Description: During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequences

Description: The brown shrimp Crangon crangon is a key component of the North Atlantic coastal food web and an important target species for the fishery economy. As the brown shrimp contains large amounts of protein and essential fatty acids, its consumption makes it a beneficial choice for humans. Commercially harvested crustaceans like C. crangon are frequently affected by bacterial shell disease, with necrotizing erosions and ulcerations of the cuticle. To determine whether shell disease influences the nutritional value of C. crangon, total protein and lipid contents, as well as fatty acid compositions of muscle tissue and hepatopancreas, together with the hepatosomatic index, were examined in healthy and affected individuals. The biochemical composition of the tissues did not differ significantly between the 2 groups. Also, the hepatosomatic index, as an indicator of energy reserves in shrimps, was similar between healthy and affected animals. Our results indicate that the nutritional value of C. crangon is not affected by shell disease, as long as it remains superficial as in the present study.

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: The prevalence of black spot shell disease is increasing among marine crustaceans worldwide. Rising seawater temperatures – often stressful for ectothermic species – are assumed to enhance the occurrence of shell disease. In the North Sea 〉 50% of local populations of the brown shrimp (Crangon crangon) are affected by the disease. While fisheries are suffering because diseased crustaceans are barely merchantable, the impact of shell disease on life history traits of crustaceans is little understood. To determine the role of temperature on the development of black spots and its implications for survival and physiology in the brown shrimp, a prolonged (3 months) thermal stress experiment was performed. We measured the increment of shell disease and the effect of molting in shrimps kept at control (15 °C = equivalent to the seafloor temperature in the North Sea during sampling) and increased temperature (20 °C = according to predictions for the end of the century). The resting metabolic rate was analyzed to determine the physiological state of diseased compared to non-diseased animals. In the present study, the warmer temperature in the range of 20 °C did not increase the spot size of shell disease and no differences were observed between the two temperatures. The process of molting thereby seemed to diminish and in most of the cases even completely remove the signs of shell disease. At 15 °C but not at 20 °C, metabolic rate was reduced in diseased in contrast to healthy individuals. This study showed that shell disease might lead to a higher mortality rate and an impairment of the physiological state in C. crangon.

Description: During Polarstern cruise ANT-XXIX/3 a previously unknown and still unnamed seamount was discovered at the deep offshore shelf of the northwestern Weddell Sea in February 2013. During a bathymetric grid survey with Polarstern’s shipboard multibeam system all flanks except for the southeast side (inaccessible due to icebergs) of the structure were covered and mapped in high resolution. The flat plateau area was crossed 4 times along the lengthwise (northwest-southeast) and 4 times across. Even though a full multibeam coverage of the structure was not possible due to ice conditions, the grid survey reveals the morphology of the seamount and allows for an initial interpretation of the influences of icebergs and currents at this seamount. The classification as seamount is based on the overall morphology of the structure that is characteristic for an eroded volcano edifice. It is furthermore supported by pillow lava structures recorded with the shipboard sediment echosounder and igneous rock trawled from the flanks of the mount. Moreover, composition and distribution of the epibenthic megafauna has been investigated by means seabed photographs taken using an Ocean Floor Observation System (OFOFS) along three transects of about two nautical miles each at the northern flank of the seamount, covering the entire depth range from an almost level and very shallow (15-30 m) summit area of approx. 5 nm length and 2 nm width, the steep flank from about 30 to 150 m depth, as well as the more gentle slope to the surrounding shelf plateau of about 400 m depth. First results of the quantitative analysis of the approximately 500 seabed photographs taken per transect, each showing an area of 1.5 x 2.3 m2, will be shown. Further studies are necessary to evaluate whether the mega-epibenthic distribution patterns at the seamount correspond with the effects of iceberg scouring and/or the distribution of morphology-driven circulation cells that may strongly affect pelagic processes such as primary production, sedimentation and, hence, food supply to the benthos.

Description: Recent advances in underwater imaging technology allow for the gathering of invaluable scientific information on seafloor ecosystems, such as direct in situ views of seabed habitats and quantitative data on the composition, diversity, abundance, and distribution of epibenthic fauna. The imaging approach has been extensively used within the research project DynAMo (Dynamics of Antarctic Marine Shelf Ecosystems) at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Bremerhaven (AWI), which aimed to comparatively assess the pace and quality of the dynamics of Southern Ocean benthos. Within this framework, epibenthic spatial distribution patterns have been comparatively investigated in two regions in the Atlantic sector of the Southern Ocean: the shelf areas off the northern tip of the Antarctic Peninsula, representing a region with above-average warming of surface waters and sea-ice reduction, and the shelves of the eastern Weddell Sea as an example of a stable high-Antarctic marine environment that is not (yet) affected by climate change. The AWI Ocean Floor Observation System (OFOS) was used to collect seabed imagery during two cruises of the German research vessel Polarstern, ANT-XXIX/3 (PS81) to the Antarctic Peninsula from January to March 2013 and ANT-XXXI/2 (PS96) to the Weddell Sea from December 2015 to February 2016. Here, we report on the image and data collections gathered during these cruises. During PS81, OFOS was successfully deployed at a total of 31 stations at water depths between 29 and 784 m. At most stations, series of 500 to 530 pictures ( 〉  15 000 in total, each depicting a seabed area of approximately 3.45 m2 or 2.3  ×  1.5 m) were taken along transects approximately 3.7 km in length. During PS96, OFOS was used at a total of 13 stations at water depths between 200 and 754 m, yielding series of 110 to 293 photos (2670 in total) along transects 0.9 to 2.6 km in length. All seabed images taken during the two cruises, including metadata, are available from the data publisher PANGAEA via the two persistent identifiers at https://doi.org/10.1594/PANGAEA.872719 (for PS81) and https://doi.org/10.1594/PANGAEA.862097 (for PS96).