A predictive model for freshwater bioassessment (Mondego River,Portugal)

We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model. At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207 taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality, substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model, the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and increasing the number of ellipses that define quality bands. Handling editor: K. Martens     

Arsenic Bioaccumulation in Freshwater Fishes

The arsenic ambient water quality criterion (AWQC) for protection of human health via ingestion of aquatic organisms is currently 0.14 μ g/L. This AWQC is derived using a bioconcentration factor (BCF) of 44, which is a consumption-weighted average based on two data points for oysters and fish that was proposed by the U.S. Environmental Protection Agency in 1980 for broad application to freshwater and marine environments. This BCF is based on the assumption that bioaccumulation is a simple linear function of the exposure concentration. In the nearly quarter of a century since this BCF was promulgated, there have been additions to the arsenic bioaccumulation database and a broader scientific understanding of bioaccumulation mechanisms and how they can be applied to estimating tissue concentrations in aquatic organisms. From this database, we identified 12 studies of arsenic bioaccumulation in freshwater fishes in order to explore differences in laboratory-generated BCFs and field-generated bioaccumulation factors (BAFs) and to assess their relationship to arsenic concentrations in water. Our analysis indicates that arsenic concentrations in tissue and arsenic BAFs may be power functions of arsenic concentration in water. A power function indicates that the highest BCF values may occur at low background levels and may decrease as environmental concentrations increase above the ambient range.     

Pre-emptive Quality Control of a Misfolded Membrane Protein by Ribosome-Driven Effects

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Wood preservation hygiene and environment in the lime-light of actually

Summary Under the ?Bois plus? scheme, the CTBA is currently developing a third party certification, based on the Scrivener law, with the aim of defending the consumers' interests. At this early stage, wood preservatives and treated wood are checked for the efficacy of treatments in order to ensure the stability and security of works in buildings and civil engineering. According to the different classes of risks in service, ?Bois plus? provides the most adeguate level of protection. In the close future, the industry is planning to incorporate, with the help of the CTBA and experts, health criteria within the frame of the ?Bois plus? certification scheme. The means could beSafety indexes, which are objectives of quality for professionals.Safety indexes are concentrations of substances in wood which can be taken as safe for humans and the general environment, while still toxic for the wood pests. This attractive experience aims to make with the brandname ?Bois plus? a synonym of efficacy and safety. This approach meets the essential requirements 1, 3, 4 of the 89/106 EEC directive: mechanical resistance and stability/hygiene, health and environment/safety in use.     

Feedbacks between nutrient cycling and vegetation predict plant species coexistence and invasion

To investigate the role of species‐specific litter decomposability in determining plant community structure, we constructed a theoretical model of the codevelopmental dynamics of soil and vegetation. This model incorporates feedback between vegetation and soil. Vegetation changes the nutrient conditions of soil by affecting mineralization processes; soil, in turn, has an impact on plant community structure. The model shows that species‐level traits (decomposability, reproductive and competitive abilities) determine whether litter feedback effects are positive or negative. The feedback determines community‐level properties, such as species composition and community stability against invasion. The model predicts that positive feedback may generate multiple alternative steady states of the plant community, which differ in species richness or community composition. In such cases, the realized state is determined by initial abundance of co‐occurring species. Further, the model shows that the importance of species‐level traits depends on environmental conditions such as system fertility.     

A comparison of three noise reduction procedures applied to bird vocal signals

ABSTRACT.   Recordings of avian vocal signals in natural habitats include ambient noise. Often this background noise corrupts across all frequencies and is of substantial amplitude. Reducing this ambient noise to prepare vocal signals for playback stimuli or to remove habitat-specific noise signatures prior to analyzing a signal's acoustic characteristics can be useful. We conducted experimental evaluations of three noise reduction procedures to determine their effectiveness. We embedded two bird vocalizations ("clean" signals) in four kinds of natural noise, resulting in eight noise-signal combinations. We then applied three noise reduction procedures (Noise Profile, Band Pass, and Noise Estimate) to each of the embedded signals and compared the recovered signals to the original (clean) signals. Noise Profile filtering was effective in reducing noise and returning fairly high-quality signals from even severe levels of masking noise. The other two noise reduction procedures did not perform as well. For the two most corrupting maskers, however, Noise Profile filtering also altered the signal properties by reducing signal amplitude at those frequencies containing high levels of noise. Apart from this loss of amplitude, the quantitative features of the filtered signals were similar to those of the original model sounds. We conclude that Noise Profile filtering produces good results for cases where noise is approximately constant over the signal duration and the signal intensity exceeds noise intensity over the frequencies of interest.     

The effect of canopy filtered light on the growth of white clover Trifolium repens

Summary Plants of white clover (Trifolium repens) were grown under canopies of clover leaves floating on shallow glass tanks of water and their growth was compared with that of plants under canopies of black polythene leaves. The experimental design allowed the growth of the clover plants in canopy filtered light to be compared with that in unfiltered light at different intensities of Photosynthetically Active Radiation (P.A.R.). The effect of canopy filtered light was to exaggerate the effects of reduced P.A.R. especially in promoting petiole extension and inhibiting stolon branching. Two clones of white clover differed in their responses to P.A.R. and to light quality and there were significant interactions between the effects of the intensity of P.A.R. and type of shade. It is argued that it may be important for both ecologists and plant breeders to recognise the role of radiation quality in regulating the dynamics of pasture.     

Internode length in Pisum. Action of gene lw

Jolly, C. J., Reid, J. B. and Ross, J. J. 1987. Internode length in Pisum. Action of gene lw.
Mutant K29 of Pisum sativum L. is shown to possess a recessive gene at a new locus, lw , which results in reduced internode length, delayed flowering and increased symptoms of water congestion compared with the parental cv. Torsdag. The interaction of gene lw with the internode length genes na, le, la and cry ⁵ is examined. Extracts from the shoots of Iw plants are shown to contain similar levels of gibberellin (GA)-like substances to comparable Lw plants, but Iw plants do not elongate to the same extent as Lw plants when treated with GA₁₉ GA₁₉, or GA₂₀. The effect of gene Iw is not graft-transmissible. Unlike essentially isogenic dwarf lines possessing the GA-synthesis genes le, Ih or Is, lw plants show a relative increase in elongation similar to Torsdag in response to photoperiod extensions from sources rich in far-red light. These results suggest that gene lw probably does not reduce elongation by influencing GA-synthesis and that the response to photoperiod extensions with far-red light may depend on the level of GA.