A seasonal stable isotope survey of the food web associated to a peri-urban rocky shore

We characterized the structure and functioning of the food web associated to an intertidal rocky shore in the harbour of Brest (Western Brittany, France), through a seasonal δ¹³C and δ¹⁵N survey. The dominance of benthic-derived organic matter, and particularly resuspended sediment, in the local pool of suspended organic matter, is highlighted. This benthic-derived organic matter dominates the diet of filter-feeders, including a certain degree of selectivity displayed by various taxa belonging to this trophic group. The food web structure appeared very stable temporally, which suggested the dominance of mixed diets, rather than the consumption of pure sources. It was constituted of 4 trophic levels, including a large diversity of predators, likely favoured by the diversity of microhabitats that characterize this intertidal habitat. From our results, the trophic functioning of this peri-urban rocky shore community does not appear functionally simplified as previously reported for other anthropized and/or artificial rocky ecosystems. We suggest that the topological complexity of rocky habitats, including a diversity of microhabitats, might be responsible of the important animal diversity, in spite of the anthropogenic disturbances characterizing this peri-urban area.     

Mitochondrial genomic divergence in coelacanths (Latimeria): slow rate of evolution or recent speciation?

Dating the divergence between the two known living species of coelacanths has remained a difficult issue because of the very ancient origin of this lineage of fish, which is more closely related to tetrapods than to other fishes. We sequenced the complete mitochondrial genome of a recently captured individual of the Indonesian coelacanth in order to solve this issue. Using an approach based on loglinear models, we studied the molecular divergence between the two species of coelacanths and three other pairs of species, one that has diverged recently (Pan) and two that have diverged more distantly in the past. The loglinear models showed that the divergence between the two species of coelacanths is not significantly different from the two species of Pan. A detailed gene by gene analysis of the patterns of nucleotide and amino acid substitutions between these two pairs of species further supports the similarity of these divergences. On the other hand, a molecular dating analysis suggested a much older origin of the two coelacanth species (between 20 and 30 million years ago). We discuss the potential reasons for this discrepancy. The analysis of new individuals of the Indonesian coelacanth will certainly help to solve this issue.     

Continuity,social change and Katrina

For some time, disaster researchers have looked for social change and mostly found continuity. This paper argues that shifting the focus from investigating social change to documenting continuity may enhance the understanding and planning of post‐disaster situations especially in industrialised societies like the United States. Drawing from qualitative data from post‐Katrina New Orleans, it proposes using the concept of continuity as an analytical device both to identify the axes of continuity and evaluate the likelihood and possible dimensions of social change. The analysis of long‐term recovery plans, along with field observations and interviews with evacuees, suggest that despite the well‐documented emergence of conflict in post‐Katrina New Orleans, the likelihood of social change appears limited.     

Photooxidation of the phenylazonaphthol AO20 on TIO2: kinetic and mechanistic investigations.

The results of the photocatalytic and photosensitized degradations of the monoazo dye AO20 in aqueous solution using suspended titanium dioxide are presented. Kinetic and mechanistic details have been elucidated using UV/Vis, FTIR and TCO techniques. It was proven that adsorption of dye molecules onto the support material is essential for the processes to be effective. Moreover, even if their mechanisms differ during the early stages, photocatalysis and photosensitization lead to very similar ultimate breakdown products. Indeed, the original dye anchored to the oxide surface systematically undergoes fast decomposition until it is transformed into CO2 or aliphatic acids (formic, acetic, oxalic acids), which react rather slowly with hydroxyl radicals or trapped holes.     

Viable skin efficiently absorbs and metabolizes bisphenol A

Skin contact has been hypothesized to contribute to human exposure to bisphenol A (BPA). We examined the diffusion and metabolism of BPA using viable skin models: human skin explants and short-term cultures of pig ear skin, an alternative model for the study of the fate of xenobiotics following contact exposure. ¹⁴C-BPA [50-800 nmol] was applied on the surface of skin models. Radioactivity distribution was measured in all skin compartments and in the diffusion cells of static cells diffusion systems. BPA and metabolites were further quantified by radio-HPLC. BPA was efficiently absorbed in short-term cultures, with no major difference between the models used in the study [viable pig ear skin: 65%; viable human explants: 46%; non-viable (previously frozen) pig skin: 58%]. BPA was extensively metabolized in viable systems only. Major BPA metabolites produced by the skin were BPA mono-glucuronide and BPA mono-sulfate, accounting together for 73% and 27% of the dose, in pig and human, respectively. In conclusion, experiments with viable skin models unequivocally demonstrate that BPA is readily absorbed and metabolized by the skin. The trans-dermal route is expected to contribute substantially to BPA exposure in human, when direct contact with BPA (free monomer) occurs.     

Intestinal absorption of the acetamiprid neonicotinoid by Caco-2 cells: Transepithelial transport,cellular uptake and efflux

The human intestinal absorption of acetamiprid (AAP) using the Caco-2 cell line reveals that AAP flux was active in a bidirectional mode with an apparent permeability coefficient of 26^.10^?6 cm·s^?1 at 37°C. Apical uptake was concentration-dependent and unsaturated for AAP concentrations up to 200 μ M. AAP cell preloading demonstrated the involvement of active transport mechanisms. Arrhenius plot analysis revealed an unusual profile with two apparent activation energies suggesting two transport processes. Uptake Vi studies indicated the involvement of a sodium-dependent transporter, the presence of a common transporter of AAP and nicotine and the involvement of Ti-sensitive ATP-dependent efflux transporters. Apical efflux investigations showed the involvement of inward active transporter(s). Whereas vincristine had no effect on intracellular accumulation, taxol and daunorubicin treatments unexpectedly led to 10% and 23% reductions respectively, suggesting that the latter shared a common inward transporter with AAP. All these results suggest full and express AAP absorption in vivo with transport involving both inward and outward, passive and active mechanisms. Thus, AAP or its metabolites could be representative of a risk for human health after its ingestion in food.     

Leaching behaviour of hazardous demolition waste

Demolition wastes are generally disposed of in unlined landfills for inert waste. However, demolition wastes are not just inert wastes. Indeed, a small fraction of demolition waste contains components that are hazardous to human health and the environment, e.g., lead-based paint, mercury-contained in fluorescent lamps, treated wood, and asbestos. The objective of this study is to evaluate the release potential of pollutants contained in these hazardous components when they are mixed with inert wastes in unlined landfills. After identification of the different building products which can contain hazardous elements and which can be potentially pollutant in landfill scenario, we performed leaching tests using three different lysimeters: one lysimeter containing only inert wastes and two lysimeters containing inert wastes mixed with hazardous demolition wastes. The leachates from these lysimeters were analysed (heavy metals, chlorides, sulphates fluoride, DOC (Dissolved Organic Carbon), phenol index, and PAH). Finally, we compared concentrations and cumulative releases of elements in leachates with the limits values of European regulation for the acceptance of inert wastes at landfill. Results indicate that limit values are exceeded for some elements. We also performed a percolation column test with only demolition hazardous wastes to evaluate the specific contribution of these wastes in the observed releases.     

Photochimie et environnement X- evaluation de la toxicite des produits de phototransformation de l'hydroquinone et des chlorophenols en milieu aqueux

A test of acute toxicity on DAPHNIA MAGNA is suggested to evaluate the efficiency of the phototransformation as a route of abiotic degradation. This test is recommended for compounds phototransformed into a complex mixture of products. Hydroquinone, 2-chloro-, 4-chloro-, 2,4-dichloro-, 2,4,6-trichloro- and pentachlorophenol were studied as examples. In any case the phototransformation is an useful depollution technique on condition the irradiation to be completed as far as the ultimate step of phototransformation.