Effects of access to preen gland secretions on mallard plumage

Preen glands exist in almost every bird species and several non-exclusive functions have been proposed for this gland and the oils that it produces. One function generally admitted is that the oily secretions of the preen gland would provide a waterproofing layer when spread over feathers. Alternatively, several authors have proposed that plumage waterproofness is mostly due to the spatial micro-structure of feathers. The purpose of this study was to examine, by manipulating the access to the preen gland, the effect of the preen oil on the plumage waterproofness and condition. To explore this question, we carried out two independent experiments where we temporarily blocked access to the preen gland secretions with a removable mechanism in one group of captive mallards (Anas platyrhynchos), whilst a second group of birds had access to gland secretions. In a long-term experiment (3 months of treatment) and a short-term experiment (10 days), we measured plumage water retention and condition. After 3 months without access to preen glands, we found a significant decrease of plumage condition and an associated increase in plumage water retention. Moreover, we found a significant correlation between plumage condition and water retention ability. In contrast, after 10 days of treatment, no significant effect was found on plumage condition and water retention. Our study shows that preen oil acts to maintain plumage condition and suggests that feather microstructure is essential to maintain plumage waterproofness.     

Implementing comprehensive plans: indicators for a task-sheet based performance evaluation process

Evaluation in spatial planning aims to raise effectiveness of plans as well as efficiency in planning processes. Given that research regarding evaluation of performance and especially plan implementation is sparse, this study presents a minimal set of indicators for a task-sheet based performance evaluation approach for Swiss cantonal comprehensive plans. Thematic task-sheets are a promising characteristic of cantonal comprehensive plans. They translate the comprehensive planning strategy into concrete evaluable tasks. The presented indicators allow assessing procedural efficiency of coordination and implementation of planning tasks (performance). We argue that if task-sheets comply with certain plan quality characteristics, a task-sheet based performance evaluation approach can support the effectiveness of plans and promote the objectives of the planning strategy. We point out plan content and characteristics necessary for effective execution of our approach. As a result, our findings can serve as a framework for designing evaluation processes for comprehensive planning documents beyond Switzerland.     

Aufnahmepfade von POPs in Biota

POPs (persistent organic pollutants) associated with aquatic sediments can pose a risk to aquatic food chains, since they can be re-introduced to the food web. One major pathway is the bioaccumulation of POPs by endobenthic, sedimentingesting invertebrates (especially tubificid oligochaetes). These worms serve as food for benthivorous fish, which thereby ingest the sediment-borne chemicals and may accumulate contaminant concentrations far higher than from water exposure alone, and consequently transfer them to organisms of higher trophic levels. In order to evaluate such a potential biomagnification, a laboratory test was developed. It consisted of a two-step food chain including the sediment dwelling freshwater oligochaete Tubifex tubifex (Müller) and the three-spined stickleback (Gasterosteus aculeatus, Linné), a small teleost fish which often feeds primarily on benthic invertebrates. Artificial sediment and reconstituted water were used. To examine the influence of benthic prey on the bioaccumulation of a POP in the predator, fish were exposed to ¹⁴C-labelled hexachlorobenzene via spiked water, spiked sediment, pre-contaminated prey organisms, and to combinations of these exposure routes. Summarising the results of these experiments, it could be shown that the exposure to HCB via different routes resulted in a significantly higher accumulation in fish than an exposure to single pathways. It was concluded that the major uptake routes for fish were the overlying water and the food, whereas the contribution of spiked sediment itself was relatively small. HCB was biomagnified in the rested laboratory food chain. Therefore, concerning secondary poisoning, the environmental risk assessment of POPs like HCB should not be based on existing bioaccumulation tests alone, since they focus only on exposure via the water pathway. Instead, the influence of food and sediment as exposure routes should be considered as well, using comprehensive food chain modelling and/or laboratory studies.     

Effects of various fatty acid amendments on a microbial digester community in batch culture

Since biogas production is becoming increasingly important the understanding of anaerobic digestion processes is fundamental. However, large-scale digesters often lack online sensor equipment to monitor key parameters. Furthermore the possibility to selectively change fermenting parameter settings in order to investigate methane output or microbial changes is limited. In the present study we examined the possibility to investigate the microbial community of a large scale (750,000 L) digester within a laboratory small-scale approach. We studied the short-term response of the downscaled communities on various fatty acids and its effects on gas production and compared it with data from the original digester sludge. Even high loads of formic acid led to distinct methane formation, whereas high concentrations of other acids (acetic, butyric, propionic acid) caused a marked inhibition of methanogenesis coupled with an increase in hydrogen concentration. Molecular microbial techniques (DGGE/quantitative real-time-PCR) were used to monitor the microbial community changes which were related to data from GC and HPLC analysis. DGGE band patterns showed that the same microorganisms which were already dominant in the original digester re-established again in the lab-scale experiment. Very few microorganisms dominated the whole fermenting process and species diversity was not easily influenced by moderate varying fatty acid amendments - Methanoculleus thermophilus being the most abundant species throughout the variants. MCR-copy number determined via quantitative real-time-PCR - turned out to be a reliable parameter for quantification of methanogens, even in a very complex matrix like fermenter sludge. Generally the downscaled batch approach was shown to be appropriate to investigate microbial communities from large-scale digesters.     

A flow-through passive dosing system for continuously supplying aqueous solutions of hydrophobic chemicals to bioconcentration and aquatic toxicity tests

A continuous supply of water with defined stable concentrations of hydrophobic chemicals is a requirement in a range of laboratory tests such as the OECD 305 protocol for determining the bioconcentration factor in fish. Satisfying this requirement continues to be a challenge, particularly for hydrophobic chemicals. Here we present a novel solution based on equilibrium passive dosing. It employs a commercially available unit consisting of ∼16 000 polydimethylsiloxane (PDMS) tubes connected to two manifolds. The chemicals are loaded into the unit by repeatedly perfusing it with a methanol solution of the substances that is progressively diluted with water. Thereafter the unit is perfused with water and the chemicals partition from the unit into the water. The system was tested with nine chemicals with log K_OW ranging from 4.1 to 6.3. The aqueous concentrations generated were shown to be largely independent of the water flow rate, and the unit to unit reproducibility was within a factor of ∼2. In continuous flow experiments the aqueous concentrations of most of the study chemicals remained constant over 8 d. A model was assembled that allows prediction of the operating characteristics of the system from the log K_OW or PDMS/water partition coefficient of the chemical. The system is a simple, safe, predictable and flexible tool that generates stable aqueous concentrations of hydrophobic chemicals.     

Dynamic simulation of a decentralized polygeneration plant providing SNG,steam and power

The behaviour of a decentralized polygeneration plant providing synthetic natural gas (SNG), steam and electrical power is simulated in three scenarios in this study. The plant size is based on an assumed capacity of decentralized polygeneration plants processing 1070 m³ h^?1 (STP) of syngas. 396 m³ h^?1 (STP) of raw SNG, 0.4 t h^?1 of steam at 5 bar and 670 kW of electrical power can be generated by the plant at the reference scenario. Methanation reactor and steam generator are modelled in detail. Further results indicate that such a polygeneration plant can provide positive and negative operation reserves for the electricity network to the extent of 100% of the reference power output, while the amount of generated steam varies by less than 40%. At the same time, the generated SNG quality keeps constant. Lower variations in the amount of generated steam are applicable when reducing the operation reserve capacity.     

Critical loads and their exceedances at intensive forest monitoring sites in Europe

Intensive forest monitoring by means of harmonised methods has been conducted in Europe for more than a decade. Risks of atmospheric nitrogen and sulphur deposition are assessed by means of calculations of critical loads and their exceedances. In the present study throughfall and bulk deposition of nitrate (N-NO(3)), ammonium (N-NH(4)) and sulphate (S-SO(4)) show marked spatial patterns and temporal trends. In the period of observation (1999-2004), sulphate deposition on intensive monitoring plots decreased by about one quarter. This is in line with the reduction of S deposition by 70% since 1981 in Europe as a result of successful air pollution control politics under the Convention on Long-range Transboundary Air Pollution (CLRTAP). However, sulphate and especially nitrate and ammonium deposition were found to still exceed critical loads at many forest sites, indicating a continued need for further implementation of air pollution abatement strategies.     

Effects of incremental increases in silt load on the cardiovascular performance of riverine and lacustrine rock bass, Ambloplites rupestris

Rock bass (Ambloplites rupestris) are a widespread centrarchid species with both riverine and lacustrine populations. After precipitation events, rivers often carry elevated silt loads, where as lakes generally remain free from suspended silt and sediment. To examine the physiological effects of silt on rock bass, we conducted a series of experiments using fish from Lake Opinicon and the Grand River in Ontario. Ultrasonic Doppler flow probes were surgically affixed around the ventral aorta to monitor cardiovascular performance. After recovery from surgery replicated treatment groups were exposed to incremental increases in silt load (made from bentonite slurry), while cardiac output and its two components, heart rate and stroke volume, were measured simultaneously. Although both groups of rock bass responded significantly to low concentrations of silt (10 NTU), the response by riverine rock bass was rapidly extinguished by acclimation or physiological adjustment. Compensatory mechanisms to minimize cardiac (and respiratory) disruption attributable to increases in suspended silt appear to be inherent in rock bass of riverine origin. These fish appear to fully compensate for interference in gas exchange at the gill surfaces 60 min after initial exposure. In contrast, individual lacustrine rock bass were highly variable in their response to elevated silt concentrations. Changes in stroke volume and cardiac output suggested no clear compensatory mechanism or strategy to cope with increased silt levels.     

Preen gland removal increases plumage bacterial load but not that of feather-degrading bacteria

The preen gland is a holocrine sebaceous gland of the avian integument which produces an oily secretion that is spread on the plumage during preening. It has been suggested that birds may defend themselves against feather-degrading bacteria (FDB) and other potential pathogens using preen gland secretions. However, besides some in vitro studies, the in vivo bacterial inhibitory effects of the preen oil on the abundance of feather-associated bacterial species has not yet been studied in passerines. Here we tested the effect of gland removal on the abundance of FDB and other-cultivable bacterial loads (OCB) of male house sparrows (Passer domesticus). Our results did not support earlier results on in vitro antibacterial activity of preen oil against FDB since the absence of the preen gland did not significantly affect their loads related to the control birds. In contrast, we found that preen gland removal led to higher loads of OCB. This result suggests that the antimicrobial spectrum of the preen oil is broader than previously thought and that, by reducing the overall feather bacterial loads, the preen gland could help birds to protect themselves against a variety of potentially harmful bacteria.