Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The collection of zooplankton swimmers and sinkers in time‐series sediment traps provides unique insight into year‐round and interannual trends in zooplankton population dynamics. These samples are particularly valuable in remote and difficult to access areas such as the Arctic Ocean, where samples from the ice‐covered season are rare. In the present study, we investigated zooplankton composition based on swimmers and sinkers collected by sediment traps at water depths of 180–280, 800–1320, and 2320–2550 m, over a period of 16 yr (2000–2016) at the Long‐Term Ecological Research observatory HAUSGARTEN located in the eastern Fram Strait (79°N, 4°E). The time‐series data showed seasonal and interannual trends within the dominant zooplankton groups including copepoda, foraminifera, ostracoda, amphipoda, pteropoda, and chaetognatha. Amphipoda and copepoda dominated the abundance of swimmers while pteropoda and foraminifera were the most important sinkers. Although the seasonal occurrence of these groups was relatively consistent between years, there were notable interannual variations in abundance, suggesting the influence of various environmental conditions such as sea‐ice dynamic and lateral advection of water masses, for example, meltwater and Atlantic water. Statistical analyses revealed a correlation between the Arctic dipole climatic index and sea‐ice dynamics (i.e., ice coverage and concentration), as well as the importance of the distance from the ice edge on swimmer composition patterns and carbon export.〈/p〉

Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Description: Federal Ministry of Education and Research (BMBF)

Description: Helmholtz‐Gemeinschaft

Description: Deep-sea sponge grounds are underexplored ecosystems that provide numerous goods and services to the functioning of the deep-sea. This study assessed the microbial diversity (by 16S rRNA gene amplicon sequencing) in embryos, juveniles and adults of Craniella zetlandica and Craniella infrequens, common and abundant representatives of deep-sea sponge grounds in the North Atlantic. For this study, in total 39 sponge individuals of the two sponge species were collected and analysed for their associated microbial community composition: C. zetlandica (8 adults, of which one was brooding, and 9 juveniles) and C. infrequens (8 adults, of which four were brooding, and 9 juveniles). We use the term 'juvenile' for small (i.e. mean diameter = 1 cm for C. infrequens; and maximal diameter = 0.3 cm for C. zetlandica), young individuals. For C. zetlandica, juveniles were sampled in September 2018 from an aquarium system (Bergen, Norway). C. zetlandica juveniles were smaller (and most likely younger) than the in situ sampled C. infrequens juveniles and therefore flash-frozen as a whole. Embryos of both sponge species were carefully picked out of the parent sponges with sterile spring steel forceps onboard the research vessel using a stereomicroscope. Ten whole embryos were pooled per adult sponge to account for the small biomass. Data such as presented here provide information on the recruitment of deep-sea sponge holobionts which is needed to develop integrated management tools of such vulnerable marine ecosystems.

Description: Video showing release of embryos (em) from a Craniella zetlandica specimen upon sampling by remotely operated vehicle at 225 m depth in Stjernsund, Northern Norway (70.2707 °N, 22.4778 °E). The footage was recorded on 2018-08-13 at 10:50 UTC by ROV Ægir (University of Bergen) during the research cruise GS2018108 onboard RV G.O. Sars (dive identifier GS2018108-78-ROV-52).

Description: Connectivity is a fundamental process driving the persistence of marine populations and their adaptation potential in response to environmental change. In this study, we analysed the population genetics of two morphologically highly similar deep-sea sponge clades (Phakellia hirondellei and the 'Topsentia-and-Petromica (TaP)' clade) at three locations in the Cantabrian Sea. Sponge taxonomy was assessed by spicule analyses, as well as by 18S sequencing and COI sequencing. The corresponding host microbiome was analysed by 16S rRNA gene sequencing. In addition we set up an oceanographic modelling framework, for which we used seawater flow cytometry data (derived from bottom depths of CTD casts) as ground-truthing data.

Description: Seamounts represent ideal systems to study the influence and interdependency of environmental gradients at a single geographic location. These topographic features represent a prominent habitat for various forms of life, including microbiota and macrobiota, spanning benthic as well as pelagic organisms. While it is known that seamounts are globally abundant structures, it still remains unclear how and to which extend the complexity of the seafloor is intertwined with the local oceanographic mosaic, biogeochemistry and microbiology of a seamount ecosystem. Along these lines, the present study aimed to explore whether and to which extend seamounts can have an imprint on the microbial community composition of seawater and of sessile benthic invertebrates, sponges. For our high-resolution sampling approach of microbial diversity (16S rRNA gene Amplicon sequencing) along with measurements of inorganic nutrients and other biogeochemical parameters, we focused on the Schulz Bank seamount ecosystem, a sponge ground ecosystem which is located on the Arctic Mid-Ocean Ridge. Seawater samples were collected at two sampling depths (mid-water: MW, and near-bed water: BW) from a total of 19 sampling sites. With a clustering approach we defined microbial micro-habitats within the pelagic realm at Schulz Bank, which were mapped onto the seamount's topography, and related to various environmental parameters (such as suspended particulate matter (SPM), dissolved inorganic carbon (DIC), silicate (SiO4−), phosphate (PO43−), ammonia (NH4+), nitrate (NO32−), nitrite (NO2), depth, and dissolved oxygen (O2)). The results of our study reveal a seamount effect (sensu stricto) on the microbial mid-water pelagic community up to approximately 200 m above the seafloor. Further, we observed a strong spatial heterogeneity in the pelagic microbial landscape across the seamount, with planktonic microbial communities reflecting oscillatory and circulatory water movements, as well as processes of bentho-pelagic coupling. Depth, NO32−, SiO4−, and O2 concentrations differed significantly between the determined pelagic microbial clusters close to the seafloor (BW), suggesting that these parameters were presumably linked to changes in microbial community structures. Secondly, we assessed the associated microbial community compositions of three sponge species along a depth gradient of the seamount. While sponge-associated microbial communities were found to be mainly species-specific, we also detected significant intra-specific differences between individuals, depending on the pelagic near-bed cluster they originated from. The variable microbial phyla (i.e. phyla which showed significant differences across varying depth, NO32−, SiO4−, O2 concentrations and different from local seawater communities) were distinct for every sponge-species when considering average abundances per species. Variable microbial phyla included representatives of both, those taxa traditionally counted to the variable community fraction, as well as taxa counted traditionally to the core community fraction. Microbial co-occurrence patterns for the three examined sponge species Geodia hentscheli (demosponge, HMA), Lissodendoryx complicata (demosponge, most likely LMA), and Schaudinnia rosea (Hexactinellida, most likely LMA) were distinct from each other. Over all, this study shows that topographic structures such as the Schulz Bank seamount can have an imprint (seamount effect sensu lato) on both, the microbial community composition of seawater and of sessile benthic invertebrates such as sponges by an interplay between the geology, physical oceanography, biogeochemistry and microbiology of seamounts.

Description: Until now few studies have explored the microbiomes of glass sponges (Hexactinellida). Vazella pourtalesii forms globally unique, monospecific sponge grounds under low-oxygen conditions on the Scotian Shelf. Using metagenomic binning we performed detailed analyses of the metabolic functional capacities of four V. pourtalesii-associated microbial taxa (SAR324, Patescibacteria, Nanoarchaeota, and Crenarchaeota).

Description: Anthropogenic pressures on marine ecosystems and organisms are steadily increasing. Whether and to which extent these pressures influence marine biodiversity is only starting to unveil. Establishment of adequate conservation areas represents a challenging but crucial task in the conservation of genetic diversity and biological variability. Using 16S rRNA gene amplicon sequencing, we analysed the microbial community structure of 32 individuals of the habitat-forming glass sponge Vazella pourtalesii, as well as reference seawater, sediment, and biofilm samples. We assessed how two anthropogenic impacts, i.e. habitat destruction by trawling and artificial substrate provision (moorings made of composite plastic), correspond with in situ V. pourtalesii microbiome variability. In addition, we evaluated the role of two bottom fishery closures in preserving sponge-associated microbial diversity on the Scotian Shelf, Canada.

Description: The collection of zooplankton swimmers and sinkers in time-series sediment traps provides a unique insight into year-round and inter-annual trends in zooplankton population dynamics. Such samples are particularly valuable in remote and difficult to access areas such as the Arctic Ocean, where samples from the ice-covered seasons are rare. In the present study, we investigated zooplankton composition based on swimmers and sinkers collected by sediment traps at water depths of 180-280 m, 800-1320 m, and 2320-2550 m, over a period of 16 years (2000-2016) at the central station of the LTER (Long-Term Ecological Research) HAUSGARTEN observatory in the Fram Strait. The time-series data include the abundance of copepoda, foraminifera, ostracoda, amphipoda, pteropoda, and chaetognatha that were collected in the sediment trap time-series.