Un Demi Siècle D’évaluation De L’activité De L’upwelling De La Côte Atlantique Marocaine

Les écosystèmes d'upwelling situés en bordures Est (EBUEs) sontparmi les écosystèmes les plus productifs au monde et leur réponse auchangement climatique d'une importance cruciale. La variabilité saisonnièreet décennale à long terme de l'activité d'upwelling de la partie nord du grandécosystème marin du Courant des Canaries (CCLME) a été étudiée dans cetravail sur une période de 53 ans (1967-2019) à deux stations situéesrespectivement au nord (31°N-10,5°O) et au sud (24,5°N-15,5°O) de la côteatlantique marocaine, en élaborant l’Indice d’Upwelling de Bakun (UI)mensuel. Les résultats obtenus montrent que l’upwelling présente unevariabilité saisonnière entre Cap Juby - Larache et une activité quasipermanente toute l’année entre Cap Juby - Cap Blanc. En relation avec lavariabilité décennale et dans la zone nord atlantique marocaine, les plus fortesactivités de l’upwelling ont été observées en saisons d’été, en particulier surla période 1998-2003 et son activité a légèrement dépassé la moyenne sur lespériodes 1972-1977, 1980-1984, 2004-2008. Les plus faibles activités del’upwelling dans cette zone ont été observés en saisons d’automne/hiver,notamment sur les périodes 1967-1970, 1995-1998 et 2000-2005. S’agissantde la zone sud atlantique marocaine, l’activité de l’upwelling a présenté uneforte activité de l’upwelling en été sur les périodes 1967-1980 et 2009-2019,avec des fluctuations annuelles à interannuelles variables entre ces deuxpériodes. Cette activité a été légèrement supérieure à la moyenne en été sur lapériode 1981-2007, sauf pour les années 1982-1983, 1988-1989, 1995-1997et 2004-2007 où il a été observé une relative tendance vers la baisse. De plus faibles activités de l’upwelling ont été observées dans cette zone sur la période2003-2010 en saisons d’automne/hiver. Eastern Boundary Upwelling Ecosystems (EBUEs) are among themost productive ecosystems in the world, meaning that their response toclimate change is of critical importance. In this work, we investigate the longterm seasonal and decadal variability of the upwelling activity along thenorthern part of the Canary Current Large Marine Ecosystem (CCLME) overa period of 53 years (1967-2019). Two stations were selected in this studyrepresentative of the upwelling activity in the moroccan atlantic coast, one inthe north (31° N-10.5°W) and the other in the south (24.5° N-15.5°W) usingthe monthly Bakun Upwelling Index (UI). The results shows a seasonalvariability in the northern region of morocco between Cap Juby - Larache andalmost permanent activity all year round in the southern region of moroccobetween Cap Juby - Cap Blanc. These results are consistent with previousstudies based on the seasonality of the upwelling regime in thisregion. Relatedto the decadal variability, the strongest activities of upwelling were observedduring summer seasons in the northern region, in particular over the periodv 1998-2003 and its activity slightly exceeded the average over the periods1972-1977, 1980-1984, 2004-2008. The weakest upwelling activities in thisregion were observed in the fall-winter seasons, particularly during the periods1967-1970, 1995-1998 and 2000-2005. In the southern region, the upwellingactivity showed strong upwelling activity in summer over the periods 1967-1980 and 2009-2019, with annual and interannual between these two periods.This activity was slightly above average in summer over the 1981-2007period, except for the years 1982-1983, 1988-1989, 1995-1997 and 2004-2007where a relative downward trend was observed. Lower upwelling activitieswere observed in this area over the 2003-2010 period in fall / winter seasons

Relationship between migratory behavior and environmental features revealed by genetic structure of Sardina pilchardus populations along the moroccan Atlantic coast

We used genetic markers, namely allozymes, to study the genetic structure (stock unit) and the sardine stocks movement along the Moroccan Atlantic coast and its relationship regarding the environmental features, especially upwelling. In this study, we have combined previous results obtained by analyzing eight samples collected during the spawning season (winter 2004) (chlaida et al.2008) and new data obtained by analyzing eight samples gathered during the feeding season (summer 2006).  Therefore, we compiled 765 individuals from an earlier study and the 2006 summer sampling and compared seasons' results. In winter, a substantial heterogeneity (Fst =0.205) is described, with a significant genetic break in the Agadir Bay (latitude 30° 48' N) that cuts the coastal sardine populations in the Moroccan Atlantic into two stocks (north and south). In summer, the genetic structure showing two groups is maintained (Fst= 0.135). Still, the genetic break separating the two stocks arises southward, near Tarfaya (latitude 28°08’10” N), suggesting a spreading out towards the south of the northern stocks. This result seems to be related to the sardine movement along the Moroccan Atlantic coast regarding reproduction needs in winter and for trophic reasons in summer. The species' observed genetic break and seasonal activity along the Moroccan coast are expected to result from the Cape Ghir Hydrological barrier, impermeable in winter and semi-permeable in summer. This barrier comprises currents, gyres, and different mesoscale structures related to upwelling dominating in this zone

Diversity and Copepods’composition off Moroccan Atlantic Coast (Northwest Africa): A Review

This overview sums up the results of main investigations and knowledge about zooplankton off Moroccan Atlantic coast. Copepods diversity, spatial distribution, seasonal variability and hydrology off Moroccan Atlantic coast are given. A compilation of taxonomic list of copepods’ species found therein was established from published studies, they accounted for 210. Diversity and richness varied strongly between seasons, an onshore offshore gradient was observed as well. Species composition differed from northern to southern Moroccan Atlantic coast although most dominant species off Morocco’s coasts were Calanus helgolandicus, Paracalanus parvus, Acartia clausi and Corycaeus typicus. In addition, the largest number of species was found in upwelling regions. A synthesis study was established in order to spatial distribution of copepods along Moroccan Atlantic coast. The Factorial Correspondence Analysis of copepod species characterizing the most important sectors has shown different patterns of copepods distribution across Moroccan Atlantic coast; three main areas were clearly segregated according to their taxonomic composition (Northern, Central and Southern Atlantic)

Chapter Phytoplankton assemblage Characterization along the Mediterranean coast of Morocco during autumn

The present study aimed to assess the composition, abundance and diversity of phytoplankton assemblage along the Moroccan Mediterranean Coast. Phytoplankton samples were collected in October 2018 at 48 stations from M’diq bay in the West to Saïdia in the East. 92 taxa have been inventoried, belonging to five groups. Diatoms dominate qualitatively and quantitatively (85.5%), followed by dinoflagellates (12%). Phytoplanktonic diversity and abundance was pronounced in the western part of Moroccan Mediterranean Sea, especially (from Jebha to M’diq) because of the influence of the Atlantic flow

Abundance and structure of copepod communities along the Atlantic coast of southern Morocco

Zooplankton composition and the spatial and temporal abundance distribution of copepods were examined on the southern Atlantic coast of Morocco. In 1998, 31 stations during March and 30 stations during July were sampled on the continent shelf between Cape Blanc (21° O’N) and Cape Boujdor (26°30’N). Holoplankton dominated the zooplankton assemblages. Copepods represented 86% of the zooplankton in March and 73% in July. Herbivorous species were the main components of the 78 identified copepod species (60 species in March and 49 in July). Four species were recorded for the first time in this area: Calanus hyperboreus, Scaphocalanus brevicornis, S. medius, and Heterocope saliens. Both zooplankton abundance and diversity were related to changes in ecological parameters resulting from upwelling currents. The uplift of cold water enriched superficial water layers with nutrients and induced strong primary production upon which zooplankton depend. This study discusses the environmental features that influence plankton resources and the relationship of plankton production to the pelagic fisheries off northwest Africa

Caractérisation Hydrologique et Sédimentaire de la Lagune de Nador (Maroc)

Une prospection océanographique a été réalisée dans la lagune de Nador, située sur la côte méditerranéenne marocaine, en Juillet 2012 dont l’objectif est l’étude de l’état hydrologique et sédimentaire de la lagune après la mise en place de la nouvelle passe en 2011. La distribution des paramètres physico-chimiques du milieu ont permis la mise en évidence une variabilité spatiale en relation avec la circulation générale dans la lagune et la présence de la station d’épuration sur la rive continentale. L’état sédimentaire observé témoigne de l’intensité de l’échange mer-lagune qui est élevée au centre par comparaison aux extrémités NO et SE. Ainsi, le maintien de l’équilibre environnemental de cet écosystème dépend du degré d’échange mer-lagune et le contrôle de l’impact des activités anthropiques. An oceanographic survey was carried out in the Nador lagoon located on the Moroccan Mediterranean coast, in July 2012. The objective is to study the hydrological and sedimentary state of the lagoon after the establishment of the new pass, in 2011. The distribution of the physicochemical parameters of the environment allowed the identification of a spatial variability in relation to the general circulation in the lagoon and the presence of the treatment station on the continental shore. The sedimentary state also shows the intensity of the sea-lagoon exchange which is elevated in the center compared to the NO and SE extremities. Thus, maintaining the environmental balance of this ecosystem depends on the degree of sea-lagoon exchange and the control of the impact of anthropogenic activities

Spatial and seasonal fluctuations of Ichthyoplankton assemblage in the Mediterranean coast of Morocco (Southwestern Alboran Sea)

Ichthyoplankton represent the first life stages of fish. The study of ichthyoplankton is crucial to understanding marine ecosystems and plays an important role in the management and durability of fisheries resources. During March and October of 2019, two oceanographic ichthyoplankton surveys were conducted in the Mediterranean Sea of Morocco from Tanger to Saadia by studying the horizontal structure of the ichthyoplankton species assemblage and its relation to environmental parameters. The average surface water temperature was (15.8°C in spring and 16.4°C in autumn). The fish eggs and larvae were more abundant in March than in October (21268 eggs/10m² and 14084 larvae/10m² in spring and 10094 eggs/10m² and 13796 larvae/10m²). In both seasons, fish eggs from the families Sternoptychidae and Sparidae were dominant (10101 eggs/10m² and 7527 eggs/10m² in spring and 4422 eggs/10m² and 3928 eggs/10m² in fall, respectively). However, Myctophidae larvae were the most abundant in the study area, reaching 7601 larvae/10m² in spring and 11021 larvae/10m² in autumn. The environmental parameters: temperature, salinity and chlorophyll-a (surface) seem to directly influence the spatial distribution of ichtyoplancton. On the other hand, it seems that predation by jellyfish (Pelagia noctiluca)was a very important factor that added to the factors that influenced the distribution of the species of fish eggs and larvae. This work represents the first survey conducted in the southwestern Alboran Sea, which studies the horizontal structure of the ichthyoplankton species assemblage and its relation to environmental factors in the spring and autumn of 2019

Variabilite Oceanographique De La Zone D’el Jadida – Jorf Lasfar (Maroc)

Une campagne océanographique côtière a été réalisée en Juillet 2018 entre El Jadida et Jorf Lasfar. Cette zone est caractérisée par la présence d'algues rouges et présente une bathymétrie très régulière de la côte à l’isobathe 20m. Les paramètres océanographiques collectés au cours de cette mission montrent que la colonne d'eau est bien stratifiée avec des eaux froides riches en nutriments au fond et relativement plus chaudes et déficientes en nutriments en surface. La zone étudiée est très influencée par la forte concentration des phosphates provenant des rejets de Jorf Lasfar. Durant la période de la campagne, la stratification verticale pourrait s’expliquer par la faible activité des résurgences des eaux froides profondes. Malgré cette stratification, la colonne d'eau était bien saturée en oxygène dissous aussi bien en surface qu’au fond. A coastal oceanographic cruise was carried out on July 2018 between El Jadida and Jorf Lasfar. This area is characterized by the presence of red algae and presents a very regular bathymetry from the coast to isobaths 20m. The collected oceanographic parameters during this cruise show that the water column is well stratified with cold waters rich in nutrients at the bottom and relatively warmer and deficient in nutrients on the surface. The area study is very influenced by the high concentration of phosphates originated from Jorf Lasfar. During this summer’s period, the vertical stratification could be explained by the low activity of the resurgences of cold deep waters. Despite this stratification, the water column is well saturated on dissolved oxygen both on the surface and at the bottom