Beschreibung: Macrofauna data was collected using a box corer (0.25m² sampling area). The sampled sediment from each box corer was divided into eight subsamples (pseudoreplicates). The uppermost 12 cm of these subsamples were analyzed. Each subsample was processed through a 500-µm mesh size sieve. After sieving, residuals were fixed with 100% ethanol and stored at room temperature. Macrofaunal organisms were identified to the lowest possible taxonomical level. Whenever identification to species level was not possible, the sample was identified to the next identifiable taxonomical category and assigned a putative species name (e.g., 'Hesionidae genus sp. 1', 'Hesionidae genus sp. 2'). Posterior fragments, exuviae, xenobionts, meiofauna taxa (Nematoda, Ostracoda, Harpacticoida) and empty tubes were excluded from the analysis. Biomass (blotted wet weight, ww) was determined by weighing each specimen. Shelled organisms, such as mollusks, were weight in their shells.

Beschreibung: The 77th cruise of the RV MARIA S. MERIAN contributed to various large national and international research and infrastructure projects (FRAM, ARCHES, INTAROS, ICOS, SIOS) as well as to the research programme PACES-II (Polar Regions and Coasts in the changing Earth System) of the Alfred-Wegener-Institute Helmholtz-Center for Polar and Marine Research (AWI). Investigations within Work Package 4 (Arctic sea ice and its interaction with ocean and ecosystems) of the PACES-II programme, aim at assessing and quantifying ecosystem changes from surface waters to the deep ocean in response to the retreating sea ice, and at exploring the most important (feedback) processes determining temporal and spatial variability. Contributions to the PACES-II Work Package 6 (Large scale variability and change in polar benthic biota and ecosystem functions) include the identification of spatial patterns and temporal trends in relevant benthic community functions, and the development of a comprehensive science community reference collection of observational data. Work carried out within WPs 4 and 6 will support the time-series studies at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN (Fig. 1.1), where we document Global Change induced environmental variations on a polar deep-water ecosystem. This work is carried out in close co-operation between the HGF-MPG Joint Research Group on Deep-Sea Ecology and Technology and the PEBCAO Group (Phytoplankton Ecology and Biogeochemistry in the Changing Arctic Ocean) at AWI as well as the working group Microbial Geochemistry at the GEOMAR and the HGF Young Investigators Group SEAPUMP (Seasonal and regional food web interactions with the biological pump).

Beschreibung: The eastern side of the Fram Strait is significantly influenced by the northern-bound warm West Spitsbergen Current (WSC) whereas the western side is affected by the cold and less saline East Greenland Current (EGC) flowing in a southerly direction. These current regimes are major factors in regulating the ice coverage in the Fram strait. In turn, this coverage plays an important role in determining the flux of food to the seafloor. The objective of this study is to compare the macrofaunal community structure along two bathymetrical transects (1000 to 2500 m) at the LTER (Long-Term Ecology Research) observatory HAUSGARTEN; one transect in the eastern Fram Strait and a second in the western region of the strait. Material was collected during RV Polarstern expedition PS99.2 in June/July 2016 using an USNEL box corer with a sampling area of 0.25 m². Samples were processed through a 500 μm mesh size sieve. Results showed a higher macrofaunal density at the stations located in the eastern Fram Strait. Species richness, biomass and biodiversity showed a trend to decrease with increase in depth on both sides of the strait. An exception was observed at one station at 2500 m depth off Greenland, which was located in the marginal ice zone. Densities and species diversity were higher at this station than at the adjacent shallower sampling locations. Polychaetes were the generally most abundant taxon, followed by crustaceans and molluscs. Species composition along the two bathymetrical transects on both sides of the strait clearly changed with increasing depth. Sea ice coverage and depth, with the associated variabilities in food quality and quantity reaching the seafloor seemed to be crucial factors driving community patterns.

Beschreibung: Macrobenthos plays an important role in ecosystem processes such as bioturbation, particle reworking and ventilation of the soil. Nevertheless, explaining the relationship between biodiversity and ecosystem function (BEF) remains a difficult task. This holds also true in remote polar regions such as the LTER observatory HAUSGARTEN in the Fram Strait. The local hydrographic regime is mainly influenced by the warm northern-bound West Spitsbergen Current, and the southwards flowing cold and less saline East Greenland Current. The currents are causing regional differences in sea-ice coverage. Distribution patterns of the sea-ice play a major role in determining the flux of potential food to the seafloor, thus shaping benthic communities. Recently, functional and biological trait analysis (BTA) became an important tool to investigate BEF-relationships in marine environments. However, this approach is relatively new for Arctic regions, especially deep-sea ecosystems. Therefore, our study aims to determine functional characteristics on a depth gradient in the deep Fram Strait. Deep-sea samples (1000 – 5500m) were collected in the Arctic autumn of 2018 on board of RV Maria S. Merian. An USNEL box corer (0.25m²) was deployed at nine sites along the bathymetric transect of the LTER observatory HAUSGARTEN offshore Svalbard. All material was treated trough a 0.5-mm sieve and fixed in 4% formalin. The specimens were identified to species level wherever possible and after assigning to modalities of selected traits used for BTA to observe functional changes along the depth gradient. Preliminary results on community structure and resulting functional differences between the benthic communities will be presented

Beschreibung: Unterhalb des lichtdurchfluteten Teils des Meeres beginnt sie – die Tiefsee. Nicht nur Dunkelheit, sondern auch hoher Druck und ein geringes Nahrungsangebot lassen die Tiefsee wie einen lebensfeindlichen Ort erscheinen. Doch manch einer fühlt sich hier besonders wohl. Welche Tiere findet man auf dem arktischen Tiefseeboden und was machen die da eigentlich? Melissa Käß vom Alfred-Wegener-Institut für Polar- und Meeresforschung (AWI) bringt heute Licht ins Dunkel.

Beschreibung: Unterhalb des lichtdurchfluteten Teil des Meers beginnt sie – die Tiefsee. Nicht nur die Dunkelheit, sondern auch der hohe Druck und ein geringes Nahrungsangebot lassen diesen Ort als lebensfeindlich erscheinen. Doch die Tiefsee ist nicht nur Lebensraum für faszinierende Geschöpfe wie Vampirtintenfische, Asselspinnen oder Schlangensterne. Sie ist auch an zentralen Prozessen wie Nährstoffkreisläufen und Kohlenstoffspeicherung beteiligt. Umweltveränderungen aufgrund des Klimawandels können in der Tiefsee z.B. zu Veränderungen in der Artenvielfalt und den Nährstoffkreisläufen führen. Mit Blick auf die arktischen Tiefseeregionen ist hier die Framstraße zwischen Grönland und Spitzbergen von besonderer Bedeutung. Sie ist die einzige tiefe Wasserstraße zwischen dem nördlichen Atlantik und dem zentralen Arktischen Ozean, wodurch ein Austausch von großen Wassermassen gewährleistet wird. Um die Auswirkungen des Klimawandels in der Framstraße besser zu erforschen, hat das Alfred-Wegner-Institut für Polar- und Meeresforschung (AWI) vor 20 Jahren das HAUSGARTEN Observatorium errichtet. Dauerhaft installierte Messstationen sowie jährliche Untersuchungen vor Ort liefern unerlässliche Daten über Veränderungen durch den Klimawandel – von der Meeresoberfläche bis hin zum Tiefseeboden. Am Beispiel der Framstraße beleuchte ich in diesem Vortrag, welche Folgen der Klimawandel für die arktische Tiefsee hat und warum diese auch direkt den Menschen betreffen.

Beschreibung: Deep-sea regions provide vast ecosystem services such as biological habitat and nutrient cycling. Even though being threatened by climate change and facing possible biodiversity loss, these deep-sea ecosystems are poorly understood. So are macrobenthic communities and their functions within these ecosystems. Biodiversity and ecosystem function relationships as well as their link to environmental drivers can be assessed with the biological trait analysis. We used this approach for the first time for macrofauna assemblages across the deep Fram Strait between Greenland and Svalbard (1000–5500 m water depth) to evaluate their community-specific function from the upper continental slope down to the deepest known Arctic depression, the Molloy Deep. We aimed to investigate whether there are changes in benthic functioning along the bathymetric gradient and if so, which environmental stressors may drive these changes. In total, 16 stations were sampled with a giant box corer (0.25 m2) in 2016 and 2018. Sediments were sieved through a 0.5 mm mesh size sieve and fauna was identified to lowest possible taxonomic entity. Functions of species were characterized by using six traits split in 24 modalities gathered in a fuzzy coded species × traits array. Environmental parameters shaping the benthic habitat and reflecting food availability were gathered from remote sensing, mooring deployments, and sediment sampling. A distance-based redundancy analysis indicated near-bottom water temperature, seabed inclination, water depth as well as phytodetritial matter at the sea surface and seafloor (indicating food availability) to be the best variables explaining the trait and station distribution. Stations clustered into three groups based on their trait composition. Shallower stations characterized by high chlorophyll a concentration with large organisms, living within the sediment as well as predating specimens clustered in one group. A second group was characterized by stations with low chlorophyll a concentration and medium-sized, suspension feeding, epifaunal living macrofauna. A third group comprised stations with water depths ≥ 3000 m and was dominated by medium sized, surface deposit feeding and infaunal living specimens. Overall, the functional structure of macrofauna communities in the Fram Strait followed a food availability-driven gradient. Based on the relationship between sea ice, surface water primary production and food availability at the seafloor, these results point to macrobenthos being sensible to predicted anthropogenically generated environmental variations in polar regions. Alterations in benthic ecosystem functions might be expected when environmental conditions change.

Beschreibung: The Fram Strait is one of the most important gateways between the Arctic Ocean and its connected water bodies as it is the deepest passage and therefore provides exchanges of deep waters. The part of the eastern Fram Strait is significantly influenced by the northern-bound warm West Spitsbergen Current (WSC) whereas the western part is influenced by the cold and less saline East Greenland Current (EGC) flowing southerly direction. Sea ice from the Arctic Ocean is passing the Fram Strait on its southward flow. Sea ice loss is affecting the entire marine ecosystem as vertical energy fluxes are coupled even to the deep sea. The objective of this study is to investigate whether there are dissimilarities in deep-sea benthic macrofaunal communities such as species composition and diversity in eastern and western parts of the Fram Strait due to different energy input to the benthic communities. Sampling sites along the bathymetric transect of the LTER (Long-Term Ecology Research) observatory HAUSGARTEN off western Svalbard and the macrofauna sampling methodology were chosen following previous studies, while the East Greenland slope has been sampled for the first time at this location. Samples were taken during RV Polarstern expedition PS99.2 in June/July 2016 using an UNSEL box corer with a sampling area of 0.25 m² at water depths of 1000 - 5500 m (Vestnesa Ridge) and 1000 - 2500 m (East Greenland slope). Samples were washed through a 500 μm mesh size sieve and fixed in ethanol 96 %. Macrobenthic organisms were identified to the lowest possible taxonomical level in the laboratory after the expedition. Recent results suggest a trend that stations located on the East Greenland slope are lower in species richness (total number of species) but higher in diversity of taxa than stations on the Vestnesa Ridge. Polychaeta are the dominant taxa at both bathymetrical transects but in noticeably varying proportions. Oweniidae and Cirratulidae show among other families highest abundance at both transects. The differences in macrofauna community structure in the western and eastern Fram Strait might be a result of differences in food availability. Sea ice coverage as well as regions of contrasting primary production could be crucial factors driving community patterns.

Beschreibung: This study compares the macrofaunal communities along two bathymetric transects (1000 – 2500 m water depth) in predominantly ice-covered western (offshore Greenland) and generally ice-free eastern (offshore Svalbard) regions of the Fram Strait. Material was collected using an USNEL 0.25 m2 box corer and all sediment samples were processed through a 500-μm sieve. A total of 1671 organisms from 169 species were found. Densities off Greenland were generally lower than those observed off Svalbard. On both sides of the Fram Strait, density, biomass and biodiversity generally decreased with increasing water depth. An exception was observed at the deepest station off Greenland (2500 m water depth), which was located within the Marginal Ice Zone. At this station, macrofaunal density was elevated (992 ± 281 ind. m−2) compared to the adjacent shallower sampling areas off Greenland (272 ± 208 ind. m−2 to 787 ± 172 ind. m−2) and the deeper stations (2000 and 2500 m water depth) off Svalbard (552 ± 155 ind. m−2 and 756 ± 182 ind. m−2). The most abundant species along both transects was the polychaete Galathowenia fragilis (off Greenland: 288 ind. m−2, off Svalbard: 740 ind. m−2). Sea ice coverage and water depth, as well as the associated food availability at the seafloor, seem to be crucial factors driving the macrofaunal community patterns. A strong pelago-benthic coupling is observed to be typical in Arctic deep-sea ecosystems, and is also confirmed by our study.