Freedom!

Immediately after departure, we started to set up the ship’s laboratories and to assemble the wide variety of measuring, recording and sampling devices. On Sunday, May 30, at 08:00 in the morning, we finally reached the first station and started this year’s “gardening season”:

Our study area, the LTER (Long-Term Ecological Research) observatory HAUSGARTEN, is re-visited by us annually in summer months, already for more than 20 years. The multidisciplinary work at HAUSGARTEN observatory is carried out to investigate the impact of Climate Change, continuously increasing water temperatures and the retreating sea-ice on the Arctic marine ecosystem.

Today, HAUSGARTEN comprises a network of 21 stations at water depths ranging between 300 and 5.500 m. These stations are sampled every year during the summer months, with observations and measurements made in both the water column and at the seabed.

To determine the various physical, chemical and biological properties of the seawater we take water samples at all permanent HAUSGARTEN sampling sites using a CTD/Rosette. This gear combines a number of physico-chemical sensors and a carousel of Niskin water sampler bottles. The CTD/Rosette is lowered close to the seafloor and collects discrete water samples for various parameters on its upcast.

Optical properties of surface waters are detected to verify satellite data. Plankton is filtered from water samples and sampled using different types of nets. In addition, special camera systems are used to detect the smallest particles and also larger zooplankton in the sea water.

To assess the proportion of organic matter from primary production finally reaching the seabed as food for benthic organisms, we collect sinking particles in funnel-shaped sediment traps attached to moorings. These moorings consist of an anchor weight, a Kevlar line of several kilometres (depending of the water depth) and flotation buoys to keep the mooring lines in an upright position in the water column. Alongside with the sediment traps, our moorings are equipped with several sensors registering current velocities and directions, water temperature, salinity and oxygen concentrations.

The sampling of sediments from the deep seafloor is conducted using different kinds of grabs, the so-called multiple corer and the box corer, which are lowered by a cable to the seabed. A steel-armoured fibre optic cable on “Polarstern” allows direct observation of the seafloor sampling in real-time on TV screens. A towed photo/video system is used to assess large-scale distribution patterns of larger organisms (megafauna) on the seabed. The comparison with images retrieved during the preceding years will allow the evaluation of temporal variations in megafauna densities and composition.

Beside these more “classical” sensing and sampling devices, there is also a number of technically highly complex systems we use at HAUSGARTEN observatory. These include autonomous mobile underwater vehicles operating in the upper water layers (Autonomous Underwater Vehicle, AUV) and at the deep seafloor (Benthic Crawler) as well as stationary free-falling systems (Bottom-Lander), which we use to perform various in-situ experiments. The next weekly report will provide detailed information on these devices and illustrate their great potential.

With the warmest regards from all scientists,

Thomas Soltwedel