ALBERT

Description: This dataset provides abundance data for macrofaunal taxa determined from sediment samples collected in the Weddell Sea (mostly South-Eastern). A minimum of three samples (cores) were collected at each station with a MUC10 multicorer or a giant box corer during PS96. Sediment cores were sliced into depth layers (stations 017, 026, 061, 072: 0–2cm, 2–5cm, 5– bottom; stations 001, 037, 048: 0–1cm, 1–2cm, 2–3cm, 3–4cm, 4–5cm, 5– bottom) and preserved in 4%-borax-buffered formaldehyde solution prior to sieving (sieve size 500 µm, 1000 µm) and counting (detailed methods in Säring et al. submitted). Abundance is presented per depth layer (note different slice volume) as ind./m². Data from different size fractions are available upon request. Macrofauna communities included individuals from 18 higher taxa. The macrofauna abundance data are part of a larger ecological study on meio- and macrofauna communities and their relation to environmental conditions and remineralisation at the sediment-water interface (see Related to below). For the larger study, sediment cores from which macrofauna abundance data are deposited here were also used for microcosm incubations: Untreated incubations (Benthic ecosystem Function Experiments BEFEx), and incubations with and without microalgae addition (Algae Feeding Experiment AFEx). Cores from BEFEx and AFEx without algae are labeled with NT (not treated), cores from AFEx with algae are labeled as T (treated).

Description: This dataset provides abundance data for meiofauna taxa determined from sediment samples collected in the Weddell Sea (mostly South-Eastern). A minimum of three samples (cores) were collected at each station with a MUC10 multicorer or taken from a giant box corer during PS96. Sediment cores were sliced into depth layers (stations 017, 026, 061, 072: 0–2cm, 2–5cm, 5– bottom; stations 001, 037, 048: 0–1cm, 1–2cm, 2–3cm, 3–4cm, 4–5cm, 5– bottom) and preserved in 4%-borax-buffered formaldehyde solution prior to sieving (upper sieve size 500 µm, lower sieve size 32 µm) and counting (detailed methods in Säring et al. submitted). Abundance is presented per depth layer from the top 5 cm (note different slice volume) as ind./10 cm². Meiofauna communities included individuals from 22 higher taxa. The meiofauna abundance data are part of a larger ecological study on meio- and macrofauna communities and their relation to environmental conditions and remineralisation at the sediment-water interface (see “Related to” below). For the larger study, sediment cores from which meiofauna abundance data are deposited here were also used for microcosm incubations: Untreated incubations (Benthic ecosystem Function Experiments BEFEx), and incubations with and without microalgae addition (Algae Feeding Experiment AFEx). Cores from BEFEx and AFEx without algae are labeled with NT (not treated), cores from AFEx with algae are labeled as T (treated).

Description: Around the Antarctic Peninsula (North-Western Weddell Sea, Bransfield Strait, Drake Passage) water samples for measurements of chlorophyll-a were collected with Niskin bottles mounted on a CTD rosette. At each station samples were taken at two depths, the chlorophyll-a maximum (Cmax, defined as the water depth with maximum fluorescence detected during in-situ profiles) and close to the seafloor (bottom). Water samples were poured over a 100-µm sieve to remove larger particles and filtered over glass fibre filters GF/C at approximately 250 mbar. Colouring of filters determined the amount of sea water used (3–5l). Filters were stored at −80°C. Chloroplastic pigments were extracted with 10ml acetone (90%), determined using a fluorimeter and expressed in µg/l. For details see Hauquier et al. (2015) and Veit-Köhler et al. (2018).

Description: To reveal the late Quaternary paleoenvironmental changes at the Antarctic continental margin, we test a lithostratigraphy, adjusted to a stable isotope record from the eastern Weddell Sea. The stratigraphy is used to produce a stacked sedimentological data set of eleven sediment cores. We derive a general model of glacio marine sedimentation and paleoenvironmental changes at the East Antarctic continental margin during the last two climatic cycles (300 kyr). The sedimentary processes considered include biological productivity, ice-rafting, current transport, and gravitational downslope transport. These processes are controlled by a complex interaction of sea-level changes and paleoceanographic and paleoglacial conditions in response to changes of global climate and local insolation. Sedimentation rates are mainly controlled by ice-rafting which reflects mass balance and behaviour of the Antarctic ice sheet. The sedimentation rates decrease with distance from the continent and from interglacial to glacial. Highest rates occur at the very beginning of interglacials, i.e. of oxygen isotope events 7.5, 5.5, and 1.1, these being up to five times higher than during glacials. The sediments can be classified into five distinct facies and correlated to different paleoenvironments: at glacial terminations (isotope events 8.0, 6.0, and 2.0), the Antarctic cryosphere adjusts to new climatic conditions. The sedimentary processes are controlled by the rise of sea level, the destruction of ice shelves, the retreat of sea-ice and the recommenced feeding of warm North Atlantic Deep Water (NADW) to the Circumpolar Deep Water (CDW). During peak warm interglacial periods (at isotope events 7.5, 7.3, 5.5., and 1.1), the CDW promotes warmer surface waters and thus the retreat of sea-ice which in turn controls the availability of light in surface waters. At distinct climatic thresholds local insolation might also influence sea-ice distribution. Primary productivity and bioturbation increase, the CCD rises and carbonate dissolution occurs in slope sediments also in shallow depth. Ice shelves and coastal polynyas favour the formation of very cold and saline Ice Shelf Water (ISW) which contributes to bottom water formation. During the transition from a peak warm time to a glacial (isotope stages 7.2-7.0, and 5.4-5.0) the superimposition of both intense ice-rafting and reduced bottom currents produces a typical facies which occurs with a distinct lag in the time of response of specific sedimentary processes to climatic change. With the onset of a glacial (at isotope events 7.0 and 5.0) the Antarctic ice sheet expands due to the lowering of sea-level with the extensive glaciations in the northern Hemisphere. Gravitational sediment transport becomes the most active process, and sediment transfer to the deep sea is provided by turbidity currents through canyon systems. During Antarctic glacial maxima (isotope stages between 7.0-6.0, and 5.0-2.0) the strongly reduced input of NADW into the Southern Ocean favours further advances of the ice shelves far beyond the shelf break and the continous formation of sea ice. Below ice shelves and/or closed sea ice coverage contourites are deposited on the slope.

Description: During R/V Maria S. Merian cruise MSM97/2 a sensor box (AddOn Box) was attached to a PocketFerryBox (4H Jena, Germany) in-line obtaining waters from the ships two autonomous measurement systems (RSWS). For the measurement of underway absorption spectra to calculate optical nitrate, the AddOn Box was equipped with two UV-process spectrophotometer (ProPS and OPUS, TriOS Mess- und Datentechnik GmbH, Germany). Data were recorded continuously in a ten-minute interval along the cruise track with an optical path length of 10 mm. The integration time was 256 ms. The ProPS photometer is equipped with a Deuterium lamp as light source whereas the OPUS photometer is equipped with a Xenon flash lamp. Baseline calibrations were done for both UV-photometer using ultrapure water. For the ProPS, the calibration was done in the laboratory before the cruise whereas the calibration for the OPUS was done by the manufacturer. The water inlet of the RSWS is allocated at approx. 6.5 m below the sea surface. While one box is measuring, the other box is being cleaned. The boxes switch after a user-defined measuring and cleaning interval. On MSM97/2, the boxes were alternating every 12 hours, including one short cleaning procedure during measurements after 4 hours. Absorption spectra obtained by the AddOn Box during the alternation process of the two RSWS, as well as during the internal cleaning procedure are not included. Spectra from station work are included. Within this dataset, absorption spectra were cut to a relevant wavelength range (from 189-360 nm (ProPS) and 199-360 nm (OPUS) to 210-260 nm). No further correction was done for the absorbance spectra in this processing step. After the cruise, gathered absorption spectra were used to improve current processing algorithms of optical nitrate detection for coastal and open ocean waters. Processing was performed according to Zielinski et al. (2011) and Frank et al. (2014) using MATLAB (R2018a). Detailed processing steps for the calculation of optical nitrate can be found on Zenodo (doi 10.5281/zenodo.4091420 ). Temperature and salinity data are necessary to compute nitrate values from derived UV-spectra and were taken from the attached PocketFerryBox using a SBE45 probe (Sea Bird Scientific, USA). A linear CDOM-offset correction was carried out. Nitrate reference spectra and salinity reference spectra were measured in the laboratory before the cruise. Corresponding nitrate reference samples using wet chemical analysis will be published separately.