Regional and global impact of CO2 uptake in the Benguela Upwelling System through preformed nutrients.

Eastern Boundary Upwelling Systems (EBUS) are highly productive ecosystems. However, being poorly sampled and represented in global models, their role as atmospheric CO2 sources and sinks remains elusive. In this work, we present a compilation of shipboard measurements over the past two decades from the Benguela Upwelling System (BUS) in the southeast Atlantic Ocean. Here, the warming effect of upwelled waters increases CO2 partial pressure (pCO2) and outgassing in the entire system, but is exceeded in the south through biologically-mediated CO2 uptake through biologically unused, so-called preformed nutrients supplied from the Southern Ocean. Vice versa, inefficient nutrient utilization leads to preformed nutrient formation, increasing pCO2 and counteracting human-induced CO2 invasion in the Southern Ocean. However, preformed nutrient utilization in the BUS compensates with ~22-75 Tg C year-1 for 20-68% of estimated natural CO2 outgassing in the Southern Ocean's Atlantic sector (~ 110 Tg C year-1), implying the need to better resolve global change impacts on the BUS to understand the ocean's role as future sink for anthropogenic CO2.

Giant sulfur bacteria (Beggiatoaceae) from sediments underlying the Benguela upwelling system host diverse microbiomes.

Due to their lithotrophic metabolisms, morphological complexity and conspicuous appearance, members of the Beggiatoaceae have been extensively studied for more than 100 years. These bacteria are known to be primarily sulfur-oxidizing autotrophs that commonly occur in dense mats at redox interfaces. Their large size and the presence of a mucous sheath allows these cells to serve as sites of attachment for communities of other microorganisms. But little is known about their individual niche preferences and attached microbiomes, particularly in marine environments, due to a paucity of cultivars and their prevalence in habitats that are difficult to access and study. Therefore, in this study, we compare Beggiatoaceae strain composition, community composition, and geochemical profiles collected from sulfidic sediments at four marine stations off the coast of Namibia. To elucidate community members that were directly attached and enriched in both filamentous Beggiatoaceae, namely Ca. Marithioploca spp. and Ca. Maribeggiatoa spp., as well as non-filamentous Beggiatoaceae, Ca. Thiomargarita spp., the Beggiatoaceae were pooled by morphotype for community analysis. The Beggiatoaceae samples collected from a highly sulfidic site were enriched in strains of sulfur-oxidizing Campylobacterota, that may promote a more hospitable setting for the Beggiatoaceae, which are known to have a lower tolerance for high sulfide to oxygen ratios. We found just a few host-specific associations with the motile filamentous morphotypes. Conversely, we detected 123 host specific enrichments with non-motile chain forming Beggiatoaceae. Potential metabolisms of the enriched strains include fermentation of host sheath material, syntrophic exchange of H2 and acetate, inorganic sulfur metabolism, and nitrite oxidation. Surprisingly, we did not detect any enrichments of anaerobic ammonium oxidizing bacteria as previously suggested and postulate that less well-studied anaerobic ammonium oxidation pathways may be occurring instead.

Harmful algal blooms of the Benguela eastern boundary upwelling system.

The Benguela Upwelling System (BUS) is subject to a high incidence of HABs. Of the major shellfish poisoning syndromes associated with HABs, Paralytic and Diarrhetic Shellfish Poisoning (PSP and DSP) pose the greatest concern, but as documented herein there are several other HAB organisms that are also present. Blooms of Alexandrium catenella have been recognised as the typical cause of PSP since 1948. In addition to the risk posed to human health A. catenella has also been the cause of large shellfish and bird mortalities. An additional risk of PSP is provided by Alexandrium minutum first detected in Cape Town harbour in 2003. DSP was identified on the South African coast for the first time in 1991. Although several Dinophysis spp. known to cause DSP have been recognized as a component of the plankton of the region, it is accepted that DSP is usually attributed to D. acuminata or D. fortii. In the southern Benguela both Pseudo-nitzschia australis and Pseudo-nitzschia multiseries have been identified and shown to produce domoic acid. Multiple Pseudo-nitzschia spp. have been identified in the northern Benguela with the potentially toxigenic Pseudo-nitzschia pungens and P. australis dominant inshore. The yessotoxin (YTX) producing dinoflagellates Gonyaulax spinifera, Lingulodinium polyedrum and Protoceratium reticulatum are all known to form blooms and YTXs have been the cause of massive mortalities of farmed abalone. Prominent fish-killing blooms include Karlodinium veneficum in the northern Benguela and Karenia cristata in the southern Benguela. Shellfish farms in an embayment of the southern Benguela have suffered reduced growth rates due to the ecosystem disruptive blooms of Aureococcus anophagefferens. High biomass dinoflagellate blooms often attributed to Tripos and Prorocentrum spp. characterise the entire region and major mortalities of marine life are regularly attributed to their decay and the subsequent development of anoxic conditions.

Tracing the upwelling process in the northern Benguela upwelling system (nBUS) by 129I.

New data on the presence of 129I in seawater in the Southern Hemisphere measured by Accelerator Mass Spectrometry (AMS) is presented. The samples were collected in 2014 along the Namibian coast during a cruise organised by the National Marine Information and Research Centre (NatMIRC), the national laboratories of the Ministry of Fisheries and Marine Resources (MFMR) in Namibia, and the IAEA Environment Laboratories (IAEA NAEL) in Monaco. The Benguela upwelling system is known as one of the most important marine upwelling regions in the world. Strong winds induce an offshore transport of surface seawater which is substituted by cool subsurface water inshore. As this water is nutrient-rich, which leads to high primary productivity, the Benguela upwelling system has a very important role as a fishing production area. The 129I concentrations in samples were between (0.66 ± 0.14) × 107 and (1.45 ± 0.30) × 107 atoms/kg. The highest 129I concentrations were found in the offshore surface samples. Deep-sea and inshore samples contained lower 129I concentrations, possibly as an effect of the upwelling process. A comparison with previously published studies suggests that the presence of 129I in the northern Benguela upwelling system (nBUS), is mainly due to the impact of nuclear weapons global fallout, without any evident impact of nuclear fuel reprocessing.

Presence of 236U and 237Np in a marine ecosystem: The northern Benguela Upwelling System, a case study.

The Benguela Upwelling System (BUS), off the south-western African coast, is one of the four major eastern boundary upwelling ecosystems in the oceans. However, this area has been overlooked in the field of environmental radioactivity. In this work, 236U and 237Np were collected off the coast of Namibia within the northern BUS. Surface seawater exhibited similar 236U and 237Np concentrations, ranging from 3.9·106 to 5.6·106 atoms kg-1 and from 4.6·106 to 8.5·106 atoms kg-1, respectively. The observed inventories in a water column from the continental margin, of (2.10 ± 0.11)·1012 atoms m-2 for 236U and (3.48 ± 0.13)·1012 atoms m-2 for 237Np, were in agreement with the global fallout (GF) source term in the Southern Hemisphere that was the main source of actinides to the region. A pattern was observed in the surface samples, with 237Np concentrations that decreased by 25-30% when moving from inshore to offshore stations, but such an effect could not be clearly discerned in the case of 236U within the data uncertainties. An explanation based on the larger particle reactivity of GF 237Np compared to GF 236U was proposed. Such an effect would have been important at the studied site due to the enhance presence of particles in the continental shelf triggered by the upwelling phenomenon. A value of 1.77 ± 0.20 was obtained for the 237Np/236U atom ratio for the GF source term in the marine environment.

First assessment on trace elements in sediment cores from Namibian coast and pollution sources evaluation.

Trace elements (TEs), Rare Earth Elements (REEs) and Pb isotope ratios were determined in six small cores sampled along the Namibian coast and different indices, such as Enrichment Factor, Geo-accumulation Index and Pollution load index, were calculated to evaluate possible metal contamination in the area. Concentrations of Pb, Cu, As and Cd were strongly enhanced at the upper 7 cm of core C5, which is located at Walvis Bay, at the major harbor and urban/industrial center of Namibia, indicating the impact from the recent anthropogenic activities. Principal Component Analysis was applied to the data set indicating possible common sources of the contaminants. Pb stable isotope ratios, combined with the dating of core C5 at Walvis Bay, further confirmed the anthropogenic provenance of Pb sources in the recent sediment deposits, which occurred after 1945, when the anthropogenic activities in the area began to increase. REEs profiles were also determined, showing enrichment in REEs for some of the samples, typical for the minerals present in the area. Ce anomaly was detected in one of the cores but the REEs profile did not reveal anomalies ascribable to anthropogenic influence.

Microbial communities associated with phosphogenic sediments and phosphoclast-associated DNA of the Benguela upwelling system.

The processes that lead to the precipitation of authigenic calcium phosphate minerals in certain marine pore waters remain poorly understood. Phosphogenesis occurs in sediments beneath some oceanic upwelling zones that harbor polyphosphate-accumulating bacteria. These bacteria are believed to concentrate phosphate in sediment pore waters, creating supersaturated conditions with respect to apatite precursors. However, the relationship between microbes and phosphorite formation is not fully resolved. To further study this association, we examined microbial community data generated from two sources: sediment cores recovered from the shelf of the Benguela upwelling region where phosphorites are currently forming, and DNA preserved within phosphoclasts recovered from a phosphorite deposit along the Benguela shelf. iTag and clone library sequencing of the 16S rRNA gene showed that many of our sediment-hosted communities shared large numbers of phylotypes with one another, and that the same metabolic guilds were represented at localities across the shelf. Sulfate-reducing bacteria and sulfur-oxidizing bacteria were particularly abundant in our datasets, as were phylotypes that are known to carry out nitrification and the anaerobic oxidation of ammonium. The DNA extracted from phosphoclasts contained the signature of a distinct microbial community from those observed in the modern sediments. While some aspects of the modern and phosphoclast communities were similar, we observed both an enrichment of certain common microbial classes found in the modern phosphogenic sediments and a relative depletion of others. The phosphoclast-associated DNA could represent a relict signature of one or more microbial assemblages that were present when the apatite or its precursors precipitated. While these taxa may or may not have contributed to the precipitation of the apatite that now hosts their genetic remains, several groups represented in the phosphoclast extract dataset have the genetic potential to metabolize polyphosphate, and perhaps modulate phosphate concentrations in pore waters where carbonate fluorapatite (or its precursors) are known to be precipitating.

Baseline study on trace and rare earth elements in marine sediments collected along the Namibian coast.

Namibia is a fast-growing country with extensive mineral extraction activities used in diamond, fluorspar, uranium, and metals production. To assess the impact of land based human activities on the Namibian coastal marine environment, 25 elements were analyzed in 22 surface sediments samples collected along the coast. After applying a variety of pollution assessment indices (Enrichment Factor, Igeo and Pollution Load Indexes) was concluded that As, Cd and Sb were considerably enriched in the sediments from several sites, while Cu, Pb and Zn showed very high enrichment near the Walvis Bay harbor. Pearson's correlation and Principal Component Analysis were used to investigate common metal sources. Additionally, the determination of Pb isotope ratios confirmed the contribution of land based human activities at Walvis Bay and Lüderitz as sources of pollution. The analysis of REEs did not reveal any important enrichment due to anthropogenic activities, but provides a needed baseline for further investigations.

Morphological, molecular and toxigenic characteristics of Namibian Pseudo-nitzschia species - including Pseudo-nitzschia bucculenta sp. nov.

A field study was undertaken to investigate the occurrence and toxin production of species in the diatom genus Pseudo-nitzschia in Namibian waters, in the extremely productive Benguela upwelling system. From surveys conducted on the R/V Mirabilis and the R/V !Anichab, 52 strains were morphologically determined to species level, supported by nuclear ITS rDNA data. Seven species were identified; P. australis, P. decipiens, P. dolorosa, P. fraudulenta, P. plurisecta, P. pungens var. cingulata, and the new species P. bucculenta F. Gai, C. K. Hedemand, N. Lundholm & Ø. Moestrup sp. nov. Molecular and morphological diversity of the Namibian Pseudo-nitzschia species is discussed. Most importantly, P. bucculenta is both morphologically and phylogenetically most similar to P. dolorosa differing mainly in valve width and densities of striae, poroids and band striae as well as by four hemi-compensatory base changes in the ITS2. Morphological and molecular differences among the strains of P. decipiens suggest a temperate and a warm water subdivision. The geographical and toxigenic characteristics of the identified Pseudo-nitzschia species are described and compared to previous studies. Initial tests of toxin production in all seven species revealed production of domoic acid (DA) in two species: one strain of P. australis (0.074 pg DA cell-1) and two strains of P. plurisecta (0.338 pg DA cell-1 and 0.385 pg DA cell-1).

Morphology and toxicity of Pseudo-nitzschia species in the northern Benguela Upwelling System.

The Benguela upwelling system, considered the world's most productive marine ecosystem, has a long record of potentially toxic diatoms belonging to the genus Pseudo-nitzschia. Species of Pseudo-nitzschia were reported as early as 1936 from the northern Benguela upwelling system (nBUS). For the current study, long-term phytoplankton monitoring data (2004-2011) for the Namibian coast were analysed to examine inshore and offshore temporal distribution of Pseudo-nitzschia species, their diversity and ultrastructure. The potentially toxigenic P. pungens and P. australis were the dominant inshore species, whereas offshore Pseudo-nitzschia showed a higher diversity that also included potentially toxic species. During a warming event, a community shift from P. pungens and P. australis dominance to P. fraudulenta and P. multiseries was documented in the central nBUS. A case study of a toxic event (August 2004) revealed that P. australis and P. pungens were present at multiple inshore and offshore stations, coincident with fish (pilchard) and bird mortalities reported from the central part of Namibia. Toxin analyses (LC-MS/MS) of samples collected from June to August 2004 revealed the presence of particulate domoic acid (DA) in seawater at multiple stations (maximum ∼180 ng DA/L) in the >0.45 µm size-fraction, as well as detectable DA (0.12 µg DA/g) in the gut of one of two pilchard samples tested. These findings indicate that DA may have been associated with the fish and bird mortalities reported from this event in the nBUS. However, the co-occurrence of very high biomass phytoplankton blooms suggests that other explanations may be possible.

Spatio-temporal variability of copepod abundance along the 20 °S monitoring transect in the Northern Benguela upwelling system from 2005 to 2011.

Long-term data sets are essential to understand climate-induced variability in marine ecosystems. This study provides the first comprehensive analysis of longer-term temporal and spatial variations in zooplankton abundance and copepod community structure in the northern Benguela upwelling system from 2005 to 2011. Samples were collected from the upper 200 m along a transect at 20 °S perpendicular to the coast of Namibia to 70 nm offshore. Based on seasonal and interannual trends in surface temperature and salinity, three distinct time periods were discernible with stronger upwelling in spring and extensive warm-water intrusions in late summer, thus, high temperature amplitudes, in the years 2005/06 and 2010/11, and less intensive upwelling followed by weaker warm-water intrusions from 2008/09 to 2009/10. Zooplankton abundance reflected these changes with higher numbers in 2005/06 and 2010/11. In contrast, zooplankton density was lower in 2008/09 and 2009/10, when temperature gradients from spring to late summer were less pronounced. Spatially, copepod abundance tended to be highest between 30 and 60 nautical miles off the coast, coinciding with the shelf break and continental slope. The dominant larger calanoid copepods were Calanoides carinatus, Metridia lucens and Nannocalanus minor. On all three scales studied, i.e. spatially from the coast to offshore waters as well as temporally, both seasonally and interannually, maximum zooplankton abundance was not coupled to the coldest temperature regime, and hence strongest upwelling intensity. Pronounced temperature amplitudes, and therefore strong gradients within a year, were apparently important and resulted in higher zooplankton abundance.

Correlation between expectations of recovery and injury severity perception in whiplash-associated disorders.

OBJECTIVE: To assess the correlation between expectations of recovery and whiplash patients' perceptions of injury severity using a simplified instrument. Expectations of recovery have been shown to predict rate of recovery from whiplash injury in population-based studies. The perception of having more severe pathology or more ominous diagnostic labels has also been associated with a worse prognosis. METHODS: Consecutive patients with whiplash-associated disorder grade 1 or 2, presenting in the acute stage to a primary care centre, were asked "do you think that your injury will…" with response options "get better soon; get better slowly; never get better; don't know." Injury severity perception (ISP) was measured with a numerical rating scale which ranged from 0-10, on which subjects were asked to rate how severe (in terms of damage) they thought their injury was. The anchors were labeled "no damage" (0) and "severe, and maybe permanent damage" (10). The primary outcome measure was the correlation between the subject's ISP score and expectation of recovery. RESULTS: A total of 94 subjects (34 males, 60 females, and mean age (40.6 ± 10.0) years, range 19-60 years) were included. The initial responses to expectation of recovery were: get better soon (29/94); get better slowly (22/94); never get better (11/94); don't know (32/94). The mean ISP score was 4.9 ± 1.7 (range 2-9 out of 10). There was a high correlation between expectations and ISP scores (Spearman's rank correlation coefficient 0.68). Those who expected to recover soon and those who expected to get better slowly had the lowest ISP scores. CONCLUSIONS: The more slowly whiplash patients expect to recover, or the less sure they are of recovery, the more severe their initial perceptions of injury.

Development of a symptom expectation questionnaire for minor head injury.

BACKGROUND AND OBJECTIVE: Expectations and beliefs are important predictors of outcome following minor head injury. In this paper, the primary purpose is to develop a simple symptom expectation questionnaire for minor head injury for use in future research studies. METHODS: An existing database of 179 injury-naive subjects who completed a 56-item checklist of expected symptoms for minor head injury was analyzed to determine which items could correctly identify an a priori case definition of an expecter (a subject who expected at least one of these symptoms would remain chronic following minor head injury). A total of six of the 56 items were found to be discriminatory, and these were tested in additional subject groups against the original questionnaire. RESULTS: From the original database of 179 subjects completing a 56-item symptom expectation checklist, 135 expected that at least one of the 56 symptoms would be chronic following minor head injury. The 135 expecters, however, all chose at least one of six items: headache, anxious or worried, depressed, difficulty concentrating, dizziness, and neck pain. Using these six items, in two new groups of subjects, all those who endorsed one of the 56 symptoms as likely to be chronic following minor head injury (expecters) could also be identified on the 6-item checklist. CONCLUSIONS: A shortened (6-item) symptom expectation checklist of commonly reported symptoms following minor head injury (headache, anxious or worried, depressed, difficulty concentrating, dizziness, and neck pain) correctly identifies subjects who expect that at least one symptom will be chronic following minor head injury (i.e., an expecter).

Coping style as a predictor of compliance with referral to active rehabilitation in whiplash patients.

The objective of the study was to determine the odds ratio for compliance with referral to an active treatment program according to coping style in a cohort of acute whiplash-injured subjects. Sixty whiplash patients were assessed within 1 week of their collision for their coping styles and were then questioned 3 weeks later to determine if they had complied with a referral for an active treatment program. Coping style was assessed with the Vanderbilt Pain Management Inventory. Adjusting for age, gender, and initial whiplash disability questionnaire scores, the odds ratio for compliance with therapy for subjects who had a low active/high passive coping style was 0.15 (P=0.03) (95% CI, 0.03-0.86) relative to all other coping style patterns, whose odds ratios did not differ from each other. As a secondary outcome, the odds ratio for reporting prescription medication use for subjects who had a low active/high passive coping style was 6.7 (P=0.038) (95% CI, 1.1-40.4). Those whiplash patients who have a low active/high passive coping style are less likely to attend an active exercise-based rehabilitation program and more likely to use prescription medications in the first 3 weeks following injury. Coping style may affect recovery from whiplash injury through issues of compliance with active therapy and increased reliance on prescription medications.

Surgical robotics for patient safety in the perioperative environment: realizing the promise.

Surgery is at a crossroads of complexity. However, there is a potential path toward patient safety. One such course is to leverage computer and robotic assist techniques in the reduction and interception of error in the perioperative environment. This white paper attempts to facilitate the road toward realizing that promise by outlining a research agenda. The paper will briefly review the current status of surgical robotics and summarize any conclusions that can be reached to date based on existing research. It will then lay out a roadmap for future research to determine how surgical robots should be optimally designed and integrated into the perioperative workflow and process. Successful movement down this path would involve focused efforts and multiagency collaboration to address the research priorities outlined, thereby realizing the full potential of surgical robotics to augment human capabilities, enhance task performance, extend the reach of surgical care, improve health care quality, and ultimately enhance patient safety.

Quantitative measures of performance in microvascular anastomoses.

OBJECTIVE: Methods of evaluating surgical performance are mainly subjective. This study introduces a method of evaluating surgical performance using a quantitative analysis of tool tip kinematics. METHODS: One experienced surgeon performed eight rat microvascular anastomoses over a 2-day interval. An optoelectronic motion analysis system acquired tool tip trajectories at frequencies of 30 Hz. On the basis of a hierarchical decomposition, the procedure was segmented into specific surgical subtasks (free space movement, needle placement and knot throws) from which characteristic measures of performance (tool tip trajectory, excursion and velocity) were evaluated. Comparisons of performance measures across each procedure were indexed (D scale) using the Kolmogorov-Smirnov statistic. RESULTS: Despite the marker occlusions, tool tip data were obtained 92 +/- 7% (mean +/- SD) of the time during manipulation tasks. Missing data segments were interpolated across gaps of less than 10 sample points with errors less than 0.4 mm. The anastomoses were completed in 27 +/- 4 min (range 20.5-31.4 min) with 100% patency. Tool tip trajectories and excursions were comparable for each hand, while right and left hand differences were found for velocity. Performance measures comparisons across each procedure established the benchmark for an experienced surgeon. The D-scale range was between 0 and 0.5. CONCLUSION: The study establishes a reproducible method of quantitating surgical performance. This may enhance assessment of surgical trainees at various levels of training.

The burgeoning disorder of technophilia.

Andreas Laupacis and William Evans have deftly accomplished the difficult task of synthesizing the major issues at hand. Their comments are timely, reflecting society's increasing preoccupation with rapid access to diagnostic imaging. Paradoxically, the recent CIHI report on medical imaging records a steady increase in scanners, without the expected reduction in wait times. The role of private facilities is unclear, and the value of screening asymptomatic patients is unproven. There are few clear guidelines for ordering images. New intraoperative, functional and molecular imaging technologies will further strain the system. This array of challenges should be urgently tackled by a decisive panel of national experts, who would in turn supervise consultants working full-time on guideline development.

Robotics in neurosurgery.

Technological developments in imaging guidance, intraoperative imaging, and microscopy have pushed neurosurgeons to the limits of their dexterity and stamina. The introduction of robotically assisted surgery has provided surgeons with improved ergonomics and enhanced visualization, dexterity, and haptic capabilities. This article provides a historical perspective on neurosurgical robots, including image-guided stereotactic and microsurgery systems. The future of robot-assisted neurosurgery, including the use of surgical simulation tools and methods to evaluate surgeon performance, is discussed.