Description: Fundamental insight on predator-prey dynamics in the deep sea is hampered by a lack of combined data on hunting behavior and prey spectra. Deep-sea niche segregation may evolve when predators target specific prey communities, but this hypothesis remains untested. We combined environmental DNA (eDNA) metabarcoding with biologging to assess cephalopod community composition in the deep-sea foraging habitat of two top predator cetaceans. Here, we are presenting the eDNA data from seawater samples obtained during a cruise on RV Pelagia in 2018 off Terceira, Azores, sampled directly in the foraging habitats of two cetacean top-predators from the surface to 1600 m. The water was collected using Niskin bottles mounted on a CTD rosette at seven or eight depths in biological triplicates and filtered on sterile Sterivex filter. After DNA extraction and PCR amplification with two universal cephalopod primer (Ceph18S, targeting the nuclear 18S rRNA gene and CephMLS targeting the mitochondrial 16S rRNA gene), the samples were sequenced on an Illumina MiSeq with the MiSeq Reagent kit v3 (600 cycles).

Description: A total of eight deployments of an autonomous baited camera lander were conducted at the Cabo Verde Abyssal Plain (tropical East Atlantic, Lat. 14.72, Lon. -25.19, Water depth ~4200 m) using either Atlantic mackerel (Scomber scombrus, n=4) or Patagonian squid (Doryteuthis gahi, n=4) bait, to photograph organisms attracted to the bait over roughly 24 hours. The deployments took place during the iMirabilis2 campaign in August 2021 from the research vessel Sarmiento de Gamboa. This data set provides information on the consumption of the different baits by abyssal fauna assessed as the reduction in wet weight over the course of the deployment.

Description: A total of eight deployments of an autonomous baited camera lander were conducted at the Cabo Verde Abyssal Plain (tropical East Atlantic, Lat. 14.72, Lon. -25.19, Water depth ~4200 m) using either Atlantic mackerel (Scomber scombrus, n=4) or Patagonian squid (Doryteuthis gahi, n=4) bait, to photograph organisms attracted to the bait over roughly 24 hours. The deployments took place during the iMirabilis2 campaign in August 2021 from the research vessel Sarmiento de Gamboa. A deep-sea time lapse camera system with an oblique view of the bait plate (12 cm x 45 cm) and surroundings took a picture every 150 seconds. The bar attached to the bait plate is 6 cm wide. The camera was located about 120 cm above the seafloor with an oblique view of 40 degrees (assuming straight down in 0 degrees). Annotations were performed in BIIGLE software (Langenkämper et al. 2017) on every second photograph, providing the morphospecies group label (or 'No ID' if to morphospecies level was not possible) and the taxonomic hierarchy to a level of best confidence for each annotation. Annotations were rectangular in shape, enclosing each individual so that the centre of the annotation was roughly the centre of mass, and the points of each rectangle corner are provided in pixels (x,y) where the lower left corner of the picture is 0,0. Images were 6000 pixels in width and 4000 pixels in height.

Description: A total of eight deployments of an autonomous baited camera lander were conducted at the Cabo Verde Abyssal Plain (tropical East Atlantic, Lat. 14.72, Lon. -25.19; Water depth ~4200 m) using either Atlantic mackerel (Scomber scombrus, n=4) or Patagonian squid (Doryteuthis gahi, n=4) bait, to photograph organisms attracted to the bait over roughly 24 hours. The deployments took place during the iMirabilis2 campaign in August 2021 from the research vessel Sarmiento de Gamboa. A deep-sea time lapse camera system with an oblique view of the bait plate and surroundings took a picture every 2.5 min. An ADCP (Aquadopp 6000 m, Nortek) mounted on top of the lander frame took a reading of near bottom currents (~2 meter above bottom) every second. This dataset includes the data downloaded from the ADCP current meter.

Description: Marine optical imaging has become a major assessment tool in science, policy and public understanding of our seas and oceans. Methodology in this field is developing rapidly, including hardware, software and the ways of their application. The aim of the Marine Imaging Workshop (MIW) is to bring together academics, research scientists and engineers, as well as industrial partners to discuss these developments, along with applications, challenges and future directions. The first MIW was held in Southampton, UK in April 2014. The second MIW, held in Kiel, Germany, in 2017 involved more than 100 attendees, who shared the latest developments in marine imaging through a combination of traditional oral and poster presentations, interactive sessions and focused discussion sessions. This article summarises the topics addressed during the workshop, particularly the outcomes of these discussion sessions for future reference and to make the workshop results available to the open public.

Description: Due to the predicted future demand for critical metals, abyssal plains covered with polymetallic nodules are currently being prospected for deep-seabed mining. Deep-seabed mining will lead to significant sediment disturbance over large spatial scales and for extended periods of time. The environmental impact of a small-scale sediment disturbance was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago.

Description: Highlights • Total modeled carbon cycling at disturbed sites is lower than at reference sites. • Projected microbial loop functioning is reduced 26 years after sediment disturbance. • Estimated faunal respiration has recovered from sediment disturbance. • Estimated microbial respiration has not recovered from the sediment disturbance. Abstract Due to the predicted future demand for critical metals, abyssal plains covered with polymetallic nodules are currently being prospected for deep-seabed mining. Deep-seabed mining will lead to significant sediment disturbance over large spatial scales and for extended periods of time. The environmental impact of a small-scale sediment disturbance was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago.

Description: Marine optical imaging has become a major assessment tool in science, policy and public understanding of our seas and oceans. Methodology in this field is developing rapidly, including hardware, software and the ways of their application. The aim of the Marine Imaging Workshop (MIW) is to bring together academics, research scientists and engineers, as well as industrial partners to discuss these developments, along with applications, challenges and future directions. The first MIW was held in Southampton, UK in April 2014. The second MIW, held in Kiel, Germany, in 2017 involved more than 100 attendees, who shared the latest developments in marine imaging through a combination of traditional oral and poster presentations, interactive sessions and focused discussion sessions. This article summarises the topics addressed during the workshop, particularly the outcomes of these discussion sessions for future reference and to make the workshop results available to the open public.

Description: Cephalopods are pivotal components of marine food webs, but biodiversity studies are hampered by challenges to sample these agile marine molluscs. Metabarcoding of environmental DNA (eDNA) is a potentially powerful technique to study oceanic cephalopod biodiversity and distribution but has not been applied thus far. We present a novel universal primer pair for metabarcoding cephalopods from eDNA, Ceph18S (Forward: 5′-CGC GGC GCT ACA TAT TAG AC-3′, Reverse: 5′-GCA CTT AAC CGA CCG TCG AC-3′). The primer pair targets the hypervariable region V2 of the nuclear 18S rRNA gene and amplifies a relatively short target sequence of approximately 200 bp in order to allow the amplification of degraded DNA. In silico tests on a reference database and empirical tests on DNA extracts from cephalopod tissue estimate that 44-66% of cephalopod species, corresponding to about 310-460 species, can be amplified and identified with this primer pair. A multi-marker approach with the novel Ceph18S and two previously published cephalopod mitochondrial 16S rRNA primer sets targeting the same region (Jarman et al. 2006 Mol. Ecol. Notes. 6, 268-271; Peters et al. 2015 Mar. Ecol. 36, 1428-1439) is estimated to amplify and identify 89% of all cephalopod species, of which an estimated 19% can only be identified by Ceph18S. All sequences obtained with Ceph18S were submitted to GenBank, resulting in new 18S rRNA sequences for 13 cephalopod taxa