Whole-mount in situ TUNEL method revealed ectopic pattern of apoptosis in cadmium treated naupliar larvae of barnacle (Balanus amphitrite Darwin)

The effect of cadmium on stage II naupliar larvae of barnacle (Balanus amphitrite Darwin) was investigated. Barnacle larvae were exposed to 0-15 microM CdCl(2) for 24 h. Apoptotic cells were stained by the terminal deoxyribonucleotidyl transferase mediated dUTP nick end labelling (TUNEL) method. Incidence of apoptosis, as measured by numbers of animals with ectopic pattern of apoptosis as well as numbers of apoptotic cells per animal, was assessed using confocal microscopy. An increase in incidence of apoptosis was observed in the experimental animals with an increase in cadmium concentration. Mortality increased, and motility decreased, when barnacle larvae were exposed to an increasing concentration of cadmium. The relationship between the occurrence of apoptosis and swimming behaviour was investigated in larvae exposed to 10 microM CdCl(2). Significant increases in apoptosis were detected in the non-motile and dead nauplii. This study suggested that whole-mount in situ TUNEL method may be used to study increased occurrence of apoptotic cells in crustacean larvae.     

Why Poor Logging Practices Persist in the Tropics

Abstract: Despite abundant evidence that both the environmental damage and the financial costs of logging can be reduced substantially by training workers, pre-planning skid trails, practicing directional felling, and carrying out a variety of other well-known forestry practices, destructive logging is still common in the tropics. Based on our collective experience with loggers in tropical forests, we discuss seven possible reasons for this seemingly irrational behavior. The principal reason poor logging practices persist is apparently that the widely heralded cost savings associated with reduced-impact logging relative to unplanned logging by untrained crews may not be realized under some conditions. In particular, where compliance with logging guidelines restricts access to steep slopes or prohibits ground-based timber yarding on wet ground, reduced-impact logging may be synonymous with reduced-income logging. Given that under such conditions loggers may not adopt reduced-impact logging methods out of self-interest, fiscal mechanisms for promoting sustainable forest management may be needed.     

Effects of zooplankton diel vertical migration on a phytoplankton community: A scenario analysis of the underlying mechanisms

A mechanistic model was applied to study the influence of diurnal vertical migration (DVM) of planktonic crustaceans on the succession and composition of the phytoplankton community. While zooplankton was restricted to only one functional group, the phytoplankton community was divided into two functional groups which are distinguished by their maximum growth rates and vulnerability to zooplankton grazing. DVM causes a pulsed grazing regime and may also entail a corresponding reduction of the cumulative daily rates of ingestion and losses of zooplankton. To study the relative importance of these two mechanisms of DVM to phytoplankton we performed a scenario analysis consisting of 5 different scenarios. The results show that DVM has a strong influence on the phytoplankton community. Well edible algae benefit during the first 3–4 weeks of summer stratification by reduced daily grazing. The typical shift from small, well edible algae to larger, poorly or non-edible phytoplankton is distinctly delayed. Under the assumption of unchanged daily grazing, however, a pulsed grazing regime has nearly no influence on the resulting phytoplankton composition. As similar effects are also found for completely non-edible phytoplankton, indirect effects via phosphorus availability must be assumed. Thus, the scenario analysis reveals that the observed effects of DVM on phytoplankton can be explained by a combination of two mechanisms: (1) reduction of the daily zooplankton grazing, and (2) changed assimilation and remineralisation of phosphorus. Surprisingly and in contradiction to earlier reports there is almost no DVM effect on phytoplankton due to the sole action of a pulsed grazing regime.     

Darstellung maskierter Nutzungseffekte auf naturraumspezifische Artengemeinschaften grasiger Feldraine mithilfe von Restvarianzmustern

Background and aim Grassy field margins have a high relevance in agricultural landscapes regarding the preservation of typical arthropod communities, their biodiversity and the ecological system functions linked with it. The structure of terrestrial communities is affected by anthropogenic impairment, which can lead to the replacement of sensitive by more tolerant species. The negative influence of pesticides on fauna and flora as well as the associated functional aspects (ecological system functions) and the reduction of biodiversity are undisputed since longer for agrarian systems and can also be assumed for grassy field margins due to spray-drift. The case study presented here examined the effect of influences related to utilization on the plant and arthropod communities of grassy field margins. Reference sites, on which due to missing farming in the direct surrounding countryside no utilization influences on the communities were present, were compared to non-target sites, on which these influences could not be excluded. Sites in three German macrochores were examined: in the Jülicher Börde, at the northeastern edge of the Leipziger low lands and in the area Mainfranken near Würzburg, all of them intensely used agricultural landscapes. Beside the vegetation, the epigeic arthropod communities of carabid beetles, spiders, springtails, hymenopterans, hover flies and ladybirds as well as abiotic parameters were included in the analysis. The aim of the study was the development of a statistical exclusion procedure which is capable to quantify the amount of variation in field community data which can be attributed to isolated factors. Special attention was paid to non-observable utilization impacts like undocumented pesticide application. The extraction of patterns of residual variance allowed for the uncovering of masked effects on a scale below the obvious abundance pattern. Materials and methods The variability in the species composition was visualized with the help of non-metric multi-dimensional scaling (NMDS). Indicator species analysis revealed those species which could be recognized as statistically significant indicators for local conditions. The relationship between the species composition and the environmental factors was statistically modeled by canonical correspondence analysis. By variance partitioning it was possible to extract the variance portion which could be bound to a set of covariables. For the remaining residual variance it could not be excluded that this resulted from a pesticide influence. Results The analyses based on the ecological distance (Bray-Curtis) showed that the communities in references sites and non-target sites could be clearly distinguished in all three landscapes. Based on the portions of variance which could be explained statistically by a utilization related influence, two different directions of reaction to the utilization related variables could be stated. On the one hand there were sensitive species, showing reduced abundances in the non-target sites, on the other hand there were species increasing in abundance in the non-target sites, recruiting from the group of strong competitors. Discussion By the use of residual variances a clear influence of utilization related parameters on the community of soil arthropods and vegetation could be shown. The observed abundances shifts between reference sites and non-target sites in the raw data were attributed to a multi-dimensional factor complex which could be split up by the use of partial ordination methods, quantifying the relationships to the utilization related parameters. It was demonstrated that special utilization correlated patterns could be found in the raw data after eliminating the influence of the covariables. Conclusions Utilization related influences in the non-target sites evened out the characteristic communities for the three landscapes towards a comprehensive, ubiquitous species composition. The hypothesis of decreasing abundance of sensitive species and the augmentation of tolerant species due to a potential pesticide influence could be underpinned and quantified. Sensitive species which showed a significant reduction in abundance between reference and non-target sites showed a much higher sensitivity to the influences and thus were assigned a higher indicator potential than tolerant species. From the group of the sensitive species Pardosa palustris and Poecilus cupreus could be isolated as two promising macrochore-specific indicator species for the masked effects. Recommendations and perspectives A macrochore-specific assessment of utilization effects was requested for future studies due to the different sensitivities of the species in the three landscapes. The elaboration and specifying of reference conditions for terrestrial agrarian systems is an important task for the future. The presented approach deduces a macrochore-specific, complex effect pattern of anthropogenic impairment on terrestrial species communities. It can be used to extract masked effects and by this facilitates a more sustainable use of e.g. plant protection products. Furthermore it provides an opportunity to validate evaluation systems for the effects of utilization impacts on terrestrial vegetation and arthropods. Additionally the species sensitivities with respect to the macrochores allow a regionalized assessment of ecotoxicological effects and the integration into spatially explicit effect assessment models.     

Modelling of dust lifting process behind propagating shock wave

Dust dispersion from a layer is a complicated problem, which has not been completely solved yet, especially if an Eulerian–Eulerian approach has to be used to model the two-phase dusty flow. In previous investigation, a phenomenological model of the dust dispersion process from a layer was developed, but the evaluation of the model revealed some weaknesses. In the current paper, the model of the dust dispersion process was presented and three improvements of the model were studied: Saffman force, Magnus force and particles collisions. The implementation of Magnus and Saffman forces into the code did not improve the numerical results and it was shown that it had very little influence on the dust lifting process, in case the phenomenological model of the layer is used. Some explanations were proposed in the paper. Besides, an empirical model of particles collisions was also added to the code and its influence on the results was studied. It was shown that the particles collisions model improved the obtained results, but further modifications are to be studied in the future.