisms) - pictures are taken by E. Bauerfeind, E.-M. Nöthig, B. Wend -
The Arctic Ocean is, in contrast to the Antarctic Ocean, characterised by broad shallow shelf regions, strong river discharge and little exchange with other oceans. Production, origin, transformation and fate of organic matter - food supply for the benthos - underlay constrains being very sensitive to climatic changes. In general, the Arctic Ocean is less productive than other oceans due to the permanent ice-cover, although, shelf areas can be very productive.
In the future, drastic changes are expected to occur due to Global Change.
Sea ice is severely decreasing, temperatures rise, acidification and stronger influence from the Atlantic Ocean are observed. Thus, it is necessary to perform continuous observations in the Arctic Ocean. Since 1991 samples were taken and analyzed and more will be taken in the future mainly as part of projects in different regions of the Arctic Ocean.
Our main goal is to understand seasonal and interannual fluctuations of particle formation, modification, and sedimentation in relation
Plankton Ecology and Biogeochemistry in the Arctic Ocean
We investigate unicellular plankton organisms including bacteria and zooplankton in the Arctic pelagic system in the HAUSGARTEN and in the central Arctic Ocean together with the PEBCAO group at AWI. On most of the stations visited by ship, net samples and pictures are taken. To the right, a variety of different phyto- and protozooplankton organisms is displayed. The large star-like organisms are acantharians - unicellular heterotrophic organisms - bearing a strontium sulfate sceleton. Cysts of these protozoans occur in large amounts in sediment traps samples from fall.
Estimation of phytoplankton biomass can be obtained by measuring chlorophyll a.
On the left, the salinity (upper panel) and the chlorophyll a distribution(lower panel) along a south to north transect east off Spitsbergen is depicted. A deep chlorophyll a maximum (lower, yellow color) occurs close to the melting sea ice, there salinity decreased (upper, blue green color). Deep maxima point to a late stage of a phytoplankton bloom, nutrients in the surface layers are depleted. Phytoplankton serves as basis food for heterotrophic zooplankton such as copepods which in turn is eaten by carnivors like pelagic amphipods.
Vertical Particle Flux
Sediment traps are deployed in order to get information about the seasonal vertical particle flux patterns. The flux patterns of biogeochemical particles and plankton organisms during consecutive sampling seasons will give information in relation to Global Change, like change in key species and thus change in organic matter fluxes.
Pictures, left upper: sediment trap is deployed; upper right: sampling bottles filled with organisms and organic matter after recovering of the traps; lower left: picked out shells (aragonite) of pteropods; lower right: piece of zooplankton fecal pellet and small broken plankton debris in the background.