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ArchiMer, Institutional Archive of Ifremer (French Research Institute for Exploitation of the Sea) (9.043 recursos)
Archimer, is the institutional repository of Ifremer (French Research Institute for Exploitation of the Sea). It provides freely available scientific or technical documents online (publications, theses, conference proceedings, etc) in all fields related to oceans (oceanography, aquaculture, fisheries, etc). The site is available in French and English.

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Mostrando recursos 1 - 20 de 66

1. Combined Fishing and Climate Forcing in the Southern Benguela Upwelling Ecosystem: An End-to-End Modelling Approach Reveals Dampened Effects - Travers-trolet, Morgane; Shin, Yunne-jai; Shannon, Lynne; Moloney, Coleen; Field, John
The effects of climate and fishing on marine ecosystems have usually been studied separately, but their interactions make ecosystem dynamics difficult to understand and predict. Of particular interest to management, the potential synergism or antagonism between fishing pressure and climate forcing is analysed in this paper, using an end-to-end ecosystem model of the southern Benguela ecosystem, built from coupling hydrodynamic, biogeochemical and multispecies fish models (ROMS-N2P2Z2D2-OSMOSE). Scenarios of different intensities of upwelling-favourable wind stress combined with scenarios of fishing top-predator fish were tested. Analyses of isolated drivers show that the bottom-up effect of the climate forcing propagates up the food...

2. Warm brine lakes in craters of active mud volcanoes, Menes caldera off NW Egypt: evidence for deep-rooted thermogenic processes - Dupre, Stephanie; Mascle, Jean; Foucher, Jean-paul; Harmegnies, Francois; Woodside, John; Pierre, Catherine
The Menes caldera is a fault-controlled depression (~8 km in diameter) at ~3,000 m water depth in the western province of the Nile deep-sea fan off NW Egypt, comprising seven mud volcanoes (MVs) of which two are active. Based on multichannel and chirp seismic data, temperature profiles, and high-resolution bathymetric data collected during the 2000 Fanil, 2004 Mimes and 2007 Medeco2 expeditions, the present study investigates factors controlling MV morphology, the geometry of feeder channels, and the origin of emitted fluids. The active Cheops and Chephren MVs are 1,500 m wide with subcircular craters at their summits, about 250 m...

3. Patterns of Rare and Abundant Marine Microbial Eukaryotes - Logares, Ramiro; Audic, Stéphane; Bass, David; Bittner, Lucie; Boutte, Christophe; Christen, Richard; Claverie, Jean-michel; Decelle, Johan; Dolan, John R.; Dunthorn, Micah; Evardsen, Bente; Gobet, Angélique; Kooistra, Wiebe H. C. F.; Mahe, Frederic; Not, Fabrice; Ogata, Hiroyuki; Pawlowski, Jan; Pernice, Massimo C.; Romac, Sarah; Shalchian-tabrizi, Kamran; Simon, Nathalie; Stoeck, Thorsten; Santini, Sebastien; Siano, Raffaele; Wincker, Patrick; Zingone, Adriana; Richards, Thomas A.; De Vargas, Colomban; Massana, Ramon
Background Biological communities are normally composed of a few abundant and many rare species. This pattern is particularly prominent in microbial communities, in which most constituent taxa are usually extremely rare. Although abundant and rare subcommunities may present intrinsic characteristics that could be crucial for understanding community dynamics and ecosystem functioning, microbiologists normally do not differentiate between them. Here, we investigate abundant and rare subcommunities of marine microbial eukaryotes, a crucial group of organisms that remains among the least-explored biodiversity components of the biosphere. We surveyed surface waters of six separate coastal locations in Europe, independently considering the picoplankton, nanoplankton, and...

4. A numerical model for ocean ultra-low frequency noise: Wave-generated acoustic-gravity and Rayleigh modes - Ardhuin, Fabrice; Lavanant, Thibaut; Obrebski, Mathias; Marie, Louis; Royer, Jean-yves; D'Eu, Jean-francois; Howe, Bruce M.; Lukas, Roger; Aucan, Jerome
The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii...

5. Spatio-Temporal Variability of the North Sea Cod Recruitment in Relation to Temperature and Zooplankton - Nicolas, Delphine; Rochette, Sebastien; Llope, Marcos; Licandro, Priscilla
The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in...

6. Slip rate estimation along the western segment of the Main Marmara Fault over the last 405–490 ka by correlating mass transport deposits - Grall, Celine; Henry, P.; Thomas, Yannick; Westbrook, Graham; Cagatay, M. N.; Marsset, Bruno; Saritas, H.; Cifci, G.; Geli, Louis
[1] High-resolution 3-D seismic data acquired in the Sea of Marmara on the Western High, along the northwestern branch of the North Anatolian Fault (also known as the Main Marmara Fault), shed new light on the evolution of the deformation over the last 500–600 ka. Sedimentary sequences in ponded basins are correlated with glacioeustatic cycles and transitions between marine and low sea/lake environments in the Sea of Marmara. In the 3 × 11 km2 of the 3-D seismic survey, deformation over the last 405–490 ka is localized along the main fault branch and north of it, where N130°–N140° trending normal...

7. Behaviour and fate of urban particles in coastal waters: Settling rate, size distribution and metals contamination characterization - Oursel, B.; Garnier, C.; Pairaud, Ivane; Omanovic, Dario; Durrieu, G.; Syakti, A.d.; Le Poupon, C.; Thouvenin, Benedicte; Lucas, Y.
The evaluation of contaminant net fluxes from the coast to the open sea requires the study of terrigeneous particles behaviour and fate. We studied the particles issued from two small coastal rivers whose waters are mixed with treated wastewater (TWW) coming from the Marseille wastewater treatment plant (WWTP) just before discharge to the Mediterranean Sea. An experimental device was developed and used to investigate particles settling rates, size distribution and metallic contamination when mixing with seawater. The particles were sampled in flood deposits of rivers and outlets during rainy periods and in the outlet water during dry periods. The flood...

8. Mesoscale spatio-temporal dynamics of demersal assemblages of the Eastern Ionian Sea in relationship with natural and fisheries factors - Tsagarakis, Konstantinos; Mytilineou, Chryssi; Haralabous, John; Lorance, Pascal; Politou, Chrissi-yianna; Dokos, John
Data from the MEDITS bottom trawl surveys in the Eastern Ionian Sea, covering a depth range of 28 to 845 m were analysed for the period 1998-2008. For each trawling location, environmental and geographical parameters were recorded, while biomass, abundance, biodiversity and size-based metrics were estimated for the total megafaunal community, as well as for four taxonomic sub-communities (Osteichthyes, Chondrichthyes, Crustacea and Cephalopoda) which were expected to respond differently to environmental changes and fishing. In addition, biomass and abundance of ten species selected based on commercial interest, depth range and life history traits were explored, with particular emphasis on deep-sea...

9. Bio-economic management strategy evaluation of deepwater stocks using the FLBEIA model - Garcia, Dorleta; Urtizberea, Agurtzane; Diez, Guzman; Gil, Juan; Marchal, Paul
Deepwater fish are characterized by long lifespans, late maturity and low productivity. This implies slow recovery from low biomass levels and it is, therefore, important to manage these stocks correctly to avoid overfishing. However, these stocks are generally data poor, which it makes difficult to apply quantitative assessment models on which to base their management. The management strategy evaluation (MSE) approach consists in evaluating the performance of management strategies by simulation before their implementation. In the evaluation, the main sources of uncertainty in a fishery system and its management process should be taken into account in order to find robust...

10. Testing CPUE-derived spatial occupancy as an indicator for stock abundance: application to deep-sea stocks - Trenkel, Verena; Beecham, Jonathan A.; Blanchard, Julia L.; Edwards, Charles T. T.; Lorance, Pascal
The status of an exploited population is ideally determined by monitoring changes in abundance and distributional range and pattern over time. Area of occupancy is a measure of the current distribution. Unfortunately, for many populations, scientific abundance and distribution information is not readily available. To evaluate the reliability of commercial fishing data for deriving occupancy indicators that could serve as proxies for stock abundance, we investigated four questions: 1) Occupancy changes with stock biomass, but is this change strong enough to make occupancy a sensitive indicator of population biomass? 2) Fishing boats follow fish, but when does such activity alter...

11. Assessing the risk of vulnerable species exposure to deepwater trawl fisheries: the case of orange roughy Hoplostethus atlanticus to the west of Ireland and Britain - Dransfeld, Leonie; Gerritsen, Hans D.; Hareide, Nils R.; Lorance, Pascal
With slow growth rates, late maturity and a high maximum age of 100 years or more, orange roughy can be classified as a vulnerable deepwater fish species that can only sustain low rates of exploitation. Historical patterns of exploitation associated with this species suggest that it is currently not possible to manage its fisheries in the Northeast Atlantic sustainably, and the total allowable catch for orange roughy has been gradually reduced to zero for European fisheries since 2010. Orange roughy to the west of Ireland and Britain occurs on distinct bathymetric features (seamounts, hills and canyons) as well as on...

12. No net loss of biodiversity or paper offsets? A critical review of the French no net loss policy - Quetier, Fabien; Regnery, Baptiste; Levrel, Harold
French regulations concerning the mitigation of development impacts have been progressively strengthened with offsets now required for impacts on forests, wetlands, and protected species, among others. In 2012, following a national consultative process called Grenelle de l’Environnement, legal requirements in terms of monitoring and effective implementation of measures aimed at avoiding, reducing and offsetting impacts were strengthened. This has created strong “demand” for offsets. The workability of these new requirements has come under scrutiny, not least because of their strong legal and financial implications for developers. In this context, official government guidance on implementing the mitigation hierarchy was published in 2012....

13. A behavioural fish movement approach within an anchovy IBM model to study fish migration patterns in the Bay of Biscay - Politikos, Dimitrios; Huret, Martin; Petitgas, Pierre
Modelling of fish movement behaviour within a heterogeneous marine environment is a challenging but also key issue for understanding the effect of environmental factors and climatic change on fish processes (growth, distribution, mortality, reproduction). Fish movement models have the capability to encompass the combined effect of environment and empirical knowledge of fish individuals as energy requirements, known preys and predators, swimming capacities into a unified framework. Following an Individual Based Model (IBM) approach, a fish movement model has been developed to simulate the active movement of adult anchovy in the Bay of Biscay (BoB) in response to the spatio-temporal variations...

14. Early individual electronic identification of sea bass using RFID microtags: A first example of early phenotyping of sex-related growth - Ferrari, Sebastien; Chatain, Beatrice; Cousin, Xavier; Leguay, Didier; Vergnet, Alain; Vidal, Marie-odile; Vandeputte, Marc; Begout, Marie-laure
Although individual electronic tagging using PIT (Passive Integrated Transponder) tags is well established, it is mainly used for fish > 60 mm in length. Since electronic tagging is an ideal identification method, we used RFID (Radio Frequency Identification) microtags (6 mm in length, 1 mm in diameter, 10 mg in mass) to characterize individual fish from the early stages of their development and throughout their lifecycles. We used sea bass, Dicentrarchus labrax, (105 day-old fish weighing between 100 and 1100 mg) and studied the effects of intra-coelomic tagging in half the population using different endpoints including survival and tag reading,...

15. Black scabbardfish, Aphanopus carbo, in the northeast Atlantic: distribution and hypothetical migratory cycle - Farias, Ines; Morales-nin, Beatriz; Lorance, Pascal; Figueiredo, Ivone
The biology, ecology, and dynamics of the deep-sea teleost black scabbardfish in the northeast Atlantic are reviewed. The black scabbardfish is a commercial bathypelagic species found in the NE Atlantic mostly from Iceland to the Canary Islands and Western Sahara, at depths from 800 to 1300 m. The spatial structure of its population is still uncertain, although the existence of one single stock that migrates around the NE Atlantic driven by feeding and reproduction is the most likely hypothesis consistent with available data. This review is based on data from commercial fisheries off the Faroe Islands, Hatton Bank, the west...

16. Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources - Obrebski, Mathias; Ardhuin, Fabrice; Stutzmann, Eleonore; Schimmel, Martin
Among the different types of waves embedded in seismic noise, body waves present appealing properties but are still challenging to extract. Here we first validate recent improvements in numerical modeling of microseismic compressional (P) body waves and then show how this tool allows fast detection and location of their sources. We compute sources at similar to 0.2 Hz within typical P teleseismic distances (30-90 degrees) from the Southern California Seismic Network and analyze the most significant discrete sources. The locations and relative strengths of the computed sources are validated by the good agreement with beam-forming analysis. These 54 noise sources...

17. Improvements of simulated Western North Atlantic current system and impacts on the AMOC - Talandier, Claude; Deshayes, Julie; Treguier, Anne-marie; Capet, Xavier; Benshila, Rachid; Debreu, Laurent; Dussin, Raphael; Molines, Jean-marc; Madec, Gurvan
Previous studies have shown that low horizontal resolution (of the order of 1°) ocean models, hence climate models, are not able to adequately represent boundary currents nor mesoscale processes which affect the dynamics and thermohaline circulation of the ocean. While the effect of mesoscale eddies can be parameterized in low resolution models, boundary currents require relatively high horizontal resolution. We clarify the impact of increasing the resolution on the North Atlantic circulation, with emphasis on the Atlantic Meridional Overturning Circulation (AMOC), by embedding a 1/8° nest covering the North Atlantic into a global 1/2° model. Increasing the resolution in the nest...

18. Combining quantitative and qualitative models to identify functional groups for monitoring changes in the Bay of Biscay continental shelf exploited foodweb - Lassalle, Geraldine; Pasqual, Jean-sebastien Nelva; Boet, Philippe; Rochet, Marie-joelle; Trenkel, Verena; Niquil, Nathalie
To develop and implement ecosystem-based management, it is critical to monitor foodweb components or functional groups which are robust to uncertainty in ecosystem structure and functioning yet sensitive to changes. To select such functional groups for the Bay of Biscay continental shelf, both quantitative and qualitative foodweb models were developed. First, functional groups for which predictions of directions of change following an increase in primary productivity, prey or predators, or in fishing activities were identical across alternative qualitative model structures were identified. Second, the robustness to model type was assessed by comparing qualitative predictions with quantitative Ecopath model results. The...

19. Development of a 3D Coupled Physical-Biogeochemical Model for the Marseille Coastal Area (NW Mediterranean Sea): What Complexity Is Required in the Coastal Zone? - Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane
Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period...

20. Isotopic Diversity Indices: How Sensitive to Food Web Structure? - Brind'Amour, Anik; Dubois, Stanislas
Recently revisited, the concept of niche ecology has lead to the formalisation of functional and trophic niches using stable isotope ratios. Isotopic diversity indices (IDI) derived from a set of measures assessing the dispersion/distribution of points in the δ-space were recently suggested and increasingly used in the literature. However, three main critics emerge from the use of these IDI: 1) they fail to account for the isotopic sources overlap, 2) some indices are highly sensitive to the number of species and/or the presence of rare species, and 3) the lack of standardization prevents any spatial and temporal comparisons. Using simulations...

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