Description: Despite low temperatures, poor nutrient levels and high pressure, microorganisms thrive in deep-sea environments of polar regions. The adaptability to such extreme environments renders deep-sea microorganisms an encouraging source of novel, bioactive secondary metabolites. In this study, we isolated 77 microorganisms collected by a remotely operated vehicle from the seafloor in the Fram Strait, Arctic Ocean (depth of 2454 m). Thirty-two bacteria and six fungal strains that represented the phylogenetic diversity of the isolates were cultured using an One-Strain-Many-Compounds (OSMAC) approach. The crude EtOAc extracts were tested for antimicrobial and anticancer activities. While antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecium was common for many isolates, only two bacteria displayed anticancer activity, and two fungi inhibited the pathogenic yeast Candida albicans. Due to bioactivity against C. albicans and rich chemical diversity based on molecular network-based untargeted metabolomics, Aspergillus versicolor PS108-62 was selected for an in-depth chemical investigation. A chemical work-up of the SPE-fractions of its dichloromethane subextract led to the isolation of a new PKS-NRPS hybrid macrolactone, versicolide A (1), a new quinazoline (−)-isoversicomide A (3), as well as three known compounds, burnettramic acid A (2), cyclopenol (4) and cyclopenin (5). Their structures were elucidated by a combination of HRMS, NMR, [α]D, FT-IR spectroscopy and computational approaches. Due to the low amounts obtained, only compounds 2 and 4 could be tested for bioactivity, with 2 inhibiting the growth of C. albicans (IC50 7.2 µg/mL). These findings highlight, on the one hand, the vast potential of the genus Aspergillus to produce novel chemistry, particularly from underexplored ecological niches such as the Arctic deep sea, and on the other, the importance of untargeted metabolomics for selection of marine extracts for downstream chemical investigations.

Description: Invertebrates in polar and deep-sea environments that have complex life histories are exposed to unique environmental conditions that may favor non-pelagic development and K-strategist reproduction. Although many polar species follow this strategy, the numerically most abundant species tend to have more r-strategist life-history characteristics. We deployed artificial substrata over 3 years in the Arctic deep sea and collected hundreds of specimens of the athecate hydroid Bouillonia cornucopia. While this species has previously been described as rare, we report dense, patchy recruitment on artificial substrata, suggesting that B. cornucopia is highly opportunistic. This species has rapid growth compared to other sessile invertebrates in the study area, high fecundity, and continuous reproduction—all characteristics of an r-selected life history. The species’ gonophores are simple, lacking an obvious spadix or radial canals. We observed nurse cells in histological sections of female gonophores, but no male gonophores were observed. Gonophores break away from the blastostyles in mature specimens and appear to have fertilization envelopes, suggesting that each gonophore is composed of a single oocyte and that embryological evelopment occurs in the water column. Hydroids are typically the first invertebrates to recruit to substrata in the Arctic but are easily overgrown. The opportunistic life histories of B. cornucopia and other hydroids may be adaptive for maintaining populations in the face of high mortality. Our study demonstrates the utility of artificial substrata for collections of otherwise rare opportunistic species.

Description: Deep-sea regions provide vast ecosystem services such as biological habitat and nutrient cycling. Even though being threatened by climate change and facing possible biodiversity loss, these deep-sea ecosystems are poorly understood. So are macrobenthic communities and their functions within these ecosystems. Biodiversity and ecosystem function relationships as well as their link to environmental drivers can be assessed with the biological trait analysis. We used this approach for the first time for macrofauna assemblages across the deep Fram Strait between Greenland and Svalbard (1000–5500 m water depth) to evaluate their community-specific function from the upper continental slope down to the deepest known Arctic depression, the Molloy Deep. We aimed to investigate whether there are changes in benthic functioning along the bathymetric gradient and if so, which environmental stressors may drive these changes. In total, 16 stations were sampled with a giant box corer (0.25 m2) in 2016 and 2018. Sediments were sieved through a 0.5 mm mesh size sieve and fauna was identified to lowest possible taxonomic entity. Functions of species were characterized by using six traits split in 24 modalities gathered in a fuzzy coded species × traits array. Environmental parameters shaping the benthic habitat and reflecting food availability were gathered from remote sensing, mooring deployments, and sediment sampling. A distance-based redundancy analysis indicated near-bottom water temperature, seabed inclination, water depth as well as phytodetritial matter at the sea surface and seafloor (indicating food availability) to be the best variables explaining the trait and station distribution. Stations clustered into three groups based on their trait composition. Shallower stations characterized by high chlorophyll a concentration with large organisms, living within the sediment as well as predating specimens clustered in one group. A second group was characterized by stations with low chlorophyll a concentration and medium-sized, suspension feeding, epifaunal living macrofauna. A third group comprised stations with water depths ≥ 3000 m and was dominated by medium sized, surface deposit feeding and infaunal living specimens. Overall, the functional structure of macrofauna communities in the Fram Strait followed a food availability-driven gradient. Based on the relationship between sea ice, surface water primary production and food availability at the seafloor, these results point to macrobenthos being sensible to predicted anthropogenically generated environmental variations in polar regions. Alterations in benthic ecosystem functions might be expected when environmental conditions change.

Description: Bathymetric patterns in standing stocks and diversity are a major topic of investigation in deep-sea biology. From the literature, responses of metazoanmeiofauna and nematodes to bathymetric gradients arewell studied, with a general decrease in biomass and abundance with increasing water depth, while bathymetric diversity gradients often, although it is not a rule, show a unimodal pattern. Spatial distribution patterns of nematode communities along bathymetric gradients are coupled with surface-water processes and interacting physical and biological factors within the benthic system. We studied the nematode communities at the Long-TermEcological Research (LTER) observatory HAUSGARTEN, located in the FramStrait at theMarginal Ice Zone, with respect to their standing stocks as well as structural and functional diversity.We evaluated whether nematode density, biomass and diversity indices, such asH0, Hinf, EG(50), Θ−1, are linkedwith environmental conditions along a bathymetric transect spanning from 1200mto 5500mwater depth. Nematode abundance, biomass and diversity, as well as food availability from phytodetritus sedimentation (indicated by chloroplastic pigments in the sediments), were higher at the stations located at upper bathyal depths (1200–2000 m) and tended to decrease with increasing water depth. A faunal shift was found below 3500 m water depth, where genus composition and trophic structure changed significantly and structural diversity indices markedly decreased. A strong dominance of very fewgenera and its high turnover particularly at the abyssal stations (4000–5500 m) suggests that environmental conditions were rather unfavorable for most genera. Despite the high concentrations of sediment-bound chloroplastic pigments and elevated standing stocks found at the deepest station (5500 m), nematode genus diversity remained the lowest compared to all other stations. This study provides a further insight into the knowledge of deep-sea nematodes, their diversity patterns and a deeper understanding of the environmental factors shaping nematodes communities at bathyal and abyssal depths.

Description: Benthic fauna constantly modifies their physical, chemical and biological environment. The permanent biological reworking of surface sediments mediates biogeochemical processes at the seafloor and is, therefore, of global importance. There are numerous studies measuring the rate and extent of bioturbation worldwide, however, information on mixing rates in the deep ocean and especially in the Polar Regions are extremely scarce; to our knowledge there is, by now, only a single study providing bioturbation rates from the deep Arctic Ocean. The present study presents mixing rates and mixed layer depths for the deep seafloor at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN in Fram Strait, Arctic Ocean. Two stations at similar water depths (2400 m and 2500 m water depth, respectively) but approx. 55 km apart from each other were chosen to carry out long-term (2 and 4 years, respectively) in situ bioturbation experiments using luminophores as a tracer. Biodiffusion-like mixing rates Db at the experimental sites were rather similar (0.26 cm2 a-1 at HG-IV; 0.28 cm2 a-1 at S3); slightly (non-significantly) higher Db values at the southern HAUSGARTEN site S3 could be explained by more favorable environmental conditions and related differences in the faunal composition. Indications for a non-local transport of sediment particles from the surface to deeper parts of the sediment, resulting in higher values for the Non-Local Index (NLI), could only be found for the central HAUSGARTEN site HG-IV. Elevated densities of burrowing megafauna at HG-IV, compared to S3, might be responsible for the subsurface maxima in luminophore distribution and comparably higher NLI values at the central HAUSGARTEN site (5.37 at HG-IV; 3.26 at S3). Mixed layer depths L at the two sites were almost identical; considerable mixing of surface sediments occurred down to max. 6-7 cm sediment depth.