Effects of traffic noise on tree frog stress levels,immunity, and color signaling

During the last decade, many studies have focused on the detrimental effects of noise pollution on acoustic communication. Surprisingly, although it is known that noise exposure strongly influences health in humans, studies on wildlife remain scarce. In order to gain insight into the consequences of traffic noise exposure, we experimentally manipulated traffic noise exposure as well as the endocrine status of animals to investigate physiological and phenotypic consequences of noise pollution in an anuran species. We showed that noise exposure increased stress hormone level and induced an immunosuppressive effect. In addition, both traffic noise exposure and stress hormone application negatively impacted H. arborea vocal sac coloration. Moreover, our results suggest profound changes in sexual selection processes because the best quality males with initial attractive vocal sac coloration were the most impacted by noise. Hence, our study suggests that the recent increases in anthropogenic noise worldwide might affect a broader range of animal species than previously thought, because of alteration of visual signals and immunity. Generalizing these results to other taxa is crucial for the conservation of biodiversity in an increasingly noisy world.     

Measurements of groundwater velocity in discrete rock fractures

Estimating groundwater velocity in fracture networks using a Darcy or cubic law calculation is complicated by the wide distribution of fracture aperture often found in these systems and by the difficulty in measuring hydraulic head in discrete fracture features. Although difficult to conduct in a fractured rock setting, the point dilution method can be utilized to collect direct measurements of groundwater velocity in individual fractures. To compare measured against calculated velocities, more than 100 point dilution experiments were conducted within a 35 x 35 m area of a single fracture and in discrete fracture features within a fracture network at a larger scale. The dilution experiments were conducted by isolating a fracture feature in a borehole, measuring the hydraulic aperture, and measuring the decay of an injected tracer due to the advective groundwater flux across the fracture. Groundwater velocity was estimated using the hydraulic aperture and the rate of decay of the injected tracer. Estimates of the local hydraulic gradient were calculated via the cubic law using the velocity estimate and the hydraulic aperture. The results of the tests conducted in the single fracture show variable (1 to 33 m/day) but on average higher velocities in comparison to that measured during a natural gradient tracer experiment conducted previously (in which the effects of matrix diffusion were accounted for) and to that which would be calculated using the cubic law. Based on these results, it was determined that the best estimate of the average groundwater velocity, at the scale of the measurement area used for the cubic law calculations, could only be obtained using the largest apertures in the aperture distribution. Variability of the velocity measurements was also observed over time. Increases in velocity were attributed to the effect of rainfall although concurrent increases in hydraulic gradient were not detected (likely within the tolerance of the measuring devices). The groundwater velocities measured in the fracture network varied over a wider range than at the scale of the single fracture (from 2 to 388 m/day). No correlation, however, was observed between the size of the fracture aperture and measured velocity.     

Use of commercial plant species in a hydroponic system to treat domestic wastewaters

The objectives in this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards. A commercial hydroponic system was adapted for this study and the wastewater was used to irrigate wooly digitalis (Digitalis lanata Ehrh.) and foxglove (Digitalis purpurea L.). These plants are medicinal and produce cardenolide compounds. Influent and effluent samples were collected once a month for six months and analyzed to determine the various parameters relating to water quality. The legal discharge levels for total suspended solids (SS), biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) were reached for the two tested plants after 48 h of wastewater treatment; the removal was 82, 93, and 79%, respectively, for wooly digitalis and 92, 92, and 84%, respectively, for foxglove. Similar results were obtained during a 6-mo period although the sewage composition varied widely. The system tended to be unable to remove N and P to concentrations below regulated levels. Compared with the nutrient solution composition, the wastewater was more concentrated in Na+ and Cl- and less in N, K+, and Ca2+. These variations can lead to the decline of wooly digitalis plants. Foxglove developed a significant root system to increase mineral absorption wastewater being used as the unique nutritive source. After 10 wk all the wooly digitalis seedlings were dead. Despite this fact, however, the root system remained in place for a significant time (< 4 mo), thus continuing to filter wastewater and to be used as a bacterial support thus making it possible to have a security period to replace the dead plants.     

A Retrospective Isotopic Study of Spruce Decline in the Vosges Mountains (France)

The objective of this study was to assess the time variation of mineral and water stress levels across the life of a declining, Mg-deficient, spruce stand, in order to clarify the factors that caused the decline. Since 1985, strong soil acidification linked to a large leaching of nitrate and base cations was measured at the study site. In 1994, 5 trees were felled and tree rings were measured and analysed for Ca, Mg, K, Sr, ¹³C¹²C and ⁸⁷Sr/⁸⁶Sr isotopic ratios. Strontium pools and fluxes as well as root Sr isotope ratio in relation to depth were also measured. Wood chemical concentrations and isotope ratios were strongly related to the dominance status of each tree. On average during the study period, the ⁸⁷Sr/⁸⁶Sr ratio of spruce wood decreased. Using a mechanistic model computing long term variations of ⁸⁷Sr/⁸⁶Sr ratio in trees and soils, we reproduced the observed trend by simulating soil acidification – increasing Sr drainage from the whole profile, and particularly from the organic horizon –, and root uptake becoming more superficial with time. Between 1952 and 1976, tree ring ¹³C decreased strongly and continuously, which, in addition to other factors, might be related to an increase in water stress. Thus, a decrease in rooting depth, possibly related to soil acidification, appeared as a possible cause for the long term increase in water stress. The extreme drought event of 1976 appears to have revealed and triggered the decline.     

Soil organic horizons as a major source for radiocesium biorecycling in forest ecosystems

Here we review some of the main processes and key parameters affecting the mobility of radiocesium in soils of semi-natural areas. We further illustrate them in a collection of soil surface horizons which largely differ in their organic matter contents. In soils, specific retention of radiocesium occurs in a very small number of sorbing sites, which are the frayed edge sites (FES) born out of weathered micaceous minerals. The FES abundance directly governs the mobility of trace Cs in the rhizosphere and thus its transfer from soil to plant. Here, we show that the accumulation of organic matter in topsoils can exert a dilution of FES-bearing minerals in the thick humus of some forest soils. Consequently, such accumulation significantly contributes to increasing 137Cs soil-to-plant transfer. Potassium depletion and extensive exploration of the organic horizons by plant roots can further enhance the contamination hazard. As humus thickness depends on both ecological conditions and forest management. our observations support the following ideas: (1) forest ecosystems can be classified according to their sensitivity to radiocesium bio-recycling, (2) specific forest management could be searched to decrease such bio-recycling.     

Cloudwater studies at a high elevation site in the Vosges Mountains (France)

Cloud and rainwater samples have been collected at a high elevation site in the Vosges Mountains. An automated collection system has been used to collect bulk cloudwater and small cloudwater droplets. Bulk cloudwater concentrations were up to 10 times more concentrated than rainwater concentrations. Small clouddroplets showed generally higher concentrations than bulk cloudwater. Nevertheless, the enrichment factors depend on the compounds under study and appear to be related to the composition of the cloud condensation nuclei forming small or large clouddroplets. Principal component analysis and factor analysis were applied to the collected datasets and confirmed the influence of the cloud condensation nuclei on the composition difference between small and large cloudwater droplets.     

Suspended particulate matter determines physical speciation of Fe,Mn, and trace metals in surface waters of Loire watershed

This study investigates the spatiotemporal variability of major and trace elements, dissolved organic carbon (DOC), total dissolved solids (TDS), and suspended particulate matter (SPM) in surface waters of several hydrosystems of the Loire River watershed in France. In particular, this study aims to delineate the impact of the abovementioned water physicochemical parameters on natural iron and manganese physical speciation (homoaggregation/heteroaggregation) among fine colloidal and dissolved (<?10 nm), colloidal (10–450 nm) and particulate (>?450 nm) phases in Loire River watershed. Results show that the chemistry of the Loire River watershed is controlled by two end members: magmatic and metamorphic petrographic context on the upper part of the watershed; and sedimentary rocks for the middle and low part of the Loire. The percentage of particulate Fe and Mn increased downstream concurrent with the increase in SPM and major cations concentration, whereas the percentage of colloidal Fe and Mn decreased downstream. Transmission electron microscopy analyses of the colloidal and particulate fractions (from the non-filtered water sample) revealed that heteroaggregation of Fe and Mn rich natural nanoparticles and natural organic matter to the particulate phase is the dominant mechanism. The heteroaggregation controls the partitioning of Fe and Mn in the different fractions, potentially due to the increase in the ionic strength, and divalent cations concentration downstream, and SPM concentration. These findings imply that SPM concentration plays an important role in controlling the fate and behavior of Fe and Mn in various sized fractions.

Physical speciation by heteroaggregation of (Fe-Mn) compounds: high [SPM]?→?[Fe-Mn] particulate faction; low {SPM]?→?[Fe-Mn] colloid-dissolved fraction.

     

Revisiting two dogmas of conservation science

Conservation science is a morally motivated field, with implicit and explicit values built into its practice. As such, conservationists must engage with conservation ethics to interrogate underlying values. We examine cutting-edge ecological science and contemporary ethics to revisit two conservation norms that have become dogmatic in the field: ecological collectives, but not individual animals, are valuable and anthropomorphism should be staunchly avoided. Emerging studies demonstrate that individuals and their intraspecific variation can be instrumentally valuable for conservation science, and there is an emerging consensus within environmental philosophy around the moral worth of individuals. Thus, we suggest conservation science should explicitly recognize the value of individuals. We also argue that avoiding anthropomorphism is detrimental to conservation because critical anthropomorphism enables a more nuanced scientific approach—allowing conservationists to ask enlightened questions with creativity and compassion. We provide evidence that both dogmatic norms are scientifically and morally outdated and propose new normative values to push conservation towards more robust science and ethical practice.