Description: As a contribution to the international Scientific Research Program "Antarctic Thresholds - Ecosystem Resilience and Adaptation" (AnT-ERA) of the "Scientific Committee on Antarctic Research" (SCAR) and to the ecological working programme "Dynamics of Antarctic Marine Shelf Ecosystems" (DynAMo) of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven (AWI) the Ocean Floor Observation System (OFOS) was deployed during expedition PS81 (ANT-XXIX/3) of RV Polarstern. Sea-bed photographs were taken along 30 drift profiles (=stations) at water depths between 35 and 780 m on both sides of the northern Antarctic Peninsula in January to March 2013. The setup and mode of deployment of OFOS was similar to that described by Bergmann and Klages (2012, doi:10.1016/j.marpolbul.2012.09.018). OFOS is a surface-powered gear equipped with a downward-looking high-resolution, wide-angle still camera (CANON® EOS 5D Mark III; lens: Canon EF 24 f/1.4L II, f stop: 13, exposure time: 1/125 sec; in-air view angles: 74° (horizontal), 53° (vertical), 84° (diagonal); image size: 5760 x 3840 px = 21 MPix; front of pressure resistant camera housing consisting of plexiglass dome port). OFOS was vertically lowered over the starboard side of the ship with a broadband fibre-optic cable, until it hovered approximately 1.5 m above the seabed. It was then towed with the slowly sailing ship at a speed of approximately 0.5 kn (0.25 m/s). The ship's POSIDONIA Positioning System, combined with the Inertial Navigation System (INS) and satellite-based Global Positioning System (GPS) of Polarstern, was used to gain highly precise underwater position data. During the profile, OFOS was kept hanging at the preferred height of 1.5. m above the seafloor by means of the live video feed and occasional minor cable-length adjustments with the winch to compensate small-scale bathymetric variations in seabed morphology. Information on water depth and height above the seafloor were continuously recorded by means of OFOS-mounted sensors (POSIDONIA transponder, Tritech altimeter). Three lasers, which are placed beside the still camera, emit parallel beams and project red light points, arranged as an equilateral triangle with a side length of 50 cm, in each photo, thus providing a scale that can be used to calculate the seabed area depicted in each image and/or measure the size of organisms or seabed features visible in the image. In addition, the seabed area depicted was estimated using altimeter-derived height above seafloor and optical characteristics of the OFOS still camera. In automatic mode, a seabed photo, depicting an area of approximately 3.45 m² (= 2.3 m x 1.5 m; with variations depending on the actual height above ground), was taken every 30 seconds to obtain series of "TIMER" stills distributed at regular distances along the profiles that vary in length depending on duration of the cast. At a ship speed of 0.5 kn, the average distance between seabed images was approximately 5 m. Additional "HOTKEY" photos were taken from interesting objects (organisms, seabed features, such as putative iceberg scours) when they appeared in the live image feed via the fibre-optic cable. If any image from this collection is used, please cite the appropriate reference.

Description: This collection contains four datasets on (1) chlorophyll a and phaeopigment concentrations, (2) nitrogen and organic carbon contents, (3) sediment oxygen uptakes and benthic boundary fluxes at the sediment-water interface and (4) macrofaunal abundance and biodiversity in sediments in the Canadian Arctic in 2008 and 2009. Data have been produced for a PhD thesis based on samples taken during the following expeditions: - Circumpolar Flaw Lead Study, Legs 9-10 - ArcticNet expedition 2008, Leg 11 (http://www.arcticnet.ulaval.ca/docs/2008_Amundsen_Expedition_Report.pdf) - ArcticNet expedition 2009, Leg 4 (http://www.arcticnet.ulaval.ca/docs/2009_Amundsen_Expedition_Report.pdf) - Malina expedition 2009 (Malina http://malina.obs-vlfr.fr/index.html; http://www.arcticnet.ulaval.ca/docs/2009_Amundsen_Expedition_Report.pdf) In general, sediment retrieved with a giant box corer were used to determine benthic boundary fluxes (oxygen, silicic acid, phosphate, nitrate, ammonium) in incubation chambers, as well as sediment pigment concentration from seperate cores, to study the effect of environmental conditions on benthic ecosystem functions. Parts of the data available in this collection have been analysed for addressing various ecological questions in spatial and temporal context in the publications listed below. A general description of the study region can be found in Link et al. 2013 (POne). Please download the metadata and methods file for more details.

Description: Within the Russian-German collaborative research project The Changing Arctic Transpolar System (CATS; see www.transdrift.info), benthic species distributions have been modelled across large geographic scales in Eurasian Arctic seas. As surficial seafloor sediment grain size is one important explanatory variable used in these modelling studies, we compiled open-access information from 23 data sets on this environmental parameter, pooling validated grain-size data from a total of 2,134 sampling sites distributed across the Barents, Kara, Laptev and East Siberian Seas, as well as some abyssal regions of the central Arctic Ocean. As grain-size distributions are differently scaled in western European and Russian sources, all data were uniformly transformed to the Udden-Wentworth scale using the "approximation" function in R prior to further processing and archiving. For this, a linear interpolation was utilized to split the 50-100 µm grain-size fraction used in Russian data sets into the silt (≤ 63 µm) and sand (〉 63 µm) fraction of the Udden-Wentworth scale. Using the kriging R package "automap", interpolated maps were created showing the geographic distribution of the percentages (%) of fine (silt and clay: ≤ 63 µm) and coarse (〉 63 µm to 2 mm) grain-size fractions in surface seafloor sediments. These maps were first created in the Sea Ice Polar Stereographic North CRS projection, followed by a transformation to the standard WGS84 CRS projection.

Description: Ascidians (Ascidiacea: Tunicata) are sessile suspension feeders that represent dominant epifaunal components of the Southern Ocean shelf benthos and play a significant role in the pelagic-benthic coupling. Here, we report the results of a first study on the relationship between the distribution patterns of eight common and/or abundant (putative) ascidian species, and environmental drivers in the waters off the northern Antarctic Peninsula. During RV Polarstern cruise XXIX/3 (PS81) in January-March 2013, we used seabed imaging surveys along 28 photographic transects of 2 km length each at water depths from 70 to 770 m in three regions (northwestern Weddell Sea, southern Bransfield Strait and southern Drake Passage), differing in their general environmental setting, primarily oceanographic characteristics and sea-ice dynamics, to comparatively analyze the spatial patterns in the abundance of the selected ascidians, reliably to be identified in the photographs, at three nested spatial scales. At a regional (100-km) scale, the ascidian assemblages of the Weddell Sea differed significantly from those of the other two regions, whereas at an intermediate 10-km scale no such differences were detected among habitat types (bank, upper slope, slope, deep/canyon) on the shelf and at the shelf break within each region. These spatial patterns were superimposed by a marked small-scale (10-m) patchiness of ascidian distribution within the 2-km-long transects. Among the environmental variables considered in our study, a combination of water-mass characteristics, sea-ice dynamics (approximated by 5-year averages in sea-ice cover in the region of or surrounding the photographic stations), as well as the seabed ruggedness, was identified as explaining best the distribution patterns of the ascidians.

Description: Seasonal dynamics in the activity of Arctic shelf benthos have been the subject of few local studies, and the pronounced among-site variability characterizing their results makes it difficult to upscale and generalize their conclusions. In a regional study encompassing five sites at 100-595 m water depth in the southeastern Beaufort Sea, we found that total pigment concentrations in surficial sediments, used as proxies of general food supply to the benthos, rose significantly after the transition from ice-covered conditions in spring (March-June 2008) to open-water conditions in summer (June-August 2008), whereas sediment Chl a concentrations, typical markers of fresh food input, did not. Macrobenthic biomass (including agglutinated foraminifera 〉500 µm) varied significantly among sites (1.2-6.4 g C/m**2 in spring, 1.1-12.6 g C/m**2 in summer), whereas a general spring-to-summer increase was not detected. Benthic carbon remineralisation also ranged significantly among sites (11.9-33.2 mg C/m**2/day in spring, 11.6-44.4 mg C/m**2/day in summer) and did in addition exhibit a general significant increase from spring-to-summer. Multiple regression analysis suggests that in both spring and summer, sediment Chl a concentration is the prime determinant of benthic carbon remineralisation, but other factors have a significant secondary influence, such as foraminiferan biomass (negative in both seasons), water depth (in spring) and infaunal biomass (in summer). Our findings indicate the importance of the combined and dynamic effects of food supply and benthic community patterns on the carbon remineralisation of the polar shelf benthos in seasonally ice-covered seas.