[ Evolution de l’écosystème de l’estuaire du Saloum au cours des derniers millénaires: Apport des diatomées ]
Volume 39, Issue 4, June 2023, Pages 1774–1782
Adama Gueye1 and El Hadji SOW2
1 Département de Géologie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar-Fann, Senegal
2 Laboratoire des Semi-conducteurs et d’Energie Solaire, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP, Dakar, Senegal
Original language: French
Copyright © 2023 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
As part of the inventory of the diatomic flora of Séné-Gambia and the reconstruction of the history of Senegal’s estuaries, a sampling mission was carried out along the Saloum estuary in the upstream parts of its three branches which are the northern branch (the main inlet), the middle branch (the Diomboss) and the southern branch (the Bandiala). The samples were taken using a Russian auger. The bottom of the mud has always been reached, but at very variable depths. A total of six cores were made and the study of diatoms carried out. A total of 150 species of diatoms belonging to 70 genera have been inventoried. The most represented genera are Nitzschia (14 species) and Coscinodiscus (8 species). The microflora is dominated everywhere by Cyclotella striata except at Néma Ba where it admits Nitzschia granulata as co-dominant. Euryhaline species dominate everywhere and confirm the dual marine/freshwater influence, the degree of which has varied over time and space. These results, combined with the lithological data, allow the following conclusions to be drawn: (i) the filling deposit of the Saloum estuary, begun in Nouakchottian, is marked by an abundance of sands and a poverty or absence of diatoms; (ii) at the end of the Nouakchottian transgression, the development of the mangrove allows the deposit, in the upstream part of the main inlet, of peat incompatible with the conservation of diatom valves; elsewhere, the sands diminish in favor of lutites and allow the development of diatoms; (iii) between 3500 and 2500 years B.P., primary paleo-productivity and specific diversity increase everywhere and the Bandiala receives fresh water from the Nema River; (iv) after 2000 years BP, the growing influence of the Nema River leads to an increase in oligohalobic forms along the Bandiala; (v) at the top of the sedimentary series, the agitation of the environment caused the deposit of coarse sediments and the absence of diatoms.
Author Keywords: Core, peat, lutites, sands, Nouakchottian, marine, freshwater.
Volume 39, Issue 4, June 2023, Pages 1774–1782
Adama Gueye1 and El Hadji SOW2
1 Département de Géologie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar-Fann, Senegal
2 Laboratoire des Semi-conducteurs et d’Energie Solaire, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP, Dakar, Senegal
Original language: French
Copyright © 2023 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
As part of the inventory of the diatomic flora of Séné-Gambia and the reconstruction of the history of Senegal’s estuaries, a sampling mission was carried out along the Saloum estuary in the upstream parts of its three branches which are the northern branch (the main inlet), the middle branch (the Diomboss) and the southern branch (the Bandiala). The samples were taken using a Russian auger. The bottom of the mud has always been reached, but at very variable depths. A total of six cores were made and the study of diatoms carried out. A total of 150 species of diatoms belonging to 70 genera have been inventoried. The most represented genera are Nitzschia (14 species) and Coscinodiscus (8 species). The microflora is dominated everywhere by Cyclotella striata except at Néma Ba where it admits Nitzschia granulata as co-dominant. Euryhaline species dominate everywhere and confirm the dual marine/freshwater influence, the degree of which has varied over time and space. These results, combined with the lithological data, allow the following conclusions to be drawn: (i) the filling deposit of the Saloum estuary, begun in Nouakchottian, is marked by an abundance of sands and a poverty or absence of diatoms; (ii) at the end of the Nouakchottian transgression, the development of the mangrove allows the deposit, in the upstream part of the main inlet, of peat incompatible with the conservation of diatom valves; elsewhere, the sands diminish in favor of lutites and allow the development of diatoms; (iii) between 3500 and 2500 years B.P., primary paleo-productivity and specific diversity increase everywhere and the Bandiala receives fresh water from the Nema River; (iv) after 2000 years BP, the growing influence of the Nema River leads to an increase in oligohalobic forms along the Bandiala; (v) at the top of the sedimentary series, the agitation of the environment caused the deposit of coarse sediments and the absence of diatoms.
Author Keywords: Core, peat, lutites, sands, Nouakchottian, marine, freshwater.
Abstract: (french)
Dans le cadre de l’inventaire de la flore diatomique de la Séné-Gambie et de la reconstitution de l’histoire des estuaires du Sénégal, une mission d’échantillonnage a été menée le long de l’estuaire du Saloum dans les parties amont de ses trois branches. Les prélèvements ont été faits au carrotier russe. Le fond de la vase a été atteint à des profondeurs très variables. Un total de 150 espèces de diatomées appartenant à 70 genres a été inventorié. La microflore est dominée partout par Cyclotella striata sauf à Néma Ba où elle admet Nitzschia granulata comme co-dominante. Les espèces euryhalines dominent partout et confirment la double influence marine/eau douce dont le degré a varié au cours du temps et de l’espace. Ces résultats, combinés aux données lithologiques, permettent de tirer les conclusions suivantes: (i) Le dépôt de remplissage de l’estuaire du Saloum, commencé au Nouakchottien, est marqué par une abondance des sables et une pauvreté ou une absence de diatomées; (ii) à la fin de la transgression nouakchottienne le développement de la mangrove permet un dépôt, dans la partie amont du bras principal, de tourbe incompatible avec la conservation des valves de diatomées; ailleurs, les sables diminuent au profit des lutites et autorisent le développement des diatomées; (iii) entre 3500 et 2500 ans B.P., la paléo-productivité primaire et la diversité spécifique augmentent partout et le Bandiala reçoit des apports d’eau douce de la rivière Néma; (iv) après 2000 ans BP, l’influence grandissante de la rivière Néma entraine une augmentation des formes oligohalobes le long du Bandiala; (v) au sommet de la série sédimentaire l’agitation du milieu a occasionné le dépôt de sédiments grossiers et l’absence de diatomées.
Author Keywords: Sondages, tourbe, lutites, sables, Nouakchottien, marine, eau douce.
How to Cite this Article
Adama Gueye and El Hadji SOW, “Evolution of the ecosystem of the Saloum estuary over the last millennia: Contribution of diatoms,” International Journal of Innovation and Applied Studies, vol. 39, no. 4, pp. 1774–1782, June 2023.
