Summary Objectives Outer membrane vesicle (OMV) vaccines are used against outbreaks of capsular group B Neisseria meningitidis (MenB) caused by strains expressing particular PorA outer membrane ...proteins (OMPs). Ferric enterobactin receptor (FetA) is another variable OMP that induces type-specific bactericidal antibodies, and the combination of judiciously chosen PorA and FetA variants in vaccine formulations is a potential approach to broaden protection of such vaccines. Methods The OMV vaccine MenPF-1 was generated by genetically modifying N. meningitidis strain 44/76 to constitutively express FetA. Three doses of 25 μg or 50 μg of MenPF-1 were delivered intra-muscularly to 52 healthy adults. Results MenPF-1 was safe and well tolerated. Immunogenicity was measured by serum bactericidal assay (SBA) against wild-type and isogenic mutant strains. After 3 doses, the proportion of volunteers with SBA titres ≥1:4 (the putative protective titre) was 98% for the wild-type strain, and 77% for the strain 44/76 FetA on PorA off compared to 51% in the strain 44/76 FetA off PorA off , demonstrating that vaccination with MenPF-1 simultaneously induced FetA and PorA bactericidal antibodies. Conclusion This study provides a proof-of-concept for generating bactericidal antibodies against FetA after OMV vaccination in humans. Prevalence-based choice of PorA and FetA types can be used to formulate a vaccine for broad protection against MenB disease.
Photosynthesis in the surface ocean produces approximately 100 gigatonnes of organic carbon per year, of which 5 to 15 per cent is exported to the deep ocean. The rate at which the sinking carbon is ...converted into carbon dioxide by heterotrophic organisms at depth is important in controlling oceanic carbon storage. It remains uncertain, however, to what extent surface ocean carbon supply meets the demand of water-column biota; the discrepancy between known carbon sources and sinks is as much as two orders of magnitude. Here we present field measurements, respiration rate estimates and a steady-state model that allow us to balance carbon sources and sinks to within observational uncertainties at the Porcupine Abyssal Plain site in the eastern North Atlantic Ocean. We find that prokaryotes are responsible for 70 to 92 per cent of the estimated remineralization in the twilight zone (depths of 50 to 1,000 metres) despite the fact that much of the organic carbon is exported in the form of large, fast-sinking particles accessible to larger zooplankton. We suggest that this occurs because zooplankton fragment and ingest half of the fast-sinking particles, of which more than 30 per cent may be released as suspended and slowly sinking matter, stimulating the deep-ocean microbial loop. The synergy between microbes and zooplankton in the twilight zone is important to our understanding of the processes controlling the oceanic carbon sink.
Particulate organic carbon (POC) generated by primary production and exported to depth, is an important pathway for carbon transfer to the abyss, where it is stored over climatically significant ...timescales. These processes constitute the biological carbon pump. A spectrum of particulate sinking velocities exists throughout the water column, however numerical models often simplify this spectrum into suspended, fast and slow sinking particles. Observational studies suggest the spectrum of sinking speeds in the ocean is strongly bimodal with >85% POC flux contained within two pools with sinking speeds of <10 m day−1 and >350 m day−1. We deployed a Marine Snow Catcher (MSC) to estimate the magnitudes of the suspended, fast and slow sinking pools and their fluxes at the Porcupine Abyssal Plain site (48°N, 16.5°W) in summer 2009. The POC concentrations and fluxes determined were 0.2 μg C L−1 and 54 mg C m−2 day−1 for fast sinking particles, 5 μg C L−1 and 92 mg C m−2 day−1 for slow sinking particles and 97 μg C L−1 for suspended particles. Our flux estimates were comparable with radiochemical tracer methods and neutrally buoyant sediment traps. Our observations imply: (1) biomineralising protists, on occasion, act as nucleation points for aggregate formation and accelerate particle sinking; (2) fast sinking particles alone were sufficient to explain the abyssal POC flux; and (3) there is no evidence for ballasting of the slow sinking flux and the slow sinking particles were probably entirely remineralised in the twilight zone.
Key Points
Fast and slow sinking POC contributes 40% and 60% of export
Slow sinking POC is not ballasted and remineralized in the twilight zone
Fast sinking POC supplies the abyss and is at least partially ballasted
Atmospheric carbon dioxide levels are strongly controlled by the depth at which the organic matter that sinks out of the surface ocean is remineralized. This depth is generally estimated from ...particle flux profiles measured using sediment traps. Inherent in this analysis is a steady state assumption that export from the surface does not significantly change in the time it takes material to reach the deepest trap. However, recent observations suggest that a significant fraction of material in the mesopelagic zone sinks slowly enough to bring this into doubt. We use data from a study in the North Atlantic during July/August 2009 to challenge the steady state assumption. An increase in biogenic silica flux with depth was observed which we interpret, based on vertical profiles of diatom taxonomy, as representing the remnants of the spring diatom bloom sinking slowly (<40 m d−1). We were able to reproduce this behavior using a simple model using satellite‐derived export rates and literature‐derived remineralization rates. We further provide a simple equation to estimate “additional” (or “excess”) particulate organic carbon supply to the dark ocean during nonsteady state conditions, which is not captured by traditional sediment trap deployments. In seasonal systems, mesopelagic net organic carbon supply could be wrong by as much as 25% when assuming steady state. We conclude that the steady state assumption leads to misinterpretation of particle flux profiles when input fluxes from the upper ocean vary on the order of weeks, such as in temperate and polar regions with strong seasonal cycles in export.
Key Points
Increased biogenic silica fluxes with depth imply nonsteady state conditions in the NE Atlantic in August 2009
Taxonomic flux analysis and simple modeling support the nonsteady state hypothesis
By assuming steady state, net organic carbon supply to the dark ocean may be wrong by ≤ 25%
The Arctic region is undergoing significant changes in climate, with a notable decrease in summertime sea ice coverage over the past three decades. This trend means an increasing proportion of Arctic ...Ocean surface waters can receive direct deposition of material from the atmosphere, potentially influencing marine biogeochemical cycles and delivery of pollutants to the Arctic ecosystem. Here, we present aerosol concentrations of selected trace elements (Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) measured during the US GEOTRACES Western Arctic cruise (GN01, also known as HLY1502) in August–October 2015. Concentrations of “lithogenic” elements (Al, Ti, V, Mn, Fe, and Co) were similar to those measured in remote and predominantly marine-influenced air masses in previous studies, reflecting the remoteness of the Arctic Ocean from major dust sources. Concentrations of Ni, Cu, Zn, Pb, and Cd showed significant enrichments over crustal values, and were often of similar magnitude to concentrations measured over the North Atlantic in air masses of North American or European provenance. We use 7Be inventory and flux data from GN01 to estimate a bulk atmospheric deposition velocity during the study period, and combine it with our aerosol concentrations to calculate atmospheric deposition fluxes of the trace elements in the Arctic region during late summer. The resulting estimates for mineral dust and Fe deposition fall at the low end of global estimates and confirm the Arctic Ocean as a low-dust environment during the summer months.
This article is part of a special issue entitled: Conway GEOTRACES - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.
•We report bulk aerosol concentrations of multiple trace elements from the western Arctic Ocean during summer 2015.•Deposition fluxes are calculated using a bulk deposition velocity calculated from aerosol and snow 7Be data.•Summertime atmospheric deposition fluxes of mineral dust and Fe to the Arctic are low relative to other oceanic regions.
The Ross Sea sustains a rich ecosystem and is the most productive sector of the Southern Ocean. Most of this production occurs within a polynya during the November–February period, when the ...availability of dissolved iron (dFe) is thought to exert the major control on phytoplankton growth. Here we combine new data on the distribution of dFe, high‐resolution model simulations of ice melt and regional circulation, and satellite‐based estimates of primary production to quantify iron supply and demand over the Ross Sea continental shelf. Our analysis suggests that the largest sources of dFe to the euphotic zone are wintertime mixing and melting sea ice, with a lesser input from intrusions of Circumpolar Deep Water and a small amount from melting glacial ice. Together these sources are in approximate balance with the annual biological dFe demand inferred from satellite‐based productivity algorithms, although both the supply and demand estimates have large uncertainties.
Key Points
Iron supply is estimated using observations and a 3‐D model of the Ross Sea
The largest sources are winter mixing from the benthos and melting sea ice
Inferred supply is sufficient to balance satellite‐based productivity estimates
Continental margin sediments provide a potentially large but poorly constrained source of dissolved iron (dFe) to the upper ocean. The Ross Sea continental shelf is one region where this benthic ...supply is thought to play a key role in regulating the magnitude of seasonal primary production. Here we present data collected during austral summer 2012 that reveal contrasting low surface (0.08 ± 0.07 nM) and elevated near‐seafloor (0.74 ± 0.47 nM) dFe concentrations. Combining these observations with results from a high‐resolution physical circulation model, we estimate dFe efflux of 5.8 × 107 mol yr−1 from the deeper portions (>400 m) of the Ross Sea continental shelf; more than sufficient to account for the inferred “winter reserve” dFe inventory at the onset of the growing season. In addition, elevated dFe concentrations observed over shallower bathymetry suggest that such features provide additional inputs of dFe to the euphotic zone throughout the year.
Key Points
Highest Ross Sea dFe concentrations are found within 50 m of the seafloorAnnual dFe efflux from the continental shelf in the Ross Sea is estimatedShallower shelf areas supply additional episodic inputs of Fe to surface waters
Melt ponds are a prominent feature of Arctic sea ice during the summer and play a role in the complex interface between the atmosphere, cryosphere and surface ocean. During melt pond formation and ...development, micronutrient and contaminant trace elements (TEs) from seasonally accumulated atmospheric deposition are mixed with entrained sedimentary and marine-derived material before being released to the surface ocean during sea ice melting. Here we present particulate and size-fractionated dissolved (truly soluble and colloidal) TE data from five melt ponds sampled in late summer 2015, during the US Arctic GEOTRACES (GN01) cruise. Analyses of salinity, δ18O, and 7Be indicate variable contributions to the melt ponds from snowmelt, melting sea ice, and surface seawater. Our data highlight the complex TE biogeochemistry of late summer Arctic melt ponds and the variable importance of different sources for specific TEs. Dissolved TE concentrations indicate a strong influence from seawater intrusion for V, Ni, Cu, Cd, and Ba. Ultrafiltration methods reveal dissolved Fe, Zn, and Pb to be mostly colloidal (0.003–0.2 μm), while Mn, Co, Ni, Cu, and Cd are dominated by a truly soluble (<0.003 μm) fraction. Isotopically light dissolved Fe in some melt ponds suggests that photochemical and/or biologically driven redox cycling also takes place. Comparisons of particulate TE/Al ratios to mean crustal values indicate influences from lithogenic sources, including natural aerosols and/or sedimentary material, with significant enrichments for some elements, including Ni, Cu, Zn, Cd and Pb, that may result from anthropogenic aerosols, biogenic material, and/or in situ scavenging of dissolved TEs. Our results indicate that melt ponds represent a transitional environment in which some atmospherically-derived TEs undergo physical and/or chemical changes before their release to the surface ocean. As a result, the ongoing changes in sea ice areal extent, thickness, and melt season length are likely to influence the bioavailability of atmospheric TE input to the surface Arctic Ocean, with material released from snow and sea ice via melt ponds earlier in the summer and with more extensive direct deposition to the ocean surface.
•Melt pond contributions from snowmelt, sea ice melt and seawater are quantified.•Influence of the three source waters on melt pond dissolved TEs varies by element.•Melt ponds processes influence biogeochemistry of TEs released to surface ocean.
Summary The efficacy of Bacillus Calmette-Guerin (BCG) vaccination in protection against pulmonary tuberculosis (TB) is highly variable between populations. One possible explanation for this ...variability is increased exposure of certain populations to non-tuberculous mycobacteria (NTM). This study used a murine model to determine the effect that exposure to NTM after BCG vaccination had on the efficacy of BCG against aerosol Mycobacterium tuberculosis challenge. The effects of administering live Mycobacterium avium (MA) by an oral route and killed MA by a systemic route on BCG-induced protection were evaluated. CD4+ and CD8+ T cell responses were profiled to define the immunological mechanisms underlying any effect on BCG efficacy. BCG efficacy was enhanced by exposure to killed MA administered by a systemic route; T helper 1 and T helper 17 responses were associated with increased protection. BCG efficacy was reduced by exposure to live MA administered by the oral route; T helper 2 cells were associated with reduced protection. These findings demonstrate that exposure to NTM can induce opposite effects on BCG efficacy depending on route of exposure and viability of NTM. A reproducible model of NTM exposure would be valuable in the evaluation of novel TB vaccine candidates.
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