As promised in our last weekly report, we would like to start with a description of the benthic work, i.e. the work carried out at the deep seafloor. Yet, there is much more to marine biological research, as you will see/read below.
For the sampling of sediments and sediment-inhabiting organisms at the deep seafloor, we use different kinds of grabs, the so-called multiple corer and the box corer, which were lowered to the seabed by a cable. Back on board and in the home lab, these sediments are/will be analysed for various biochemical parameters (e.g. microbial activity, proxy for the amount of settling matter), bacterial numbers and biomasses, and faunal components covering all size classes from the so-called meiofauna (<1 mm) to larger invertebrates.
The fibre optic cable on “Polarstern” allows following the seafloor sampling online on TV screens. The camera system attached to the multiple corer transmits high-resolution footage from a hidden world. A towed photo/video system was repeatedly used to assess large-scale distribution patterns of larger organisms (megafauna) on the seabed at HAUSGARTEN. The comparison with images retrieved during the preceding 15 years will allow us to evaluate temporal variations in megafauna densities and composition.
Freefalling devices, so-called bottom-lander, were deployed to conduct various physical and chemical measurements and to collect deep-sea organisms at the seabed. Such devices consist of a metal frame, weights for the descent, and floats bringing the gear back to the surface after releasing the weights. Bottom-landers may be equipped with a variety of instruments. During this cruise, we use a bottom-lander carrying incubation chambers and a microprofiler to study re-mineralization processes at the sediment-water interface.
Except for a very few spots in the World’s ocean where benthic organisms thrive on chemosynthetic processes (“hot vents”, “cold seeps”), life at the deep seafloor depends on the settling organic matter produced in the uppermost layers of the water column. Therefore, benthic research needs background information provided by colleagues working in the water column (e.g. the quantity and quality of the settling matter) to explain processes at the seafloor as well as the community structure of benthic organisms.
Therefore, in addition to the pelagic work already presented in the 2nd Weekly Report, we also use an Autonomous Underwater Vehicle (AUV) to study physical, chemical, and biological processes in the surface layers of the ocean. The AUV is equipped with sensors measuring temperature, conductivity and pressure, the concentration of nitrate, chlorophyll a, oxygen, CO2, coloured dissolved organic matter (CDOM), and the intensity of photosynthetically active radiation (PAR). An integrated water sampler which is able to collect 22 samples with an overall volume of 4.8 litres is used to assess the composition of plankton communities and to calibrate the nitrate and the chlorophyll a sensors. At the beginning of the last week we conducted a very successful AUV dive in the vicinity of the ice edge, more explicitly in the hydrographically and biologically extremely interesting melt water front, separating less saline waters surrounding the melting ice flows and water masses of the open ocean exhibiting higher salinities.
The AUV dive was accompanied by (manned) helicopter flights to conduct a mapping of the marginal ice zone, and by flights with small Unmanned Aerial Vehicles (UAVs), which we use to track the ice drift in the region to allow safe navigation of the AUV during dives along and across the ice edge. The UAVs are equipped with GPS transponders. They land on larger ice flows and transmit their position (and thus the position of the ice flows) continuously to the AUV control container. This year, we conducted first trials to return the UAVs autonomously (i.e. not remotely controlled, as in the past) to the ship.
I guess this short report already showed that modern marine biological research brings together scientists from a number of different disciplines working in all compartments of the marine ecosystem. The synthesis of information gathered at the deep seafloor, in the water, and in the air will finally help to understand how the polar marine system works and how it may develop facing global environmental changes.
There is a lot of fog surrounding the ship during the last days; however, nothing affects the generally positive atmosphere on board.
I am closing this report with the warmest regards from all scientists,
Thomas Soltwedel
