Expedition „ROBEX-DM“

The robotic systems have been developed since 2012 within the Helmholtz-Alliance ROBEX (Robotic Exploration of Extreme Environments) where 120 scientists and engineers from 16 space and deep-sea institutions all over Germany are working together. On the one hand expedition PS108 is aiming to verify mission critical robotic technology required to operate in extreme environments, on the other hand PS108 will contribute to investigations in Arctic ecosystems: long-term experiments at the HAUSGARTEN deep sea observatory and research at the gas hydrate stability zone (GHSZ). The “Remotely Operated Vehicle, ROV” KIEL6000 (GEOMAR) will support our scientific investigations as well as the verification of the robotic developments.

The journey to the first destination at the HAUSGARTEN observatory was used to become familiar with life on board and also for preparation of the different units and instruments for their first deployments.  In addition regular observations of litter were performed in order to understand the distribution of litter at the surface of the Arctic Ocean.

On Thursday, August 24, we reached our working area and started the research program with the deployment of two bottom lander systems capable to measure oxygen consumption rates at the seafloor. These measurements are part of the long-term investigations performed at HAUSGARTEN since 1999. During the night a “Catamaran”, an instrument that is dragged over the surface of the sea, was used in order to collect litter and micro plastic. Some of the plastic pieces could already be recognized with the naked eyes.

In the morning of August 25 the ROV „KIEL6000“ (GEOMAR) was deployed, directly at the start position of the crawler TRAMPER deployment one year ago. During its one year operation TRAMPER should perform measurements of the oxygen distribution in the seafloor. The search for the starting point was quite short and then the observers were able to recognize the tracks of TRAMPER in the sediment. The ROV followed them and after 20 minutes TRAMPER was recognized standing there vertically to its tracks. The reason was that after around 350 m and 24 weeks of traveling at the seafloor the right caterpillar didn´t work anymore and TRAMPER stayed the rest of the year in a mode of circling. Because of the weather recovery of the crawler was not possible at this time. The rest of the ROV dive was used for collecting animals and taking pictures of the seafloor.

With the towed video and photo system OFOS a survey transect to the deepest point of the Arctic Ocean, the Molly Deep (5.500 m depth), was performed. The last operation in this area was 20 years ago. On the photos a bustle of life was recognized with countless small sea cucumbers and sea anemones. Furthermore a lot of wood and unfortunately much more litter could be seen. The new dataset will be compared with the data from 1997 and might provide hints about the change of this ecosystem.

The second ROV dive focused on a biological long-term experiment, which was started last year. A common feature in polar deep-sea regions is the occurrence of so-called “dropstones” at the seafloor, which enhance the topographic heterogeneity and alter related hydrodynamic patterns. These dropstones of different sizes are transported by sea ice and after melting of the ice they finally sink to the bottom of the ocean. There is abundant evidence that habitat structures have important effects on spatial distribution patterns of benthic fauna populations in deep-sea environments. Changed flow regimes around dropstones can have a direct effect on colonization and settlement of benthic individual organisms and indirect effects on community structures by the amount of potential food trapped around dropstones and changing sediment characteristics. Until now we do not know how fast benthic communities react on new dropstones. Therefore 9 artificial dropstones of different shapes were deployed at 2500 m water depth in 2016. During the ROV-dive sediment cores were retrieved from surface sediments influenced by the dropstone and nearby undisturbed areas as controls. The cores will be sub-sampled for meiofauna/nematode analyses and different biochemical parameters indicating food availability. At the end of the ROV dive the artificial dropstones were moved to different places nearby and will be sampled again in 2019.