Probing densified silica glass structure by molecular oxygen and E' center formation under electron irradiation.

This study aims to learn more about the structure of densified silica with focus on the metamict-like silica phase (density = 2.26 g/cm3) by examining the formation of E' point defects and interstitial molecular oxygen O2 by 2.5 MeV electron irradiation. High-dose (11 GGy) irradiation creates a metamict-like phase and a large amount of interstitial O2, which is destroyed upon subsequent additional lower-dose electron irradiation. The O2 cathodoluminescence (CL) data indicate that the formation of O2 from peroxy linkages Si-O-O-Si in silica network is strongly dependent on the intertetrahedral void sizes. The position and shape of the O2 emission line support the idea that the configuration of these voids in metamict phase is close to that of non-densified silica. Moreover, data support the strong correlation between the formation of 3-membered rings of Si-O bonds and E'-centers when silica density increases from 2.20 to 2.26 g/cm3.

Effects of dispersant-treated oil upon behavioural and metabolic parameters of the anti-predator response in juvenile European sea bass (Dicentrarchus labrax).

Acute exposure to oil and oil dispersants can cause a wide range of physiological dysfunctions in marine fish species and evidences for consequences on behaviour are also increasing. In response to the presence of predators or to food availability, the modulation of locomotor activity and schools' behaviour enable fish to maximize their survival rates. However, the degree to which this regulatory process is affected by exposure to oil and/or dispersants is yet unknown. Here we investigated the effect of a 62-h experimental exposure to dispersant-treated oil on the behavioural (shoal cohesion, spontaneous activity) and metabolic (oxygen consumption) responses to simulated predation in juvenile European sea bass, Dicentrarchus labrax L. Our results suggest that exposure to petroleum hydrocarbons may affect negatively individual fitness through impaired ability to respond to predation. Shoal cohesion was not affected, but fish swimming activity was higher than control individuals under predation pressure and the amplitude of their metabolic response was significantly reduced. Fish recovered from alteration of their metabolic response 7 days post-exposure. Additionally, a strong habituation component was observed in C fish and the absence of such pattern in E fish suggest altered capacity to habituate over time to the surrounding environment and possible impairments of the related cognitive performances. Altogether, our data show that juvenile sea bass exposed to oil exhibit transient physiological dysfunctions and impairments of complex behaviours that may have major population-level consequences.

Proteome changes in muscles, ganglia, and gills in Corbicula fluminea clams exposed to crude oil: Relationship with behavioural disturbances.

The use of online remote control for 24/7 behavioural monitoring can play a key role in estimating the environmental status of aquatic ecosystems. Recording the valve activity of bivalve molluscs is a relevant approach in this context. However, a clear understanding of the underlying disturbances associated with behaviour is a key step. In this work, we studied freshwater Asian clams after exposure to crude oil (measured concentration, 167 ± 28 µg·L-1) for three days in a semi-natural environment using outdoor artificial streams. Three complementary approaches to assess and explore disturbances were used: behaviour by high frequency non-invasive (HFNI) valvometry, tissue contamination with polycyclic aromatic hydrocarbons (PAH), and proteomic analysis. Two tissues were targeted: the pool adductor muscles - retractor pedal muscle - cerebral and visceral ganglia, which is the effector of any valve movement and the gills, which are on the frontline during contamination. The behavioural response was marked by an increase in valve closure-duration, a decrease in valve opening-amplitude and an increase in valve agitation index during opening periods. There was no significant PAH accumulation in the muscle plus nervous ganglia pool, contrary to the situation in the gills, although the latter remained in the low range of data available in literature. Major proteomic changes included (i) a slowdown in metabolic and/or cellular processes in muscles plus ganglia pool associated with minor toxicological effect and (ii) an increase of metabolic and/or cellular processes in gills associated with a greater toxicological effect. The nature of the proteomic changes is discussed in terms of unequal PAH distribution and allows to propose a set of explanatory mechanisms to associate behaviour to underlying physiological changes following oil exposure. First, the first tissues facing contaminated water are the inhalant siphon, the mantle edge and the gills. The routine nervous activity in the visceral ganglia should be modified by nervous information originating from these tissues. Second, the nervous activity in the visceral ganglia could be modified by its own specific contamination. Third, a decrease in nervous activity of the cerebral ganglia close to the mouth, including some kind of narcosis, could contribute to a decrease in visceral ganglia activity via a decrease or blockage of the downward neuromodulation by the cerebro-visceral connective. This whole set of events can explain the decrease of metabolic activity in the adductor muscles, contribute to initiate the catch mechanism and then deeply modify the valve behaviour.

Measuring the biological impact of drilling waste on the deep seafloor: An experimental challenge.

The depletion of traditional oil fields is driving the oil & gas industry to explore new exploitation sites previously considered as unprofitable. Deep-sea oil fields represent one of these new areas of exploitation. Well drilling during exploration and production operations generate large quantities of drilling waste whose biological impact on the deep-sea floor remains largely unknown. Because of the harsh abiotic factors characterizing this environment, the evaluation of this impact remains challenging. High hydrostatic pressure is the prominent factor which will affect in-situ biological processes. This review will examine the feedback on the various strategies used to evaluate the biological impact of deep-sea drilling waste deposition as well as the current technological limitations. Given the complexity of this issue, a good perspective strategy would be to trend towards the research and development of more relevant bioassays, especially considering the crucial factor of hydrostatic pressure.

Asiatic clam Corbicula fluminea exhibits distinguishable behavioural responses to crude oil under semi-natural multiple stress conditions.

Aquatic ecosystems are subject to many anthropogenic disturbances, and understanding their possible impacts is a real challenge. Developing approaches based on the behaviour of bivalve mollusks, an integrating marker of the state of the organisms, and therefore of their environment, is relevant, whether within a natural ecosystem or an ecosystem subject to industrial activities. The main objective of this study was to identify by HFNI Valvometry a reliable and reproducible clam behavioural response in the presence of crude oil in a multistress context. To closely replicate actual field conditions, Corbicula fluminea was exposed in outdoor artificial streams that were subject to natural variations and were continuously fed by fresh water from the Gave de Pau (S.W. France). After a period of 26 days in these artificial streams, the clams (n = 14-16 per condition) were separately exposed for 10 days to crude oil alone, crude oil and barium, crude oil and noise pollution, crude oil and turbidity pulses, barium alone, noise pollution alone, turbidity pulses alone or natural changes alone. The secondary objective was to characterize the accumulation of polycyclic aromatic hydrocarbons (PAH) in 3 tissues (gills, adductor muscles and foot) in clams exposed for 10 days to crude oil alone or under multistress conditions (n = 5 clams per condition) and then to compare the accumulation and behaviour of clams under these conditions. The response of clams to crude oil alone or under multistress conditions was visually and statistically significant and not confounded by the other disturbances tested, despite large variations in water temperature. In the presence of crude oil, the behaviour of clams was characterized by an increase in valve-closure duration, a decrease in valve-opening amplitude and an increase in valve agitation index. In the presence of crude oil, the clam behaviour showed no direct relationship with PAH accumulation in the gills, adductor muscles or foot, although hypothetical mechanisms are discussed. This work supports the growing interest in studying the behaviour of bivalve mollusks in the context of biomonitoring of the aquatic environment surrounding oil facilities.

Effects of acute exposure to dispersed oil and burned oil residue on long-term survival, growth, and reproductive development in polar cod (Boreogadus saida).

The present study investigates the potential long-term physiological effects on maturing polar cod (Boreogadus saida), an Arctic key species, after an acute exposure (48 h) to environmentally realistic concentrations of either mechanically dispersed oil (MDO), chemically dispersed oil (CDO) or burned oil residues (BO) (N = 58-60 per treatment). Following exposure, fish were monitored in a common tank supplied with clean water for a seven-month period coinciding with the period of reproductive development. Females exposed to BO residues were more frequently found in an earlier phase of gonadal maturation compared to unexposed females while no effects of different oil spill response (OSR) actions were seen in the reproductive development of males. Mechanically and chemically dispersed oil induced a transient short-term reduction in growth in the first week post-exposure. Overall, no significant long-term effects of exposure were seen in growth or mortality. Ultimately, this study provides information for the assessment of population consequences of different OSR actions as part of a net environmental benefit analysis.

River Continuity Restoration and Diadromous Fishes: Much More than an Ecological Issue.

Ecosystem fragmentation is a serious threat to biodiversity and one of the main challenges in ecosystem restoration. River continuity restoration (RCR) has often targeted diadromous fishes, a group of species supporting strong cultural and economic values and especially sensitive to river fragmentation. Yet it has frequently produced mixed results and diadromous fishes remain at very low levels of abundance. Against this background, this paper presents the main challenges for defining, evaluating and achieving effective RCR. We first identify challenges specific to disciplines. In ecology, there is a need to develop quantitative and mechanistic models to support decision making, accounting for both direct and indirect impacts of river obstacles and working at the river catchment scale. In a context of dwindling abundances and reduced market value, cultural services provided by diadromous fishes are becoming increasingly prominent. Methods for carrying out economic quantification of non-market values of diadromous fishes become ever more urgent. Given current challenges for rivers to meet all needs sustainably, conflicts arise over the legitimate use of water resources for human purposes. Concepts and methods from political science and geography are needed to develop understandings on how the political work of public authorities and stakeholders can influence the legitimacy of restoration projects. Finally, the most exciting challenge is to combine disciplinary outcomes to achieve a multidisciplinary approach to RCR. Accordingly, the co-construction of intermediary objects and diagrams of flows of knowledge among disciplines can be first steps towards new frameworks supporting restoration design and planning.

Assessing chronic fish health: An application to a case of an acute exposure to chemically treated crude oil.

Human alteration of marine ecosystems is substantial and growing. Yet, no adequate methodology exists that provides reliable predictions of how environmental degradation will affect these ecosystems at a relevant level of biological organization. The primary objective of this study was to develop a methodology to evaluate a fish's capacity to face a well-established environmental challenge, an exposure to chemically dispersed oil, and characterize the long-term consequences. Therefore, we applied high-throughput, non-lethal challenge tests to assess hypoxia tolerance, temperature susceptibility and maximal swimming speed as proxies for a fish's functional integrity. These whole animal challenge tests were implemented before (1 month) and after (1 month) juvenile European sea bass (Dicentrarchus labrax) had been acutely exposed (48h) to a mixture containing 0.08gL(-1) of weathered Arabian light crude oil plus 4% dispersant (Corexit© EC9500A), a realistic exposure concentration during an oil spill. In addition, experimental populations were then transferred into semi-natural tidal mesocosm ponds and correlates of Darwinian fitness (growth and survival) were monitored over a period of 4 months. Our results revealed that fish acutely exposed to chemically dispersed oil remained impaired in terms of their hypoxia tolerance and swimming performance, but not in temperature susceptibility for 1 month post-exposure. Nevertheless, these functional impairments had no subsequent ecological consequences under mildly selective environmental conditions since growth and survival were not impacted during the mesocosm pond study. Furthermore, the earlier effects on fish performance were presumably temporary because re-testing the fish 10 months post-exposure revealed no significant residual effects on hypoxia tolerance, temperature susceptibility and maximal swimming speed. We propose that the functional proxies and correlates of Darwinian fitness used here provide a useful assessment tool for fish health in the marine environment.

Permanently densified SiO2 glasses: a structural approach.

Densified silica can be obtained by different pressure and temperature paths and for different stress conditions, hydrostatic or including shear. The density is usually the macroscopic parameter used to characterize the different compressed silica samples. The aim of our present study is to compare structural modifications for silica glass, densified from several routes. For this, densified silica glasses are prepared from cold and high temperature (up to 1020 °C) compressions. The different densified glasses obtained in our study are characterized by micro-Raman spectroscopy. Intertetrahedral angles from the main band relative to the bending mode decrease and their values are larger for densified samples from high temperature compression than those samples from cold compression. The relative amount of 3-membered rings deduced from the D2 line area increases as a function of density for cold compression. The temperature increase during the compression process induces a decrease of the 3 fold ring population. Moreover, 3 fold rings are more deformed and stressed for densified samples at room temperature at the expense of those densified at high temperature. Temperature plays a main role in the reorganization structure during the densification and leads to obtaining a more relaxed structure with lower stresses than glasses densified from cold compression. The role of hydrostatic or non-hydrostatic applied stresses on the glass structure is discussed. From the Sen and Thorpe central force model, intertetrahedral angle average value and their distribution are estimated.

Responses of juvenile sea bass, Dicentrarchus labrax, exposed to acute concentrations of crude oil, as assessed by molecular and physiological biomarkers.

In the present study, juvenile sea bass were exposed for 48 and 96 h to an Arabian light crude oil and their responses were assessed at the molecular and physiological levels. The aim of the study was therefore to assess (i) the short term effects of crude oil exposure by the measurement of several molecular biomarkers, (ii) the consequences of this short term exposure on fish health by using growth and condition indices measured after a decontamination period of 28 and 26 d in seawater. Hydrocarbon petroleum concentrations was monitored during the 96 h experiments and an increase of PAH concentrations were found in fish following both exposure times. An 7-ethoxyresorufin-O-deethylase (EROD) induction was observed after 48 h of exposure, while a significant decrease in the sea bass specific growth rate in length and for the RNA:DNA ratio was observed 28 d after that exposure ceased. The EROD induction doubled after the 96 h exposure, and a significant increase in GST activities was observed. A significant decrease in the specific growth rates, the otolith recent growth, the RNA:DNA ratio and the Fulton's K condition index were then observed in sea bass 26 d after the 96 h exposure to mechanically dispersed crude oil compared to the control. The present study shows that growth and condition indices can prove useful in assessing fish health status following an oil spill. Their complementary analysis with sensitive molecular biomarkers as EROD could improve the determination of oil spill impact on fish populations.

Enhanced immunological and detoxification responses in Pacific oysters, Crassostrea gigas, exposed to chemically dispersed oil.

The aim of this study was to evaluate the effects of chemically dispersed oil on an economically and ecologically important species inhabiting coasts and estuaries, the Pacific oyster Crassostrea gigas. Studies were carried out with juveniles, known to generally be more sensitive to environmental stress than adults. A set of enzyme activities involved in immune defence mechanisms and detoxification processes, i.e. superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), catecholase-type phenoloxidase (PO), laccase-type PO and lysozyme were analysed in different oyster tissues, i.e. the gills, digestive gland and mantle, and in the plasma and the haemoycte lysate supernatant (HLS) of the haemolymph. Results indicated that total PAH body burdens were 2.7 times higher in the presence than in the absence of the chemical dispersant. After 2 days of exposure to chemically dispersed oil, alkylated naphthalenes accounted for 55% of the total PAH body burden, whereas alkylated fluorenes and alkylated dibenzothiophenes accounted for 80% when the chemical dispersant was absent. Importantly, a higher number of enzyme activities were modified when oil was chemically dispersed, especially in the plasma and gills. Moreover, independently of the presence or absence of chemical dispersant, oil exposure generally inhibited enzyme activities in the gills and plasma, while they were generally activated in the mantle and haemocytes. These results suggest that the gills and plasma constitute sensitive compartments in C. gigas, and that the mantle and haemocytes may play an important role in protection against xenobiotics. Among the six enzyme activities that were analysed in these body compartments, five were modulated in the chemical dispersion (CD) treatment while only half of the enzyme activities were modulated in the mechanical dispersion treatment. Furthermore, CD treatment effects were often observed following exposure, but also during depuration periods. These results suggest that immune and/or detoxification responses are likely to be affected when dispersants are used to treat oil spills in shallow waters.

Effects of two oils and 16 pure polycyclic aromatic hydrocarbons on plasmatic immune parameters in the European sea bass, Dicentrarchus labrax (Linné).

The in vitro effects of polycyclic aromatic hydrocarbons (PAHs) on two plasmatic immune parameters, lysozyme concentration and haemolytic alternative complement activity, of the European sea bass, Dicentrarchus labrax, were tested using field (10(-7) and 10(-9) mg mL(-1)) and high concentrations (10(-3) and 10(-5) mg mL(-1)) observed during oil spills. Peripheral blood from 105 fish was collected, centrifuged at 1200 g, for 10 min, at 4 degrees C and three plasma pools, each of 35 fish, were constituted. Two oils (heavy fuel oil and light cycle oil) and 16 pure PAHs, selected on the basis of the American Environmental Protection Agency list (US EPA), were tested in vitro on the two humoral immune parameters. Only three pure PAHs (anthracene, chrysene and dibenz[a,h]anthracene) modulated lysozyme concentration. Acenaphthene, acenaphthylene, anthracene, benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, pyrene and light cycle oil modified the haemolytic alternative complement activity after 4h of incubation. This study investigates the direct effects of several PAHs on fish humoral immune functions and describes the haemolytic complement activity of fish as suitable biomarkers of oil pollution.

Effects of oil and bioremediation on mussel (Mytilus edulis L.) growth in mudflats.

Mussels (Mytilus edulis L.) were exposed to crude oil during a field experiment to evaluate two bioremediation strategies (nutrient addition and nutrient addition with tilling). The mussels were placed in 4 mesocosms: Control, Oil, Oil + Nutrients, and Oil + Nutrients + Tilled. Tilling appeared to be clearly detrimental to mussel growth. Additionally, this field experiment demonstrated that at temperatures below 5 degrees C, growth was reduced to rates undetectable by the laser diffraction method. The data on mussel shell length show that this technique does offer very sensitive and useful comparative measurements of physiological function. Measurement of shell growth has the advantage over other techniques in that it is non-invasive and non-destructive and thus may be used continuously without disturbing critical physiological and biochemical functions; however, bivalve physiology is strongly linked to environmental conditions, so it is important to include such measures (i.e. seawater temperature and turbidity) in the design of the biomonitoring program. Elevated polycyclic aromatic hydrocarbon (PAH) levels reflected bioaccumulation in mussels from all the oiled mesocosms. This correlated with reduction in growth rate. Maximum reduction in growth was observed in mussels from the tilled mesocosm which contained the lowest phenanthrene and dibenzothiophene concentrations. The tilling caused an increase in suspended solids which inhibited filter feeding activity, and resulted in suppressed growth and slower intake of PAH-laden sediment.