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Auteur Moreau, S.; Mostajir, B.; Bélanger, S.; Schloss, I.R.; Vancoppenolle, M.; Demers, S.; Ferreyra, G.A.
Titre Climate change enhances primary production in the western Antarctic Peninsula Type Article scientifique
Année 2015 Publication (up) Revue Abrégée Glob Change Biol
Volume 21 Numéro 6 Pages 2191-2205
Mots-Clés ozone hole; photoinhibition; primary production; regional warming; sea ice; seawater temperature; ultraviolet radiation
Résumé Intense regional warming was observed in the western Antarctic Peninsula (WAP) over the last 50 years. Here, we investigate the impact of climate change on primary production (PP) in this highly productive region. This study is based on temporal data series of ozone thickness (1972–2010), sea ice concentration (1978–2010), sea-surface temperature (1990–2010), incident irradiance (1988–2010) and satellite-derived chlorophyll a concentration (Chl-a, 1997–2010) for the coastal WAP. In addition, we apply a photosynthesis/photoinhibition spectral model to satellite-derived data (1997–2010) to compute PP and examine the separate impacts of environmental forcings. Since 1978, sea ice retreat has been occurring earlier in the season (in March in 1978 and in late October during the 2000s) while the ozone hole is present in early spring (i.e. August to November) since the early 1990s, increasing the intensity of ultraviolet-B radiation (UVBR, 280–320 nm). The WAP waters have also warmed over 1990–2010. The modelled PP rates are in the lower range of previously reported PP rates in the WAP. The annual open water PP in the study area increased from 1997 to 2010 (from 0.73 to 1.03 Tg C yr−1) concomitantly with the increase in the production season length. The coincidence between the earlier sea ice retreat and the presence of the ozone hole increased the exposure to incoming radiation (UVBR, UVAR and PAR) and, thus, increased photoinhibition during austral spring (September to November) in the study area (from 0.014 to 0.025 Tg C yr−1). This increase in photoinhibition was minor compared to the overall increase in PP, however. Climate change hence had an overall positive impact on PP in the WAP waters.
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ISSN 1365-2486 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 1339
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Auteur Boukef, I.; Bejaoui, B.; Hassan, M.B.; Mraouna, R.; Got, P.; Harzallah, A.; Elbour, M.
Titre Spatial distribution and decay rates of coliforms in the sediments and water column of the bizerte lagoon Type Article scientifique
Année 2012 Publication (up) Revue Abrégée Vie Milieu
Volume 62 Numéro 1 Pages 29-36
Mots-Clés bizerte lagoon; coastal waters; contamination; environmental-conditions; escherichia coli decay; estuarine; fecal indicator bacteria; pathogenic bacteria; pollution; recreational waters; seasonal survey; seawater; sunlight; sunlight inactivation; total coliform
Résumé In order to assess the impact of bacterial input loads in Bizerte lagoon (Northern Tunisia), a seasonal survey was done for total coliform bacteria covering the whole lagoon area, to reproduce and prevent dispersion of input loads of terrestrial discharges in the lagoon. Effect of solar radiation on Escherichia coli strains was investigated using seawater microcosms comparatively exposed to sunlight and dark conditions. The results revealed (i) high charges of coliforms in the sediment rather than in the water column, (ii) total coliforms increased periodically with season in both compartments, (iii) anthropogenic discharges influence coastal areas of the lagoon, and (iv) solar radiation has an effect on decay rate of E. coli maintained in microcosm experiments.
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Volume de collection Numéro de collection Edition
ISSN 0240-8759 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 846
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Auteur Boukef, I.; El Bour, M.; Al Gallas, N.; El Bahri, O.; Mejri, S.; Mraouna, R.; Ben Aissa, R.; Boudabous, A.; Got, P.; Troussellier, M.
Titre Survival of Escherichia coli Strains in Mediterranean Brackish Water in the Bizerte Lagoon in Northern Tunisia Type Article scientifique
Année 2010 Publication (up) Revue Abrégée Water Environ Res
Volume 82 Numéro 11 Pages 2249-2257
Mots-Clés bizerte lagoon; brackish water; coastal waters; cytotoxicity; enteric bacteria; escherichia coli; fecal-coliforms; marine waters; salmonella-typhimurium; seawater microcosms; sewage; shigella-dysenteriae type-1; sunlight; survival; viability; virulence
Résumé This study investigated survival and virulence of Escherichia coli strains exposed to natural conditions in brackish water. Two E. coli strains (O126:B16 and O55:B5) were incubated in water microcosms in the Bizerte lagoon in Northern Tunisia and exposed for 12 days to natural sunlight in June (231 to 386 W/m(2), 26 +/- 1 degrees C, 30 g/L) and in April (227 to 330 W/m(2), 17 +/- 1 degrees C, 27 g/L) or maintained in darkness for 21 days (17 +/- 1 degrees C, 27 g/L). The results revealed that sunlight was the most significant inactivating factor (decrease of 3 Ulog within 48 hours for the two strains) compared to salinity and temperature (in darkness). Survival time of the strains was prolonged as they were maintained in darkness. Local strain (E. coli O55:B5) showed better survival capacity (T(90) = 52 hours) than E. coli O126:B16 (T(90) = 11 h). For both, modifications were noted only for some metabolic activities of carbohydrates hydrolysis. Cytotoxicity of the two strains, tested on Vero cell, was maintained during the period of survival. Water Environ. Res., 82, 2249 (2010).
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Volume de collection Numéro de collection Edition
ISSN 1061-4303 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 864
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Auteur Maugars, G.; Manirafasha, M.-C.; Grousset, E.; Boulo, V.; Lignot, J.-H.
Titre The effects of acute transfer to freshwater on ion transporters of the pharyngeal cavity in European seabass (Dicentrarchus labrax) Type Article scientifique
Année 2018 Publication (up) Revue Abrégée Fish Physiol. Biochem.
Volume 44 Numéro 5 Pages 1393-1408
Mots-Clés atlantic salmon; atpase alpha-1 isoforms; branchial chloride cells; carbonic-anhydrase; Dicentrarchus labrax; gill na+/k+-atpase; Gills and extrabranchial organs; Ion transporters; k+-atpase; mitochondrion-rich cells; Osmoregulation; salinity transfer; salmon salmo-salar; seawater acclimation; Seawater to freshwater transfer; Teleost fish
Résumé Gene expression of key ion transporters (the Na+/K+-ATPase NKA, the Na+, K+-2Cl(-) cotransporter NKCC1, and CFTR) in the gills, opercular inner epithelium, and pseudobranch of European seabass juveniles (Dicentrarchus labrax) were studied after acute transfer up to 4days from seawater (SW) to freshwater (FW). The functional remodeling of these organs was also studied. Handling stress (SW to SW transfer) rapidly induced a transcript level decrease for the three ion transporters in the gills and operculum. NKA and CFTR relative expression level were stable, but in the pseudobranch, NKCC1 transcript levels increased (up to 2.4-fold). Transfer to FW induced even more organ-specific responses. In the gills, a 1.8-fold increase for NKA transcript levels occurs within 4days post transfer with also a general decrease for CFTR and NKCC1. In the operculum, transcript levels are only slightly modified. In the pseudobranch, there is a transient NKCC1 increase followed by 0.6-fold decrease and 0.8-fold CFTR decrease. FW transfer also induced a density decrease for the opercular ionocytes and goblet cells. Therefore, gills and operculum display similar trends in SW-fish but have different responses in FW-transferred fish. Also, the pseudobranch presents contrasting response both in SW and in FW, most probably due to the high density of a cell type that is morphologically and functionally different compared to the typical gill-type ionocyte. This pseudobranch-type ionocyte could be involved in blood acid-base regulation masking a minor osmotic regulatory capacity of this organ compared to the gills.
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Volume de collection Numéro de collection Edition
ISSN 0920-1742 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2417
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Auteur Auguet, J.C.; Montanie, H.; Lebaron, P.
Titre Structure of virioplankton in the Charente Estuary (France): transmission electron microscopy versus pulsed field gel electrophoresis Type Article scientifique
Année 2006 Publication (up) Revue Abrégée Microb Ecol
Volume 51 Numéro 2 Pages 197-208
Mots-Clés Capsid/chemistry *Electrophoresis; Electron Plankton Rivers/*virology Seasons Seawater/*microbiology/*virology Viruses/genetics/*isolation & purification/ultrastructure *Water Microbiology; Gel; Pulsed-Field Environmental Monitoring/methods France Genome; Viral/genetics *Microscopy
Résumé Changes in the composition of viral communities were investigated along a salinity gradient and at different times by means of transmission electron microscopy (TEM) and pulsed field gel electrophoresis (PFGE). Samples were collected in fresh (Charente River), estuarine (Charente Estuary), and coastal (Pertuis d'Antioche, French Atlantic coast) waters. Both methods revealed similar patterns in viral community structure with a dominance of small viral particles (capsid and genome size). Viruses with a head size below 65 nm made up 71 +/- 5% of total virus-like particles, and virus-like genomes (VLG) below 100 kb accounted for 89 +/- 9% of total VLG. Despite this apparent stability of virioplankton composition over spatial scale (salinity gradient), the occurrence of large viruses (capsid and genome size) in estuarine and seawater samples indicated the presence of viral populations specific to a geographical location. Temporal changes in the structure (capsid and genome size) of viral communities were more pronounced than those reported at the spatial scale. From January to May 2003, seasonal changes in viral abundance and bacterial production occurred concomitantly with an increase in viral genomic diversity (richness), suggesting that virioplankton composition was strongly linked to changes in microbial activity and/or in the structure of the host communities. Although PFGE and TEM yielded complementary results in the description of virioplankton structures, it seems that the use of PFGE alone should be enough for the monitoring of community changes.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1297
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