Evaluating the performance of benthic multi-metric indices across broad-scale environmental gradients

The usefulness of benthic multi-metric indices when assessing seafloor integrity across broad environmental gradients should be deliberated, as their lack of transparency might hide important sources of variation and fail to identify environmental change. This study compares the performance of two multi-metric indices; the Benthic Quality Index (BQI) and the Brackish water Benthic Index (BBI) between three sub-basins in the Baltic Sea. Both indices reflect the salinity-driven gradient in macroinvertebrate diversity and composition as well as changes in bottom water oxygen concentrations. The relative contribution of predictor variables for explaining index variation does, however, differ between sub-basins, resulting in the indices representing different aspects of the benthic community along the environmental gradient. This context-dependency is caused by inherent differences in benthic community characteristics between the sub-basins of the Baltic Sea, and how the communities are portrayed by the indices. An increased transparency of the importance of the different predictors for directing index values is needed for coherent classifications over broad environmental gradients, such as those occurring in large estuarine water bodies. Use of a weight of evidence table to combine multiple indicators would preserve transparency and be more likely to provide a robust assessment method that would detect seafloor degradation at an early stage.     

Thermosensitive respiratory deficiency in yeast associated with specific effects on particulate cytochrome oxidase.

A mutant of Saccharomyces cerevisiae, unable to grow at the expense of non fermentable carbon sources at 37 degrees C, has been selected; at 25 degrees C the mutant strain behaves like the parental wild strain. Evaluations of respiration rates during aerobic growth at restrictive temperature on one hand, enzymatic and/or spectral evaluations of the individual components of the respiratory chain on the other hand show that the respiratory deficiency is specifically correlated with a reduced level of cytochrome oxidase. The decrease of enzyme activity is the direct consequence of a lowering of hemoprotein (a,a3) concentration. Temperature-activity relationship of cytochrome oxidase elaborated at the permissive temperature by the mutant strain is modified as far as the particulate enzyme is concerned, but no difference is observed after partial solubilization of the enzyme by non ionic surfactant. Genetic analysis shows that the mutant phenotype results from a nuclear gene mutation.     

Responses of aquatic macrophyte assemblages to nutrient enrichment in a lowland river basin of western Greece

Abstract

In Greece, as in many other Mediterranean countries, there is a lack of information enabling the use of aquatic macrophytes as biological indicators of the water trophic status. This research aimed to investigate the trophic preferences of the aquatic macrophyte assemblages encountered in selected standing water bodies of a lowland river basin of western Greece. It also aimed to assess the response of the macrophyte species that occur in the studied water bodies to different nutrient concentrations. A total of 56 macrophyte species were identified. TWINSPAN analysis distinguished four main vegetation groups potentially related to three trophic types. The Trophic Ranking Score developed in the UK was applied in order to investigate the trend in aquatic macrophytes in response to the different trophic conditions. The results indicated that TRS_UK was not in accordance to the water trophic indices. After the addition of 14 new species and the re-scoring of the plants from the UK list, the re-calculation of TRS enabled a better classification of the trophic status convergent with the information from the water trophic indices. The current study constitutes a reference document providing basic information, and must be improved by updating the plant list with new data from other sites.     

Cytoplasmic free calcium concentration in porcine platelets: Regulation by an intracellular nonmitochondrial calcium pump and increase after thrombin stimulation

Mechanisms are assumed to exist in the resting platelet which maintain the concentration of cytoplasmic free calcium below that level required to activate cellular responses. To assess such processes the porcine platelet plasma membrane was selectively lysed with digitonin and the uptake (or flux) of free calcium monitored by an extracellular calcium electrode. Lysis resulted in an immediate lowering of the extracellular free calcium, due to the action of intracellular organelle(s) acting on the extracellular space through the permeabilized plasma membrane. In resting platelets, the rate of calcium uptake was first order with respect to the extracellular prelytic calcium concentration, and hence the cytoplasmic free concentration was found to be 1·10^?7 M by extrapolation to a point of zero flux (i.e., the null point). This approach could not be used with thrombin-stimulated platelets, as external calcium was required for both secretion of ATP + ADP and aggregation. Nevertheless, evidence for an increase in cytoplasmic free calcium after thromin stimulation was obtained. Metabolic inhibitors and agents known to inhibit calcium uptake by mitochondria had no effect on the calcium flux following lysis, indicating different mechanisms for calcium homeostasis in the platelet when compared with other cell types (e.g., liver). Levels of ionophore A23187, which caused platelet aggregation, gave a massive release of the nonmitochondrial pool of calcium into the cytoplasmic space. Thus, in porcine platelets an intracellular energy-requiring calcium pump, which sequesters calcium in a nonmitochondrial membranous compartment, is crucial for intracellular calcium homeostasis.     

Habitat degradation and trout stocking can reinforce the impact of flash floods on headwater specialist Alpine bullhead Cottus poecilopus – A case study from the Carpathian Mountains

In freshwater streams, flooding is a typical source of natural disturbance that plays a key role in the dynamics of animal populations and communities. However, habitat degradation and fish stocking might increase the severity of its impact. We tested the effects of a flash flood on the abundance of three size classes of headwater dwelling Alpine bullhead, Cottus poecilopus, in the streams of the Carpathian Mountains in the Czech Republic, that are stocked with hatchery‐reared brown trout, Salmo trutta. We showed that the overall abundance of Alpine bullhead was highest at the sites with the least degraded habitat (i.e., natural habitat) and we caught almost no Alpine bullhead at the sites with the most degraded habitat. The flash flood had a strong negative effect on the abundance of the largest individuals of Alpine bullhead. Abundance of small and medium size Alpine bullhead was negatively affected by the abundance of adult stocked brown trout before as well as after the flash flood. However, negative effect of adult brown trout abundance on abundance of large Alpine bullhead was not significant before the flash flood, and it became significant after the flash flood. This could indicate an accumulation of negative impacts of trout stocking and flash flood on this size class. Overall, our results suggest that stocking of hatchery trout and habitat degradation can reinforce the impact of flash floods on the population of Alpine bullhead in the streams of the Carpathian Mountains.     

Occupational exposure to electromagnetic fields. The situation in Greece

PurposeThe management of the occupational exposure to electromagnetic fields (EMF), an Occupational Health and Safety (OHS) issue of great scientific, social and economic significance, was under intense negotiations at European level over the last twenty years; the Directive 2013/35/EU is the new legislative tool. The presented study deals with the practical aspects of the Directive’s implementation.MethodsThe appropriate, extensive measurements and the overall EMF exposure assessments (i.e. exposure mapping, identification of hot spots, proposition of solutions) were conducted in specific workplaces, including power production, railway, broadcasting, clinical Magnetic Resonance Imaging (MRI) systems, industrial and research sites, as well as common office workplaces.ResultsThe vast majority of the performed EMF assessments did not reveal occupational overexposures; moreover in most of the cases, even the general public exposure limits (in the above occupational areas) were not exceeded. The very few localized overexposures detected, were manageable on the basis of the technical and organizational OHS principles.On the contrary, the maintenance procedures of the EMF emitting equipment, as recorded in this survey, presented overexposures revealing a challenging field.ConclusionsThis study lays a firm basis for the clarification of the occupational EMF environment, where potential exposures might be high. The proper risk assessment demands precise exposure identification and deep understanding of the EMF nature and hazards. Misconceptions range from the common exposure overestimation to the rarer case of the maintenance hazards underestimation, while attention is needed concerning the proper application of the complex limiting system of the Directive.     

Protein kinase C and calmodulin effects on the plasma membrane Ca2+-ATPase from excitable and nonexcitable cells

We have purified Ca2+-ATPase from synaptosomal membranes (SM)1 from ratcerebellum by calmodulin affinity chromatography. The enzyme was identifiedas plasma membrane Ca2+-ATPase by its interaction with calmodulin andmonoclonal antibodies produced against red blood cell (RBC) Ca2+-ATPase, andby thapsigargin insensitivity. The purpose of the study was to establishwhether two regulators of the RBC Ca2+-ATPase, calmodulin and protein kinaseC (PKC), affect the Ca2+-ATPase isolated from excitable cells and whethertheir effects are comparable to those on the RBC Ca2+-ATPase. We found thatcalmodulin and PKC activated both enzymes. There were significantquantitative differences in the phosphorylation and activation of the SMversus RBC Ca2+-ATPase. The steady-state Ca2+-ATPase activity of SMCa2+-ATPase was approximately 3 fold lower and significantly less stimulatedby calmodulin. The initial rate of PKC catalyzed phosphorylation (in thepresence of 12-myristate 13-acetate phorbol) was approximately two timesslower for SM enzyme. While phosphorylation of RBC Ca2+-ATPase approachedmaximum level at around 5 min, comparable level of phosphorylation of SMCa2+-ATPase was observed only after 30 min. The PKC-catalyzedphosphorylation resulted in a statistically significant increase inCa2+-ATPase activity of up to 20-40%, higher in the SM Ca2+-ATPase.The differences may be associated with diversities in Ca2+-ATPase functionin erythrocytes and neuronal cells and different isoforms composition.