Heterogeneous energetic pathways and carbon sources on deep eastern Mediterranean cold seep communities

Cold seep communities in the Mediterranean Sea have only been discovered two decades ago, and their trophic ecology has been the subject of very few studies. We investigated the benthic food web of two deep chemosynthesis-based ecosystems on the Napoli and Amsterdam mud volcanoes (MVs) in the eastern Mediterranean Sea (~2,000 m depth). Seeping methane has been detected at the surface of both MVs during pioneering cruises and has been hypothesised to be assimilated by benthic fauna as observed in other oceans’ margins. Given the extreme oligotrophic character of the eastern Mediterranean Sea, we a priori expected that chemosynthetic food sources, especially methane-derived carbon (MDC), played a major trophic role in these deep seep communities relative to what has been observed in other seep systems worldwide. We aimed at unravelling the trophic relationships on Napoli and Amsterdam MVs through the analysis of carbon, nitrogen and sulphur isotopes both in the dominant benthic invertebrates including the small endofauna (300 μm < size < 1 cm) and in the sedimented organic matter. In particular, we assessed the fraction of MDC in the tissue of several heterotrophic and symbiotic species. Low mean δ³⁴S and δ¹³C values (0.4 ± 4.8‰ and −31.6 ± 5.7‰, respectively) obtained for mega- and macrofauna suggested that the investigated benthic food webs are virtually exclusively fuelled by carbon of chemosynthetic origin. A few grazer invertebrates (δ³⁴S up to 11‰) depart from this trend and could complement their diet with sedimented and decayed phytoplanktonic organic matter. Faunal δ¹³C values indicated that the oxidation of sulphur is likely the predominant energetic pathway for biosynthesis on both MVs. Nevertheless, mytilid bivalves and small capitellid, ampharetid and spionid polychaetes were ¹³C-depleted (δ¹³C < −37‰) in a way indicating they assimilated a significant portion of MDC. For these later heterotrophic species, MDC ranged between 21 and 31% (lower estimates) and 97 and 100% (upper estimates). However, our results highlighted that the origin of assimilated carbon may be complex for some symbiotic species. The vestimentiferan tubeworm Lamellibrachia sp., which exclusively depends on its sulphur-oxidising endosymbionts, showed a ~20‰ inter-individual δ¹³C variability on a very small spatial scale (<1 m) at the summit of Napoli MV. This mostly reflects the variable isotopic composition of pore-water-dissolved inorganic carbon (DIC) and evidenced that tubeworms (and subsequently their endosymbionts) uptake DIC derived from multiple methane oxidation processes in varying proportions. The lower and upper MDC estimates for the vestimentum of Napoli’s individuals were 11–38 and 21–73%, respectively. Finally, data on trophic ecology of Napoli and Amsterdam MVs clearly corroborate previous geophysical results evidencing the spatial heterogeneity of Mediterranean MV environmental conditions.     

Detection of Hepatitis E Virus in Sewage After an Outbreak on a French Island

A hepatitis E outbreak, which occurred on a small isolated island, provided an opportunity to evaluate the association between the number of hepatitis E cases in the community and the concentration of virus detected in sewage. Samples were collected from the different sewage treatment plants from the island and analyzed for the presence of hepatitis E (HEV) virus using real-time RT-PCR. We demonstrated that if 1–4 % of inhabitants connected to a WWTP were infected with HEV, raw sewage contained HEV at detectable levels. The finding that such a small number of infected people can contaminate municipal sewage works raises the potential of the further distribution of the virus. Indeed, investigating the routes of transmission of HEV, including the potential for sewage effluent to contain infectious HEV, may help us to better understand the epidemiology of this pathogen, which is considered to be an emerging concern in Europe.     

Pyrrolizidine alkaloids and pentacyclic triterpene saponins in the defensive secretions of Platyphora leaf beetles

Summary. Field collected exocrine defensive secretions of nine neotropical Platyphora species were analyzed for the presence of plant acquired pyrrolizidine alkaloids (PAs) and pentacyclic triterpene saponins. All species secrete saponins. In addition, five species feeding on Tournefortia (Boraginaceae), Koanophyllon (Asteraceae, tribe Eupatorieae) and Prestonia (Apocynaceae) were shown to sequester PAs of the lycopsamine type, which are characteristic for species of the three plant families. The PA sequestering species commonly store intermedine, lycopsamine and their O^3′-acetyl or propionyl esters as well as O⁷- and O⁹-hydroxyisovaleryl esters of retronecine. The latter as well as the O^3′-acyl esters were not found in the beetles’ host plants, suggesting the ability of the beetles to esterify plant derived retronecine and intermedine or its stereoisomers. Despite the conformity of the beetles’ PA patterns, considerable inconsistencies exist regarding the PA patterns of the respective host plants. One host plant was devoid of PAs, while another contained only simple necines. Since the previous history of the field collected beetles was unknown this discrepancy remains obscure. In contrast to the Palearctic chrysomeline leaf beetles, e.g. some Oreina species which ingest and store PAs as their non-toxic N-oxides, Platyphora leaf beetles absorb and store PAs as the toxic free base (tertiary PA), but apparently avoid to accumulate PAs in the haemolymph. This suggests that Chrysolina and Platyphora leaf beetles developed different lines of adaptations in their parallel evolution of PA mediated chemical defense. Received 30 November 2000; accepted 5 February 2001     

Life Cycle Assessment of landfill biogas management: Sensitivity to diffuse and combustion air emissions

Goal and scopeThe life cycle inventory of landfill emissions is a key point in Life Cycle Assessment (LCA) of waste management options and is highly subject to discussion. Result sensitivity to data inventory is accounted for through the implementation of scenarios that help examine how waste landfilling should be modeled in LCA.MethodFour landfill biogas management options are environmentally evaluated in a Life Cycle Assessment perspective: (1) no biogas management (open dump), conventional landfill with (2) flaring, (3) combined heat and power (CHP) production in an internal combustion engine and (4) biogas upgrading for use as a fuel in buses. Average, maximum and minimum literature values are considered both for combustion emission factors in flares and engines and for trace pollutant concentrations in biogas.ResultsBiogas upgrading for use as a fuel in buses appears as the most relevant option with respect to most non-toxic impact categories and ecotoxicity, when considering average values for trace gas concentrations and combustion emission factors. Biogas combustion in an engine for CHP production shows the best performances in terms of climate change, but generates significantly higher photochemical oxidant formation and marine eutrophication impact potentials than flaring or biogas upgrading for use as a fuel in buses.Interpretation and discussionHowever the calculated environmental impact potentials of landfill biogas management options depend largely on the trace gas concentrations implemented in the model. The use of average or extreme values reported in the literature significantly modifies the impact potential of a given scenario (up to two orders of magnitude for open dumps with respect to human toxicity). This should be taken into account when comparing landfilling with other waste management options. Also, the actual performances of a landfill top cover (in terms of oxidation rates) and combustion technology (in terms of emission factors) appear as key parameters affecting the ranking of biogas management options.     

Mild hydrolysis of 2-trifluoromethylphenol: kinetics, mechanism and environmental relevance

2-Trifluoromethylphenol was hydrolysed in a phosphate buffer at neutral pH. At mild temperatures ranging from 34 degrees C to 69 degrees C this compound liberates consecutively fluorine anions to form salicylic acid. This process is energetically driven by the hydration of the fluorine anions. No intermediates have been detected by HPLC and (19)F-NMR and this was confirmed by computer calculations which favor the first step in the whole reaction sequence being rate-limiting. Accordingly, the reaction energy of the first dehalogenation of the trifluoromethyl anion is 28.4 kcal mol(-1) higher than for the second dehalogenation. The pseudo-first-order kinetic was determined and from an Arrhenius diagram an activation energy of E(a)=25.1 kcal mol(-1) has been estimated. At 37 degrees C and a pH of 7.4 the half-life was 6.9 h. The rate of hydrolysis was favored at higher pH and it was not influenced by oxygen, sunlight or trace elements found in natural water. The latter was shown by incubations with lake water instead of distilled water.     

Biodegradation of polyethylene films with prooxidant additives

Prooxidant additives represent a promising solution to the problem of the environment contamination with polyethylene film litter. Prooxidants accelerate photo- and thermo-oxidation and consequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. The question not fully resolved remains the biodegradation itself, its mechanism and especially the factors influencing the time-frame in which it can occur. The presented review is aimed to provide comprehensible information for both microbiologists and polymer scientists, who need participate in the research leading to an understanding of the microorganism action on the oxidized polyethylene and to design of new materials.     

EFFECTS OF THE TOPOGRAPHIC INDEX DISTRIBUTION ON PREDICTED RUNOFF USING GRASS1

ABSTRACT: The effects of digital elevation model resolutions and contour lengths on the distribution of the topographic index, a fundamental parameter for the hydrologic model, TOPMODEL, and their influence on the predicted peak flows are investigated in this paper. A small agricultural catchment (3.38 km²) is used to determine the catchment response modeled by TOPMODEL for three rainfall events.