A new species of Anobothrus (Polychaeta, Ampharetidae) from the Weddell Sea (Antarctica), with notes on habitat characteristics and an updated key to the genus

Benthic samples were collected during two expeditions near the Antarctic Peninsula and in the South-Eastern Weddell Sea. During these studies, a new species of Ampharetidae Malmgren, 1867, Anobothrus konstantini Säring & Bick sp. nov., was found. Here we present a detailed description of this species. We used the traditional light microscope and scanning electron microscope (SEM) to identify and describe the diagnostic characters: a circular glandular band on segment 6; an elongate ridge between the notopodia on segment 12 and modified notochaetae on this segment; 16 thoracic, two intermediate and ten abdominal segments. For the first time, micro-computed tomography (micro-CT) was used for a species description of Anobothrus. Micro-CT provided information on the shape of the prostomium (Ampharete-type) and the arrangement of branchiae (four pairs in two rows, without a gap). In addition, we provide quantitative information on the environmental niche based on sediment parameters (chlorophyll a content, organic matter content, chloroplast equivalent, grain size) for the new Anobothrus species, relevant for, e.g., species distribution modelling. Finally, an identification key for all Anobothrus species is provided

Macrofauna abundance from multicorer and box corer samples for seven stations from the Weddell Sea (POLARSTERN cruise PS 96, ANT-XXXI/2, December 2015–February 2016)

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)

Macrofauna abundance from multicorer and box corer samples for ten stations around the Antarctic Peninsula (POLARSTERN cruise PS 81, ANT-XXIX/3, January–March 2013)

This dataset provides abundance data for macrofaunal taxa determined from sediment samples collected around the Antarctic Peninsula. A minimum of three samples (cores) were taken at each station with a MUC10 multicorer or giant box corer during PS81. The whole sediment cores (top to bottom) were preserved in a in 4%-borax-buffered formaldehyde solution prior to sieving (sieve size 500 µm) and counting (detailed methods in Säring et al. submitted). Only at station 241, cores were sliced into depth layers (0–2 cm, 2–5 cm, 5– bottom) and size fractions distinguished (sieve size 500 µm, 1000 µm). Abundances are presented per whole core as ind./m². Data from different layers and size fractions (station 241) are available upon request. Macrofauna communities included individuals from 13 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)

Biotic and abiotic water-column characteristics (Chla, Phaeo, TC, TN, δ13C, δ15N) at stations in the Weddell Sea (POLARSTERN cruise PS 96, ANT-XXXI/2, December 2015–February 2016)

This dataset contains biotic and abiotic data from water-column samples taken with Niskin bottles mounted on the CTD rosette from 14 sites in the Weddell Sea (mostly South-Eastern). Data are provided for water-column pigments (chlorophyll a and phaeopigment content through fluorometry), total carbon (TC) and nitrogen (TN) and stable isotope values of carbon and nitrogen (δ13C, δ15N) from the chlorophyll maximum (Cmax, defined as the water depth with maximum fluorescence detected during in-situ profiles) and close to the sea bottom. Water was filtered onto glass fiber filters (GF/C for pigments, combusted GF/F for C and N analyses) and stored at -80°C prior to analysis. Detailed methods are described in Säring et al. (submitted) except for stable isotopes: Flash combustion in a Flash 2000 (Thermo) elemental analyser to a Delta V advantage (Thermo) isotope ratio masspectrometer. δ values are reported relative to atmospheric N₂ (δ15N) and Vienna PeeDee Belemnite (δ13C). Reference materials for stable isotope analysis: IAEA-N1, IAEA-N2, IAEA-N3, NBS 22, IAEA-CH-3 and IAEA-CH-6; calibration material: Acetanilide (Merck). The analytical precision for both stable isotope ratios was <±0.2‰. Samples were not acidified to avoid loss of material. We assumed low inorganic carbon content in the water column for our analyses. This data table is part of a larger study analysing the role of environmental parameters for meio- and macrofaunal community composition (see Related to below)

Meiofauna abundance from multicorer and box corer samples for seven stations from the Weddell Sea (POLARSTERN cruise PS 96, ANT-XXXI/2, December 2015–February 2016)

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)

Sediment characteristics (Chla, Phaeo, TOC, TN, δ13C, δ15N, grain size) at stations in the Weddell Sea (POLARSTERN cruise PS 96, ANT-XXXI/2, December 2015–February 2016)

This dataset contains abiotic and biotic data from sediment samples from nine sites in the Weddell Sea (mostly South-Eastern). Data are provided for sediment pigments (chlorophyll a and phaeopigment content through fluorometry), total organic carbon (TOC), total nitrogen (TN), stable isotope values of carbon and nitrogen (δ13C, δ15N) and grain size (silt&clay 1000 µm). Before the TOC and carbon isotope analysis the sediment samples were acidified to eliminate inorganic carbon. A minimum of three replicate samples (cores) were collected using a MUC10 multicorer or giant box corer. Sediment cores were subsampled with a 60-ml syringe (inner diameter 2.7 cm) for stations 017, 026, 061, 072, and with a 10-ml syringe (inner diameter 1 cm) for stations 001, 037, 048, 104, 115. Subsamples were sliced in 1-cm steps down to 5 cm depth. Detailed methods are described in Säring et al. (submitted) except for stable isotopes: Flash combustion in a Flash 2000 (Thermo) elemental analyser to a Delta V advantage (Thermo) isotope ratio masspectrometer. δ values are reported relative to atmospheric N2 (δ15N) and Vienna PeeDee Belemnite (δ13C). Reference materials for stable isotope analysis: IAEA-N1, IAEA-N2, IAEA-N3, NBS 22, IAEA-CH-3 and IAEA-CH-6; calibration material: Acetanilide (Merck). The analytical precision for both stable isotope ratios was <±0.2‰. Cores with the label -e (Environment) were only used to collect the above data. Environmental and fauna data were collected from cores with the label -i (Incubation). This data table is part of a larger study analysing the role of environmental parameters for meio- and macrofaunal community composition (see Related to below)