Plant communities in relation to flooding and soil contamination in a lowland Rhine River floodplain

Using canonical correspondence analysis (CCA), relationships were investigated between plant species composition and flooding characteristics, heavy metal contamination and soil properties in a lowland floodplain of the Rhine River. Floodplain elevation and yearly average flooding duration turned out to be more important for explaining variation in plant species composition than soil heavy metal contamination. Nevertheless, plant species richness and diversity showed a significant decrease with the level of contamination. As single heavy metal concentrations seemed mostly too low for causing phytotoxic effects in plants, this trend is possibly explained by additive effects of multiple contaminants or by the concomitant influences of contamination and non-chemical stressors like flooding. These results suggest that impacts of soil contamination on plants in floodplains could be larger than expected from mere soil concentrations. In general, these findings emphasize the relevance of analyzing effects of toxic substances in concert with the effects of other relevant stressors.     

Availability of copper from phytoplankton and water for the bivalveMacoma balthica. II. Uptake and elimination from64Cu-labelled diatoms and water

The amount of copper taken up via algae and water byMacoma balthica from the Oosterschelde sea arm, S.W. Netherlands, was established using the radioisotope⁶⁴Cu. As far as we know, this isotope has never been used before in marine flod chain studies. As a model food source the marine diatomPhaeodactylum tricornutum was allowed to accumulate⁶⁴Cu for 1 d. These labelled algae were fed to the clams in the presence of the complexing agent EDTA (0.27mM). EDTA was added to prevent uptake of dissolved⁶⁴Cu that could be leaking from the labelled diatoms. In control experiments, unlabelled diatoms were fed toM. balthica in the presence of dissolved⁶⁴Cu (with and without EDTA) in order to assure a similar filtration activity. In repeated experiments with varying particulate/dissolved copper ratios, uptake through food always turned out to be at least as efficient as uptake from the water. It was concluded that Cu, associated with food, is well available for uptake byM. balthica.     

Spawning behaviour and sex hormone levels in adult and precocious brown trout (Salmo trutta L.) males and the effect of anosmia

Summary. In the present experiment the behaviour and endocrine status of males of the brown trout, Salmo trutta L., (Salmoniformes: Salmonidae) were studied when males were kept in a stream tank with a nest digging female. Groups of mature adult males and precocious intact or anosmic male parr were placed with the nesting female so that the group resembled a natural spawning situation with big anadromous fish acting as dominant males and precocious parr acting as “sneakers”. A control experiment was also run with only males without a female present. In intact parr there were significant positive correlations between the per cent of the total observation time spent with a female, milt volume, and plasma concentration of 17α, 20β-dihydroxy-4-pregnen-3-one. Anosmic parr had significantly lower volumes of strippable milt and gonadal steroid hormone levels compared with intact parr. However, no differences were found in the control experiment. Significantly fewer anosmic parr attended and courted the nesting female and those anosmic fish that attended the female had significantly lower plasma levels of gonadal hormones. Intact parr also displayed a greater number of agonistic acts against other parr without any difference in fighting ability. No differences in aggression occured in the control experiment. In adult males together with a female, post-experimental gonadal steroid hormone levels were higher than pre-experimental levels. Positive correlations between aggression and androgen hormone levels were observed in adult males. No differences in plasma hormone levels were observed between adult males and intact precocious males. The results show that olfactory occlusion results in low steroid hormone levels and milt volumes in precocious males placed in a spawning situation. The courting behaviour was also affected by anosmia. Odours from the nesting female may have caused the enhanced plasma hormone levels and stimulated the males to attend the female. Received 15 May 1997; accepted 29 June 1997.     

Testing sustainability by prospective and retrospective demographic analyses: evaluation for palm leaf harvest.

Harvesting nontimber forest products (NTFPs) is a major economic activity in tropical forests. As many NTFPs are overexploited, sustainability analyses are required to set harvest guidelines. Here we introduce and apply a new approach to evaluating sustainability, which combines prospective (elasticity) and retrospective (Life Table Response Experiments [LTRE]) demographic analyses of matrix population models. We relate the elasticity of vital rates (representing their importance for population growth rate, lamda) to their contribution to harvest-induced change in lamda ("LTRE contribution"). When high-elasticity vital rates have a low LTRE contribution, exploitation is potentially sustainable as negative effects for population growth are buffered. If the reverse is found, there is little scope for sustainability because crucial vital rates are affected. Our approach is less sensitive to chance fluctuations than the commonly used sustainability criterion of lamda = 1.0, as it does not depend on the absolute value of lamda. We applied this analysis to Geonoma deversa, a clustered forest understory palm. We studied three experimentally defoliated and control populations in a Bolivian rainforest during two years. Cutting all leaves of large ramets did not change mortality but strongly affected growth and reproduction. In spite of severe changes in some vital rates, population growth rate was not significantly reduced after defoliation. A literature review revealed that six other understory palms species responded very similarly to defoliation. The combination of LTRE contributions and elasticity analyses showed that low-elasticity vital rates were mainly responsible for the defoliation-induced change in lamda for Geonoma deversa. For two other understory palms (Astrocaryum mexicanum and Chamaedorea radicalis) new demographic analyses yielded very similar results. For Geonoma, the LTRE contribution-elasticity relation strongly changed when we mimicked harvest damage. Adding 5% mortality to defoliated palms caused stronger change in lamda, mainly due to changes in a high-elasticity vital rate (survival). Therefore, harvest practices that involve stem killing are clearly unsustainable. Our results show that commercial leaf cutting in Geonoma deversa is potentially sustainable, and that this is likely the case for understory palms in general. Our approach to evaluating harvest sustainability can be applied to other NTFPs.     

Availability of copper from phytoplankton and water for the bivalveMacoma balthica. I. Separation of uptake pathways using the radiotracer64Cu

To study the role of food in Cu accumulation by bivalves, algae spiked with Cu can be used. With spiked algae, however, redistribution of Cu between the disolved solved and the particulate phase hampers the assessment of the contribution of food. This occurred in efforts to label algae with the radiotracer⁶⁴Cu. A method was designed to overcome this problem of redistribution. By adding excess EDTA to seawater, the biological availability of dissolved Cu was minimized. The effectiveness of complexation by EDTA was controlled through adsorption onMacoma balthica shells and uptake inM. balthica tissue.Communication number 644 of the Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands     

Consumer Attitudes Towards the Development of Animal-Friendly Husbandry Systems

Recent policy developments in the area of livestock husbandry have suggested that, from the perspective of optimizing animal welfare, new animal husbandry systems should be developed that provide opportunities for livestock animals to be raised in environments where they are permitted to engage in “natural behavior.” It is not known whether consumers regard animal husbandry issues as important, and whether they differentiate between animal husbandry and other animal welfare issues. The responsibility for the development of such systems is allocated jointly between farmers, regulators, different actors in the food chain, and consumers. This research focuses on understanding consumer attitudes and preferences regarding the development and introduction of such systems, to ensure that they are acceptable to consumers as well as producers, regulators, and scientists. Consumer perceptions of animal welfare and animal husbandry practices were evaluated using quantitative consumer survey, which focused on two animal husbandry issues – farmed pigs and farmed fish. Following pilot work, 1000 representative Dutch consumers were sampled about their attitudes to either pig or fish husbandry. The results indicated that consumers think about animal welfare in terms of two broad categories related to their health and living environment, but do not think about welfare issues at a more detailed level. Greater concern was expressed about the welfare of pigs compared to fish. Consumer trust in labeling also emerged as an important issue, since consumers need to trust different food chain actors with responsibility for promoting animal welfare, and are reluctant to consider the details of animal husbandry systems. As a consequence, a transparent, enforceable, and traceable monitoring system for animal welfare friendly products is likely to be important for consumers.     

Sensitivity of characteristic riverine insects, the caddisfly Cyrnus trimaculatus and the mayfly Ephoron virgo, to copper and diazinon

This study reports the effects of two model toxicants, copper and diazinon, on two characteristic riverine insect species, the caddisfly Cyrnus trimaculatus and the mayfly Ephoron virgo. It was demonstrated that these species are very sensitive to both compounds in comparison with aquatic insects traditionally used in ecotoxicity tests. For diazinon, the 96-h LC(50) value of Cyrnus trimaculatus (1.1 microg/l) is lower than for any other insect species known from the literature and for copper it was demonstrated that Ephoron virgo is among the most sensitive aquatic insect species. The observed low LC(50) values stress the importance of using these indigenous species in assessing the risk of environmental contaminants in large European rivers and in defining conditions for ecological recovery.     

Understanding “communication gaps” among personnel in high-risk workplaces from a dialogical perspective

Our primary aim in this paper is to argue for a discourse analytical take on questions of how risk and safety are managed by personnel in high-risk workplaces, with a special focus on constructions of “us” and “them”. Thus, we approach the same issue investigated in many other studies, i.e., diverging safety-related understandings between people representing various occupational groups. We choose to examine so-called communication gaps as they are “talked into being” in discourse, meaning that we treat them as primarily socially constructed. A case analysis based on interviews will be used to illustrate how we can understand this phenomenon from a communicative perspective inspired by Linell’s (1998a) dialogue theory. While previous discourse and safety culture research emphasizes broad patterns and differences between entire professions and departments, we argue that researchers should hesitate to reinforce the notion of homogeneous groups. Instead, there is great value in demonstrating collective social construction processes and commonalities so as to facilitate inter-group solidarity and possibly productive change.     

Deltas,freshwater discharge,and waves along the Young Sound,NE Greenland

A wide range of delta morphologies occurs along the fringes of the Young Sound in Northeast Greenland due to spatial heterogeneity of delta regimes. In general, the delta regime is related to catchment and basin characteristics (geology, topography, drainage pattern, sediment availability, and bathymetry), fluvial discharges and associated sediment load, and processes by waves and currents. Main factors steering the Arctic fluvial discharges into the Young Sound are the snow and ice melt and precipitation in the catchment, and extreme events like glacier lake outburst floods (GLOFs). Waves are subordinate and only rework fringes of the delta plain forming sandy bars if the exposure and fetch are optimal. Spatial gradients and variability in driving forces (snow and precipitation) and catchment characteristics (amount of glacier coverage, sediment characteristics) as well as the strong and local influence of GLOFs in a specific catchment impede a simple upscaling of sediment fluxes from individual catchments toward a total sediment flux into the Young Sound.