ALBERT

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: Plumes of re-suspended sediment potentially smother and clog the aquiferous system of filter-feeding sponges with unknown implications for their health. For the first time, we examined the physiological responses of repeated exposure to natural sediment in the glass sponge Vazella pourtalesii, which forms dense sponge grounds in Emerald Basin off Nova Scotia, Canada. Ex situ chamber-based measurements of bacterial clearance and oxygen consumption (respiration) rates indicated that individuals subjected to elevated concentrations of suspended sediment expressed normal clearance and respiration rates over 7 days of sediment exposure, indicating an ability to cope with elevated concentrations of indigestible sediment particles. However, clearance rates significantly declined after 14 days of sediment exposure, suggesting an inability to cope with long-term exposure to increased sediment load. Therefore, long-term exposure to elevated concentrations of suspended sediment should be avoided in order to minimize adverse effects on the abundant Vazella sponge grounds.

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 prokaryotic diversity in embryos, recruits, and adults of Craniella zetlandica and Craniella infrequens, common and abundant representatives of deep-sea sponge grounds in the North Atlantic. Our results reveal that symbiont transmission in the two Craniella sponge species likely occurs vertically, as highly similar microbial consortia have been identified in adults, embryos, and recruits. Moreover, transmission electron microscopy revealed high abundances of sponge-associated microorganisms, among which Chloroflexi (SAR202) were identified as common representatives by amplicon sequencing and fluorescence in situ hybridization (FISH). Equal diversity metrices, a similar overall prokaryotic community composition and a distinct dominance of the phylum Chloroflexi within all life stages are the key findings of our analyses. Information such as presented here provide understanding on the recruitment of deep-sea sponge holobionts which is needed to develop integrated management tools of such vulnerable marine ecosystems.

Description: In northern Chilean Patagonia the scleractinian cold-water coral Caryophyllia huinayensis (Cairns, Häussermann & Försterra 2005) occurs in depths from 16 m up to 265 m. Knowledge about ecological parameters and its response to environmental changes in the habitat are still rare. With global ocean warming and ongoing ocean acidification cold-water corals face possible harmful impacts. To predict the influence of these changes on C. huinayensis and other scleractinian cold-water corals growth rates, abundance, respiration rates and feeding strategies have to be known. Furthermore complex relationships within cold-water reefs need to be revealed. In order to quantify abundance frame based individual census have been carried out in two Chilean fjords. The frame based census showed that C. huinayensis can be abundant with up to 2211 ± 180 individuals per square meter and thrives on a temperature range of 9,5 to 16 °C. In the Comaufjord C. huinayensis is widespread along a natural pH gradient. Due to this natural horizontal pH gradient down to values of pH 7,4 the Comaufjord allows growth experiments in pH conditions that are predicted for the next century. For estimations of growth rates and the influence of changing water parameters on coral growth a cross transplantation experiment has been carried out. Individuals from pH 7.94 ± 0.03 and pH 7.76 ± 0.09 have been cross transplanted, respectively. With a growth rate of 3,39 ± 2,52 μmol CaCO3×cm-2×d-1 transplanted individuals under low pH conditions showed comparable growth rates with the control group under high pH conditions. Maximum growth of 3,2 mm in height and 2,1 mm in calice diameter indicate the ability of C. huinayensis for growing under pH conditions that have been suspected to be harmful for coral skeletons. Individual respiration rates have shown that oxygen consumption under conditions of pH 7,4 was increased by 250 % compared with the control group of pH 8,0. An increased energy demand under low pH conditions could indicate a physiological adaptation of C. huinayensis enabling this species to up-regulate internal pH in tissues where biologically induced calcification takes place. In vitro-feeding-experiments revealed a zooplankton uptake of two prey organisms per hour. Carbon uptake showed that the ingested food could not provide enough energy for important metabolic activities. Dissolved organic substances or other particulate matter might have an importance for nutrition of C. huinayensis. Also zooplankton-uptake might increase with higher in situ prey densities. The present study shows that the scleractinian cold-water coral C. huinayensis has the ability to cope with future acidified seawater. Deep-water coral biocenosis might face harmful impacts of a shoaling aragonite saturation horizon. Despite the potential of calcification under decreased seawater pH the dissolution of seawater-exposed aragonite structures will limit the future distribution of scleractinian cold-water corals in ocean depths.