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International audience; A study on the current state of zooplankton diversity in the pelagic zone of Lake Tanganyika along Bujumbura City was conducted from April to July 2020. The objective of the study was to assess zooplankton diversity for sustainable management of fishery resources and the conservation of this ecosystem. Two sampling sites were chosen. The first station was supposed to be polluted whereas the second one was considered as less polluted (or control). Zooplankton was collected with 50μm plankton net at different depths. The results obtained showed a total of 12 species identified in all the sampling stations among which, the copepods group was dominant while the rotifers group was found diversified with seven species (58.3%). The group of cladocerans represented by Moina macrocopa was identified for the first time in the pelagic zone. The calculation of the diversity index has reflected that the waters of Lake Tanganyika are classified into low level pollution category with a tolerable threshold. Therefore, the protection of Lake Tanganyika is necessary for sustainable fishery production and the future studies shall be carried out at several sites with annual sampling at a regular frequency to demonstrate the effect of seasons on the abundance of zooplankton communities.

International audience; Media additives are believed to influence biomineralization in vitro mediated by mantle cells of P. malabarica. CaCl 2 and MgCl 2 were tested as media additives in the present study using 2 x L-15 solution to establish primary cultures for evaluation of their effect on biomineralization. Primary culture inoculated with media composition without additives was also designed to serve as control experiment. Results were collected through an inverted microscope-Olympus (Model no. CKX41). Our results demonstrate that both CaCl 2 and MgCl 2 additives influence biomineralization by increasing the rate of crystal deposition and the number of crystals in mantle cells primary cultures of Paphia malabarica.

Lake Tanganyika is one of the largest lakes of Africa and second biggest Lake Considering the area after Lake Victoria. Worldwide, it is the longest fresh water lake and holds second position in terms of depth after Lake Baikal and third place in terms of volume after the Caspian Sea and Lake Baikal (Wetzel, 1983 and Kar, 2013). The lake is subject to frequent fluctuations in the chemistry of its water and to desiccation (Wetzel, 2001) due to sudden changes in weather conditions. It is facing a serious pollution problem from various sources, such as discharge of domestic sewage, population growth, rise of industrialization, use of pesticides and chemical fertilizers in agriculture, sedimentation and erosion resulting from deforestation. So, the surface waters of Lake Tanganyika are highly polluted by different harmful contaminants from human activities in large cities established on its catchment areas.

The present study was conducted at 4 sampling sites of Lake Tanganyika and was intending to identify and estimate the spatial abundance of phytoplankton in relation to physico-chemical attributes. The species composition analysis of the samples has listed 115 species of phytoplanktons belonging to 7families from all sampling sites. The relative diversity index of families has indicated that Bacillariophyceae is the most dominant family in comparison to others families with 50 species (43.4%) followed by the family Chlorophyceae with 31 species (27%). The family Cyanophyceae was found very scarce with 3species (2.6%). Regarding quantitative data, the results of species richness and the Cumulative abundance of the sampling sites showed that phytoplankton species and density were variable among stations. Rumonge site holds first position with 115species which was the maximum of all species identified comprising 3450 individuals per liter followed by Kajaga site with 107species comprising 2482individuals per liter, then Mvugo site with 101species containing 1506individuals per liter and in the last position was Nyamugari site with 86 species comprising1031individuals per liter. Furthermore the results of Canonical Correlation Analysis (CCorA) between the environmental parameters and phytoplankton composition at sampling sites have shown that the abundance and proliferation of some phytoplankton species are negatively or positively affected by the physico-chemical parameters concentration because, some physico-chemical variables were found either inhibitors or accelerators for phytoplankton species growth.

The present study was conducted on Burundian coast of Lake Tanganyika in 4 sampling sites to identify and to estimate the spatial abundance of zooplankton community and to analyze whether physicochemical properties of water influence significantly the occurrence of zooplankton population. During the survey, it has been realized that zooplankton organisms were very few in number and taxonomic diversity and was comprising of 3 orders: Cyclopoida, Calanoida (Copepods) and Cladocera represented by Diaphanosoma. 12species belonging to 4families have been noted from all study sites. The relative diversity index of families revealed that the family Diaptomidae was dominant with 5species (41.7%) followed by family Cyclopidae with 4species (33.3%), then family Sididae with 2species (16.7%) while the Temoridae family was last with a single species (8.3%) The results of species richness and the Cumulative abundance of the sampling sites showed that zooplankton species and density were variable among stations. 11species were identified at Rumonge site comprising 1152 individuals per liter followed by Kajaga and Mvugo sites with same specific richness of 10 species but with different cumulative abundance of 830 and 502 individuals per liter respectively and Nyamugari site was in last position with 8 species comprising 219 individuals per liter. Besides, the results of Canonical Correlation Analysis (CCorA) between the environmental parameters and zooplankton biomass have shown that the abundance and proliferation of some zooplankton species are affected by the physico-chemical parameters concentration by acting as either inhibitors or accelerators for zooplankton species growth.

Lake Tanganyika is one of the largest lakes of Africa and second biggest Lake Considering the area after Lake Victoria. Worldwide, it is the longest fresh water lake and holds second position in terms of depth after Lake Baikal and third place in terms of volume after the Caspian Sea and Lake Baikal (Wetzel, 1983 and Kar, 2013). The lake is subject to frequent fluctuations in the chemistry of its water and to desiccation (Wetzel, 2001) due to sudden changes in weather conditions. It is facing a serious pollution problem from various sources, such as discharge of domestic sewage, population growth, rise of industrialization, use of pesticides and chemical fertilizers in agriculture, sedimentation and erosion resulting from deforestation. So, the surface waters of Lake Tanganyika are highly polluted by different harmful contaminants from human activities in large cities established on its catchment areas.

The water of Lake Tanganyika is subject to changes in physicochemical characteristics resulting in the deterioration of water quality to a great pace. The present investigation was carried out on Lake Tanganyika at 4 sampling sites and aimed to assess the water quality with reference to (i) its suitability for fish culture purposes, (ii) determining the trophic and pollution status of the sampled stations, (iii) assessing the qualitative and quantitative pattern of planktons diversity as fish food, (iv) establishing an inventory and taxonomic characterization of fish species diversity and (v) highlighting the effect of pollutants on the abundance and spatial distribution of fish species. The physico-chemical and biological parameters of water samples were compared to desirable and acceptable international standards for fish culture and the results of comparative analysis indicated that the Lake has a high fish potential as the most important of the water quality parameters were suitable for fish culture. The investigation revealed the occurrence of 75 species belonging to 7different orders and 12 families in all sampling sites and among the different species recorded, those belonging to the order Perciformes and the family Cichlidae were most dominant. The values of transparency, chlorophyll a and total phosphorus were indicative of eutrophication phenomenon. Besides, Kajaga and Nyamugari stations were found heavily polluted while Rumonge and Mvugo Stations were moderately polluted and for this purpose, three categories of fish species have been distinguished, depending on their adaptation level to pollution: polluosensitive species, polluotolerant species and polluoresistant species. With respect to planktons community results, it was found that all the values obtained were within the permissible limits recommended in pisciculture and, the abundance and diversity of phytoplankton species were far greater than those of zooplankton species with 115species belonging to 7differet families for phytoplanktons against 10species belonging to 4families for zooplankton population in all sampling stations., L'eau du lac Tanganyika est sujette à des changements dans les caractéristiques physico-chimiques entraînant une détérioration de la qualité de l'eau à une allure remarquable. La présente étude a été réalisée sur le lac Tanganyika dans 4 sites d'échantillonnage et visait à évaluer la qualité de l'eau en référence à (i) son adéquation à la pisciculture, (ii) la détermination de l'état trophique et de pollution des stations échantillonnées, (iii) évaluer la structure qualitative et quantitative de la diversité des planctons en tant que nourriture pour les poissons, (iv) établir un inventaire et une caractérisation taxonomique de la diversité des espèces de poissons et (v) mettre en évidence l'effet des polluants sur l'abondance et la répartition spatiale de l’Ichtyofaune.Les paramètres physico-chimiques et biologiques des échantillons d'eau ont été comparés aux normes internationales souhaitables et acceptables pour la pisciculture et les résultats de l'analyse comparative ont indiqué que le Lac Tanganyika a un potentiel piscicole élevé parce que la plupart des paramètres analysés ont donné des résultats convenables à la pisciculture. L'étude a aussi révélé la présence de 75 espèces piscicoles appartenant à 7 ordres différents et 12 familles dans tous les sites d'échantillonnage et parmi les différentes espèces enregistrées, celles appartenant à l'ordre des Perciformes et à la famille des Cichlidae étaient les plus dominantes.Les valeurs de transparence, de chlorophylle a et de phosphore total indiquent un phénomène d'eutrophisation. Par ailleurs, les stations de Kajaga et Nyamugari ont été trouvées fortement polluées tandis que les stations de Rumonge et Mvugo se sont montrées modérément polluées et à cet effet, trois catégories d'espèces de poissons ont été distinguées en fonction de leur niveau d'adaptation à la pollution: Espèces sensibles à la pollution, espèces tolérantes à la pollution et espèces résistantes à la pollution. En ce qui concerne les résultats planctoniques, il a été constaté que toutes les valeurs obtenues se situaient dans les limites acceptables recommandées en pisciculture et que l'abondance et la diversité des espèces phytoplanctoniques étaient bien supérieures à celles des espèces zooplanctoniques avec 115 espèces appartenant à 7 familles différentes pour les phytoplanctons contre 10espèces appartenant à 4 familles pour la population des zooplanctons dans toutes les stations d'échantillonnage.

The current limnological study was carried out on Lake Tanganyika in 4 sampling sites to assess the physico-chemical properties and trophic status for pisciculture purpose. The estimated values of physical and chemical parameters of water samples were compared to the desirable, permissible and acceptable ranges for pisciculture recommended standards. In this regards, 9 physico-chemical parameters have been analyzed and the results of the comparative analysis showed that most of the water quality parameters were suitable for fish culture because 7important parameters (77.8%) were within the permissible limits and 2parameters (22.2%) were found inappropriate for pisciculture. The values of transparency, chlorophyll a and Total phosphorus revealed clearly that all sampling stations were in hypereutrophic status which indicate eutrophication phenomenon., La présente étude limnologique a été réalisée sur le lac Tanganyika dans 4 sites d'échantillonnage pour évaluer les propriétés physico-chimiques et l'état trophique à des fins piscicoles. Les valeurs estimées des paramètres physiques et chimiques des échantillons d'eau ont été comparées aux plages souhaitables, permises et acceptables pour les normes recommandées pour la pisciculture. À cet égard, 9 paramètres physico-chimiques ont été analysés et les résultats de l'analyse comparative ont montré que la plupart des paramètres de qualité de l'eau étaient adaptés à la pisciculture car 7 paramètres importants (77,8%) se situaient dans les limites autorisées et 2 paramètres (22,2%). ont été jugés inappropriés pour la pisciculture. Les valeurs de transparence, de chlorophylle a et de phosphore total ont clairement révélé que toutes les stations d'échantillonnage étaient en état hypereutrophique, ce qui indique un phénomène d'eutrophisation.

The current limnological study was carried out on Lake Tanganyika in 4 sampling sites to assess the physico-chemical properties and trophic status for pisciculture purpose. The estimated values of physical and chemical parameters of water samples were compared to the desirable, permissible and acceptable ranges for pisciculture recommended standards. In this regards, 9 physico-chemical parameters have been analyzed and the results of the comparative analysis showed that most of the water quality parameters were suitable for fish culture because 7important parameters (77.8%) were within the permissible limits and 2parameters (22.2%) were found inappropriate for pisciculture. The values of transparency, chlorophyll a and Total phosphorus revealed clearly that all sampling stations were in hypereutrophic status which indicate eutrophication phenomenon., La présente étude limnologique a été réalisée sur le lac Tanganyika dans 4 sites d'échantillonnage pour évaluer les propriétés physico-chimiques et l'état trophique à des fins piscicoles. Les valeurs estimées des paramètres physiques et chimiques des échantillons d'eau ont été comparées aux plages souhaitables, permises et acceptables pour les normes recommandées pour la pisciculture. À cet égard, 9 paramètres physico-chimiques ont été analysés et les résultats de l'analyse comparative ont montré que la plupart des paramètres de qualité de l'eau étaient adaptés à la pisciculture car 7 paramètres importants (77,8%) se situaient dans les limites autorisées et 2 paramètres (22,2%). ont été jugés inappropriés pour la pisciculture. Les valeurs de transparence, de chlorophylle a et de phosphore total ont clairement révélé que toutes les stations d'échantillonnage étaient en état hypereutrophique, ce qui indique un phénomène d'eutrophisation.

Worldwide coliform bacteria are used as indicators of environmental and fecal contamination and hence, the possible presence of pathogenic organisms. As most people living on the shores of Lake Tanganyika use its water for cooking, drinking and washing; the monitoring of organisms indicating water pollution is more predictive of the presence of certain pathogens to protect public health. This study was carried out along the Burundian coast at 4 sampling sites (Kajaga, Nyamugari, Rumonge and Mvugo) in the months of January, February and March 2018, to assess quantitatively the presence of coliform bacteria in comparison to the standards recommended by BIS-10500 (1991, 2012) and WWF-Pakistan (2007) for drinking and recreational water quality and to sensitize the populace using the untreated water about the potential health risks. The ColonyForming Unit (CFU) method was used and the results showed that total coliformbacteriaobtained was in the range of 9000 to 60000 CFU/100 mLand are indicative of environmental contamination of all sampling stations with an average of 33250 CFU/100 mL. Fecal coliform bacteria ranged from 0 to 5000 CFU/100 mL with an overall average of 2000 CFU/100 mL and Kajaga site appeared free of contamination as fecal coliform count there was nil. The Escherichia coli count recorded ranged from 0 to 3000 CFU/100 mL with an average of 1350CFU/100 mL. At Kajaga stations, Escherichia coli count was 0 and therefore there is no evidence of recent fecal contamination. Thus, if only fecal contamination is taken into account, the water from Kajaga station can be considered as safe for drinking and bathing purposes but incidentally total coliforms were found at Kajagastation. The water from all sampling stations require treatment before any use.

Lake Tanganyika is one of the largest lakes of Africa and second biggest Lake Considering the area after Lake Victoria. Worldwide, it is the longest fresh water lake and holds second position in terms of depth after Lake Baikal and third place in terms of volume after the Caspian Sea and Lake Baikal (Wetzel, 1983 and Kar, 2013). In fact, Lake Tanganyika has a volume of 18 900km3, covers an area of 34,000 km2 with a length of 677 km and a width of 72km and is spread on a watershed of 231,000km2. Its altitude rises to 775m; its average depth is 770m with a maximum of 1433m. Lake Tanganyika is surrounded by four countries sharing unequally 1,838km of its entire perimeter (Hanek and al., 1993): Burundi in the North-East controlling 159 km (9% of the coast), Democratic.Republic.of.Congo (DRC) to the West with 795 km (43% of the coast), Tanzania to the East and South-East with 669 km (36% of the coast) and Zambia to the south with 215 km (12% of the coast). Seven main towns and cities are established on the edge of Lake Tanganyika such as: Baraka, Kalemie and Uvira in DRC, Bujumbura and Rumonge inBurundi, Kigoma in Tanzania and Mpulungu in Zambia. Its waters join the Congo River in DRC via the Lukuga River, then the Atlantic Ocean. However, many decisions in favor of Lake Tanganyika future have been taken at the time of the first International Conference on Conservation and Biodiversity of Lake Tanganyika, held in Burundi-Bujumbura in 1991, where regional and international scientists were present to discuss about the wealth and increasing threats of Lake Tanganyika (Cohen, 1991). Despite all these initiatives, the lake is still subject to frequent fluctuations in the chemistry of its water and to desiccation (Wetzel, 2001) due to sudden changes in weather conditions. It is facing a serious pollution problem from various sources, such as discharge of domestic sewage, population growth, rise of industrialization, use of pesticides and chemical fertilizers in agriculture, sedimentation and erosion resulting from deforestation. So, the surface waters of Lake Tanganyika are highly polluted by different harmful contaminants from human activities in large cities established on its catchment areas.

International audience; Worldwide coliform bacteria are used as indicators of environmental and fecal contamination andhence, the possible presence of pathogenic organisms. As most people living on the shores ofLake Tanganyika use its water for cooking, drinking and washing; the monitoring of organismsindicating water pollution is more predictive of the presence of certain pathogens to protect publichealth. This study was carried out along the Burundian coast at 4 sampling sites (Kajaga,Nyamugari, Rumonge and Mvugo) in the months of January, February and March 2018, to assessquantitatively the presence of coliform bacteria in comparison to the standards recommended byBIS-10500 (1991, 2012) and WWF-Pakistan (2007) for drinking and recreational water quality andto sensitize the populace using the untreated water about the potential health risks. TheColonyForming Unit (CFU) method was used and the results showed that total coliform bacteriaobtained was in the range of 9000 to 60000 CFU/100 mLand are indicative ofenvironmental contamination of all sampling stations with an average of 33250 CFU/100 mL. Fecalcoliform bacteria ranged from 0 to 5000 CFU/100 mL with an overall average of 2000 CFU/100 mLand Kajaga site appeared free of contamination as fecal coliform count there was nil. TheEscherichia coli count recorded ranged from 0 to 3000 CFU/100 mL with an average of 1350CFU/100 mL. At Kajaga stations, Escherichia coli count was 0 and therefore there is no evidenceof recent fecal contamination. Thus, if only fecal contamination is taken into account, the waterfrom Kajaga station can be considered as safe for drinking and bathing purposes but incidentallytotal coliforms were found at Kajagastation. The water from all sampling stations require treatmentbefore any use.

Une étude portant sur l’évaluation des performances zootechniques des caprins de race locale et croisés Boer en fonction des systèmes d’élevage dans lesquels ils se trouvent a été faite dans la région naturelle de Buyenzi. Ladite étude a été menée dans les communes Gashikanwa et Mwumba de la province Ngozi où la pression démographique compromet dangereusement le système agro-pastoral. L'élevage du gros bétail, jadis prospère, ne trouve plus sa place dans les exploitations familiales et doit céder le pas à celui des petits ruminants comme la chèvre. L’objectif de notre travail est d’évaluer les paramètres zootechniques des groupes génétiques (race locale et croisés Boer) selon les systèmes d’élevages dans lesquels ils sont élevés afin d’identifier les systèmes d’élevage les plus rentables pour chaque groupe génétique. A cet effet, une enquête a été menée dans 70 ménages disposant d’au moins 2 caprins par ménage, à raison de 35 ménages par commune. 352 caprins dont 95 croisés Boer et 257 caprins de race locale ont fait objet d’étude au cours de notre enquête. Les résultats de notre étude montrent que la stabulation semi-permanente est le premier mode de conduite pratiqué dans le milieu d’étude, au taux de 50% des ménages enquêtés, suivie de la stabulation permanente qui représente 35,7% et en dernier lieu, le système extensif combinant le gardiennage et l’attachement au piquet avec 14,3% des ménages enquêtés. Concernant l’évaluation des performances zootechniques, l’analyse descriptive a montré que pour tous les paramètres zootechniques étudiés pour chaque groupe génétique, les caprins affichent les meilleures performances dans le système intensif ou en stabulation permanente, suivi du système semi-intensif ou en semi-stabulation et en dernier lieu vient le système extensif. Ce qui signifie que les performances zootechniques des animaux diminuent du système intensif au système extensif, la semi-stabulation étant intermédiaire entre les deux systèmes extrêmes. A part la mortalité juvénile qui serait influencée par d’autres facteurs, les résultats obtenus par analyse de la variance(ANOVA) ont montré une influence du système d’élevage sur les performances zootechniques étudiées: la stabulation permanente et la semi-stabulation se sont révélées plus productives par rapport au système extensif pour tous les groupes génétiques. Ce qui signifie que les performances zootechniques varient selon les systèmes d’élevage dans lesquels, les animaux sont conduits.