Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species

Goodwin, Claire E., Berman, Jade, Janussen, Dorte, Göcke, Christian, Hendry, Katharine R. (2016): Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species. Zootaxa 4126 (2): 207-220, DOI: http://doi.org/10.11646/zootaxa.4126.2.

Silicon isotopes of deep-sea sponges:new insights into biomineralisation and skeletal structure

The silicon isotopic composition (δ30Si) of deep sea sponges’ skeletal element – spicules – reflects the silicic acid (DSi) concentration of their surrounding water and can be used as natural archives of bottom water nutrients. In order to reconstruct the past silica cycle robustly, it is essential to better constrain the mechanisms of biosilicification, which are not yet well understood. Here, we show that the apparent isotopic fractionation (δ30Si) during spicule formation in deep sea sponges from the equatorial Atlantic ranges from −6.74 ‰ to −1.50 ‰ in relatively low DSi concentrations (15 to 35 μM). The wide range in isotopic composition highlights the potential difference in silicification mechanism between the two major classes, Demospongiae and Hexactinellida. We find the anomalies in the isotopic fractionation correlate with skeletal morphology, whereby fused framework structures, characterised by secondary silicification, exhibit extremely light δ30Si signatures compared with previous studies. Our results provide insight into the processes involved during silica deposition and indicate that reliable reconstructions of past DSi can only be obtained using silicon isotope ratios derived from sponges with certain spicule types.ACKNOWLEDGEMENTS. We acknowledge the science team and the crew of JC094 and Laura Robinson for cruise organisation. We would also like to thank Paul Curnow for constructive com- ments, Stuart Kearns for his SEM training and assistance, and Maria López-Acosta for her help. Finally, the funding from the Royal Society (grant code RG130386) and from the European Research Council is acknowledged. Joana R. Xavier received support from the European Union's Horizon 2020 research and innovation program through the SponGES project (grant agreement no. 679849). SAMPLE AVAILABILITY. Samples and sample images are available at the University of Bristol; for further detail contact Katharine R. Hendry, email address: [email protected]

The isotope composition of inorganic Germanium in seawater and deep sea sponges

Although dissolved concentrations of germanium (Ge) and silicon (Si) in modern seawater are tightly correlated, uncertainties still exist in the modern marine Ge cycle. Germanium stable isotope systematics in marine systems should provide additional constraints on marine Ge sources and sinks, however the low concentration of Ge in seawater presents an analytical challenge for isotopic measurement. Here, we present a new method of pre-concentration of inorganic Ge from seawater which was applied to measure three Ge isotope profiles in the Southern Ocean and deep seawater from the Atlantic and Pacific Oceans. Germanium isotopic measurements were performed on Ge amounts as low as 2.6 ng using a double-spike approach and a hydride generation system coupled to a MC-ICP-MS. Germanium was co-precipitated with iron hydroxide and then purified through anion-exchange chromatography. Results for the deep (i.e. > 1000 m depth) Pacific Ocean off Hawaii (nearby Loihi Seamount) and the deep Atlantic off Bermuda (BATS station) showed nearly identical δ74/70Ge values at 3.19 ± 0.31 ‰ (2SD, n = 9) and 2.93 ± 0.10 ‰ (2SD, n = 2), respectively. Vertical distributions of Ge concentration and isotope composition in the deep Southern Ocean for water depth > 1300 m yielded an average δ74/70Ge = 3.13 ± 0.25 ‰ (2SD, n = 14) and Ge/Si = 0.80 ± 0.09 μmol/mol (2SD, n = 12). Significant variations in δ74/70Ge, from 2.62 to 3.71 ‰, were measured in the first 1000 m in one station of the Southern Ocean near Sars Seamount in the Drake Passage, with the heaviest values measured in surface waters. Isotope fractionation by diatoms during opal biomineralization may explain the enrichment in heavy isotopes for both Ge and Si in surface seawater. However, examination of both oceanographic parameters and δ74/70Ge values suggest also that water mass mixing and potential contribution of shelf-derived Ge also could contribute to the variations. Combining these results with new Ge isotope data for deep-sea sponges sampled nearby allowed us to determine a Ge isotope fractionation factor of -0.87 ± 0.37 ‰ (2SD, n = 12) during Ge uptake by sponges. Although Ge has long been considered as a geochemical twin of Si, this work underpins fundamental differences in their isotopic behaviors both during biomineralization processes and in their oceanic distributions. This suggests that combined with Si isotopes, Ge isotopes hold significant promise as a complementary proxy for delineating biological versus source effects in the evolution of the marine silicon cycle through time

Long-Term Outcomes in IgA Nephropathy

BACKGROUND: IgA nephropathy can progress to kidney failure, and risk assessment soon after diagnosis has advantages both for clinical management and the development of new therapeutics. We present relationships among proteinuria, eGFR slope and lifetime risks for kidney failure. METHODS: The IgA nephropathy cohort (2,299 adults, 140 children) of the UK National Registry of Rare Kidney Diseases (RaDaR) was analyzed. Patients enrolled had a biopsy-proven diagnosis of IgA nephropathy, plus proteinuria >0.5 g/day or eGFR <60 mL/min/1.73m 2 . Incident and prevalent populations were studied as well as a population representative of a typical phase 3 clinical trial cohort. Analyses of kidney survival were conducted using Kaplan-Meier and Cox regression. eGFR slope was estimated using linear mixed models with random intercept and slope. RESULTS: Median (Q1, Q3) follow-up was 5.9 (3.0, 10.5) years; 50% of patients reached kidney failure or died in the study period. Median (95% CI) kidney survival was 11.4 (10.5, 12.5) years; mean age at kidney failure/death was 48 years, and most patients progressed to kidney failure within 10-15 years. Based on eGFR and age at diagnosis, almost all patients are at risk of progression to kidney failure within their expected lifetime unless a rate of eGFR loss ≤1 ml/min/1.73m 2 /year can be maintained. Time-averaged proteinuria was significantly associated with worse kidney survival and more rapid eGFR loss in incident, prevalent, and "clinical trial" populations. 30% of patients with time-averaged proteinuria of 0.44 to <0.88 g/g and approximately 20% of patients with time-averaged proteinuria <0.44 g/g developed kidney failure within 10 years. In the "clinical trial" population each 10% decrease in time-averaged proteinuria from baseline was associated with a hazard ratio (95% CI) for kidney failure/death of 0.89 (0.87-0.92). CONCLUSIONS: Outcomes in this large IgA nephropathy cohort are generally poor with few patients expected to avoid kidney failure in their lifetime. Significantly, patients traditionally regarded as being "low-risk", with proteinuria <0.88 g/g (<100 mg/mmol), have high rates of kidney failure within 10 years

Who is our cohort: Recruitment, representativeness, baseline risk and retention in the "Watch Me Grow" study?

Background: The "Watch Me Grow" (WMG) study examines the current developmental surveillance system in South West Sydney. This paper describes the establishment of the study birth cohort, including the recruitment processes, representativeness, follow-up and participants' baseline risk for future developmental risk. Methods: Newborn infants and their parents were recruited from two public hospital postnatal wards and through child health nurses during the years 2011-2013. Data was obtained through a detailed participant questionnaire and linked with the participant's electronic medical record (EMR). Representativeness was determined by Chi-square analyses of the available clinical, psychosocial and sociodemographic EMR data, comparing the WMG participants to eligible non-participants. Reasons for non-participation were also elicited. Participant characteristics were examined in six, 12, and 18-month follow-ups. Results: The number of infants recruited totalled 2,025, with 50 % of those approached agreeing to participate. Reasons for parents not participating included: lack of interest, being too busy, having plans to relocate, language barriers, participation in other research projects, and privacy concerns. The WMG cohort was broadly representative of the culturally diverse and socially disadvantaged local population from which it was sampled. Of the original 2025 participants enrolled at birth, participants with PEDS outcome data available at follow-up were: 792 (39 %) at six months, 649 (32 %) at 12 months, and 565 (28 %) at 18 months. Participants with greater psychosocial risk were less likely to have follow-up outcome data. Almost 40 % of infants in the baseline cohort were exposed to at least two risk factors known to be associated with developmental risk. Conclusions: The WMG study birth cohort is a valuable resource for health services due to the inclusion of participants from vulnerable populations, despite there being challenges in being able to actively follow-up this populatio

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 204 (2017): 286-299, doi: 10.1016/j.gca.2017.01.043.We diagnose the relative influences of local-scale biogeochemical cycling and regional-scale ocean circulation on Atlantic barium cycling by analyzing four new depth profiles of dissolved Ba concentrations and isotope compositions from the South and tropical North Atlantic. These new profiles exhibit systematic vertical, zonal, and meridional variations that reflect the influence of both local-scale barite cycling and large-scale ocean circulation. Previously reported epipelagic decoupling of Ba and Si in the tropics is also found to be associated with significant Ba isotope heterogeneity. We contend that this decoupling originates from the depth segregation of opal & barite formation but is exacerbated by weak vertical mixing, as in the tropics. Zonal influence from isotopically-‘heavy’ water masses in the western North Atlantic evidence the advective inflow of Ba-depleted Upper Labrador Sea Water, which is not seen in the eastern basin or the South Atlantic. Meridional variations in Atlantic Ba isotope systematics below 2,000 m appear entirely controlled by conservative mixing. Using an inverse isotopic mixing model, we calculate the Ba isotope composition of the Ba-poor northern end member as +0.45 ‰ and the Ba-rich southern end member +0.26 ‰, relative to NIST SRM 3104a. The near-conservative behaviour of Ba in the deep ocean indicates that Ba isotopes may serve as an independent tracer of the provenance of advected water masses in the Atlantic Ocean. The clearly resolved Ba-isotope signatures of northern- and southern-sourced waters may also prove useful in paleoceanographic studies, should appropriate sedimentary archives be identified. Overall, our results offer new insights into the controls on Ba cycling in seawater and thus the mechanisms that underpin the utility of Ba-based proxies in paleoceanography.D357/GA10E was funded by the UK-GEOTRACES National Environment Research Council Consortium Grant (NE/H006095/1) and JC094 by the European Research Council. KH thanks The Royal Society (University Research Fellowship UF120084) and FP7-PEOPLE-2012-CIG Proposal No 320070 for funding; TJH thanks The Andrew W. Mellon Foundation Endowed Fund for Innovative Research, NSF (OCE-1443577), and the Agouron Institute Geobiology Postdoctoral Fellowship Program for supporting isotope research at NIRVANA

Biosilicification Drives a Decline of Dissolved Si in the Oceans through Geologic Time

Biosilicification has driven variation in the global Si cycle over geologic time. The evolution of different eukaryotic lineages that convert dissolved Si (DSi) into mineralized structures (higher plants, siliceous sponges, radiolarians, and diatoms) has driven a secular decrease in DSi in the global ocean leading to the low DSi concentrations seen today. Recent studies, however, have questioned the timing previously proposed for the DSi decreases and the concentration changes through deep time, which would have major implications for the cycling of carbon and other key nutrients in the ocean. Here, we combine relevant genomic data with geological data and present new hypotheses regarding the impact of the evolution of biosilicifying organisms on the DSi inventory of the oceans throughout deep time. Although there is no fossil evidence for true silica biomineralization until the late Precambrian, the timing of the evolution of silica transporter genes suggests that bacterial silicon-related metabolism has been present in the oceans since the Archean with eukaryotic silicon metabolism already occurring in the Neoproterozoic. We hypothesize that biological processes have influenced oceanic DSi concentrations since the beginning of oxygenic photosynthesis

Reconstructing Circumpolar Deep Water: A new Mg/Ca-Temperature calibration for the benthic foraminifer Trifarina angulosa around Antarctica

The West Antarctic Ice Sheet (WAIS) represents a large potential source of sea level rise. Observations of ice sheet instabilities in the region have increased in recent decades, with a 77% recorded increase in the net loss of glaciers the Amundsen Sea Embayment (ASE) sector of the WAIS since 1973. This has been attributed to increasing basal melting of floating ice shelves caused by warmer Circumpolar Deep Water (CDW) upwelling onto the shelf. Understanding the role of CDW in glacial retreat in the ASE over longer timescales is key to reducing the uncertainty of future sea level predictions. The aim of this research is to reconstruct CDW incursions onto the ASE continental shelf and correlate them to the glacial history of the area since the Last Glacial Maximum. To achieve this, it is crucial to develop a proxy for detecting the presence or absence of CDW. Whilst foraminiferal preservation is rare in this locality due to the corrosive nature of water masses around the Antarctic Peninsula, several cores from the ASE contain specimens including the benthic species Trifarina angulosa, which is a shallow infaunal species therefore ideal for Mg/Ca temperature reconstructions. Here we present a core-top calibration for T. angulosa for temperatures between -1.75°C and +1.5°C from sites situated in the Southern Ocean. We apply this Mg/Ca temperature calibration to down-core archives at several sites, which are well-dated using radiocarbon. The results are presented here along with benthic and planktonic foraminiferal stable isotope data and complementary trace metal data. Keywords: Circumpolar deep water, foraminifera, Mg/C