TRANSSIZ Expedition – Facts and Figures of the different scientific programmes

To all reports Quelle: 19 June 2015
Shannon MacPhee, Meri Korhonen, Kirstin Werner, and Christian März
We have now started our seventh ice station and thought it is about time to summarize the amount of samples that were collected within the past few weeks during our TRANSSIZ cruise. Because we are scientists, we approached this summary quantitatively. In order to study the sea-ice habitat, the sea ice biology team has collected over 560 kg of sea-ice cores of about 200 m length in total for a variety of biogeochemical studies ranging from algal and bacterial production and respiration to studies on neodymium (a compound that can indicate different water mass sources) as well as volatile organic compounds (VOCs) in sea ice. 250 l of snow have been collected so far for analysis of rare earth elements. The sea-ice physics team has surveyed almost twenty kilometres of under-ice habitat using their Remotely Operated Vehicle (ROV) to measure parameters such as under-ice light transmission. They have also completed eight helicopter surveys covering about 700 km using an EM-bird to measure sea-ice thickness. To-date about 4400 measurements of the snow thickness have been carried out; the average snow cover was about 28.6 cm thick. For studies of the water column, we have now photographed more than 600,000 phytoplankton cells (algae that live in the water column) using an Imaging Flow Cytobot, and hand-picked more than 5000 copepods (small crustaceans that feed on phytoplankton), of which about 100 are to be analyzed for biomarkers such as stable isotopes and fatty acids. Zooplankton caught with a Bongo net and kept alive for 24 hours in tubes, however, have respired so far only about 1 mmol (ca 23 ml) of oxygen. The biologists have fished for about ten hours in total, including about 20 km of under-ice habitat survey. They have caught about 6500 living animals with both their Rectangular Midwater Trawl and the Surface and Under-Ice Trawl, including 1800 krill individuals, over 1000 ice amphipods, and eleven young squids. The Conductivity-Temperature-Depth (CTD) sensor attached to a ring of bottles called a ‘rosette’, one of the most in-demand instruments on this vessel, has been used to collect more than 8500 l of seawater while measuring water properties of more than 40 km of water (Figure 4). Most of the collected water has been filtered by scientists working on a wide variety of biogeochemical studies; yet estimating the numbers of collectively generated filter papers need to be postponed until the end of the cruise. The scientists measuring Volatile Organic Compounds (VOCs) have used 100 ml of gas mixed with 20 ml of collected water per minute on our way to the Arctic Ocean – that’s more than 10,000 minutes of online seawater measurements. In addition, this group has studied trace gases in 30 l of melted water from sea-ice cores and 60 l of additional seawater from the CTD. More than 1000 l of water have been pumped by a flow-through system (in-situ pump) to collect organic particles from the turbidity maximum. One of the goals of this research cruise is to establish linkages between sea-ice processes and conditions in the water column and on the seafloor. A sediment trap, deployed at every ice station, has been used to collect sinking particles at multiple depths throughout the water column. These sinking particles originate from a variety of sources including under-ice material and zooplankton fecal pellets, and represent an important food source for animals living in the benthic (bottom) zone.  So far, these sediment trap particles have been collected on 245 filters. The sediment trap also attracted the attention of one fat baby seal. The benthic ecologists are interested in small animals living within the sediment. They collect mud from a box corer that must be passed through a sieve. To-date, the group has sieved ca 1.5 t of mud. Bugs inhabiting in the cold Arctic sediments live life in the slow lane. Kept alive in tubes they have so far consumed only 28 mmol of oxygen in two weeks. A human consumes about 1000 times more oxygen in just one day! To study the history of the Arctic Ocean, geologists have collected several short but also long sediment cores, but undeniably take the prize for highest amount of mud collected from a single cast after the successful retrieval of about 1.3 t of sediment from just one Kastenlot corer! Another 200 kg of seafloor sediment were sampled from multicorer tubes, and around 1.5 l of pore waters were extracted from sediment cores to be analysed for dissolved nutrients and metals. We look forward to continuing our sampling and generating more data points during the final weeks of the TRANSSIZ cruise. Until next time, your Friday blog team.