Recent Submissions

  • Directory of Atmospheric, Hydrographic and Biological datasets for the Canary Current Large Marine Ecosystem. 2nd Edition: Revised and Expanded

    Déniz-González, Itahisa; Pascual-Alayón, Pedro J.; Chioua, Jamal; García-Santamaría, M. Teresa; Valdés, Luis (IOC-UNESCOParis, France, 2016)
    The Canary Current Large Marine Ecosystem (CCLME) is a major upwelling region off the coast of northwest Africa. A total of 429 datasets, 30 databases and 21 time-series sites have been identified in the area. A substantial part of them were rescued from archives supported in paper copy. The current directory refers to 107 datasets, databases and time-series sites. This catalogue and the recovered data offer an exceptional opportunity for the researchers in the CCLME to study the dynamics and trends of a multiplicity of variables, and will enable them to explore different data sources and create their own baselines and climatologies under a spatial and temporal perspective.
  • Directory of Atmospheric, Hydrographic and Biological datasets for the Canary Current Large Marine Ecosystem

    Déniz-González, Itahisa; Pascual-Alayón, Pedro J.; Chioua, Jamal; García-Santamaría, M. Teresa; Valdés, Luis (IOC-UNESCOParis, France, 2014)
    The Canary Current Large Marine Ecosystem (CCLME) is a major upwelling region off the coast of northwest Africa. A total of 425 datasets, 27 databases and 21 time-series sites have been identified in the area. A substantial part of them were rescued from archives supported in paper copy. The current directory refers to 85 datasets, databases and time-series sites. This catalogue and the recovered data offer an exceptional opportunity for the researchers in the CCLME to study the dynamics and trends of a multiplicity of variables, and will enable them to explore different data sources and create their own baselines and climatologies under a spatial and temporal perspective.
  • Ocean acidification in the Canary Current Large Marine Ecosystem

    Santana-Casiano, J. Magdalena; González-Dávila, Melchor; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    The Canary Current Large Marine Ecosystem (CCLME) covers a series of different oceanographic conditions which evolves from the open ocean to an upwelling coastal margin. In the Eastern Atlantic Ocean, the European Station for Time series in the Ocean (ESTOC) shows that the pH in total scale at in situ conditions presents a decrease of 0.0019 ± 0.0003 as a consequence of an increase in the seawater partial pressure of carbon dioxide (pCO2) of 1.9 ± 0.3 µatm yr-1. Most of the seasonal variability in pCO2 at the ESTOC is explained by the thermodynamic effect of changes in temperature. In the Mauritanian area, the pCO2 increased at a rate of 4.6 µatm yr-1 from 2005 to 2008, showing values higher than at the ESTOC. The seasonal pCO2 variability observed in the Mauritanian upwelling area has been highly correlated with the upwelling index and it is higher than that observed at the ESTOC. Due to the heterogeneity of the CCLME it is not possible to generalize the observed trends. The rate of decrease of pH in the upwelling areas is the result of complex processes. These are determined by the intensity of the upwelling that can be modified by the variations in oceanographic conditions as a result of climate change.
  • Trends in phytoplankton and primary productivity off Northwest Africa

    Demarcq, Hervé; Benazzouz, Aïssa; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    This study is an attempt to update spatial trends previously observed in the productivity of the Canary Current Upwelling System (CCUS) from satellite SeaWiFS datasets (Demarcq, 2009) from the assembling of data from the SeaWiFS (1997-2010) and MODIS (2002-present) sensors. Data blending or simultaneous use of several sensors is a challenge in ocean color, especially in the highly productive coastal waters of the CCUS. An empirical cross-correction of both sensors shows that the estimate of linear trends is possible with an adequate level of precision, valid at least in the CCUS. Common trends between sensors show coherent spatio-temporal patterns, while it is shown that the previously contrasted trends of the 1998-2007 period tend to weaken significantly during the 1998-2014 period while being more homogeneously negative, except in the Guinean region and northern Morocco, i.e. in the extreme parts of the CCUS. These estimates also show the importance of constructing the longest as possible time series of phytoplankton biomass or primary productivity in order to minimize the effects of the decadal variability. A new challenge will be searching qualitative changes in the composition of the phytoplankton, probably more important in an ecological point of view than relatively minor quantitative changes.
  • Recent changes and trends of the upwelling intensity in the Canary Current Large Marine Ecosystem

    Benazzouz, Aïssa; Demarcq, Hervé; González-Nuevo, Gonzalo; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    We provide a summary of current knowledge for the recent trends of the coastal upwelling intensity in the region from 8°N to 43°N, computed from both wind and sea surface temperature (SST) remotely sensed, from 1982 to 2011. In particular, the impact of changes possibly linked to global warming is estimated in the form of spatial linear trends. Statistical analysis of trends and seasonal changes of the upwelling activity are carried out in order to verify the hypothesis of Bakun (1990), which anticipates an intensification of the upwelling favorable winds and therefore a cooling of coastal waters. Our study brings new insights on the spatial patterns of the changes. The results indicate distinct and questionable trends of the two categories of upwelling indices, in a region associated with a strong SST warming, especially in the southern part of the system. While the central and southern parts of the system display an increase of upwelling-favorable winds, no significant upwelling trend is found in the same sub-regions from SST-based upwelling indices. It is stated that changes in the internal structure of the upper ocean, as a result of global warming, may be responsible of such differences: a significant warming of the surface upwelled waters possibly combined with a thickening of the surface mixed layer.
  • Sea level variability and trends in the Canary Current Large Marine Ecosystem

    Pérez-Gómez, Begoña; Álvarez-Fanjul, Enrique; Marcos, Marta; Puyol, Bernat; García, María Jesús; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    This article describes different aspects of sea level variability for the Canary Current Large Marine Ecosystem (CCLME) based on previous publications and existing data from both tide gauges (mainly from the Canary Islands, due to the lack of information in the African coastline) and satellite altimeter. An increase of the rate of mean sea level rise since the 1990s is found from tide gauge data, which is coherent with global studies. The uncertainty of these trends is addressed by comparison with nearby altimetry data, revealing a general high correlation but a significant difference in the trend. The latter should be further explored and complemented with monitoring the vertical land movement at the tide gauges in the future. Analysis of the spatial variations of sea level variability and trends in the CCLME is performed from altimetry data: confirmation is found of the main oceanographic features in the region as well as larger trends of mean sea level since 1992 in the southern part of the domain.
  • Open ocean temperature and salinity trends in the Canary Current Large Marine Ecosystem

    Vélez-Belchí, Pedro; González-Carballo, Marta; Pérez-Hernández, María Dolores; Hernández-Guerra, Alonso; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    The Sea Surface Temperature in the Canary Current Large Marine Ecosystem (CCLME) for the 32 years in the period 1982-2013 shows a mean warming trend of 0.28°C decade-1. However, this overall warming trend shows significant changes due to the influence of the different dynamical regimes that coexist in the CCLME. Near the coast, in the area under the influence of the upwelling, between Cape Blanc and Cape Beddouza, the warming trend is not statistically different from zero. Near the coast, but in the waters under the influence of downwelling, between Cape Verde and Cape Blanc, the warming trend is higher (>0.5°C decade-1), and statistically significant. In the oceanic regions, there is a statistically significant trend of 0.25°C decade-1, a trend that is also observed in waters shallower than the permanent thermocline (200-600 dbar). This warming rate is density compensate, with an increase in salinity of 0.02 decade-1. Neither the intermediate waters nor the upper deep waters show any statistically significant trend. The deep waters (2600-3600 dbar) in the oceanic waters north of the Canary Islands, show a warming rate of -0.01°C decade-1 and a freshening of -0.002 decade-1.
  • Biodiversity of cetaceans in coastal waters of Northwest Africa: new insights through platform-of-opportunity visual surveying in 2011-2013

    Djiba, Abdoulaye; Bamy, Idrissa Lamine; Samba Ould Bilal, Abdellahi; Van Waerebeek, Koen; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    We summarize diversity, group size and habitat of cetaceans documented through ship-based visual survey effort (13,694 km; 1163.5 h) off NW Africa (Conakry to Tangier) in spring and fall of 2011-2013. Study area covered mainly continental shelf with some slope waters. Platform-of-opportunity surveying yielded 270 primary sightings of 14 species. Due to passing mode, 35.7% were identifiable only to family/category: unidentified Delphinidae (25.0%), unidentified rorquals (5.88%) and unidentified whales (4.78%). Delphinus delphis predominated with 28.7% of total sightings (32.7%, including probable) and a massive 71.3% (76.5%) of total number of cetaceans observed (n=15,595). Encounter rate was 81.2 common dolphins 100 km-1; mean group size 124.92. Tursiops truncatus, primarily inshore ecotype (median depth, 44.5 m), accounted for 9.56% (11.4%) of sightings and 1.35% (1.83%) of total cetaceans. Megaptera novaeangliae (6.25%) was regularly seen south of Dakar with a Southern Hemisphere seasonality. Other species showed a relatively low % occurrence: Globicephala spp. (2.57), Orcinus orca (1.10), Grampus griseus (0.73), Stenella frontalis (1.84), S. attenuata (0.37), S. clymene (0.37), S. coeruleoalba (0.37), Balaenoptera brydei (1.10), B. musculus (0.37), beaked whale (0.37), probable-B. borealis (0.37). Baleen plates recovered from a bottom-trawl also evidenced B. borealis presence. Seven new range state records included: G. griseus, S. coeruleoalba (Atlantic Morocco), O. orca, B. musculus (The Gambia), G. macrorhynchus, S. frontalis (Guinea-Bissau), S. attenuata (Guinea).
  • Sea turtles off Northwest Africa

    Marco, Adolfo; Martins, Samir; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Six sea turtle species inhabit the waters of the Canary Current Large Marine Ecosystem. The loggerhead and the green turtles are the most common and the only two species that nest regularly on its beaches (loggerheads in Cape Verde and greens in the Bijagós islands, Guinea-Bissau). The Kemp’s ridleys, the most restricted and endangered in the world, are very rare although migrant juveniles can be found along the northwestern coast of Morocco. Leatherbacks, hawksbills, and olive ridleys can be also found in the waters of the CCLME. Most of adult move after nesting to the continental African coast to feed. Some green females migrate from Poilão (Guinea-Bissau) to the Park National du Banc D’Arguin (Mauritania). Moreover, there is an important feeding area for leatherback turtles coming from the American coast. Small juvenile turtles are known to disperse extensively on a transatlantic scale and are commonly associated with convergence zones, upwellings, major gyre systems, and eddies. Increasing fishing efforts worldwide and marine debris put all sea turtle species at risk. The high concentration of turtle nesting on small beach stretches makes the population extremely vulnerable to any kind of environmental disaster. Turtle-watching activities are known as important alternative sources of income for local communities.
  • Biodiversity and biogeography of decapods crustaceans in the Canary Current Large Marine Ecosystem

    García-Isarch, Eva; Muñoz, Isabel; Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
    Decapods constitute the dominant benthic group in the Canary Current Large Marine Ecosystem (CCLME). An inventory of the decapod species in this area was made based on the information compiled from surveys and biological collections of the Instituto Español de Oceanografía. A total number of 228 species belonging to 54 families were registered. Brachyura, with 87 different species was the most diversified taxa, followed by Caridea and Anomura with 61 and 33 species, respectively. The high diversity of this group in the CCLME is favoured by the presence of typically temperate species in the North (Morocco-Western Sahara), subtropical-temperate species from Morocco to Mauritania, and typically tropical species in the South (Guinea-Bissau‒Guinea). The diversity in the most temperate and northern zone was higher than in the most tropical and southern zone, with exceptionally high values in Mauritania mainly explained by its special biogeographic and oceanographic conditions. Some decapod species have been exploited by both artisanal and industrial fisheries for decades, providing significant incomes to the coastal states. However, the intense shrimp fishing activities have some negative effects like the overexploitation of certain stocks and the impact on benthic communities by disturbing their physical structures and habitats.
  • Cephalopods in the Canary Current Large Marine Ecosystem

    Rocha, Francisco; Cheikh, Inejih; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    This work presents a brief review of cephalopod fauna found in the Canary Current Large Marine Ecosystem waters in terms of biodiversity, ecology and fisheries. This large marine ecosystem presents 139 cephalopod species, including high commercial value groups (Ommastrephids, Loliginids, Octopods and Sepiids), corresponding to a transitional zone between different Atlantic zoogeographic provinces where tropical, temperate and cold water cephalopod species mix. Several assemblages can be identified in the coastal, shelf, slope and deep waters. Coastal assemblages are dominated by sepiids, loliginids and shallow-water octopus, while more oceanic assemblages are largely dominated by ommastrephid and deep-water octopus species. Cephalopod populations in the area can maintain local and international fisheries for these resources. Loliginid and sepiid species constitute substantial resources exploited by coastal fisheries. Ommastrephid squids probably represent the main potential resource for cephalopod pelagic and trawl fisheries in the area. Three species (Todarodes sagittatus, Illex coindetii and Todaropsis eblanae) present great potential for fisheries in the zone.
  • The benthos of Northwest Africa

    Ramos, Ana; Ramil, Fran; Mohamed, Sidi; Barry, Amadou O.; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Despite to play a key role in the marine ecosystems and to be under serious threat, the knowledge on the benthos of the Canary Current Large Marine Ecosystem is currently scarce and comes from the historical expeditions carried out in the region after the end of 19th century. Results of the last Spanish and regional Norwegian surveys show that it does not seem to exist a latitudinal pattern of the biodiversity along the Northwest African coast and that the highest diversity values are located off Western Sahara. Although an important faunistic boundary between tropical and temperate biota seems to be located at Cape Blanc latitude, epibenthic communities maintain a similar structure throughout the region. Decapods are the most representative group in terms of richness, abundance and biomass, being echinoderms, mainly holothuroids, clearly dominant in deep waters. Despite having endured an intense fishing pressure for more than 50 years, suspension-feeder assemblages and vulnerable ecosystems — as the giant cold-water coral reef, the canyon systems, the seamount and the grounds of sponges and gorgonians — already exist in deep waters of the continental slope in Mauritania, Western Sahara and Morocco.
  • Demersal fish in the Canary Current Large Marine Ecosystem

    Fernández-Peralta, Lourdes; Sidibé, Aboubacar; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Demersal ichthyofauna is both the most diverse and the most abundant component in terms of biomass, of the marine shelf and slope ecosystems. Within the Canary Current Large Marine Ecosystem (CCLME), Northwestern African waters hold a fish fauna even more diverse than that of Northeast Atlantic. The convergence of ichthyofaunal components of both temperate and tropical affinities results in a very biodiverse central zone, mainly in Mauritanian waters, where the transition from one faunal type to another is observed. The CCLME supports substantial demersal fish resources whose total catches decline constantly. The FAO assessments show that many important stocks are here overexploited. Species richness is minimum in waters shallower than 400 m, probably due to the heavy fishing pressure exerted over the shelf and upper slope in past decades. Conversely, deep waters are the most biodiverse, particularly between 1000 m and 1700 m depth. Northwestern African waters need to be managed both to avoid overexploitation and to ensure the protection of highly vulnerable species living on very sensitive marine ecosystems of the middle and deep continental slopes, still unexploited. A great effort of cooperation within the various actors involved in the regional fishing policies is required to ensure a sustainable management of the marine resources.
  • Pelagic fish stocks and their response to fisheries and environmental variation in the Canary Current Large Marine Ecosystem

    Braham, Cheikh-Baye; Corten, Ad; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Pelagic fish stocks are the most important fish stocks in terms of biomass and catches in the Canary Current Large Marine Ecosystem. The small pelagic stocks include species with an affinity for temperate waters (sardine, chub mackerel and Atlantic horse mackerel) and species that prefer tropical waters (sardinella and Cunene horse mackerel). Hence, the distribution of the various stocks is strongly determined by the seasonal displacement of the tropical front. As small pelagic fish feed primarily on plankton, changes in primary production may affect the abundance of the stocks. The waters of the Canary Current have shown a drop in primary production over the past three decades, which may be related to the observed increase in water temperature. However, the drop in primary production is not yet reflected by the pelagic fish catches. On the other hand, changes in the abundance and distribution of sardine and sardinella are probably the effect of climatic change. Present management of small pelagics is hampered by a lack of scientific data. Because these stocks are very important to the human population of the region, good quality data should be collected in order to improve the assessments.
  • Zooplankton in the Canary Current Large Marine Ecosystem

    Berraho, Amina; Somoue, Laila; Hernández-León, Santiago; Valdés, Luis; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Copepod species in the CCLME accounted for 60-95% of the zooplankton abundance being the bulk of the mesozooplankton biomass. Two main groups of copepod species can be identified, representing biogeographical and ecological characteristics: tropical and subtropical species, related to a sub region with a low influence of the upwelling nutrient enriched waters (Cape Verde, Canary Islands and Cape Blanc); and subtropical and luso-boreal species identified along the Northwest Africa coast (Cape Spartel-Cape Blanc) with a strong seasonality of upwelling and coastal nutrient rich waters. A succession from small to medium and large calanoids and gelatinous organisms from the upwelled waters to the ocean is the rule and this pattern is coupled with a switch of the feeding mode of the zooplankters. A phytoplankton-based diet was observed in the inshore upwelling zone whereas a microzooplankton based diet was observed offshore under more oligotrophic conditions. More studies are needed to verify that the patterns observed in zooplankton composition and distribution 30-35 years ago are still valid and that climate change and variability of upwelling strength is neither altering the cycles nor the productivity of the CCLME. Also the zooplankton physiology deserves future work as these organisms live longer than any other plankton and are the food of diel vertical migrants (large zooplankton and micronekton).
  • Harmful algal bloom events in the Canary Current Large Marine Ecosystem

    Pitcher, Grant C.; Fraga, Santiago; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    We provide a review of Harmful Algal Blooms (HABs) within the Canary Current Large Marine Ecosystem (CCLME). As yet all documented HABs within the region have been associated with the production of one or another toxin. The diversity of harmful algae recorded within the region is similar to that found in other eastern boundary upwelling systems, and includes those species responsible for paralytic shellfish poisoning, diarrhetic shellfish poisoning, amnesic shellfish poisoning and azaspiracid poisoning. Also present off Northwest Africa, but generally absent from the other major upwelling systems, are those species responsible for ciguatera fish poisoning and microcystin-producing cyanobacterial blooms. Their presence is afforded by the subtropical habitat provided by the island archipelagos found within the CCLME. It is intended that this brief review will provide the foundation and stimulus for further studies of the ecology and dynamics of HABs, of their toxins, and of the public health and socioeconomic impacts of HABs within this region.
  • Phytoplankton and primary productivity off Northwest Africa

    Demarcq, Hervé; Somoue, Laila; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Eastern boundary upwelling ecosystems (EBUEs) cover 2% of the ocean surface, but contribute 7% of the global marine production, that sustain 20% to 30% of global marine fisheries production (FAO, 2012). The Canary Current Upwelling System (CCUS) is the most productive EBUEs after the Humboldt system, because of its permanent or seasonal coastal upwelling, enhanced by a high average solar radiation. The seasonality of the Net Primary Production of the phytoplanktonic compartment (including algae and photosynthetic bacterias) is well described from satellite-based spatial data, which display strong seasonal patterns, especially in the southern part of the system, from Mauritania to Senegal. Rich upwelled waters in this part of the system alternate with warm Guinean waters, making the southern part of the CCUS a major ecological hot spot. The diversity of this system is described here through 217 taxa of micro-phytoplankton, identified in the area between 21°N and 32°N. Few planktonic species have been described in Senegal waters so far, and further research efforts need to be conducted in the CCUS in order to characterize its richness and to the determine if its diversity may be affected by climate changes.
  • Organic matter dynamics in the Canary Current

    Álvarez-Salgado, Xosé Antón; Arístegui, Javier; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    The distribution and cycling of biogenic organic matter in the Canary Current Large Marine Ecosystem is strongly affected by the intense mesoscale activity of the area, mainly in the form of meanders, filaments and eddies, and their interaction. Filaments contribute significantly to the offshore export of coastal upwelling primary production in the form of dissolved and suspended organic matter. Cyclonic and anticyclonic eddies (mostly generated by flow perturbation by Madeira and the Canary Islands) may enhance the production of fresh organic matter during their early stages of formation, favouring the vertical sinking of particles. Additionally, they may accumulate and transport suspended particles and dissolved organic matter through a permanent westward corridor of eddies. Organic matter deposited in coastal sediments is also transported laterally to the adjacent ocean in the form of intermediate and bottom nepheloid layers resulting from the erosion of the shelf and slope sediments by the intense and variable coastal currents. All these mechanisms contribute exporting the biogenic materials produced in the coast hundreds of kilometres into the open ocean.
  • Inorganic carbon, pH and alkalinity in the Canary Current Large Marine Ecosystem

    González-Dávila, Melchor; Santana-Casiano, J. Magdalena; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    The vertical distribution of the carbon dioxide (CO2) variables in the Canary Current Large Marine Ecosystem (CCLME) along the last fifteen years have clearly indicated significant changes over, at least, the first 1000 m affecting the inorganic carbon content and the acidity of the seawater. In the surface, the normalized total dissolved inorganic carbon increased at a rate of 0.9 mol kg-1, the pH in total scale decreased each year on average 0.0019 units, while the normalized total alkalinity keeps constant at a value of 2292 mol kg-1. This increase in total dissolved inorganic carbon (CT) is controlling the total column inventory of anthropogenic CO2 that has reached a value of 66 ± 3 mol m-2 for the reference year 2000. It has been shown that upwelled waters in the Mauritanian upwelling area provide high contents of inorganic carbon that lead to low calcium carbonate saturation states. The uptake of carbon by phytoplankton acts by decreasing CT and consequently increasing saturation states. The Eastern North Atlantic Ocean at the CCLME is increasing its storage capacity for excess CO2 by 0.85 mol m-2 yr-1. Model results indicate the importance of physical and environmental conditions in shaping the sensitivity of CCLME to potential climate change induced upwelling-favorable wind intensification.
  • Inorganic nutrients and dissolved oxygen in the Canary Current Large Marine Ecosystem

    Pelegrí, Josep L.; Peña-Izquierdo, Jesús; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
    Inorganic nutrients increase with depth as a result of the enhanced remineralization of organic matter with aging waters (the time since they were last near the sea surface), and the opposite happens with dissolved oxygen (except within the saturated surface mixed layer). In the Canary Current Large Marine Ecosystem there is also a marked latitudinal gradient, with the Cape Verde Front separating relatively nutrient-poor and oxygen-rich subtropical waters from the nutrient-rich and oxygen-poor tropical waters. Along a latitudinal band off North-West Africa, coastal upwelling brings the subsurface waters towards the sea surface, locally raising the inorganic nutrient levels. This becomes an important lateral source to both gyres, especially to the nutrient-poor subtropical one, taking place through lateral mixing (mainly as a result of the instability of the coastal-upwelling baroclinic jet) and localized coastal filaments (in those regions, typically capes, where the coastal flow converges and offshore advection takes place). In the southernmost portion of our domain, within tropical waters, there is also high (wind-induced) offshore primary production. This, together with the slow ventilation of the subsurface waters, leads to much enhanced remineralization, producing a region with very low oxygen and high inorganic nutrient levels, the oxygen minimum zone of the North Atlantic Ocean.

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