Top predator sea stars are the benthic equivalent to polar bears of the pelagic realm.

The marine pelagic compartment spans numerous trophic levels and consists of numerous reticulate connections between species from primary producers to iconic apex predators, while the benthic compartment is perceived to be simpler in structure and comprised of only low trophic level species. Here, we challenge this paradigm by illustrating that the benthic compartment is home to a subweb of similar structure and complexity to that of the pelagic realm, including the benthic equivalent to iconic polar bears: megafaunal-predatory sea stars.

Unraveling the spectral signatures of solvent ordering in K-edge XANES of aqueous Na.

The aqueous solvation structure of the Na+ ion is studied both by molecular dynamics (MD) simulations and K-edge X-ray absorption near edge spectroscopy (XANES). We present a systematic study contrasting the differences in the predicted XANES spectra, using molecular configurations generated from classical and quantum MD. Using a set of suitable order parameters, we elucidate how the spectroscopic features are influenced by the local solvation structure around the Na+ ion. Our findings suggest that XANES is sensitive to fluctuations between the first and second solvation shells and can distinguish between classical and quantum interaction representations used to generate molecular ensembles.

Thermal source Fourier transform infrared microtomography applied to Arctic sea ice diatoms.

We have used thermal source Fourier Transform Infrared (FTIR) microtomographic imaging to compare sea ice diatoms growing under different light conditions. A prototype tomography accessory was designed to have sufficient degrees of freedom to align any tilted cylindrical sample relative to the axis of rotation, minimizing the off-axis path traced during rotation. The lightweight device rests on the motorized stage to position the sample in the field-of-view and enable mosaic imaging. Reconstruction routines were tested with simulated and real phantoms, to assess limitations in the Radon back-projection method employed. The distribution and abundance of biochemicals is analysed for targets larger than a single FPA tile. Two and three dimensional (2D and 3D) FTIR spectrochemical images were obtained with a Focal Plane Array (FPA, nominal 1.1 µm pixel edges) for phantoms (polystyrene beads in polyvinyl alcohol matrix) and diatom cells harvested from land fast, first-year ice sites in Resolute Passage (74 43.628'N; 95 33.330'W) and Dease Strait (69° 1.11'N; 105° 21.29'W), Nunavut, Canada. The analysis of relative concentrations of organic matter within the encapsulating silica frustules of diatoms is important for a better understanding of both the physiological state and the individual cellular response to environmental pressures. Analysis of 3D FTIR images of Nitzschia frigida collected from beneath high (17-19 cm) and low (3-7 cm) snow depth revealed higher concentrations of lipids in diatoms collected under low snow cover, uniquely based on spectroscopically determined total 3D cell volume and biochemical content.

Revisiting the hydration structure of aqueous Na.

A combination of theory, X-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) are used to probe the hydration structure of aqueous Na+. The high spatial resolution of the XRD measurements corresponds to Qmax = 24 Å-1 while the first-reported Na K-edge EXAFS measurements have a spatial resolution corresponding to 2k = Qmax = 16 Å-1. Both provide an accurate measure of the shape and position of the first peak in the Na-O pair distribution function, gNaO(r). The measured Na-O distances of 2.384 ± 0.003 Å (XRD) and 2.37 ± 0.024 Å (EXAFS) are in excellent agreement. These measurements show a much shorter Na-O distance than generally reported in the experimental literature (Na-Oavg ∼ 2.44 Å) although the current measurements are in agreement with recent neutron diffraction measurements. The measured Na-O coordination number from XRD is 5.5 ± 0.3. The measured structure is compared with both classical and first-principles density functional theory (DFT) simulations. Both of the DFT-based methods, revPBE and BLYP, predict a Na-O distance that is too long by about 0.05 Å with respect to the experimental data (EXAFS and XRD). The inclusion of dispersion interactions (-D3 and -D2) significantly worsens the agreement with experiment by further increasing the Na-O distance by 0.07 Å. In contrast, the use of a classical Na-O Lennard-Jones potential with SPC/E water accurately predicts the Na-O distance as 2.39 Å although the Na-O peak is over-structured with respect to experiment.

The structure of liquid water up to 360 MPa from x-ray diffraction measurements using a high Q-range and from molecular simulation.

X-ray diffraction measurements of liquid water are reported at pressures up to 360 MPa corresponding to a density of 0.0373 molecules per Å(3). The measurements were conducted at a spatial resolution corresponding to Q(max) = 16 Å(-1). The method of data analysis and measurement in this study follows the earlier benchmark results reported for water under ambient conditions having a density of 0.0333 molecules per Å(3) and Q(max) = 20 Å(-1) [J. Chem. Phys. 138, 074506 (2013)] and at 70 °C having a density of 0.0327 molecules per Å(3) and Q(max) = 20 Å(-1) [J. Chem. Phys. 141, 214507 (2014)]. The structure of water is very different at these three different T and P state points and thus they provide the basis for evaluating the fidelity of molecular simulation. Measurements show that at 360 MPa, the 4 waters residing in the region between 2.3 and 3 Å are nearly unchanged: the peak position, shape, and coordination number are nearly identical to their values under ambient conditions. However, in the region above 3 Å, large structural changes occur with the collapse of the well-defined 2nd shell and shifting of higher shells to shorter distances. The measured structure is compared to simulated structure using intermolecular potentials described by both first-principles methods (revPBE-D3) and classical potentials (TIP4P/2005, MB-pol, and mW). The DFT-based, revPBE-D3, method and the many-body empirical potential model, MB-pol, provide the best overall representation of the ambient, high-temperature, and high-pressure data. The revPBE-D3, MB-pol, and the TIP4P/2005 models capture the densification mechanism, whereby the non-bonded 5th nearest neighbor molecule, which partially encroaches the 1st shell at ambient pressure, is pushed further into the local tetrahedral arrangement at higher pressures by the more distant molecules filling the void space in the network between the 1st and 2nd shells.

Rapid biodiagnostic ex vivo imaging at 1 µm pixel resolution with thermal source FTIR FPA.

A recent upgrade to the optics configuration of a thermal source FTIR microscope equipped with a focal plane array detector has enabled rapid acquisition of high magnification spectrochemical images, in transmission, with an effective geometric pixel size of ∼1 × 1 µm(2) at the sample plane. Examples, including standard imaging targets for scale and accuracy, as well as biomedical tissues and microorganisms, have been imaged with the new system and contrasted with data acquired at normal magnification and with a high magnification multi-beam synchrotron instrument. With this optics upgrade, one can now conduct rapid biodiagnostic ex vivo tissue imaging in-house, with images collected over larger areas, in less time (minutes) and with comparable quality and resolution to the best synchrotron source FTIR imaging capabilities.

Mercury accumulation, biomagnification, and relationships to δ13C, δ15N and δ34S of fishes and marine mammals in a coastal Arctic marine food web.

Combining mercury and stable isotope data sets of consumers facilitates the quantification of whether contaminant variation in predators is due to diet, habitat use and/or environmental factors. We investigated inter-species variation in total Hg (THg) concentrations, trophic magnification slope between δ15N and THg, and relationships of THg with δ13C and δ34S in 15 fish and four marine mammal species (249 individuals in total) in coastal Arctic waters. Median THg concentration in muscle varied between species ranging from 0.08 ± 0.04 µg g-1 dw in capelin to 3.10 ± 0.80 µg g-1 dw in beluga whales. Both δ15N (r2 = 0.26) and δ34S (r2 = 0.19) best explained variation in log-THg across consumers. Higher THg concentrations occurred in higher trophic level species that consumed more pelagic-associated prey than consumers that rely on the benthic microbial-based food web. Our study illustrates the importance of using a multi-isotopic approach that includes δ34S when investigating trophic Hg dynamics in coastal marine systems.

Monitoring a changing Arctic: Recent advancements in the study of sea ice microbial communities.

Sea ice continues to decline across many regions of the Arctic, with remaining ice becoming increasingly younger and more dynamic. These changes alter the habitats of microbial life that live within the sea ice, which support healthy functioning of the marine ecosystem and provision of resources for human-consumption, in addition to influencing biogeochemical cycles (e.g. air-sea CO2 exchange). With the susceptibility of sea ice ecosystems to climate change, there is a pressing need to fill knowledge gaps surrounding sea ice habitats and their microbial communities. Of fundamental importance to this goal is the development of new methodologies that permit effective study of them. Based on outcomes from the DiatomARCTIC project, this paper integrates existing knowledge with case studies to provide insight on how to best document sea ice microbial communities, which contributes to the sustainable use and protection of Arctic marine and coastal ecosystems in a time of environmental change.

On the impact of wastewater effluent on phytoplankton in the Arctic coastal zone: A case study in the Kitikmeot Sea of the Canadian Arctic.

We present a case study on the impact of effluent from a wastewater lagoon-wetland system on phytoplankton and local primary production near a coastal Arctic community (Cambridge Bay) over spring to fall 2018. Results are also placed within an interannual and regional context for the surrounding Kitikmeot Sea. We find the shallow, relatively fresh Kitikmeot Sea is one of the most nutrient-deplete regions of the Arctic Ocean with NO3- + NO2- concentrations below the surface mixed layer rarely exceeding 2 µmol L-1 and a N:Si:P ratio of 1:6:1. The fjordal-type bathymetry of the main study site and a persistent pycnocline below the bay's exit sill led to slightly elevated N:Si:P of 3:11:1 through trapping of wastewater-sourced N at depth via sinking and remineralization of primary production. Total production in Cambridge Bay over the 3-month open water period was 12.1 g C m-2 with 70% of this production occurring during the 1-month discharge of wastewater into the system. Local primary production responded rapidly to high NO3- + NO2-, NH4+ and PON concentrations provided by wastewater effluent, comprising up to 20% of the production during the discharge period. Remaining production was mostly explained by the deep nutrient pool in the bay, which was only accessed towards the end of the discharge period as the diatom-dominated deep chlorophyll maximum settled below the pycnocline. Although not yet eutrophic, caution is raised at the rapid response of the marine system to wastewater release with a strong recommendation to develop a research and monitoring plan for the bay.

A new species of Monstrillopsis (Crustacea, Copepoda, Monstrilloida) from the lower Northwest Passage of the Canadian Arctic.

A new species of monstrilloid copepod, Monstrillopsis planifronssp. n., is described from an adult female that was collected beneath snow-covered sea ice during the 2014 Ice Covered Ecosystem - CAMbridge bay Process Study (ICE-CAMPS) in Dease Strait of the Canadian Arctic Archipelago. Currently, up to six species of this order are known to occur in polar latitudes. The new species described herein shares similarities with Monstrillopsis dubia (Scott, 1904) but differs in its body proportions and cephalothorax ornamentation; the cephalothorax is covered by minute scattered papillae on dorsal and ventral surfaces; this species has a reduced fifth leg endopod, fifth leg exopod armed with three setae, antennule with fused segments 3-4, and the genital double-somite bears unique posterolateral processes. This is the second species of this genus recorded in the Arctic, after Monstrillopsis ferrarii (Suárez-Morales & Ivanenko, 2004), described from the White Sea, and is the first record of Monstrillopsis in Canadian waters. With the addition of this new species and the recognition of Monstrillopsis bernardensis comb. nov. as a member of this genus, the number of nominal species is now 15. Overall, this genus has a tendency to be distributed in temperate and cold waters, while only three species have been found in tropical and subtropical latitudes.

The release of wastewater contaminants in the Arctic: A case study from Cambridge Bay, Nunavut, Canada.

The treatment of municipal wastewater in the Arctic is challenging due to a variety of financial, operational, climatic and technical issues. To better understand the efficacy of current wastewater treatment in this region and the hazard posed to receiving waters, we assessed the occurrence of nutrients and contaminants (i.e., pharmaceuticals, antibiotic resistance genes) as they moved through a lagoon-based treatment system in Cambridge Bay, Nunavut, Canada. Wastewater treatment in this community is performed by the use of a lagoon-tundra wetland system that is discharged into the marine environment and is representative of current common practices throughout the region. In 2014, samples were collected before and during lagoon discharge from two locations in the main lagoon, one location downstream from the lagoon effluent and three locations offshore. Grab samples were collected to measure nutrients (e.g., total nitrogen and phosphorus) and the presence of antibiotic resistance gene-bearing microbes, and Polar Organic Chemical Integrative Samplers (POCIS) were deployed to collect passively organic contaminants in all locations. A total of six pharmaceuticals were detected from a screen of twenty-eight analytes during the study: atenolol, carbamazepine, clarithromycin, metoprolol, sulfamethoxazole and trimethoprim. The greatest concentrations of nutrients, antibiotic resistance genes (ARGs), and pharmaceuticals were found in sampling locations within the treatment lagoon. Offshore of the release point, we observed limited to no detection of pharmaceuticals and ARGs, but no change in total nitrogen and phosphorus from pre-release. We conclude that the current concentrations of monitored pharmaceuticals do not pose a significant hazard at this time to aquatic organisms in Cambridge Bay.

Reversion from suppression to nonsuppression in SUQ5 [psi+] strains of yeast: the classificaion of mutations.

Reversion from the suppressed to nonsuppressed phenotype in strains of geno;type SUQ5 [psi+] ade2-1 his5-2 lys1-1 can1-100 ura3-1 has been induced by treatment with ethyl methanesulphonate, nitrosoguanidine or UV (254 nm) light. Spontaneously occurring revertants have also been selected by two different methods. Reversion has been shown to occur through a variety of nuclear mutations and through mutation of [psi+] to [psi-]. Nuclear mutations included back-mutation of SUQ5, antisuppressor mutations that were recessive, semi-dominant or dominant, and dominant or recessive mutations of genes required for the maintenance of the [psi+] factor. Complementation tests by which the various kinds of mutations could be distinguished from one another were designed. The spectra of spontaneously occurring and induced mutations have been described.

'Lost' smear-positive pulmonary tuberculosis cases: where are they and why did we lose them?

SETTING: Ntcheu District, rural Malawi. OBJECTIVES: 1) To locate smear-positive pulmonary tuberculosis patients who were identified during the first 6 months of 2000 but did not start treatment ('lost cases'); 2) to describe these patients' pathways to diagnosis, health status and socio-demographic characteristics; and 3) to explore why these patients did not start treatment. METHODS: Lost cases were traced from programme registers and interviewed using the qualitative research critical incidents narrative (CIN) interviews technique. Results were triangulated with responses from health care workers through focus group discussions. RESULTS: The laboratory registered 157 new smear-positive patients. Twenty three (15%) of these were 'lost' (did not appear in the treatment register). CIN interviews were conducted with five lost patients and 14 carers of lost patients who had died. Long pathways to diagnosis were the norm. Health system structural barriers were the main factors behind these pathways, including requirement for hospital attendance, delays in symptom recognition and receipt of sputum results, and the misconception that negative smears excluded tuberculosis. CONCLUSION: Some smear-positive cases experience very long pathways to diagnosis and are lost from this free public health system. The diagnostic process needs to become more responsive to patients' needs.

Safety in laboratories carrying out sputum smear microscopy: a dilemma for resource-poor countries.

Laboratory conditions and procedures for sputum smear microscopy (acid-fast bacilli) were assessed in 38 hospitals throughout Malawi. Of these, 17 (45%) had an area of less than 25 m2, eight (21%) had a separate room for tuberculosis work, and five (13%) had a safety cabinet. All laboratory personnel wore gloves, but in several hospitals there was no white coat, face mask, protective apron or soap for washing hands. Different disinfectants were used to clean work surfaces, only one laboratory decontaminated sputum specimens before disposal, and the laboratory cleaner was usually responsible for waste disposal. Laboratory conditions and safety procedures in Malawi are poor, indicating a need for education, training and supervision of staff.

Quality assessment of sputum transportation, smear preparation and AFB microscopy in a rural district in Malawi.

SETTING: Ntcheu District, Central Region of Malawi. OBJECTIVES: To assess 1) the feasibility of introducing simple internal quality control procedures for acid-fast bacilli (AFB) microscopy, and 2) the quality of the district sputum smear microscopy service. DESIGN: A simple internal quality control system was piloted in which district laboratory staff assessed: 1) specimen suitability, 2) time between sputum submission and smear examination, 3) smear preparation and staining, and 4) microscopy. Actual times for processing specimens were compared with recommended times. External quality validation was carried out. RESULTS: Of 4805 sputum specimens: 1) documentation was complete in 95%, 2) 93% reached the laboratory within 7 days of collection, 3) 96% of smears were well prepared and stained, and 4) 97% concordance (96.4% smear-positive and 97.6% smear-negative) was demonstrated when 208 smears were re-examined by a second technician. The aggregate index of reliability was 86%. The mean time spent on microscopic examination was 3.8 minutes, compared with the recommended time of 10 minutes. When all smears from 164 patients were assessed externally, 98.2% concordance (98.1% smear-positive and 98.2% smear-negative) was demonstrated. False smear-negative and smear-positive rates were less than 2% each. CONCLUSION: District laboratory staff were able to incorporate simple quality control procedures for AFB microscopy into their routine practice, resulting in a reliable service. The lessons learnt are widely relevant and potentially useful for implementation of a national quality assurance scheme.

The operation, quality and costs of a district hospital laboratory service in Malawi.

Laboratory services are run down in many low-income countries, severely constraining their input to patient care and disease surveillance. There are few data about the quality and cost of individual components of the laboratory service in poorer countries, yet this information is essential if optimal use is to be made of scarce resources. Staff time, range of tests, workload, and safety procedures were monitored over 12 months (1997-98) in a typical district hospital laboratory in Malawi. Data were collected to calculate the total economic cost of these services. Of the 31203 tests performed, 84% were to support blood transfusion and diagnosis of malaria and tuberculosis (TB). Test quality was reasonable for malaria and TB microscopy and blood transfusion, but poor for haemoglobin estimation. The cost per test ranged from US dollars 0.35 for haemoglobin to US dollars 11.7 per unit of blood issued and the total annual cost of the laboratory service was US dollars 32618. Blood transfusion and microscopy for malaria and TB comprised the majority of tests. Ensuring that these tests are of the highest quality will therefore have the most impact in reducing wastage of laboratory resources. Inadequate quality of haemoglobin estimations is a particular problem. The findings of this study are likely to be relevant to other low-income countries with similar disease burdens.

Source identification of the Arctic sea ice proxy IP25.

Analysis of the organic geochemical biomarker IP25 in marine sediments is an established method for carrying out palaeo sea ice reconstructions for the Arctic. Such reconstructions cover timescales from decades back to the early Pleistocene, and are critical for understanding past climate conditions on Earth and for informing climate prediction models. Key attributes of IP25 include its strict association with Arctic sea ice together with its ubiquity and stability in underlying marine sediments; however, the sources of IP25 have remained undetermined. Here we report the identification of IP25 in three (or four) relatively minor (<5%) sea ice diatoms isolated from mixed assemblages collected from the Canadian Arctic. In contrast, IP25 was absent in the dominant taxa. Chemical and taxonomical investigations suggest that the IP25-containing taxa represent the majority of producers and are distributed pan-Arctic, thus establishing the widespread applicability of the IP25 proxy for palaeo Arctic sea ice reconstruction.