Affiner votre recherche
Résultats 521-530 de 1,506
Spatial and temporal dynamics of size-structured photosynthetic parameters (PAM) and primary production (¹³C) of pico- and nano-phytoplankton in an atoll lagoon
2012
Lefebvre, Sébastien | Claquin, Pascal | Orvain, Francis | Véron, Benoît | Charpy, Loïc
Atoll lagoons display a high diversity of trophic states due mainly to their specific geomorphology, and probably to their level and mode of human exploitation. We investigated the functioning of the Ahe atoll lagoon, utilized for pearl oyster farming, through estimations of photosynthetic parameters (pulse amplitude modulation fluorometry) and primary production (¹³C incorporation) measurements of the size structured phytoplankton biomass (<2μm and >2μm). Spatial and temporal scales of variability were surveyed during four seasons, over 16months, at four sites within the lagoon. While primary production (P) was dominated by the picophytoplankton, its biomass specific primary productivity (Pᴮ) was lower than in other atoll lagoons. The variables size fraction of the phytoplankton, water temperature, season, the interaction term station*fraction and site, explained significantly the variance of the data set using redundancy analysis. No significant trends over depth were observed in the range of 0–20m. A clear spatial pattern was found which was persistent over the seasons: south and north sites were different from the two central stations for most of the measured variables. This pattern could possibly be explained by the existence of water cells showing different water residence time within the lagoon. Photoacclimation strategies of the two size fractions differed through their light saturation coefficient (higher for picophytoplankton), but not through their maximum photosynthetic capacity (ETRₘₐₓ). Positive linear relationships between photosynthetic parameters indicated that their dynamic was independent of light availability in this ecosystem, but most probably dependent on nutrient availability and/or rapid changes in the community structure. Spatial and temporal patterns of the measured processes are then further discussed in the context of nutrient availability and the possible role of cultured oysters in nutrient recycling.
Afficher plus [+] Moins [-]Deep-sea foraminifera from the Cassidaigne Canyon (NW Mediterranean): Assessing the environmental impact of bauxite red mud disposal
2012
Fontanier, C. | Fabri, M.-C. | Buscail, R. | Biscara, L. | Koho, K. | Reichart, G.J. | Cossa, D. | Galaup, S. | Chabaud, G. | Pigot, L.
Benthic foraminiferal assemblages were investigated from two sites along the axis of the Cassidaigne Canyon (NW Mediterranean Sea). Both areas are contaminated by bauxite red mud enriched in iron, titanium, vanadium and chromium. These elemental enrichments are related to bauxite-derived minerals and various amorphous phases. At the shallowest station located very close to the pipe outlet, the benthic living foraminiferal community is characterised by a very low diversity and by an unusual dominance of Gyroidina umbonata and Bulimina marginata. The mechanical stress related to downslope transport of red mud is a likely source of hydro-sedimentary pollution precluding the settlement of diverse fauna. The living and dead foraminiferal faunas from the deepest site are typical of oligo-mesotrophic conditions prevailing in natural environments. There, bauxite residues have obviously no environmental impact on foraminiferal faunas. The bioavailability of trace metals is likely low as elemental enrichments were not observed in foraminiferal test chemistry.
Afficher plus [+] Moins [-]Terrestrial pollutant runoff to the Great Barrier Reef: An update of issues, priorities and management responses
2012
Brodie, J.E. | Kroon, F.J. | Schaffelke, B. | Wolanski, E.C. | Lewis, S.E. | Devlin, M.J. | Bohnet, I.C. | Bainbridge, Z.T. | Waterhouse, J. | Davis, A.M.
The Great Barrier Reef (GBR) is a World Heritage Area and contains extensive areas of coral reef, seagrass meadows and fisheries resources. From adjacent catchments, numerous rivers discharge pollutants from agricultural, urban, mining and industrial activity. Pollutant sources have been identified and include suspended sediment from erosion in cattle grazing areas; nitrate from fertiliser application on crop lands; and herbicides from various land uses. The fate and effects of these pollutants in the receiving marine environment are relatively well understood. The Australian and Queensland Governments responded to the concerns of pollution of the GBR from catchment runoff with a plan to address this issue in 2003 (Reef Plan; updated 2009), incentive-based voluntary management initiatives in 2007 (Reef Rescue) and a State regulatory approach in 2009, the Reef Protection Package. This paper reviews new research relevant to the catchment to GBR continuum and evaluates the appropriateness of current management responses.
Afficher plus [+] Moins [-]Do human activities affect the picoplankton structure of the Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia)?
2012
Bouvy, Marc | Dupuy, Christine | Pagano, Marc | Barani, Aude | Charpy, Loïc
The spatial variations of the picoplankton (photoautotrophic and heterotrophic microorganisms) in the Ahe atoll lagoon were studied in May and October 2008 to assess whether they were affected by human activities along the atoll. Spatial patterns were studied using 10 sampling stations chosen according to the location of the anthropogenic activities (pearl farming, harbor). Experiments were also carried out to determine whether bacterial growth, with or without predators, was limited by inorganic (N and P) substrates. The results showed that heterotrophic bacterioplankton abundance was superior to the photoautotrophic organisms, especially in May. Significant increases in bacterial abundance were observed in May after 24h incubation with +P and +N (but not in October). All samples complied with the quality levels for fecal indicator bacteria (FIB) defined by the European Union and there was no evidence that human sewage had any impact on picoplankton over the whole atoll.
Afficher plus [+] Moins [-]Occurrence and partitioning of endocrine-disrupting compounds in the marine environment of Thermaikos Gulf, Northern Aegean Sea, Greece
2012
Arditsoglou, Anastasia | Voutsa, Dimitra
An integrated study was conducted to determine the presence of phenolic and steroid endocrine-disrupting compounds (EDCs), in the marine environment of Thermaikos Gulf, Northern Aegean Sea, Greece. Seawater, suspended particulate matter, sediments and biota were examined for nonylphenol, octylphenol, their mono- and diethoxylate oligomers, bisphenol A, estrone, 17α-estradiol, 17β-estradiol, estriol, mestranol and 17 α -ethynylestradiol. Phenolic compounds were detected in all of the compartments, with nonylphenol and its ethoxylates being the dominant pollutants. The occurrence of nonylphenol in sediments presents a significant risk to the biota. Mussels exhibited relatively low concentrations and low bioconcentration factors for NP and OP. The effect of terrestrial sources of the EDCs on the marine environment is discussed. The influence of suspended particulate matter and organic carbon in the partition of the EDCs between the dissolved and the particulate phase was investigated.
Afficher plus [+] Moins [-]Effect of zinc sacrificial anode degradation on the defence system of the Pacific oyster, Crassostrea gigas: Chronic and acute exposures
2012
Mottin, Elmina | Caplat, Christelle | Latire, Thomas | Mottier, Antoine | Mahaut, Marie-Laure | Costil, Katherine | Barillier, Daniel | Lebel, Jean-Marc | Serpentini, Antoine
Two types of exposures were performed to assess the effects of zinc released from sacrificial anode degradation: a chronic exposure, in which oysters were exposed to 0.53±0.04mgZnL⁻¹ for 10weeks, and an acute exposure, where oysters were exposed to 10.2±1.2mgZnL⁻¹ for 1week. At the end of the acute exposure experiment, 81.8% mortality was recorded. In contrast, no mortality was detected after 10weeks exposure. Moreover, all of the immune system biomarkers studied, except the number of circulating haemocytes, were stimulated by a moderate level of zinc and inhibited by a high level. Our exposure conditions did not induce SOD or MXR mRNA expression in gills and digestive gland. However, an increase of MT mRNA is observed in these tissues. The results indicate that oysters are sensitive to acute zinc toxicity but are only moderately affected by a mild zinc concentration.
Afficher plus [+] Moins [-]Persistent organic pollutants in juvenile Magellan penguins (Spheniscus magellanicus) found on the northern shore of the state of São Paulo and southern shore of the state of Rio de Janeiro, Brazil
2012
Baldassin, Paula | Taniguchi, Satie | Gallo, Hugo | Silva, Reinaldo José | Montone, Rosalinda Carmela
In the present study, persistent organic pollutants (POPs) were determined in 25 livers from Magellanic penguins, Spheniscus magellanicus, found on the state of São Paulo and Rio de Janeiro (Brazil). The following concentrations of POPs (wet weight) were found: ∑ PCBs: 18.9–775.8ngg⁻¹; ∑ DDTs: 2.3–275ngg⁻¹; and ∑ HCHs: 1.0–11.8ngg⁻¹. Among the PCBs, there was a predominance of hexachlorobiphenyls (138 and 153) and heptachlorobiphenyls (180 and 187). Among the organochlorines, DDT predominated. Through histopathologic exams a positive correlation was found between HCB and cardiovascular failure (p=0.012), as HCB values (wet weight) were 6.33–96.49ngg⁻¹ for positive animals and 2.45–19.63ngg⁻¹ for negative animals. Studies on POPs in Magellan penguins contribute to a better understanding of the distribution and trends of these pollutants in the western South Atlantic Ocean.
Afficher plus [+] Moins [-]Relationship between metal enrichments and a biological adverse effects index in sediments from Todos Santos Bay, northwest coast of Baja California, México
2012
Muñoz-Barbosa, A. | Gutiérrez-Galindo, E.A. | Daesslé, L.W. | Orozco-Borbón, M.V. | Segovia-Zavala, J.A.
In 1992 and 2004, heavy metals concentrations were measured in surficial sediments from Todos Santos Bay, located in Ensenada, Baja California, Mexico. The aim was to search for relationships between metal enrichment factors and a biological adverse effects index. Unlike Ni, the elements Cd, Cu and Zn showed significant correlations (p<0.05) between enrichment factors and the biological adverse effects index. Cu showed a 0.74:1 relationship, which means that any enrichment above 0.74 could represent biological adverse effects. On the other hand, Cd and Zn enrichments must be >5.5 and >1.5, respectively, in order for the sediments to be considered toxic. In general, data showed that most of the metal concentrations in Todos Santos Bay sediments could not cause adverse effects to biota. Only Ensenada’s harbor and the zone next to a dredging dumping site showed metal enrichments that could be toxic.
Afficher plus [+] Moins [-]Numerical modeling with application to tracking marine debris
2012
Potemra, James T.
This paper describes different numerical models of ocean circulation the output of which can be applied to study patterns and pathways of drifting marine debris. The paper focuses on model output that is readily available rather than on numerical models that could be configured and run locally. These include operational models from the US Navy (the Navy Layered Ocean Model (NLOM), Coastal Ocean Model (NCOM), and Hybrid Coordinate Ocean Model (HYCOM)), data assimilating reanalysis models (the Simple Ocean Data Assimilation (SODA), the Global Ocean Data Assimilation Experiment (GODAE) models), and the European Center for Medium-Range Weather Forecasts (ECMWF) ocean reanalysis (Ocean Reanalysis System, ECMWF/ORA-S3). The paper describes the underlying physics in each model system, limitations, and where to obtain the model output.
Afficher plus [+] Moins [-]Vitellogenin and Lipovitellin from the prawn Macrobrachium borellii as hydrocarbon pollution biomarker
2012
García, C Fernando | Heras, Horacio
During reproduction vitellogenin (VTG) is transported to vitellogenic oocytes as a precursor of egg yolk lipovitellin (LV). As VTG synthesis is affected by environmental stressors, it is widely used as biomarker in endocrine disruption studies. However, it has seldom been employed to evaluate invertebrate hydrocarbon pollution. An ELISA with anti-LV antibody was developed to evaluate the impact of water-soluble fraction of crude oil (WSF) on Macrobrachium borellii vitellogenesis. Prawn VTG concentration was within the range reported for other crustaceans; LV values were positively correlated with gonadosomatic index (GSI). Females at different vitellogenic stages were exposed to a sub-lethal concentration of WSF for 7days. Exposed animals with GSI>7 increased their VTG and LV titer as compared to control organisms (190% and 140%, respectively). VTG levels in M. borellii were upregulated and highly sensitive to WSF exposure. This assay could be employed as a biomarker for freshwater hydrocarbon pollution.
Afficher plus [+] Moins [-]