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See detailHypoxia in macrophytodetritus accumulation: Species specific harpacticoid copepod adaptation?
Mascart, Thibaud ULg; De Troch, Marleen; Gobert, Sylvie ULg et al

Poster (2014, May 05)

Mediterranean Posidonia oceanica seagrass meadows generate high primary production and support large biodiversity of associated fauna and flora. The majority of the foliar material falls on the ... [more ▼]

Mediterranean Posidonia oceanica seagrass meadows generate high primary production and support large biodiversity of associated fauna and flora. The majority of the foliar material falls on the unvegetated sea floor during the autumnal leaf senescence, fuelling the detrital food web. Whilst laying on the sea floor the freshly formed macrophytodetritus pile up into accumulations according to the local hydrodynamics and seafloor geomorphology. In these litter accumulations, harpacticoid copepods (Crustacea, Copepoda) are the main meiofaunal players (metazoans in the size range of 38µm – 1mm) and show a high specific diversity. They are primarily grazers, but their high specific diversity suggests that they occupy also a large variety of trophic niches. This large morphological and trophic diversity can partly be promoted by the complexity of the phytodetritus in seagrass accumulations. On the other hand, macrophytodetritus degradation and flux of reduced compounds from the sediments is responsible for oxygen consumption inside the accumulation of seagrass litter. Therefore, concentration of oxygen inside the accumulation is very variable and often under the concentration observed in the water column just above the litter. Frequently, oxygen levels reach very low values. The present study aims to link the oxygen variability inside the accumulation to the densities of the five most dominant harpacticoid copepods found living in the P. oceanica litter. Standardized samples were collected seasonally in two contrasting sites of the Calvi Bay (Corsica) during one year. Our results showed no correlation between the oxygen concentrations and harpacticoid community diversity or their total abundances. The five most dominant species showed divergent results, but none had a clear correlation with the oxygen concentration. This contrasts with observation done for sediment meiofaunal community where most harpacticoid copepods are sensitive to oxygen level and where nematodes often dominate the community. This could be explained by their high mobility and the patchiness and variability of the oxygen concentrations present in the accumulations. Harpacticoid copepods, whilst being sensitive to hypoxia and anoxia developed a strategy to live in this fast oxygen changing environment. To conclude, our results underline the importance of species-specific analysis of correlation data. Especially in complex and dynamic environments where a variety of potential trophic niches are present and species competition is very likely to occur. The overall abundance pattern and diversity of the copepod community showed no relation to the oxygen concentration while the most abundant copepod species did not responded to fluctuating oxygen concentrations. [less ▲]

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See detailCorrelation between the acoustic noise field measured in a Posidonia oceanica bed and the photosynthetic activity
Felisberto, P; Zabel, F; Rodriguez, O et al

Poster (2014, May 05)

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See detailRates of microbial sulfur oxidation in low oxygen environments
Crowe, SA; Canfield, DE; Sturm, A et al

Poster (2014, May 05)

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See detailAmmonia Oxidising Archaea in the OMZ of a freshwater African Lake
Lliros, M; Ingeoglu, O; Garcia-Armisen, T et al

Poster (2014, May 05)

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See detailAnaerobic methane oxidation in two tropical freshwater systems
Roland, Fleur ULg; Darchambeau, François ULg; Crowe, SA et al

Poster (2014, May 05)

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See detailHexis
Durand, Pascal ULg

E-print/Working paper (2014)

Définition et discussion du concept d'« Hexis » dans la sociologie de Pierre Bourdieu.

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See detailCapital symbolique
Durand, Pascal ULg

E-print/Working paper (2014)

Présentation et discussion du concept de « Capital symbolique » dans la sociologie de Pierre Bourdieu.

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See detailIllusio
Durand, Pascal ULg

E-print/Working paper (2014)

Définition et discussion du concept d'« Illusio » dans la sociologie de Pierre Bourdieu.

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See detailNo performance reduction at the present northern edge of Ambrosia artemisiifolia L. invasion range
Ortmans, William ULg

Conference (2014, May 05)

Plant populations at range edges may exhibit reduction of performances and fitness. In the case of biological invasions, such a reduction could be associated with a slowing down of the spread and explain ... [more ▼]

Plant populations at range edges may exhibit reduction of performances and fitness. In the case of biological invasions, such a reduction could be associated with a slowing down of the spread and explain the non-naturalization of a species outside its present invasion range. Common ragweed (Ambrosia artemisiifolia L.) is an ideal model to investigate such processes, since it is invasive in France but not naturalized in northern countries, such as Belgium and the Netherlands. In this study, we test if the performances of ragweed populations vary among different invasion zones. Three populations were selected in each of four invasion zones in Western Europe: 1) French invasion area; 2) northern and 3) southern invasion edges; and 4) outside the invasion area (Belgium and Netherlands). Field performances (growth, reproduction, stress resistance) were recorded on 25 plants per population. Furthermore, the competition by the native flora was assessed around each plant. Generalized Linear Models were used to compare performance among invasion zones and populations, with competition as covariate. Regressions were also performed to assess the influence of climatic data on population performances. No evidence of decreasing performances was found at the edges of the invasion area, neither outside of it, suggesting that the invasion front has the potential to keep going northwards. Competition by native flora had a significant impact on stress resistance, but did not decrease reproduction or growth. These results are discussed in the light of other ongoing experiments in Belgium. [less ▲]

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See detailGenetic screening in pituitary patients
Beckers, Albert ULg

Scientific conference (2014, May 04)

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See detailHeroin-assisted treatment showed better efficacy than methadone
ANSSEAU, Marc ULg; Demaret, Isabelle ULg

Poster (2014, May 04)

Background: A fraction of patients receiving methadone treatment pursues their use of street heroin. In Switzerland, a new treatment with prescribed diacetylmorphine (pharmaceutical heroin) was developed ... [more ▼]

Background: A fraction of patients receiving methadone treatment pursues their use of street heroin. In Switzerland, a new treatment with prescribed diacetylmorphine (pharmaceutical heroin) was developed to help these heroin addicts resistant to methadone treatment to decrease their street heroin use. In this heroin-assisted treatment (HAT), diacetylmorphine is prescribed to severe heroin user and diacetylmorphine is administered by patients under the supervision of nurses in a specific centre. Six randomised controlled trials compared HAT to methadone treatment: in Switzerland, The Netherlands, Spain, Germany, Canada and United- Kingdom. HAT showed better efficacy than methadone. Patients used less street heroin, their health improved and their criminal behaviour decreased. A new trial assessed in Belgium the feasibility and efficacy of this treatment compared to methadone treatment. Methods: The TADAM (Treatment Assisted by Diacetylmorphine) was an open label randomised controlled trial developed on the Swiss model of HAT developed in 1994. Main inclusion criteria were 5 years of heroin addiction, (almost) daily use of street heroin and a previous attempt of methadone treatment. As in the Dutch experiment, patients could choose to inhale or to inject diacetylmorphine in the new HAT centre. HAT was stopped after 12 months and the best available treatment was offered to the patient. The research team assessed subjects every three months with standardised questionnaires (EuropASI, MAP-HSS, SCL-90-R) and questions on involvement in a criminal milieu. We completed our reported data with toxicological analysis and criminal proceedings. Results: 74 subjects were randomised in the trial: 36 in the experimental group and 38 in the control group. According to the primary efficacy criterion, the experimental group counted at least 30% more responders than the control group after 3 months (p<0.05), 6 months (p<0.05) and 9 months (p<0.01). At the 12 month assessment, the number of responders was still higher in the experimental group but the difference (11%) was no more significant (p=0.35). At the 12 month assessment, the condition of patients in the experimental group worsened compared to the 9 month assessment. This effect was not seen in the control group were patients could continue their methadone treatment after the 12 months. Conclusion: As in other countries, HAT is an effective treatment for severe heroin addicts resistant to methadone treatment. However, a predetermined duration of 12 month counteracts the efficacy of this treatment. [less ▲]

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