N and C Isotope Variations Along an Extreme Eutrophication and Salinity Gradient in the Coorong Lagoon, South Australia

The Coorong Lagoon is a unique hydrological and depositional system at the terminus of the Murray–Darling Basin, the largest river system in Australia. It exhibits large salinity, nutrient, and organic matter gradients, providing a modern analogue to study and validate the use of δ15N and δ13C as tracers of past and contemporary geochemical cycles in estuarine environments. To this end, water and surface sediment samples were analyzed for particulate organic nitrogen (PON) and carbon (POC) concentrations, and the respective δ15N and δ13C signatures of particulate nitrogen and carbon. PON and POC exhibited positive relationships to chlorophyll-a, indicating the dominance of phytoplankton production upon suspended organic matter. There was also a general trend of increasing δ15N of PON (δ15NPON) values and decreasing δ13C of particulate carbon (δ13CPC) values with increasing salinity and eutrophication in the restricted South Lagoon. In a multiple linear regression for δ15NPON, the best two predictors in combination are PON and C:N molar ratio, highlighting the importance of productivity and the type or source of organic matter. For δ13CPC, the best two predictors are total dissolved phosphorus and latitude, suggesting influences from productivity and proximity to the ocean. Sediment δ15N values across the Coorong Lagoon overlap with the δ15NPON in the water column, suggesting that PON derived from algal material represents the main source of nitrogen to lagoon sediments. We hypothesize that limited N loss via denitrification leads to PON being recycled almost exclusively to ammonium, due to low rates of nitrification and dominance of dissimilatory nitrate reduction to ammonium (DNRA). We propose that preferential volatilization of 14N in ammonia increases the δ15N of ammonium assimilated by phytoplankton, thereby increasing the δ15N within suspended organic matter and surface sediment in the South Lagoon. By contrast, the gradient exhibited in δ13CPC data was countered by a relatively constant sedimentary organic carbon δ13C. Data from the Coorong, therefore, suggest that δ15N values in sediments can be used to infer palaeoproductivity in this hypereutrophic and hypersaline depositional environment, however, the measured δ13CPC may be influenced by δ13CDIC or preferential loss of 13C during sedimentation that alter the sedimentary δ13C record of organic carbon.Stacey C. Priestley, Jonathan Tyler, Savannah R. Liebelt, Luke M. Mosley, Wei Wen Wong, Yuexiao Shao, Zara Woolston, Mark Farrell, David T. Welsh, Justin D. Brookes, Alan S. Collins, Chris Keneally, and Juraj Farka

School-Based Programs to Reduce Bullying and Victimization

School bullying has serious short-term and long-term effects on children’s physical and mental health. Various anti-bullying programs have been implemented world wide and, more rarely, evaluated. Previous narrative reviews, summarizing the work done on bullying prevention, as well as previous meta-analyses of anti-bullying programs, are limited. The definition of school bullying includes several key elements: physical, verbal, or psychological attack or intimidation that is intended to cause fear, distress, or harm to the victim; an imbalance of power (psychological or physical), with a more powerful child (or children) oppressing less powerful ones; and repeated incidents between the same children over a prolonged period. School bullying can occur in school or on the way to or from school. It is not bullying when two persons of the same strength (physical, psychological, or verbal) victimize each other. This report presents a systematic review and meta-analysis of the effectiveness of programs designed to reduce school bullying perpetration and victimization (i.e. being bullied). The authors indicate the pitfalls of previous reviews and explain in detail how the present systematic review and meta-analysis addresses the gaps in the existing literature on bullying prevention

Hypoxic Pulmonary Vasoconstriction in Humans:Tale or Myth

Hypoxic Pulmonary vasoconstriction (HPV) describes the physiological adaptive process of lungs to preserves systemic oxygenation. It has clinical implications in the development of pulmonary hypertension which impacts on outcomes of patients undergoing cardiothoracic surgery. This review examines both acute and chronic hypoxic vasoconstriction focusing on the distinct clinical implications and highlights the role of calcium and mitochondria in acute versus the role of reactive oxygen species and Rho GTPases in chronic HPV. Furthermore it identifies gaps of knowledge and need for further research in humans to clearly define this phenomenon and the underlying mechanism

The role of compatible solutes in the adaptation and survival of Escherichia coli

SIGLEAvailable from British Library Document Supply Centre-DSC:D195104 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Bacterial nitrification activity directly associated with isolated benthic marine animals.

Potential nitrification rates (PNR) directly associated with isolated marine macrobenthic invertebrates were measured for a range of benthic epifaunal and infaunal species (bivalves, gastropods, polychaetes and crustaceans) collected from the Sacca di Goro, Po River delta, Italy. In the case of the filter-feeding bivalves, Tapes philippinarum and Mytilus galloprovicialis the PNR associated with the shell surfaces and dissected animal tissues (gills, siphons and residual tissue) were determined separately, in order to assess the distribution of the nitrifier populations. Significant PNR was found associated with all the tested macrofaunal species with activities ranging between 12 and 2,250 nmol ind.)1 day)1 and specific activities between 150 and 18,400 nmol g)1 dry weight day)1. However, no simple relationships were observed between PNR and the animals taxonomic or functional group, or with animal comportment (infaunal or epifaunal) or size class, indicating that more complex interactions may regulate the degree of colonisation of the animals by nitrifier populations. Incubations of shells alone and dissected tissues of the bivalves T. philippinarum and M. galloprovicialis demonstrated that approximately 50% of the total PNR activity was associated with the shell surfaces and 50% with the internal animal tissues, with the highest specific activities of 950 and 1,970 nmol g)1 dry weight day)1 determined for the gills of T. philippinarum and M. galloprovicialis, respectively. Thus, specific relationships may exist between the nitrifiers and their animal hosts. Overall, our data indicate that the macrofaunal stimulation of nitrification and/or coupled nitrification–denitrification observed in previous studies may not be solely due to the animals burrow walls serving as sites for nitrification, but also to the fact that the internal and external surfaces of the animals themselves are also colonised by nitrifying bacteria. Tentative calculations based on reported animal densities in the Sacca di Goro and the determined PNRs indicate that animal-associated nitrifier populations could contribute significantly to overall nitrification rates in situ, although further experiments are required to determine to what extent the potential rates measured in this study are realised under in situ conditions

Utilization of the compatible solutes sucrose and trehalose by purple sulfur and nonsulfur bacteria

International audienceOwing to their ubiquity as compatible solutes, sucrose and trehalose and their constituent monosaccharides, glucose and fructose, may represent a significant source of carbon for the growth of other bacteria. We investigated sugar utilization by 34 strains of purple sulfur and nonsulfur bacteria isolated from coastal lagoons. Amongst the purple nonsulfur bacteria, sugar utilization was common with almost all strains utilizing the tested monosaccharides and 70 and 50% of strains utilizing sucrose and trehalose, respectively. Sugar utilization was rarer amongst the purple sulfur bacteria, with none of the strains using glucose or trehalose. Fructose, was utilized by 50% of isolates and sucrose was utilized only by strains of Thiorhodococcus. Surprisingly, although unable to use glucose directly, Thiorhodococcus strains used both the glucose and fructose moieties of sucrose and utilized glucose slowly in the presence of fructose, indicating that these strains may be impaired in glucose transport, rather than glucose metabolism per se. Disaccharide metabolism was dependent on sugar uptake and none of the strains produced trehalases or sucrases. Efficacy of sugar utilization varied widely with specific growth yield between 0.09 and 0.78 g dry weight·g sugar-1, and was dependent upon both the sugar and the strain. Similarly, specific growth rates were highly variable with strain and the sugar present and ranged between 5.4 and 0.5 x 10-2·h-1. Overall, data indicate that in natural high salinity ecosystems, purple sulfur and particularly purple nonsulfur bacteria may be able to efficiently exploit compatible solutes released to the environment by other members of the bacterial community