Wavelet analysis on upwelling index along the Moroccan Atlantic coast

Wavelet analysis is a relatively new technique, an enormous interest in the application of wavelets has been observed in the recent years. In this paper, we use the wavelet analysis on the upwelling index based on sea surface temperature data from 1993 to 2014 along the Moroccan Atlantic coast, mainly at Cape Cantin, Cape Ghir, Cape Juby, Dakhla and Cape Blanc. We noticed that from Jan 1993 to Oct-1998 and from Sep-2007 to Nov 20014, the upwelling in the five research latitudes increases with fluctuations. The period of Upwelling varies sensitively with the change of time scale. The value of upwelling index in the five latitudes appears similar and present an obvious period of one year in all latitudes studied. This study can be considered an important tool for time series analysis, which can help the studies concerning the upwelling variability

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

CIRCULATION MARINE DE LA LAGUNE DE NADOR (MAROC) PAR MODELISATION HYDRODYNAMIQUE

The marine circulation of Nador lagoon (Morocco) have been studied from April to July 2011 by hydrodynamic 3D model, under the new configuration of its new inlet which is operational from 2011. This study aims to understand the new mode of hydrodynamic functioning of this lagoon. The circulation in the lagoon is wind driven circulation, as the wind is contributing to mixing internally the lagoon waters. During the neap tides, the surface currents are very strong in the new inlet (> 1 m.s-1), less than 0.5 m.s-1 in the centre and 0.3 m.s-1 near the continental sides of the lagoon. The bottom currents are in the opposite direction from the surface currents and less than 0.2 m.s-1

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

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

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

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