We finished our scientific program in the western Fram-Strait at the East-Greenland slope and went back to our main research area of the long-term observatory LTER-HAUSGARTEN – west off Svalbard. Like every summer here we realize an extensive sampling program from the sea-surface through the water column down to the seafloor. Here we are analyzing at almost twenty stations within water depth between 200 m and 5500 m seawater, plankton is caught, deep-sea sediments are sampled and photos and videos from the seafloor were made. By a multidisciplinary approach we try to investigate the influence of the climate change and the impact of the sea-ice retreat on polar marine ecosystems.
The fibre optic cable on “Polarstern” allows following the seafloor sampling online on a screen. The camera system attached to the multiple corer transmits high-resolution images from a hidden world. A towed photo/video system was used to assess large-scale distribution patterns of larger organisms (megafauna) on the seabed at HAUSGARTEN. The comparison with images retrieved during the preceding years will allow us to evaluate temporal variations not only in mega fauna densities and composition but also for less favorable influences of human civilization on the deep-sea of the Arctic Ocean. Sightings of litter at the seafloor have increased significantly within the recent years. And that’s why we started to investigate this phenomenon systematically.
Marine litter has long been on the political and public agenda, as it has been recognized as a rising pollution problem affecting all oceans and coastal areas of the world. There is currently a discrepancy of several orders of magnitude between estimates of global inputs of plastic litter, wıth figures derived from field measurements highlighting again the question: ‘Where is all the plastic?’ Degradation of larger litter items into smaller particles termed ‘micro plastics’ may be one reason for this discrepancy. Another possibility is that certain ecosystem compartments have not been considered so far with the latest research suggesting that the Arctic is an accumulation area for marine plastic. A newly added component to the open-ocean infrastructure FRAM (FRontiers in Arctic marine Monitoring) allows for the observation of marine litter and micro plastics and other pollutants in different ecosystem compartments over long time scales.
Our sampling campaign during this expedition has aimed to collect samples from different marine compartments to answer these open questions. Five different sampling campaigns were executed to assess the spatial and temporal distribution of macro litter and micro plastic. Photographic surveys undertaken by the OFOS – as already mentioned - were done to observe the change of the amount of macro litter on the seafloor. The upper layer of sediment was sampled with a video-guided Multi Corer for further analysis of micro plastic particles in deep-sea sediment. In-situ pumps were deployed to get filtered water samples from different target depths of the water column. A towed neuston micro plastic catamaran was used at locations where ıt was feasıble to tow through ice sheets to assess the amount of micro plastic particles in surface waters. Visual litter surveys were done to observe the amount of floating marine litter during the transit from Tromsø and around the Fram Strait.
Unfortunately, observations during litter surveys and OFOS transects showed considerable amounts of macro litter around the Fram Strait. Vast amounts of floating sea-ice in the area during our sampling campaign raises again the question if sea-ice is a transport vehicle for marine litter. We will analyze our samples from sediments, water column and surface waters for micro plastic after the cruise, but already the observed amounts of marine litter during the OFOS and Visual Litter Surveys are concerning.
Yearly sampling campaigns give us on the one hand a very good spatial overview of the status of the ecosystems within the HAUSGARTEN area on the other hand these are mostly just snap shots of the situation during the summer months. It is, however, also very important to get temporal information of variations in ecosystem processes within the annual cycle. Due to this we exchange also during this year’s expedition instruments and sensors, capturing data over longer periods of time in the water column and at the seafloor. Many of those measuring-systems are combined within so called moorings. Moorings are deployed for several months or years. A mooring consists of up to several kilometres of Kevlar rope, on which various instruments are mounted. Buoyant floats attached to the rope keep the mooring almost vertical in the water column. Each mooring carries various physical and chemical sensors for water temperature, current velocity and direction, salinity and oxygen. Our moorings are additionally equipped with so-called sediment traps to collect sinking particles. These particles are, at least partly, of organic origin (phyto- and zooplankton) and thus, the main food and energy source for deep-sea organisms. Particles were caught with huge funnels and collected in plastic bottles arranged in a loop at the lower end of the cone. A stepper motor exchanges these bottles in pre-programmed time intervals, permitting the recognition of seasonal variations in the food supply to the deep sea.
Many of these particles arise within the phytoplankton. The smallest marine organisms, the marine microbes, are of highest relevance for the functioning of marine ecosystems. Among them, the phytoplankton is in analogy to land plants, able to use energy from sunlight and carbon dioxide to generate biomass. This biomass is the major feeding ground of the oceans. The composition, abundance and distribution of phytoplankton is from high relevance for survival and reproduction of small marine animals feeding on the phytoplankton, as some phytoplankton species are from higher nutritional value than others. It is expected that environmental change in the marine realm will lead to changes in the composition and abundance of phytoplankton. Laboratory experiments suggest that small phytoplankton might benefit e.g. from rising water temperatures and increase in abundance, while larger organisms decrease in abundance at the same time. Such changes would have significant impacts on the organization and functioning of marine ecosystems. The Arctic Ocean has gained increasing attention over the past years because of the drastic decrease in sea ice and increase in temperature, which is about twice as fast as the global mean rate. The effects of changes in the environmental conditions on the polar plankton community can only be detected through long-term observations. In 2008 a group of 6 scientists from AWI and GEOMAR initiated PEBCAO (Phytoplankton Ecology and Biogeochemistry in a Changing Arctic Ocean) in order to study the impact of Arctic environmental change on phytoplankton ecology and biogeochemistry. Since then the group carried out regular field campaigns to collect samples for plankton studies in the area of the AWI LTER Hausgarten (Fram Strait) and the central Arctic Ocean. These studies are based e.g. on cutting edge molecular analyses or high resolution microscopy that require highly sophisticated equipment. On board ship the operation of this equipment is difficult. Therefore the analyses of PEBCAO are carried out mainly at home in the land-based laboratory. Thus, on board Polarstern the major task of the PEBCAO team is sampling of microorganisms via filtration of water samples and subsequent conservation for analyses in the laboratory. During the past three weeks we were able to take and conserve hundreds of samples via filtration of at least 5000 liter sea water. Preliminary results of the physical environment suggest a highly variable distribution of water masses in Fram Strait this year. Thus, the scientists of the PEBCAO team are looking forward to accomplish their marine analyses and expect interesting insights into the phytoplankton composition in a highly variable environment.
In any case for our long-term investigations within HAUSGARTEN it is of exceptional importance to get a holistic picture of processes within the different ecosystems. It becomes most exciting if after all analyses in our home laboratories we can start to put together all pieces of the puzzle and to see them in the context of the results of former years.
We will continue our research program at HAUSGARTEN until next Tuesday evening. Then we will start to wrap up our equipment and to steam back to Tromsø. In any case we can resume an extremely successful expedition this year. But this wouldn’t be possible without the exceptional and professional support of the POLARSTERN crew.
Warmest regards from all cruise members.
Ingo Schewe
(supported by Katja Metfies & Susanne Töller sowie Mine Tekmann & Melissa Käß)
