• 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.
    • Waves and tides in the Canary Current Large Marine Ecosystem

      Gómez, Marta; Pérez-Gómez, Begoña; De Alfonso, Marta; Pérez, Susana; Ruiz, Mª Isabel; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      In recent decades, and in parallel to the increase in the computational capabilities and improvements in telecommunications, a remarkable progress in the development of equipment for marine environment monitoring has been carried out. Many countries are implementing permanent measurement networks, as well as climate forecast and data management systems. The information generated by these tools is distributed to the whole society. This article describes waves and tides regime and variability in the Canary Current Large Marine Ecosystem (CCLME). The study is based on those sources of data with adequate and relevant information (products) that allow a reasonable description of these two oceanographic variables, being Puertos del Estado equipment and numerical models the main source of information. A review of existing buoys, tide gauges and numerical models available in the region was performed by contacting different institutions from the affected countries as well as international organizations.
    • 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).
    • Eastern boundary currents off North-West Africa

      Pelegrí, Josep L.; Peña-Izquierdo, Jesús; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      The Cape Verde Front (CVF) separates the North Atlantic subtropical gyre (NASG) from the north-eastern North Atlantic tropical gyre (NATG). Within the NASG, the Canary Current (CC) and the Canary Upwelling Current (CUC) comprise a relatively shallow (down to about 200-300 m) flow of North Atlantic Central Waters (NACW): the CC is found far offshore as a wide and poorly defined current while the CUC is a near-slope intense baroclinic jet linked to the coastal upwelling front. Within the top 300 m of the NATG, the along-slope Mauritania Current and the Cape Verde Current (CVC, a north-eastern extension of the North Equatorial Counter Current that broadly rotates around the Guinea Dome) carry South Atlantic Central Waters northwards. As a result, the frontal system is the site of intense along-slope flow convergence and offshore transport in the top 300 m of the water column. Further deep, down to some 500 m, the interior flow is very weak in both gyres, likely dominated by mesoscale features, except along the continental slope, where the northward Poleward Undercurrent (PUC) feeds through localized inputs from the interior ocean; in particular, within the NATG the CVC appears as responsible for southward transfer of NACW, across the CVF, which eventually reaches the PUC.
    • 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.
    • Main geomorphologic features in the Canary Current Large Marine Ecosystem

      Agudo-Bravo, Luis M.; Mangas, José; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      The Canary Current Large Marine Ecosystem shelf has the typical size and composition, of passive continental margins. In general, it has a mean width between 40-50 km, with exceptions like Bank D´Arguin or Dakar. The maximum age of the sedimentary rocks is 200 Ma. The geomorphological variations are the result of the sedimentary contributions associated to the river basins, which also influence the genesis and presence of canyons in the shelf and slope. These canyons are the main geomorphological features in the region. Seamounts, salt domes, pockmarcks and gravitational processes like debris flows are also observed. The tectonic processes are generally extensive, but have a small influence. It is remarkable the presence of a coral reef with more than 400 km of length in the shallowest Mauritania slope. The geomorphological studies in the intraplate volcanic islands (Canary Islands and Cape Verde), confirm the presence of developed shelves in the older islands, not observed in the younger ones. There are gravitational slides and canyons in all the islands. The region was divided in 4 areas: Morocco–Western Sahara; Mauritania; Canary Islands; and Senegal –Gambia –Guinea–Bissau – Guinea–Cape Verde. Within each of these areas, different geomorphological and geological domains are described.
    • 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.
    • 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).
    • 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.
    • Oceanic intraplate volcanic islands and seamounts in the Canary Current Large Marine Ecosystem

      Mangas, José; Quevedo-González, Luis Á.; Déniz-González, Itahisa; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      The Canary Islands and the Cape Verde Islands Volcanic Provinces show sets of islands and seamounts related to magma-driven processes over tens of millions of years at the Canary and Cape Verde hotspots. Continuous volcanism has been reported for the last 142 Ma on the Canaries and the last 26 Ma on the Cape Verde islands to these days. The oldest ones constitute volcanic edifices formed in tens of million years, whereas the youngest ones were formed within the last hundreds of thousand years up to a few million years. Indeed, these edifices have experienced different stages from submarine-subaerial volcanic to submarine inactive post-stages, which formed volcanic materials with varied compositions, sedimentary rocks and bioclast-rich, non-consolidated marine sediments. Islands and seamounts appear with complex or simple morphologies, dome-shaped to irregular relieves, and total heights ranging 4000-8000 m from the bottom to the island highest peaks, but less than 3500 m on seamounts. A set of several deep-water ecosystems is enhanced in both flora and fauna, known as traditional fishing areas expected to become protected under preservation plans, and potential mineral resources need to be further investigated. The LIFE+ INDEMARES project has provided new geological data from three Canary seamounts.
    • Saharan dust inputs to the Northeast Atlantic

      Gelado-Caballero, María Dolores; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      Mineral aerosol inputs to the Canary Current Large Marine Ecosystem (CCLME) are among the highest in the world, due to its proximity to the Sahara and Sahel deserts in Africa. North Africa accounts for approximately 55% of global dust emissions. An annual average deposition resulting from different models for the Northeast Atlantic ranges between 140 Tg yr-1 and 276 Tg yr-1. Aerosol deposition is an important source of essential and limiting nutrients and trace metals (Fe, Co, Mn, Cu and Al) to the ocean, which may stimulate the autotrophic components (nitrogen fixation and diatoms). The impact of dust inputs on oceanic carbon uptake and climate is dependent on total dust deposition fluxes as well as the bioavailability of nutrients and metals in the dust. However, dust deposition measurements are very scarce in the CCLME region and there are very few sets of long-term measurements of aerosol concentrations, although such data is invaluable in quantifying atmospheric inputs to this important region. Moreover, these measurements are critical for constraining climate and biogeochemical models in the CCLME region, especially because the land use and the climate change could be increasing dust emissions from the African sources.
    • Canary Islands eddies and coastal upwelling filaments off North-west Africa

      Sangrà, Pablo; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      Mesoscale eddies are almost continuously spun off from the Canary Islands constituting a unique eddies source that is not present in other Eastern Boundary Upwelling Systems. The main forcing mechanism is the Canary Current perturbation by the islands topography. Wind forcing also contributes to their generation lowering the threshold of the Canary Current intensity for triggering of the eddy shedding process. They rotate initially in solid body rotation losing it when they reach their mature stage. They are also the main source of long lived eddies for the NE subtropical Atlantic building up the Canary Eddy Corridor. This eddy corridor plays an important role as a zonal conduit carrying both physical and biogeochemical properties from the cold nutrient-rich upwelling eastern boundary towards the interior ocean. Coastal upwelling filaments are recurrently observed near Cape Ghir, Cape Jubi, Cape Bojador and Cape Blanc. Although they have common characteristics, such as low temperature and high chlorophyll-a signals, their structure and origin are different. They play a key role in transferring biogeochemical properties from the coastal upwelling eutrophic region towards the interior oligotrophic subtropical gyre, contributing thus to its enrichment and to the setting up of the Coastal Transition Zone.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • Water masses in the Canary Current Large Marine Ecosystem

      Pastor, María V.; Vélez-Belchí, Pedro; Hernández-Guerra, Alonso; Valdés, L.; Déniz-González, I. (IOC-UNESCOParis, France, 2015)
      In the Canary Current Large Marine Ecosystem (CCLME) water masses of very different origin converge. In the upper layer, the North Atlantic Central Waters (NACW) and the South Atlantic Central Waters (SACW); at intermediate levels the Antarctic Intermediate Water (AAIW) and the warmer and saltier Mediterranean Water (MW); and at the deeper levels the North Atlantic Deep Water (NADW). Here we describe the origin and distribution of these waters masses.
    • Oceanographic and biological features in the Canary Current Large Marine Ecosystem.

      Valdés, Luis; Déniz-González, Itahisa (IOC-UNESCOParis, France, 2015)
      The Canary Current Large Marine Ecosystem (CCLME) is one of the 4 major upwelling systems in the world. 54 marine scientists from 25 institutions have worked in a collaborative manner to make a complete characterization of the CCLME. The result is a detailed description of: (i) the ocean geomorphology and geological materials; (ii) the hydrographic structure and the ocean circulation; (iii) the biogeochemical characteristics of the marine ecosystem; (iv) the life in the sea; (v) and the interannual, interdecadal and long‐term variability. Here we present a summary of the oceanographic and biological features of the CCLME, based in reviews of the scientific knowledge built over decades of research in the area, combined with new data shared by the authors of each of the articles. The main conclusions of this global analysis are presented below, followed by the challenges for scientific research and management goals in the CCLME, which can be used to guide new scientific projects in the region
    • 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.