Geochemical evidence of denitrification in the Benguela upwelling system

This paper presents analysis of nitrate, phosphate and silicate data from the Benguela upwelling system. Evidence is presented that suggests denitrification occurring close to shore, and also nutrient trapping. Denitrification leaves an imprint on the water properties in terms of a nitrate deficit, that is to say nitrate concentrations that are significantly less than predicted by multiplying the phosphate concentrations by the Redfield ratio. It is probable that denitrification also causes a decoupling of nitrate and carbon compared to Redfield processes, and large-scale losses of nitrate in the Benguela which are not accompanied by losses of carbon. Nitrate-driven CO2 drawdown following upwelling will be less than it might otherwise be, because of denitrification. Nutrient trapping (secondary remineralisation) is apparent as enhanced phosphate concentrations, some of which are several Full-size image (<1 K) higher than in the offshore source waters for upwelling. Waters also become enriched in silicate and to a lesser extent nitrate as they advect across the shelf. By implication the same process should also “supercharge” waters in dissolved inorganic carbon, leading to stronger outgassing of CO2 immediately after upwelling. The effect is again to increase the size of the estimated Benguela upwelling system CO2 source

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Four carbonate system variables were measured in surface waters during a cruise aimed at investigating ocean acidification impacts traversing northwestern European shelf seas in the summer of 2011. High-resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pH using the total pH scale (pHT), in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom), which allowed us to evaluate the level of agreement between the variables on a cruise whose main aim was not intercomparison, and thus where conditions were more representative of normal working conditions. Calculations of carbonate system variables from other measurements generally compared well with direct observations of the same variables (Pearson’s correlation coefficient always greater than or equal to 0.94; mean residuals were similar to the respective accuracies of the measurements). We therefore conclude that four of the independent data sets of carbonate chemistry variables were of high quality. A diurnal cycle with a maximum amplitude of 41 μatm was observed in the difference between the pCO2 values obtained by the two independent analytical pCO2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on future research cruises

In Vitro Anti-Hepatitis B Virus Activities of 5’-O-Myristoyl Analogue Derivatives of 3’-Fluoro-2’,3’-dideoxythymidine (FLT) and 3’-Azido-2’,3’- dideoxythymidine (AZT)

Purpose: The objective of this study was to evaluate a dual action prodrug concept wherein an unnatural myristic acid analogue is coupled via an ester moiety to the 5’-position of FLT or AZT. Subsequent intracellular cleavage of the prodrug ester would simultaneously release FLT or AZT that could inhibit reverse transcriptase (RT), and the myristic acid analogue that could inhibit myristoyl- CoA:protein N-myristoyltransferase (NMT). Methods: Cytotoxicity (2.2.15 cell culture), and antihepatitis B activity of 5’-O-myristoyl analogue prodrug derivatives of FLT and AZT (2-8) were evaluated in vitro using human liver hepatitis B virus (HBV) producing 2.2.15 cell lines. Results: The 5’- O-(12-methoxydodecanoyl) ester derivatives of AZT (2, EC50 = 2.7 ± 0.3 mM; CC50 = 727 ± 19 μM) and FLT (4, EC50 = 2.8 ± 0.3 μM; CC50 = 186 ± 20 μM) were the most effective anti-hepatitis B virus (anti-HBV) compounds of this series in a replication assay. In the series of 5’-O-myristic acid analogue ester prodrug derivatives of FLT, the relative anti-HBV potency order was MeO(CH2)11CO2- \u3e N3(CH2)11CO2- and Br(CH2)11CO2- \u3e EtS(CH2)nCO2-(n = 10 or 11) \u3e Me(CH2)12CO2- (myristoyl). Conclusions: The in vitro data suggest that the 5’-Omyristoyl analogue prodrug concept offers a potential drug design approach to design dual acting antiiviral agents, with superior pharmacokinetic, biodistribution, reduced cytotoxicity and/or increased efficacy. In this regard, the 5’-O-(12-methoxydodecanoyl) prodrug ester of 3’-thia-3’-deoxythymidine (3TC) may offer the greatest potential for the treatment of HBV infection

Environmental drivers of coccolithophore abundance and calcification across Drake Passage (Southern Ocean)

Although coccolithophores are not as numerically common or as diverse in the Southern Ocean as they are in subpolar waters of the North Atlantic, a few species, such as Emiliania huxleyi, are found during the summer months. Little is actually known about the calcite production (CP) of these communities or how their distribution and physiology relate to environmental variables in this region. In February 2009, we made observations across Drake Passage (between South America and the Antarctic Peninsula) of coccolithophore distribution, CP, primary production, chlorophyll a and macronutrient concentrations, irradiance and carbonate chemistry. Although CP represented less than 1% of total carbon fixation, coccolithophores were widespread across Drake Passage. The B/C morphotype of E. huxleyi was the dominant coccolithophore, with low estimates of coccolith calcite ( 0.01 pmol C coccolith-/ from biometric measurements. Both cell-normalised calcification (0.01–0.16 pmol C cell-1 d-1/ and total CP (< 20 μmol C m-1 d-1/were much lower than those observed in the subpolar North Atlantic where E. huxleyi morphotype A is dominant. However, estimates of coccolith production rates were similar (0.1–1.2 coccoliths cell-1 h-1/ to previous measurements made in the subpolar North Atlantic. A multivariate statistical approach found that temperature and irradiance together were best able to explain the observed variation in species distribution and abundance (Spearman’s rank correlation D0.4, p < 0.01). Rates of calcification per cell and coccolith production, as well as community CP and E. huxleyi abundance, were all positively correlated (p < 0.05) to the strong latitudinal gradient in temperature, irradiance and calcite saturation states across Drake Passage. Broadly, our results lend support to recent suggestions that coccolithophores, especially E. huxleyi, are advancing polewards. However, our in situ observations indicate that this may owe more to sea-surface warming and increasing irradiance rather than increasing CO2 concentrations

The requirement for calcification differs between ecologically important coccolithophore species

Summary Coccolithophores are globally distributed unicellular marine algae that are characterized by their covering of calcite coccoliths. Calcification by coccolithophores contributes significantly to global biogeochemical cycles. However, the physiological requirement for calcification remains poorly understood as non‐calcifying strains of some commonly used model species, such as Emiliania huxleyi, grow normally in laboratory culture. To determine whether the requirement for calcification differs between coccolithophore species, we utilized multiple independent methodologies to disrupt calcification in two important species of coccolithophore: E. huxleyi and Coccolithus braarudii. We investigated their physiological response and used time‐lapse imaging to visualize the processes of calcification and cell division in individual cells. Disruption of calcification resulted in major growth defects in C. braarudii, but not in E. huxleyi. We found no evidence that calcification supports photosynthesis in C. braarudii, but showed that an inability to maintain an intact coccosphere results in cell cycle arrest. We found that C. braarudii is very different from E. huxleyi as it exhibits an obligate requirement for calcification. The identification of a growth defect in C. braarudii resulting from disruption of the coccosphere may be important in considering their response to future changes in ocean carbonate chemistry

Investigation into levels of dioxins, furans, polychlorinated biphenyls and brominated flame retardants in fishery produce in Ireland

The Food Safety Authority of Ireland in collaboration with the Marine Institute and An Board Iascaigh Mhara (Sea Fisheries Board) has carried out a surveillance study of levels of dioxins (PCDDs), furans (PCDFs) polychlorinated biphenyls (PCBs), and brominated flame retardants (BFRs), specifically polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCD), in a variety of fish species and fishery products, including fresh and processed products available on the Irish market. The study was undertaken because of concern about the possible effects on human health of these bio-persistent environmental contaminants, known to be present in a number of foodstuffs, notably meat, fish, eggs and dairy products. The study showed that levels of PCDDs and PCDFs in Irish fish and fishery products available on the Irish market were well below existing EC legal limits for these contaminants as laid down in Regulation 466/2001. The lowest level was found in a sample of canned tuna (0.012 ng WHO TEQ/kg whole weight) with the highest level found in a farmed salmon sample (0.82 ng WHO TEQ/kg whole weight), compared with the maximum level under the legislation of 4 ng WHO TEQ/kg whole weight. The levels found were also below the new limits for dioxin-like PCBs (dl-PCBs) and for the sum of WHO-TEQs for PCDDs, PCDFs and dioxin-like PCBs, which were introduced in November, 2006 via Regulation 199/2006. The upper-bound mean levels of PCDDs, PCDFs and dioxin-like PCBs expressed as total WHOTEQs ranged from 0.05 – 2.15 ng/kg WHO TEQ whole weight, which can be compared with the new maximum level of 8 ng WHO TEQ/kg whole weight for the sum of PCDDs, PCDFs and dioxin-like PCBs. Results of this study are in line with those from previous FSAI studies on PCDD and PCDF levels in fish and also in meat, milk and eggs, and indicate relatively low levels of these contaminants in fishery produce available in the Irish marketplace. Reductions of PCDD/Fs and dl-PCBs in Irish farmed salmon were observed in comparison to levels measured in a previous FSAI/MI survey in 2001, in which a mean level of 4.02 ng WHO TEQ/kg whole weight was detected compared with 2.15 ng/kg WHO TEQ whole weight in the present study. Similar observations can be made for levels reported in a study carried out by An Board Iascaigh Mhara in 2004, in which a mean level of 1.75 ng WHO TEQ/kg whole weight was reported. Concentrations of brominated flame retardants were also low. The mean PBDE concentrations ranged from <0.31 to 3.71 µg/kg whole weight in canned tuna to farmed salmon respectively. Although there are no acceptable daily intake (ADI) or maximum limits set for PBDEs or HBCD, the levels of these contaminants found in the study were low, and are very unlikely to present a health risk to Irish consumers. Although fish is a recognised dietary source of PCDDs, PCDFs and PCBs, the health benefits of eating fish are well established, and on the basis of these results the FSAI considers that there is no need to alter current advice on fish consumption. Current advice is that consumers should eat two portions of fish a week, one of which should be oily. The full study report follows, providing further sampling details, analytical methodologies and discussion of the resulting datasets.Funder: Marine Institut

Global Existence and Regularity for the 3D Stochastic Primitive Equations of the Ocean and Atmosphere with Multiplicative White Noise

The Primitive Equations are a basic model in the study of large scale Oceanic and Atmospheric dynamics. These systems form the analytical core of the most advanced General Circulation Models. For this reason and due to their challenging nonlinear and anisotropic structure the Primitive Equations have recently received considerable attention from the mathematical community. In view of the complex multi-scale nature of the earth's climate system, many uncertainties appear that should be accounted for in the basic dynamical models of atmospheric and oceanic processes. In the climate community stochastic methods have come into extensive use in this connection. For this reason there has appeared a need to further develop the foundations of nonlinear stochastic partial differential equations in connection with the Primitive Equations and more generally. In this work we study a stochastic version of the Primitive Equations. We establish the global existence of strong, pathwise solutions for these equations in dimension 3 for the case of a nonlinear multiplicative noise. The proof makes use of anisotropic estimates, $L^{p}_{t}L^{q}_{x}$ estimates on the pressure and stopping time arguments.Comment: To appear in Nonlinearit

Scholarly communication in transition: The use of question marks in the titles of scientific articles in medicine, life sciences and physics 1966–2005

The titles of scientific articles have a special significance. We examined nearly 20 million scientific articles and recorded the development of articles with a question mark at the end of their titles over the last 40 years. Our study was confined to the disciplines of physics, life sciences and medicine, where we found a significant increase from 50% to more than 200% in the number of articles with question-mark titles. We looked at the principle functions and structure of the titles of scientific papers, and we assume that marketing aspects are one of the decisive factors behind the growing usage of question-mark titles in scientific articles

Language and cultural capital in school experience of Polish children in Scotland

This article addresses the complex relationship between migration and education in the context of recent intra-European labour mobility. It considers how this mobility impacts the education and life chances of migrant students attending schools in Scotland, UK. By examining the experiences of Polish migrant children and youth at schools in Scotland, the article engages with the issues of language, cultural capital transferability and social positioning. Drawing on qualitative data from 65 in-depth interviews with school children aged 5–17 years, their parents and teachers, as well as observations in the contexts of school and home, the article points to a range of factors affecting the transition of migrant pupils to new schools and social environments