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

Etat Oceanographique De La Lagune De Oualidia, Maroc (2011-2012)

The study of the Oualidia lagoon aims to establish the state of knowledge of the environment of this ecosystem after the construction of an inner dam in 2011 and the ecological functioning of the lagoon. For that, several campaigns were carried out between February 2011 and October 2012 and were the subject of a seasonal monitoring for the collection of the main biotic and abiotic parameters of the environment of this ecosystem. During the construction of the inner dam on 2011, a hydrological variability was marked in summer by low oxygen levels and maximum temperature variation between the two tides. Since the completion of the construction of the inner dam, there has been a significant increase in nutrients, mainly nitrogenous elements, and an increase in turbidity caused by an improvement in hydrodynamics, which has particularly increased of the sandpit modified the morphology and moved on south, creating a new main channel structure in 2011. This hydrodynamic was manifested on the upstream area by a decrease of the sedimentary organic matter due to the trapping of fine sediments in the inner dam. At the immediate level of the upstream area (Slikkes and Schorres), the hydrodynamic is relatively low, which has reduced the sedimentation rate on the upstream of the lagoon. The Oualidia lagoon is situated in a littoral zone influenced by the enrichment in deep cold waters loaded with nutritive salts, which invade it during the high tide, and would be, consequently after construction of the inner dam, protected from any confinement of the ecosystem

Short-term variation of zooplankton community in Cintra Bay (Northwest Africa)

Summary: This is the first study that describes the spatial-temporal distributions of the zooplankton community and potential control factors in Cintra Bay. Zooplankton were sampled using a bongo net, 150 μm mesh size, during two surveys, in autumn 2015 and spring 2016, extending from the coast to the open sea. Fourteen zooplankton groups were identified, where copepods represented 49.1% and 92.5% of the total abundance in autumn 2015 and spring 2016, respectively. Tintinnids accounted for 39.7% and 4.7%, respectively. The total zooplankton abundance was higher in autumn (55 992 ind m−3) than in spring (2123 ind m−3). Nineteen species of copepods, belonging to 14 families, were identified. Euterpina acutifrons and Oithona nana were the most common and abundant species. The Acartiids were represented by three species (Acartia clausi, A. tonsa and A. bifilosa) in autumn and one species in spring (A. clausi). The copepods diversity was significantly different between the two seasons showing high values at the entrance and the center of the bay in autumn 2015 and in the southern half of the bay in spring 2016. The copepod structure was characterized by 13 species at different degrees of contribution in autumn 2015. In spring 2016, only four species qualified as indicator species although their contribution was not significant. Given its large opening on the ocean, Cintra Bay benefits largely from the conditions of the oceanic environment, particularly the upwelling. This situation is likely to have an impact on the spatiotemporal variability of the composition and distribution of zooplankton, especially the copepods. Keywords: Cintra Bay, Zooplankton, Copepods, Diversity indices, Environmental parameter

Influence of ocean - lagoon exchanges on spatio-temporal variations of phytoplankton assemblage in an Atlantic Lagoon ecosystem (Oualidia, Morocco)

The Oualidia Lagoon is a semi enclosed marine ecosystem connected to the Atlantic Ocean of Morocco and exposed to human activities, mainly agriculture and oyster farming. The present study aims to characterize the spatio-temporal variation of the phytoplankton assemblage and to highlight the effect of the main environmental parameters on this important planktonic component evolving in a vulnerable anthropized ecosystem. For this purpose, a field survey was carried out during four seasons in 2011 to determine the biotic (phytoplankton, chlorophyll a) and abiotic (temperature, salinity and nutrients) variables during low and high tide periods. Results highlight an established spatial variation of physico-chemical parameters especially at low tide, with contrasted environmental conditions between the upstream and downstream zones. The phytoplankton diversity and abundance were characterized by a pronounced seasonal pattern. The Oualidia Lagoon is a nutrient rich ecosystem, especially in its upstream part. We also showed that both planktonic diversity and abundance were maximum in autumn and summer. The phytoplankton richness is governed by two main factors: the seasonality of nutrient enrichment and the regular supply of Atlantic seawater. Nitrate and ammonium were the main environmental abiotic factors determining the development of phytoplankton populations. The dynamic of phytoplankton in the Oualidia Lagoon is highly influenced by marine waters incoming from the Atlantic Ocean especially during the upwelling season. Finally, potential harmful algal species belonging to different genera such as Pseudo-nitzschia, Alexandrium, Prorocentrum, Dinophysis, Ostreopsis, Karenia, Coolia, Gonyaulax, Gymnodinium, Dictyocha and Chattonella were encountered showing a potential in this ecosystem to develop noxious blooms