Description: During horizontal video transects in the Norwegian Sea pelagic in situ observation system (PELAGIOS), video was collected of the water column and fauna at 4 stations, from 50 m to 1200 m. Fauna were annotated and these annotations are here presented. They include ctenophores, medusae, siphonophores, crustaceans, fishes. The dataset presents diversity, distribution and abundance data. Abundances were estimated based on conversions presented in Hoving et al 2019 (see related to).

Description: To investigate scavenging communities associated with carcasses of animals from the water column, we performed experimental food fall studies. We deployed baited camera landers with squid (Illex coindetii), jellyfish (Periphylla periphylla) and fish (Scomber scombrus) for 9-25 hours at 1360-1440 m in the Southern Norwegian Sea. The dataset includes all raw count data of scavengers on the food falls sorted by taxon based on image analysis annoated using ImageJ with the Cell Counter plugin and stored long-term in BIIGLE. Scavengers included lysianassid amphipods (mainly Eurythenes gryllus), ophiuroids, decapod shrimp (Bythocaris spp.) as well as Lycodes frigidus (probably a secondary consumer).

Description: The dataset includes taxon counts of the observed background community at the stations prior to the baited lander deployments as well as area calculations per image. Framegrab images from the OFOS videos were extracted in VLC media player (3.0.11 Vetinari) using the snapshot-tool. Framegrabs were taken every 1.5 minute and additionally as close to the seafloor as possible to have the highest possible resolution. Because of variable image quality, the images were classified into good, medium, and poor quality. In each collected image, organisms were identified to the highest possible taxonomic unit and counted with the Multi-Point tool in ImageJ (ImageJ 1.53g). The annotated area in each image was calculated by setting the scale in ImageJ and then calculating the area with the measure-tool. The total area surveyed was calculated by the sum of the analysed images (total = 8-53 m2 per study region).

Description: Onboard, cephalopods were identified morphologically to the lowest taxonomic level possible (species, genus or family), and whole specimens were preserved in formalin as voucher. In addition, tissue samples of some specimen were collected and preserved in ethanol for barcoding and the genetic reference database used for eDNA metabarcoding.

Description: Pelagic video transects with the Pelagic In-Situ Observation System (PELAGIOS, (Hoving et al., 2019a)) were conducted during the cruises MSM49 (Christiansen et al., 2016) (transects between 30 and 1000 m, total towing duration 〉 80h), MSM61 (Fiedler et al., 2020) (transects between 80 and 1200 m, total hours of observations 〉 32h), POS520 (Hoving et al., 2018, p. 520) (transects between 30 and 2500 m, total hours of observations 27h), POS532 (Hoving et al., 2019b) (transects between 30 and 990 m, total hours of observations 19h) and M119 (Brandt, 2016) (transects between 50 and 700 m, total hours of observations 〉 20h) between 2015 and 2019 (Figure 1). PELAGIOS is a battery powered, high-definition camera system that is towed horizontally via a single-wired conductive sea-cable at 0.5 m s -1. Around 0.45 m2 of the water column in front of the camera is illuminated with an LED array. The attached depth sensor and/or a sensor for conductivity, temperature and depth (CTD) with oxygen sensor allows for hydrographic measurements and depth monitoring during transects. Pelagic video transects were conducted between 11-33 minutes per depth, towing the camera horizontally at specified depths. A deep-sea telemetry system allows for transmission of a low-resolution preview of the recorded video. During the cruises POS520 and POS532 the manned submersible JAGO (GEOMAR, Helmholtz Centre for Ocean Research) was used for 30 deployments of about four hours each between the surface and 350 m water depth. During the dives, video was recorded by a high-resolution camera. The videos taken during the PELAGIOS and JAGO dives were annotated manually using the Video Annotation and Reference System (VARS) developed at the Monterey Bay Aquarium Research Institute, which allows annotation and congruent collection of video frames. We also provide raw data on environmental DNA samples taken during POS532 in February 2019 at five stations. The stations off the islands Santo Antão and Fogo were close to the coast (maximum sampled depth 2500 m), CVOO was a reference station in the open ocean (maximum sampled depth 3000 m) and the stations Cyclone and Anticyclone were located eddies that had formed in the wake of Fogo and had propagated southwards (maximum sampled depths 2200 and 600 m, respectively). Per sampled depth, three biological replicates of two liters of seawater each were collected from three different 10 liter Niskin bottles mounted on a CTD rosette. For filtration, 0.22 µm pore size Sterivex-GP filter (Merck Millipore) were directly connected to the Niskin bottle with sterile tubing. The weight of the water in the Niskin bottles was sufficient to filter two liters of seawater per filter. The filters were closed with sterile plastic caps and stored at -80°C until further processing in the laboratory.

Description: Net catches of cephalopods were obtained during the cruises POS320/2 (March 2005), MSM49 (November/December 2015) and WH383 (March/April 2015) off Cabo Verde at a total of 18 stations at depths between 0 and 1000 m. Cephalopods were caught during POS320/2 with either a Isaacs-Kidd midwater trawl (IKMT) with a 6 m2 net opening, 4 mm mesh size equipped with a flowmeter, a Hydro-Bios Multinet Maxi with a 0.5 m2 net opening and 500 µm mesh size between the surface and 250 m water depth, or an 80 feet bottom trawl. Net sampling during MSM49 was conducted with two types of multiple opening/closing nets (MOCNESS) and an IKMT. The smaller MOCNESS had a net opening of 1 m2 opening (three nets with a mesh size of 2 mm and six nets with a mesh size of 335 μm) and the larger MOCNESS a net opening of 10 m2 opening (five nets, mesh size: 1.5 mm) and were deployed between the surface to 1000 m. The IKMT had a net opening of 7 m2 and ended in a cod end of 500 µm mesh size. It was deployed to a maximum depth of 500 m. During WH383 a pelagic trawl ('Aalnetz', Engel Netze, Bremerhaven, Germany) with a mouth opening of 16 x 30 m, length of 150 m including multiple opening-closing device, 260 meshes by 180 cm stretched mesh size at the front, a cod end 20 mm stretched mesh-opening and a 1.8 mm inlet sewn into last 1 m of cod end was used with a multisampler (Construction Services AS, Bergen, Norway) allowing depth-stratified sampling. During WH383 three strata (mean vertical extension of ca. 40 m) were trawled mostly during night and one time during daytime at depths between 30 and 700 m in horizontal tows for 30 minutes per stratum with a mean speed of three knots (2.8-3.3 kn). During this cruise, night trawls took place at 22:00 local time, and the day-time trawl at 12:00 local time. Onboard, cephalopods were identified morphologically to the lowest taxonomic level possible (species, genus or family), and whole specimens were preserved in formalin as voucher. In addition, tissue samples of some specimen were collected and preserved in ethanol for barcoding and the genetic reference database used for eDNA metabarcoding. Pelagic video transects with the Pelagic In-Situ Observation System (PELAGIOS, (Hoving et al., 2019a)) were conducted during the cruises MSM49 (Christiansen et al., 2016) (transects between 30 and 1000 m, total towing duration 〉 80h), MSM61 (Fiedler et al., 2020) (transects between 80 and 1200 m, total hours of observations 〉 32h), POS520 (Hoving et al., 2018, p. 520) (transects between 30 and 2500 m, total hours of observations 27h), POS532 (Hoving et al., 2019b) (transects between 30 and 990 m, total hours of observations 19h) and M119 (Brandt, 2016) (transects between 50 and 700 m, total hours of observations 〉 20h) between 2015 and 2019 (Figure 1). PELAGIOS is a battery powered, high-definition camera system that is towed horizontally via a single-wired conductive sea-cable at 0.5 m s -1. Around 0.45 m2 of the water column in front of the camera is illuminated with an LED array. The attached depth sensor and/or a sensor for conductivity, temperature and depth (CTD) with oxygen sensor allows for hydrographic measurements and depth monitoring during transects. Pelagic video transects were conducted between 11-33 minutes per depth, towing the camera horizontally at specified depths. A deep-sea telemetry system allows for transmission of a low-resolution preview of the recorded video. During the cruises POS520 and POS532 the manned submersible JAGO (GEOMAR, Helmholtz Centre for Ocean Research) was used for 30 deployments of about four hours each between the surface and 350 m water depth. During the dives, video was recorded by a high-resolution camera. The videos taken during the PELAGIOS and JAGO dives were annotated manually using the Video Annotation and Reference System (VARS) developed at the Monterey Bay Aquarium Research Institute, which allows annotation and congruent collection of video frames. We also provide raw data on environmental DNA samples taken during POS532 in February 2019 at five stations. The stations off the islands Santo Antão and Fogo were close to the coast (maximum sampled depth 2500 m), CVOO was a reference station in the open ocean (maximum sampled depth 3000 m) and the stations Cyclone and Anticyclone were located eddies that had formed in the wake of Fogo and had propagated southwards (maximum sampled depths 2200 and 600 m, respectively). Per sampled depth, three biological replicates of two liters of seawater each were collected from three different 10 liter Niskin bottles mounted on a CTD rosette. For filtration, 0.22 µm pore size Sterivex-GP filter (Merck Millipore) were directly connected to the Niskin bottle with sterile tubing. The weight of the water in the Niskin bottles was sufficient to filter two liters of seawater per filter. The filters were closed with sterile plastic caps and stored at -80°C until further processing in the laboratory.

Description: Net catches of cephalopods were obtained during the cruises POS320/2 (March 2005), MSM49 (November/December 2015) and WH383 (March/April 2015) off Cabo Verde at a total of 18 stations at depths between 0 and 1000 m. Cephalopods were caught during POS320/2 with either a Isaacs-Kidd midwater trawl (IKMT) with a 6 m2 net opening, 4 mm mesh size equipped with a flowmeter, a Hydro-Bios Multinet Maxi with a 0.5 m2 net opening and 500 µm mesh size between the surface and 250 m water depth, or an 80 feet bottom trawl. Net sampling during MSM49 was conducted with two types of multiple opening/closing nets (MOCNESS) and an IKMT. The smaller MOCNESS had a net opening of 1 m2 opening (three nets with a mesh size of 2 mm and six nets with a mesh size of 335 μm) and the larger MOCNESS a net opening of 10 m2 opening (five nets, mesh size: 1.5 mm) and were deployed between the surface to 1000 m. The IKMT had a net opening of 7 m2 and ended in a cod end of 500 µm mesh size. It was deployed to a maximum depth of 500 m. During WH383 a pelagic trawl ('Aalnetz', Engel Netze, Bremerhaven, Germany) with a mouth opening of 16 x 30 m, length of 150 m including multiple opening-closing device, 260 meshes by 180 cm stretched mesh size at the front, a cod end 20 mm stretched mesh-opening and a 1.8 mm inlet sewn into last 1 m of cod end was used with a multisampler (Construction Services AS, Bergen, Norway) allowing depth-stratified sampling. During WH383 three strata (mean vertical extension of ca. 40 m) were trawled mostly during night and one time during daytime at depths between 30 and 700 m in horizontal tows for 30 minutes per stratum with a mean speed of three knots (2.8-3.3 kn). During this cruise, night trawls took place at 22:00 local time, and the day-time trawl at 12:00 local time. Onboard, cephalopods were identified morphologically to the lowest taxonomic level possible (species, genus or family), and whole specimens were preserved in formalin as voucher.

Description: The presence of an extended salinity gradient of the Baltic Sea reveals a variety of species occur at the limit of their physiological tolerance and preference, i.e. in areas and habitats not representing their marine or fresh water origin. Hence, the Baltic Sea is known for its high share of non-indigenous species, which have established. In this study, we compiled extraordinary sightings of transient, non-native or potentially range expanding species, such as jellyfish, squid, fishes and marine mammals in the SW Baltic Sea for a period from 2001 to 2018. We focused on jellyfish, squid, fishes and marine mammals. Hydrographic conditions, such as water temperature and salinity, obtained from a high spatio-temporally resolved hydrodynamic Baltic Sea model, covering a daily resolved 40-year time series were linked to the sightings of these extraordinary species. Our hydrodynamic modelling results demonstarted that changes in the occurrence of exceptional species reflect the dynamics of water mass exchange between the Kattegat/Skagerrak and the SW Baltic Sea. Our analyses show that these changes could be related to the presence of anomalously high saline water masses. This documents that the hydrographically highly dynamic SW Baltic Sea needs special attention for monitoring of non-indigenous species, as high saline and warm water intrusions are more frequent than currently believed and ii) can be linked to sightings of exceptional species in the SW Baltic Sea.

Description: The boreoatlantic gonate squid (Gonatus fabricii) represents important prey for top predators—such as marine mammals, seabirds and fish—and is also an efficient predator of crustaceans and fish. Gonatus fabricii is the most abundant cephalopod in the northern Atlantic and Arctic Ocean but the trace element accumulation of this ecologically important species is unknown. In this study, trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) were analysed from the mantle muscle and the digestive gland tissue of juveniles, adult females, and adult males that were captured south of Disko Island off West-Greenland. To assess the feeding habitat and trophic position of this species, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were measured in their muscle tissue. Mercury concentrations were positively correlated with size (mantle length) and trophic position. The Hg/Se ratio was assessed because Se has been suggested to play a protective role against Hg toxicity and showed a molar surplus of Se relative to Hg. Cadmium concentrations in the digestive gland were negatively correlated with size and trophic position (δ15N), which suggested a dietary shift from Cd-rich crustaceans towards Cd-poor fish during ontogeny. This study provides trace element concentration data for G. fabricii from Greenlandic waters, which represents baseline data for a northern cephalopod species. Within West-Greenland waters, G. fabricii appears to be an important vector for the transfer of Cd in the Arctic pelagic food web.

Description: Highlights: • The pace of life of life of vampire squid and Japetella were examined. • Japetella diaphana and Vampyroteuthis infernalis have contrasting reproductive strategies. • Brooding in Japetella is estimated to last for two years in water temperature ~4 °C. • Feeding ecology and metabolic rates suggest non-daily deposition of beak growth increments. • Both species’ life-history traits suggest a slow pace of life and longer lifespans.The pelagic cephalopods Japetella diaphana and Vampyroteuthis infernalis are charismatic and widely distributed members of deep pelagic ecosystems. Their habitat temperatures, metabolic rates, feeding and reproductive strategies all together suggest that the pace of life in these species is reduced when compared to neritic octopod species, but information on longevity, growth rates and age estimations are absent to date. To estimate the pace of life in pelagic octopods, this study investigated size at maturity, reproductive strategy, and the number of growth-increments in the upper beak lateral walls (LWS) of J. diaphana (an octopod) and V. infernalis (a vampyromorph). Daily deposition of growth increments in hard body structures (e.g., beaks and stylets) has been validated experimentally in some temperate and tropical octopods, but remains unquantified and not yet validated for most deep-sea and high-latitude cephalopods. We used a diverse assemblage of specimens ranging from early juveniles to adults for both species. Mature J. diaphana had a mantle length (ML) of 53–144 mm and a body mass (BM) of 18–235 g. A brooding female of J. diaphana captured at 1352 m in the Gulf of California was carrying 1419 eggs in pre-organogenetic stage that measured ~2.5 mm in diameter. The size range of mature V. infernalis was ML 66–122 mm and BM 34–286 g. The number of growth increments in the beaks ranged from 21 to 207 in J. diaphana and from 89 to 375 in V. infernalis. If the growth increments are formed daily, like in tropical octopod species, age estimates are incongruent with the low metabolic rates and reproductive strategies of the two species. These observations suggest that growth increments may require more than one day to be formed. To better understand the life histories of invertebrates in the largest but least studied habitat on the planet, age and growth validation studies are critical.