Effets à court terme et à long terme d'un narcotique sur quelques activités enzymatiques chez le copépode harpacticoïde Tisbe holothuriae

The anaesthetic properties of clomethiazole ethane disulfonate (hydrochloric ester of thiazole fraction of Vitamin B 1) were tested on the harpacticoid copepod Tisbe holothuriae Humes. Concentrations of 0.250, 0.50, 0.625, 0.714 and 0.833 in sea water were tested. The copepod was exposed to the anaesthetic solutions for periods of 30 min and 1 h. A concentration of 0.250 was sufficient to induce immobility within a few minutes; the lethal concentration is 1. Immediate and delayed effects of narcosis on the activities of the enzymes esterases (EST), leucine aminopeptidase (LAP), alkaline phosphatase (ALP), malate dehydrogenase (MDH), malic enzyme (ME) and phosphoglucomutase (PGM) were studied using electrophoresis in polyacrylamide gel. No change in EST, LAP and ALP zymograms was observed during 48 h postnarcosis, whatever the clomethiazole concentration used, but changes in MDH, ME and PGM activity were observed after anaesthesia in 0.714 and 0.833 clomethiazole. The stronger the concentration used, the earlier and longer-lasting was the decrease in activity. For MDH, which is coded by two loci, electrophoresis revealed that one locus (the fast fraction) is more sensitive to the narcotic than the other, slow one.     

Risk assessment in the face of a changing environment: gypsy moth and climate change in Utah.

The importance of efficaciously assessing the risk for introduction and establishment of pest species is an increasingly important ecological and economic issue. Evaluation of climate is fundamental to determining the potential success of an introduced or invasive insect pest. However, evaluating climatic suitability poses substantial difficulties; climate can be measured and assessed in a bewildering array of ways. Some physiological filter, in essence a lens that focuses climate through the requirements and constraints of a potential pest introduction, is required. Difficulties in assessing climate suitability are further exacerbated by the effects of climate change. Gypsy moth (Lymantria dispar L.) is an exotic, tree-defoliating insect that is frequently introduced into the western United States. In spite of an abundance of potential host species, these introductions have yet to result in established populations. The success of eradication efforts and the unsuccessful establishment of many detected and undetected introductions may be related to an inhospitable climate. Climatic suitability for gypsy moth in the western United States, however, is potentially improving, perhaps rapidly, due to a general warming trend that began in the mid 1970s and continues today. In this work, we describe the application of a physiologically based climate suitability model for evaluating risk of gypsy moth establishment on a landscape level. Development of this risk assessment system first required amassing databases that integrated the gypsy moth climatic assessment model, with host species distributions, and climate (historical, present, and future). This integrated system was then used to evaluate climate change scenarios for native host species in Utah, with the result that risk of establishment will dramatically increase during the remainder of the 21st century under reasonable climate change scenarios. We then applied the risk assessment system to several case histories of detected gypsy moth introductions in Utah. These applications demonstrated the general utility of the system for predicting risk of establishment and for designing improved risk detection strategies.     

Population structure of the common sole (<Emphasis Type="Italic">Solea solea</Emphasis>) in the Northeastern Atlantic and the Mediterranean Sea: revisiting the divide with EPIC markers

Spatial and temporal population genetic structures of the common sole, Solea solea, were studied in Northeastern Atlantic and Mediterranean Sea populations, using three polymorphic exon-primed intron-crossing (EPIC) markers. Results demonstrated significant multilocus differentiation among Eastern Mediterranean and a group composed by Western Mediterranean and Atlantic populations (θ = 0.150, P < 0.001), but also suggested unrecorded genetic differentiation of the Adriatic Sea population. No pattern of isolation-by-distance was recorded across the range covered by sampling, from the Kattegat to the Aegean Sea. Conversely to genetically structured Mediterranean populations, Atlantic populations ranging from Denmark to Portugal could be considered as representative of the same panmictic unit (θ = 0.009, not significant). Results further demonstrated stability of multilocus genetic structure among temporarily replicated cohort samples [0+, 1+, subadults] from several coastal and estuarine locations from Bay of Biscay, excepted for the amylase locus Am2B3-2 at one location (Pertuis d’Antioche). Despite coherence of such observed patterns of multilocus differentiation with previous allozymic surveys in sole, and with patterns generally obtained for other marine fish species, single-locus results from EPICs indicated divergent coalescence schemes supporting a complex response to ecology and history of sole’s populations. Results stress the use of nuclear genes such as EPIC markers to investigate population structure, but also historical, demographic, and possibly selective processes in marine fishes.     

Anomalies on capture nets of Hydropsyche slossonae larvae (Trichoptera; Hydropsychidae) following a sublethal chronic exposure to cadmium

A laboratory study on the sublethal effects of cadmium (Cd) on the net-spinning process of the larvae of Hydropsyche slossonae was conducted in order to assess the potential of net anomalies as an indicator of chronic exposure to Cd. Two major anomalies with different frequency levels were identified after chronic exposure to 0.37, 1.2, 11.6, 21.4 and 43.3 microg l(-1) of Cd. The first was a distortion of the midline meshes where the diamond-shape structure is disrupted and the meshes are separated by extra strands (called 'midline' anomaly). The second aberration consisted of a distortion of the rectilinear structure of net opening by strands being fused or added over the meshes (called 'crossover' anomaly). The midline distortion may be linked to a physiological stress caused by Cd, which can affect the control of the net-spinning process. It was not possible to relate the crossover aberrations to a specific toxic action of Cd, but data indicated that both anomalies are independent from each other and that two modes of action could be implicated. Protein analyses of capture nets have revealed silk polypeptide modifications at the highest Cd concentration tested, indicating a possible effect of Cd interaction with silk proteins. However, neither a gradient-concentration nor a time-dependent response could be established with both aberration frequencies. Silk protein modifications would rather play a secondary role in the appearance of both net anomalies, and mostly at a high concentration level. Finally, the toxicity curves (EC(50)) show that the sensitivity threshold for both types of aberration ranged from 1 to 5 microg l(-1) which is highly sensitive compared with other sublethal effects of Cd on other macroinvertebrate species. Hence, the use of capture-net anomalies of hydropsychid larvae would represent a valuable indicator of sublethal toxicity induced by Cd and possibly by other metals in running waters.     

Xenobiotics: Substrates and inhibitors of the plant cytochrome P450

The ability of a plant cytochrome P450 to bind and metabolise plant endogenous molecules and xenobiotics was investigated. The work was performed on the yeast-expressed CYP73A1, a cinnamate 4-hydroxylase isolated fromHelianthus tuberosus. CYP73 controls the general phenylpropanoid pathway and is likely to be one of the most abundant sources of P450 in the biosphere. The enzyme shows a high selectivity toward plant secondary metabolites. Nevertheless, it oxygenates several small and planar xenobiotics with low efficiency, including an herbicide (chlorotoluron). One xenobiotic molecule, 2naphthoic acid, is hydroxylated with an efficiency comparable to that of the physiological substrate. This reaction was used to devise a fluorimetric test for the rapid measurement of enzyme activity. A series of herbicidal molecules (hydroxybenzonitriles) are shown to bind the active site without being metabolised. These molecules behave as strong competitive inhibitors of CYP73 with a K_i in the same micromolar range as the K_m for the physiological substrate. It is proposed that their inhibition of the phenylpropanoid pathway reinforces their other phytotoxic effects at the level of the chloroplasts. All our results indicate a strong reciprocal interaction between plant P450s and xenobiotics.     

Nutrient transfer by runoff from sewage sludge amended soil under simulated rainfall

Wastewater sludges are used in agriculture as soil amendment and fertilizer, with regard to their organic matter and nutrient content. However, availability of nitrogen and phosphorus from sludge-amended soils and their transfer in runoff may lead to eutrophication of downstream surface water. The aim of this study is to establish and compare the effect of two different sludges on these transfers: an anaerobically digested and thermically stabilised sludge (Seine-Aval treatment plant, sludge no. 1), and a limed sludge (Saint-Quentin treatment plant, sludge no. 2). Experiments were performed on 12 sloping micro-plots (1 m × 1 m) submitted to sludge spreading and controlled rainfall simulation. Runoff water was sampled and analysed for concentrations in nitrogen species and phosphorus. Results show that spreading of sludge no. 1 increased both ammonium nitrogen (mean of 1.1 mg L^–1 N-NH₄ vs. 0.2 mg L^–1 N-NH₄ for control micro-plots) and particulate phosphorus concentrations (mean of 2 mg L^–1 P vs. 1.1 mg L^–1 P for control micro-plots) in runoff water. On the other hand, sludge no. 2 did not induce any significant effect on nutrient concentrations in runoff. These results are related to chemical composition and physical treatment of sludges. This study underlines the existence of a short-term risk of nutrient mobilisation by runoff after sludge spreading on soil, and the need to check precisely the impact of this practice on water quality.     

Effect of Potassium Dichromate and Fenitrothion on Hemoglobins of Chironomus Riparius Mg. (Diptera, Chironomidae) Larvae: Potential Biomarker of Environmental Monitoring

In an attempt to identify Chironomus hemoglobins as biomarkers for environmental monitoring, alterations in the hemoglobins in Chironomus riparius Mg. (Diptera: Chironomidae) larvae, exposed to potassium dichromate and fenitrothion, were investigated under laboratory conditions. The hemoglobins were evaluated in terms of their total contents by a cyanomethemoglobin procedure, individual components by electrophoresis of isoelectric focusing, and their oxidation by multi wavelength rapid-scanning spectrophotometry. The total hemoglobin contents increased at the high level of fenitrothion exposure. No variations in the individual hemoglobin component levels were found, by exposure to either fenitrothion or potassium dichromate. Whereas, the absorption spectra of the hemoglobins showed decreases in the peaks corresponding to the oxyhemoglobins by exposure to both compounds, but more sensitively by the chromium, which probably reflects the increase of the autoxidation of the oxyhemoglobins to methemoglobins by these compounds. These results suggest that autoxidation of the hemoglobins in Chironomus riparius seems to be a sensitive parameter in response to redox-active chemical exposure, and this biochemical parameter could be developed as a biomarker in environmental monitoring.     

Environmental Stewardship and Ecological Solidarity: Rethinking Social-Ecological Interdependency and Responsibility

This paper explores and discusses the various meanings of the stewardship concept in the field of sustainability science. We highlight the increasing differences between alternative approaches to stewardship and propose a typology to enable scientists and practitioners to more precisely identify the basis and objectives of the concept of stewardship. We first present the two dimensions we used to map the diversity of stances concerning stewardship. Second, we analyse these positions in relation to the limits of the systemic approach, ideological manipulation, responsibility, and solidarity. In the final section we explain how the concept of ecological solidarity, a core principal in recent French law on biodiversity conservation and national park governance can contribute to the underpinning of a specific form of social-ecological stewardship.     

Single and mixture effects of pesticides and a degradation product on fluvial biofilms

The Morcille River located in the Beaujolais vineyard area (Eastern France) is subjected to strong vine-growing pressure leading to the contamination by a range of herbicides and fungicides of the surrounding freshwater environment. Particularly high concentrations of norflurazon, desmethyl norflurazon and tebuconazole were recorded in spring 2010 at the downstream site of the river. Despite their occurrence in rivers, scarce toxicity data are available for these products, in particular in the case of desmethyl norflurazon (main norflurazon degradation product). Furthermore, the toxicity data are generally available only for single compounds and are issued from single species toxicity tests, leading to a lack of ecological relevance. Consequently, this study was undertaken to evaluate the toxic effects of norflurazon, desmethyl norflurazon and tebuconazole singly and in a ternary mixture on fluvial biofilm. Toxicity tests were performed in microplates for 48 h. Photosynthetic endpoints were measured using pulse amplitude-modulated fluorometry; diatom densities and taxonomic composition were determined. After 48 h of exposure, significant effects on optimal quantum yield (F _v/F _m) for desmethyl norflurazon and mixture were observed.