Consistent increase in dimethyl sulfide (DMS) in response to high CO2 in five shipboard bioassays from contrasting NW European waters

The ubiquitous marine trace gas dimethyl sulfide (DMS) comprises the greatest natural source of sulfur to the atmosphere and is a key player in atmospheric chemistry and climate. We explore the short-term response of DMS production and cycling and that of its algal precursor dimethyl sulfoniopropionate (DMSP) to elevated carbon dioxide (CO2) and ocean acidification (OA) in five 96 h shipboard bioassay experiments. Experiments were performed in June and July 2011, using water collected from contrasting sites in NW European waters (Outer Hebrides, Irish Sea, Bay of Biscay, North Sea). Concentrations of DMS and DMSP, alongside rates of DMSP synthesis and DMS production and consumption, were determined during all experiments for ambient CO2 and three high-CO2 treatments (550, 750, 1000 μatm). In general, the response to OA throughout this region showed little variation, despite encompassing a range of biological and biogeochemical conditions. We observed consistent and marked increases in DMS concentrations relative to ambient controls (110% (28–223%) at 550 μatm, 153% (56–295%) at 750 μatm and 225% (79–413%) at 1000 μatm), and decreases in DMSP concentrations (28% (18–40%) at 550 μatm, 44% (18–64%) at 750 μatm and 52% (24–72%) at 1000 μatm). Significant decreases in DMSP synthesis rate constants (μDMSP, d−1) and DMSP production rates (nmol d−1) were observed in two experiments (7–90% decrease), whilst the response under high CO2 from the remaining experiments was generally indistinguishable from ambient controls. Rates of bacterial DMS gross consumption and production gave weak and inconsistent responses to high CO2. The variables and rates we report increase our understanding of the processes behind the response to OA. This could provide the opportunity to improve upon mesocosm-derived empirical modelling relationships and to move towards a mechanistic approach for predicting future DMS concentrations

Lagrangian evolution of DMS during the Southern Ocean gas exchange experiment: The effects of vertical mixing and biological community shift

Concentrations of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) are highly variable in time and space. What is driving the variability in DMS(P), and can those variability be explained by physical processes and changes in the biological community? During the Southern Ocean Gas Exchange Experiment (SO GasEx) in the austral fall of 2008, two 3He/SF6 labeled patches were created in the surface water. SF6 and DMS were surveyed continuously in a Lagrangian framework, while direct measurements of air-sea exchange further constrained the gas budgets. Turbulent diffusivity at the base of the mixed layer was estimated from SF6 profiles and used to calculate the vertical fluxes of DMS and nutrients. Increasing mixed layer nutrient concentrations due to mixing were associated with a shift in the phytoplankton community structure, which in turned likely affected the sulfur dynamics on timescales of days. DMS concentration as well as air-sea DMS flux appeared to be decoupled from the DMSP concentration, possibly due to grazing and bacterial DMS production. Contrary to expectations, in an environment with high winds and modest productivity, physical processes (air-sea exchange, photochemistry, vertical mixing) only accounted for a small fraction of DMS loss from the surface water. Among the DMS sinks, inferred biological consumption most likely dominated during SO GasEx

Dimethylsulfide (DMS) production in polar oceans is resilient to ocean acidification

Emissions of dimethylsulfide (DMS) from the polar oceans play a key role in atmospheric processes and climate. Therefore, it is important we increase our understanding of how DMS production in these regions may respond to environmental change. The polar oceans are particularly vulnerable to ocean acidification (OA). However, our understanding of the polar DMS response is limited to two studies conducted in Arctic waters, where in both cases DMS concentrations decreased with increasing acidity. Here, we report on our findings from seven summertime shipboard microcosm experiments undertaken in a variety of locations in the Arctic Ocean and Southern Ocean. These experiments reveal no significant effects of short term OA on the net production of DMS by planktonic communities. This is in contrast to identical experiments from temperate NW European shelf waters where surface ocean communities responded to OA with significant increases in dissolved DMS concentrations. A meta-analysis of the findings from both temperate and polar waters (n=18 experiments) reveals clear regional differences in the DMS response to OA. We suggest that these regional differences in DMS response reflect the natural variability in carbonate chemistry to which the respective communities may already be adapted. Future temperate oceans could be more sensitive to OA resulting in a change in DMS emissions to the atmosphere, whilst perhaps surprisingly DMS emissions from the polar oceans may remain relatively unchanged. By demonstrating that DMS emissions from geographically distinct regions may vary in response to OA, our results may facilitate a better understanding of Earth's future climate. Our study suggests that the way in which processes that generate DMS respond to OA may be regionally distinct and this should be taken into account in predicting future DMS emissions and their influence on Earth's climate

Limitation of dimethylsulfoniopropionate synthesis at high irradiance in natural phytoplankton communities of the Tropical Atlantic

Predictions of the ocean-atmosphere flux of dimethyl sulfide will be improved by understanding what controls seasonal and regional variations in dimethylsulfoniopropionate (DMSP) production. To investigate the influence of high levels of irradiance including ultraviolet radiation (UVR), on DMSP synthesis rates (μDMSP) and inorganic carbon fixation (μPOC) by natural phytoplankton communities, nine experiments were carried out at different locations in the low nutrient, high light environment of the northeastern Tropical Atlantic. Rates of μDMSP and μPOC were determined by measuring the incorporation of inorganic 13C into DMSP and particulate organic carbon. Based on measurements over discrete time intervals during the day, a unique μDMSP vs. irradiance (P vs. E) relationship was established. Comparison is made with the P vs. E relationship for μPOC, indicating that light saturation of μDMSP occurs at similar irradiance to μPOC and is closely coupled to carbon fixation on a diel basis. Photoinhibition during the middle of the day was exacerbated by exposure to UVR, causing an additional 55–60% inhibition of both μDMSP and μPOC at the highest light levels. In addition, decreased production of DMSP in response to UVR-induced photoxidative stress, contrasted with the increased net synthesis of photoprotective xanthophyll pigments. Together these results indicate that DMSP production by phytoplankton in the tropical ocean is not regulated in the short term by the necessity to control increasing photooxidative stress as irradiance increases during the day. The study provides new insight into the regulation of resource allocation into this biogeochemically important, multi-functional compatible solute

Intra-Firm and Inter-Firm Agglomeration: The Location Decisions of Multi-Unit Firms

abstract: Agglomeration research has investigated a key research question, i.e., why do firms in a specific industry co-locate geographically? In the agglomeration literature, it has been assumed that each firm has one business establishment in a cluster such that firms always co-locate with competitors. However, it is often observed that firms operate several business establishments in a cluster, so they co-locate not only with competitors (i.e., inter-firm agglomeration) but also with their own business establishments (i.e., intra-firm agglomeration). While inter-firm agglomeration is a counterpart to the traditional concept of agglomeration, intra-firm agglomeration is a new concept in agglomeration research. The separation between intra-firm and inter-firm agglomeration raises two research questions – 1) how does intra-firm agglomeration differ from inter-firm agglomeration? and 2) do firms decide their locations for intra-firm vs. inter-firm agglomeration differently? These questions actually extend the key question in agglomeration research into a new setting in which firms have several business establishments in a cluster. I proposed that firms can extract more benefits but neutralize more threats from agglomeration through intra-firm agglomeration than through inter-firm agglomeration. I further developed research hypotheses to test this argument in a research context in which multi-unit firms decide their new establishments’ distances to competitors and their other establishments at the same time. The hypotheses received empirical support in an empirical setting in which 10 large multi-unit hotel firms established new hotels in 20 U.S. cities, and several supplementary analyses show that these results are robust.Dissertation/ThesisDoctoral Dissertation Business Administration 201

Delayed reception of live blowfly (Calliphora vicina and Chrysomya rufifacies) larval samples: implications for minimum postmortem interval estimates.

Forensic entomology evidence collected by police and mortuary staff may be delayed in getting to the entomologist. Live samples may continue developing and alter minimum postmortem interval (PMImin) estimates. This study investigated development of simulated evidential samples of Calliphora vicina Robineau-Desvoidy and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) maggots. Maggots of each species were studied in three developmental classes: "small" (late second/early third instar), "mid" (mid third instar) and "large" (late third instar). Seven replicates of 11 maggots in each class were assigned without food to four treatments: (1) 24 h at 20 °C; (2) 24 h at 4 °C; (3) 48 h at 20 °C and (4) 48 h at 4 °C. There was a significant difference in absolute length change across treatments, reflecting size for C. vicina, and interaction between size, time and temperature for Ch. rufifacies. Calliphora vicina maggots showed minimal mortality, and most second instar larvae moulted by the experiment's end. Chrysomya rufifacies showed heavy mortality and minimal moulting from the second to third instar. Only "large" Ch. rufifacies maggots kept at room temperature for 48 h pupariated. Since these results confirm that development can continue in live unfed maggot samples after their collection, it is not advisable to delay their preservation

Female senior secondary physics students’ engagement in science: a qualitative study of constructive influences

Background: Prompted by fewer females compared to males enrolling in physics and advanced mathematics at both secondary and university levels, our research investigated the views and experiences of female students currently studying upper secondary school physics. We interviewed 18 female students about influences they considered important to their own science education, interest in science, and future science-related aspirations. Our purpose was to identify the experiences that these students most strongly associated with the generation and maintenance of their engagement in science, particularly represented in this research by their enrolment in upper secondary physics. Results: The research team used a systematic, iterative process to identify the main themes in the transcribed interview data. We identified the influence each girl reported as the strongest (ranked first). We also combined all influences that the participants had nominated, regardless of their ranking, to further examine all factors participants suggested as influential in their sustained engagement in school science (represented by their decision to study upper secondary physics). Systematic analysis of the interview data confirms that the influences on these females’ choices to study physics at upper secondary originate from a combination of their teachers, their school’s science culture, members of their family, the participants themselves and their peers. Conclusions: The interviews highlighted the idiographic complexities in understanding the wide range of important influences on these students studying physics at upper secondary school and their engagement in science. The unique contribution of this work is giving voice to the participants and reflecting on what these high achieving females have to say about the influential factors in their decisions to pursue science. Supportive teachers and the school science culture play essential roles, and other cultural and/or social factors such as family members and peers are identified as important. References to the culture and expectations of the school, family holidays, and conversations with siblings are support factors that seem to interact and overlap. At the same time, the importance of policy-amenable factors such as competent and caring science teachers, and science-supportive school cultures should be emphasised and encouraged

High-level production of violacein by the newly isolated Duganella violaceinigra str. NI28 and its impact on Staphylococcus aureus

A violacein-producing bacterial strain was isolated and identified as a relative of Duganella violaceinigra YIM 31327 based upon phylogenetic analyses using the 16S rRNA, gyrB and vioA gene sequences and a fatty acid methyl ester (FAME) analysis. This new strain was designated D. violaceinigra str. NI28. Although these two strains appear related based upon these analyses, the new isolate was phenotypically different from the type strain as it grew 25% faster on nutrient media and produced 45-fold more violacein. When compared with several other violacein producing strains, including Janthinobacterium lividum, D. violaceinigra str. NI28 was the best violacein producer. For instance, the crude violacein yield with D. violaceinigra str. NI28 was 6.0 mg/OD at 24 hours, a value that was more than two-fold higher than all the other strains. Finally, the antibacterial activity of D. violaceinigra str. NI28 crude violacein was assayed using several multidrug resistant Staphylococcus aureus. Addition of 30 mu M crude violacein led to a 96% loss in the initial S. aureus population while the minimum inhibitory concentration was 1.8 mu M. Consequently, this novel isolate represents a phenotypic variant of D. violaceinigra capable of producing much greater quantities of crude violacein, an antibiotic effective against multidrug resistant S. aureusopen

Plausible self-reported dietary intakes in a residential facility are not necessarily reliable

Background/Objectives: Comparing reported energy intakes with estimated energy requirements as multiples of basal metabolic rate (Ein:BMR) is an established method of identifying implausible food intake records. The present study aimed to examine the validity of self-reported food intakes believed to be plausible. Subjects/Methods: One hundred and eighty men and women were provided with all food and beverages for two consecutive days in a residential laboratory setting. Subjects self-reported their food and beverage intakes using the weighed food diary method (WDR). Investigators covertly measured subjects’ actual consumption over the same period. Subjects also reported intakes over four consecutive days at home. BMR was measured by indirect calorimetry. Results: Average reported energy intakes were significantly lower than actual intakes (11.2 and 11.8 MJ/d, respectively, P<0.001). Two-thirds (121) of the WDR were under-reported to varying degrees. Only five of these were considered as implausible using an Ein:BMR cut-off value of 1.03*BMR. Under-reporting of food and beverage intakes, as measured by the difference between reported and actual intake, was evident at all levels of Ein;BMR. Reported energy intakes were lower still (10.2 MJ/d) while subjects were at home. Conclusions: Under-recording of self-reported food intake records was extensive but very few under-reported food intake records were identified as implausible using energy intake to BMR ratios. Under-recording was evident at all levels of energy intake