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The Global Coastal Ocean: Interdisciplinary Regional Studies and Syntheses. Oceanography and fisheries of the Canary Current/Iberian Region of the Eastern North Atlantic
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... The location of the front varies in latitude due to the seasonal variation of the Intertropical Convergence Zone and the associated high pressure centers that drive the trade winds (Schneider et al. 2014). The frontal system is shaped by the westward turn of the Canary Current (Barton 1987) forced by the wind curl stress (Arístegui et al. 2006;Pastor et al. 2013). The confluence of the southward and northward currents along the front drives the nutrient and chlorophyll rich waters from the tropical gyre and the coastal upwelling into the eastern edge of the subtropical gyre, giving rise to a giant filament Biogeochemistry that sustains high productivity year round (Gabric et al. 1993;Pastor et al. 2013). ...
We investigated dinitrogen (N2) fixation activity and diazotroph community composition across the Cape Verde Frontal Zone (CVFZ), from photic epipelagic waters (0-200 m) to aphotic meso- (200–1000 m) and bathypelagic (> 1000 m) waters. The highest N2 fixation rates of 4.1 ± 2.2 nmol N l− 1 day− 1 and 7.8 ± 2.3 nmol N l− 1 day− 1 were in epipelagic waters south of the front. We detected aphotic N2 fixation in 5 out of 32 samples, primarily south of the front, and sporadically down to 3,000 m, with rates ranging from 0.03 ± 0.01 nmol N l− 1 day− 1 to 0.07 ± 0.01 nmol N l− 1 day− 1. Cyanobacteria dominated the diazotroph community and nitrogenase gene (nifH) expression profiles in surface waters and, surprisingly, in aphotic waters. The detection of cyanobacterial nifH genes by DNA sequencing and quantitative PCR in the aphotic zone, together with nifH expression in meso- and bathypelagic waters, indicates a downward flux of metabolically active cyanobacteria, and points to a contribution to the observed aphotic N2 fixation rates. In the photic zone, UCYN-A dominated north of the front, whereas Trichodesmium was mainly found in the southern region. However, our results also show that cross-frontal advection of cyanobacterial diazotrophs can occur via intrusions of surface water. Salinity, temperature, and mixed layer depth were the main determinants of the diazotroph composition and distribution of the key cyanobacteria. Thus, the front appeared to act as a dynamic barrier controlling the distribution of cyanobacterial diazotrophs.
... Fisheries play an important role in the socio-economy of coastal states of the Canary current upwelling system [Arístegui et al., 2006, Binet et al., 1998]. In this region, a population of about 58 million of which 70% are related to the Canary Current ecosystem [Heileman and Tanstad, 2008], this population is distributed over to the country's GDP (Gross Domestic Product) and 500, 000 opportunities between direct and indirect jobs. ...
Studying physical processes of an upwelling system is essential to understand its present variability and its past and future changes. This thesis presents an interdisciplinary study of the coastal upwelling system from different satellite acquired data, with the main focus placed on the North West African (NWA) upwelling system. This interdisciplinary study covers (1) the problem of the automatic identification and extraction of the upwelling phenomenon from biological and physical satellite observations. (2) A statistical study of the spatio-temporal variation of the NWA upwelling throughout its extension and different upwelling indices. (3) A Study of the nonlinear relationships between the surface mixing and biological activity in the upwelling regions. (4) Lagrangian studies of coherent eddies; their physical properties and automatic identification. (5) The study of transport made by Lagrangian eddies off the NWA Upwelling and their impact on the open ocean. [...]
... The proportion of mineralized nutrients increases through the upwelling season from 30% in May to 70% in October ( Álvarez-Salgado et al., 2010). Thus, pulses between upwelling/relaxation (nutrient enrichment/subsequent remineralisation) explain the high productivity of the Rías (Tenore et al., 1995), a rich and diverse ecosystem that supports important fisheries including the fishery for cephalopods (Arístegui et al., 2006;). (www.pescadegalica.com). ...
... Our study indicated that larger specimens of P. narval were more predominant in Madeira archipelago compared to specimen size reported by González et al. (1997) for the Canary Islands. The difference obtained in CL distribution between archipelagos may be due to the greater availability of food, the highest water temperature and larger continental slope in the Canary Islands (Arístegui et al., 2006). P. narval presented a CL distribution pattern per sex characterized by the predominance of males in the lower classes and females in the higher, showing that females had a mean size significantly higher than males. ...
Analysis of abundance and population structure of Plesionika narval was performed on data concerning 5,255 specimens obtained from 62 fishing sets carried out off the Madeira archipelago (Northeastern Atlantic) between 2004 and 2008 in a depth range from 101 to 350 m. Abundance ranged from 0.01 to 19.74 specimens-per-trap and significant differences were found between seasons, probably as a result of an increment of population in the spring during the recruitment season. The analysis of size distribution revealed that the carapace length (CL) ranged from 2.45 to 28.61 mm and that mean female size consistently exceeded that of males. Differences in mean CL were statistically significant between depth strata and seasons. Of the specimens sampled, 57.00% were males, 41.88% females and 1.42% undetermined. Sex ratio also differed significantly between seasons according to depth strata, consolidating the hypothesis of the existence of seasonal migrations related with the reproductive cycle of this species. Ovigerous females showed larger sizes and occurred all year around and remain in shallow waters in winter, summer and autumn and move to deeper waters in spring. The highest frequency of ovigerous females was recorded in summer, between 151 and 200 m deep supporting the hypothesis that spawning of this species occurs in shallow waters, especially in late summer.
... Additionally, the wind pattern is highly significant for sea-surface biological processes within the Gulf of Cadiz (Navarro and Ruiz, 2006 ): the wind-related mixing phenomenon cumulates with the wind-driven coastal upwelling regime, active mainly from late May/early June to late September/early October in the Portugal–Canary system (e.g. Haynes et al., 1993; Aristegui et al., 2005; Peliz et al., 2005 ). This seasonal upwelling functioning is itself dependent on seasonal migrations of the Azores High coupled to the Intertropical Convergence Zone dynamics (Hsu and Wallace, 1976). ...
New dinoflagellate cyst (dinocyst) analyses were carried out at high resolution in core MD99-2339, retrieved from a contouritic field in the central part of the Gulf of Cadiz, for the Marine Isotope Stage (MIS) 3 interval, allowing for discussion of palaeohydrological changes over the last 50 ky in the subtropical NE Atlantic Ocean. Some index dinocyst taxa, according to their (palaeo)ecological significance, shed light on significant sea-surface changes. Superimposed on the general decreasing pattern of dinocyst export to the seafloor over the last 50 ky, paralleling the general context of decreasing aeolian dust fertilization, a complex variability in dinocyst assemblages was detected at the millennial timescale. Enhanced fluvial discharges occurred during Greenland Interstadials (GIs), especially GI 1, 8 and 12, while enhanced upwelling cell dynamics were suggested during the Last Glacial Maximum and Heinrich Stadials. Finally, during the early Holocene, and more specifically during the Sapropel 1 interval (around 7-9 ka BP), we evidenced a strong decrease in dinocyst fluxes, which occurred synchronously to a strong reduction in Mediterranean Outflow Water strength and which we attributed to an advection of warm and nutrient-poor subtropical North Atlantic Central Waters. Over the last 50 ky, our study thus allows for capturing and documenting the fine tuning existing between terrestrial and marine realms in North Atlantic subtropical latitudes, in response to not only the regional climate pattern but also monsoonal forcing interfering during precession-driven Northern Hemisphere insolation maxima. This mechanism, well expressed during the Holocene, is superimposed on the pervasive role of the obliquity as a first major trigger for explaining migration of dinocyst productive centres in the NE Atlantic margin to the subtropical (temperate) latitudes during glacial (interglacial) periods.
... Due to their political designation as an autonomous community of Spain, they are the southern-most point of the European Union (EU) and thus are in a geographically unique position as a navigation base between Europe, Africa, and the Americas. Another distinguishing trait of the archipelago is its role as a barrier to the Canary Current and the northern trade winds that generate the upwelling system of the Northwest African coast, one of the richest regions worldwide in fishery production (Barton et al. 1998; Pelegrí et al. 2005; Aristegui et al. 2006). In contrast to the neighboring African coast, the productivity of waters within the Exclusive Economic Zone (EEZ) of the Canary Islands are low (Bas et al. 1995), compounded by the narrow insular shelf which limits demersal life. ...
Total marine fisheries catches within the Exclusive Economic Zone (EEZ) of the Canary Islands, Spain, were reconstructed to include catches of the various small-scale artisanal fleets and their discards, as well as subsistence, recreational, and other unreported catch. Total reconstructed catch was estimated at 38,600 t in 1950, increasing to 81,200 t in 1985, declining to approximately 43,700 t·year-1 in the early-2000s and finally spiking to about 65,300 t·year-1 by the late-2000s. These catches coincide with a severe depletion of fish stocks, especially those of bentho-demersal species, due in part to fishing overcapacity in the artisanal sector, despite attempts to limit effort by the government. Only starting in 2006 were catches reported in national statistics and from 2006 to 2010 reconstructed catch was seven times the reported catch. Nearly 70% of this catch was from the recreational fishing sector, due in part to technological advancements and increased investments in the construction and improvement of secondary ports.
Depuis le début du vingtième siècle, le Maroc et l’ensemble des littoraux méditerranéens ont connu un processus spectaculaire de littoralisation, avec des pressions environnementales multiples dues essentiellement à une forte concentration humaine et une polarisation économique très poussée. Autant de signes de déséquilibres et de dégradations, par effet de surexploitation des ressources et des espaces. De là on aboutit à un état des lieux avec des problèmes complexes, une urbanisation linéaire, une bétonisation du cordon dunaire, une salinisation des nappes phréatiques et une érosion des plages et falaises. L’ensemble des écosystèmes côtiers sont déséquilibrés et de plus en plus pollués, avec des submersions marines et des inondations fluviales parfois graves.
Ces dernières années, cette tendance à la dégradation environnementale continue sans relâche, s’affirmant de plus en plus, sans signes visibles d’une régression à court ou à moyen terme.
Ainsi, le littoral atlantique marocain se présente sous une forme structurante du territoire national, subissant les effets négatifs des différents enjeux immobiliers et la confrontation des acteurs aux intérêts multiples et contradictoires. Un espace où se concentrent des enjeux sociétaux et économiques majeurs, industriels, touristiques, agricoles et urbanistiques... Une biodiversité remarquable, faisant du littoral un défi majeur pour le développement durable de notre pays.
Dans le contexte des pressions anthropiques multiples et croissantes, la gestion du littoral reste encore sans grande efficacité, étant donné les lourds handicaps, les multiples intervenants et les fragmentations des politiques sectorielles.La surexploitation des ressources naturelles persistent, dans le cadre de l’économie rentière (occupation du domaine public maritime, carrières de sables, pêche…). Les contraintes politiques et économiques existantes ont jusqu’à présent empêché l’orientation vers une intégration et une gestion équilibrée du littoral.
La « loi Littoral », qui devrait normalement permettre d’établir une bonne gouvernance et un cadre juridique globale, rénové, avec des règles d’utilisation du littoral adaptées à la nouvelle organisation territoriale du pays, est toujours en projet depuis plusieurs années. Le littoral marocain inspire une forte inquiétude, liée surtout à l’absence d’une politique basée sur une stratégie nationale de gestion intégrée des zones côtières.
Dans ce contexte de forte pression démographique et économique, encadrée par une législation surannée, inadaptée et non dissuasive, il faut ajouter un autre élément de perturbation et d’évolution, à savoir le changement climatique. La publication du 5ème rapport de la GIEC, en novembre 2014, montre que les connaissances scientifiques ont suffisamment progressé pour que l’on puisse sans attendre commencer à intégrer la variable climatique dans la gestion du littoral. A partir de là, de nombreuses interrogations s’imposent :
Quels seront les impacts de l’élévation du niveau de la mer, de son acidification, de l’évolution du régime des houles, des vents et des précipitations sur les écosystèmes côtiers marocains et méditerranéens ?
Quelles seront alors les conséquences sur les zones urbanisées, les infrastructures et la qualité et la disponibilité des ressources en eau ?
Comment préparer dès aujourd’hui l’adaptation de nos sociétés à ces changements, et quels outils mobiliser pour mieux gérer et protéger ces territoires à risques?
Les catastrophes naturelles telles que les surcotes, comme celles ayant frappé la côte atlantique marocaine surtout entre Rabat, Casablanca et Safi en Janvier 2014, témoignent de la vulnérabilité des territoires littoraux et montrent que les déséquilibres actuels et les dégradations en cours risquent de s’aggraver, du fait de l’effet multiplicateur du changement climatique.
Des études de prospective sont nécessaires, à différentes échelles territoriales, spécifiques aux enjeux et aux risques induits par le changement climatique, doivent permettre de mieux comprendre les chaines d’impacts pour mieux s’adapter aux changements et réduire les risques éventuels. Ceci demande un croisement et une implication de différentes disciplines de recherche, le but de ce colloque international qui se tiendra à Marrakech entre le 28 et 29 octobre 2015, et qui permettra de nouer un dialogue entre les gestionnaires du littoral, les responsables des collectivités locales et les chercheurs de différentes universités méditerranéennes. Dans le contexte de cette problématique si riche et à multiples ramifications, le comité d’organisation propose aux participants quelques grands axes de recherche et de discussion majeurs, sous forme de communications ou de posters.
1- Géomorphologie des littoraux marocains et méditerranéens : dynamique actuelle et aspects du dysfonctionnement.
2- Gouvernance et gestion du littoral marocain : le projet de « loi littoral » et la stratégie nationale de la gestion intégrée du littoral.
3- Changement climatique et impacts pour les littoraux marocains et méditerranéens
4- Risques et vulnérabilité des territoires littoraux marocains et méditerranéens
Sepiolid paralarvae are poorly studied, at least in part, because of the difficulty of accurate identification using morphological analysis. To unravel the biodiversity of sepiolid paralarvae collected in the Ría de Vigo during the upwelling season (2012–2014), and to overcome the difficulties of traditional identification, sepiolid paralarvae were identified by amplifying the barcoding gene cytochrome c oxidase subunit I (COI). In addition, morphometric analysis (Generalised Lineal Models, GLM and Discriminant Analysis, DA) was used to identify morphometric patterns useful for paralarval species identification. Genetic barcoding successfully identified 34 Sepiola pfefferi, 31 Rondeletiola minor, 30 Sepiola tridens, 4 Sepiola atlantica, 2 Sepietta neglecta and 1 Sepiola ligulata. COI analysis also allowed us to infer that the paralarvae of the three most abundant species belonged to the same populations independently of the year sampled. GLM suggested that total length (statistically different among the three species) and tentacle length (statistically larger in S. pfefferi from the other two species) were good variables to distinguish among species. DA succeeded in separating S. pfefferi from S. tridens, but R. minor overlapped along the first axes with both species, decreasing the accurate classification rate to 67%.
The growth and reproductive biology of the limpet Patella aspera were studied in the north-eastern Atlantic, Madeira archipelago, to enhance the knowledge concerning biological parameters and population dynamics of this species. This study comprised the estimation of growth rates, sexual maturity, reproduction, recruitment patterns, mortality coefficients and the exploitation rate, and yield-per-recruit (Y/R) based on monthly shell-length frequency data. A total of 16,941 specimens were sampled from January to December 2015. The relative growth pattern exhibited a negative allometric nature of growth for both sexes. The estimated von Bertalanffy growth parameters showed an asymptotic length of 84.15 mm for females and 80.51 mm for males with a growth coefficient of 0.36 and 0.32 year−1 respectively. P. aspera in this geographical area is a moderately long-lived limpet with a predominance of specimens younger than 3 years old. This species is a winter breeder with a reproductive cycle encompassing three main periods namely development, spawning and resting with a synchronous gametogenesis for both sexes. Gonadal development lasts from October to December, spawning likely occurs from January until April and resting occurs from May to September. The mean size at sexual maturity was determined as 41.78 mm for females and 38.29 mm for males and the length at first capture as 42.62 mm. The recruitment pattern was continuous throughout the year with a major peak identified in March. The natural, fishing and total mortalities were similar between sexes, with fishing mortality exerting greatest pressure on this resource. However, yield-per-recruit analysis showed that the stock of P. aspera, in the study area, is exploited at levels below the fishing mortality that returns maximum sustainable yield. This study revealed that currently the stock of P. aspera is under-exploited, nonetheless due to it’s slow growth and long life, continuous monitoring and the enforcement of the existing harvest regulations must be accomplished if future over-exploitation is to be avoided. Further genetic studies are necessary to establish connectivity of the populations and improve present conservation strategies.
During the cruise F/S Poseidon 212/3 (September 30-October 8, 1995) determination of carbon system variables was carried out over the section of La Palma-La Graciosa and at the ESTOC station in the Canary Island area. Total alkalinity and pH in the total scale at 25°C were determined at 24 stations from surface to bottom. In this area, the presence of different water masses can be traced by the carbon system variables. NACW is defined by a strong gradient of AT and pH from 150 to 750 m. MW is characterised by high values of AT and pH between 1000 to 1200 m and AAIW signals are found at around 900 m in the strait between Gran Canaria and Fuerteventura with low AT, low pH and a maximum of fCO2. Assuming an atmospheric mean value of fCO2 of 360 μatm and an average surface value of 393±7 μatm, we can conclude that during this cruise this oceanic area tends to release CO2 into the atmosphere, acting as a weak source with a carbon flux towards the atmosphere of +8.0±1.8 mmol.m-2d-1. The saturation levels in the Canary Island area have been found to be higher than 3600 m for calcite and 2700 m for aragonite. The inorganic carbon/organic carbon ratio (IC/OC) varies from 0.07 at 300 m to 0.5 at 3000 m. The IC/OC ratio shows that about a 34% increase in the CT of the deep water is contributed by the inorganic CaCO3 dissolution. The IC at 300 m is around 7 μmol kg-1, increasing with depth to 37.5 μmol kg-1 at 3700 m.
Greenland ice-core data have revealed large decadal climate variations over the North Atlantic that can be related to a major source of low-frequency variability, the North Atlantic Oscillation. Over the past decade, the Oscillation has remained in one extreme phase during the winters, contributing significantly to the recent wintertime warmth across Europe and to cold conditions in the northwest Atlantic. An evaluation of the atmospheric moisture budget reveals coherent large-scale changes since 1980 that are linked to recent dry conditions over southern Europe and the Mediterranean, whereas northern Europe and parts of Scandinavia have generally experienced wetter than normal conditions.
Presents a cross-disciplinary approach to the study of marine ecosystems. Attention is focused upon the ecological basis for maintenance and variability of populations of exploitable marine fish and invertebrates. The use of nested scales, where a variety of different processes act simultaneously but with different characteristic extents and durations, is emphasised as a basic conceptual framework for study of the marine ecosystem.