Variation saisonnière des paramètres abiotiques de la lagune Aghien (Côte d’Ivoire)

Objectifs: Les autorités dans la quête d’une source d’eau complémentaire pour alimenter en eau potable la population d’Abidjan (Côte d’Ivoire) sans cesse croissante ont envisagé exploiter la lagune Aghien. Ce présent travail a pour objectif d’améliorer les connaissances sur la variation spatiale et saisonnière des paramètres abiotiques de la lagune Aghien.Méthodologie et résultats: Pour atteindre ce but, quatre campagnes d’échantillonnages ont été menées. Ainsi, les échantillons d’eau ont été prélevés de manière saisonnière dans onze (11) stations reparties sur l’ensemble de la lagune. Les paramètres tels que la température, le pH, la conductivité, l’oxygène dissous, le potentiel redox ont été mesurés in situ. La matière en suspension, le phosphate, le nitrate, le nitrite, l’ammonium, la demande chimique en oxygène (DCO) et la demande biochimique en oxygène cinq jours (DBO5) ont été mesurés selon les méthodes conventionnelles ou au laboratoire. Les résultats ont montré que les eaux de la lagune Aghien présentent un pH en général proche du pH neutre (pH entre 6,94 et 7,85). Les teneurs en Plomb sont supérieures à la norme. Les concentrations élevées du plomb dans la lagune Aghien constituent donc un danger potentiel. L’analyse saisonnière a donné des valeurs élevées en ammonium, en phosphate, en nitrite, en DCO, en DBO5, en conductivité, en oxygène dissous respectivement en petite et grande saison des pluies ainsi que de faibles valeurs de potentiel redox pendant la petite saison pluvieuse. Les paramètres tels que les MES, la turbidité et le nitrate enregistrent des valeurs plus marquées en petite saison sèche.Conclusions et application des résultats: Les résultats de cette étude montrent que les eaux de la lagune Aghien sont menacées par les effluents domestiques à caractère biodégradable. Les concentrations en sels nutritifs sont encore dans la limite de l’acceptabilité. Cependant, les zones sous influence continentale ont enregistré les concentrations les plus élevées des paramètres de pollution. Il est nécessaire de mettre en place un mécanisme de surveillance chimique en respectant toutes les normes de protection de la lagune Aghien.Mots clés: Lagune Aghien-paramètres abiotiques- saison-pollutionEnglish Title: Seasonal variation of the abiotic parameters of the waters of the Aghien lagoon (Côte d’Ivoire)English AbstractObjectives: The government seeking to provide the population of Abidjan with clean water apply, envisioned to exploit the Aghien lagoon as a supplement source of water. The aim of this work is to improve the knowledge on the spatial and seasonal variation of the abiotic parameters of the Aghien lagoon.Methodology and results: Four sampling campaigns were conducted on a seasonal basis from February to November 2016 in eleven (11) stations spread over the lagoon. Parameters such as temperature, pH, conductivity, dissolved oxygen, redox potential were measured in situ and suspended solids, phosphate, nitrate, nitrite, ammonium, chemical oxygen demand (COD) and biochemical oxygen demand five days (BOD5) by conventional chemical methods. The results showed that the waters of the Aghien lagoon have a pH generally close to the neutral pH (pH between 6.94 and 7.85). The heavy metal studies are mainly absent in the water. The quantity of plumb is higher than normal. So the higher concentration of plumb in the Aghien lagoon constitutes a potential danger. Seasonal analysis yielded high values of ammonium, phosphate, nitrite, COD, BOD5 and conductivity, oxygen dissolved respectively in small and large rainy season as well as low values of redox potential during the short rainy season. Parameters such as suspended solids, turbidity and nitrate recorded higher values in the short dry season.Conclusion and applications of results: The results of this study also show that the waters of the Aghien lagoon are threatened by domestic biodegradable effluents. Concentrations of nutrient salts are still within the limits of acceptability. However, areas under continental influence have recorded the highest concentrations of pollution parameters. It is necessary to set up a chemical monitoring mechanism respecting all the protection standards of the Aghien lagoon.Keywords: Aghien lagoon, abiotic parameters, clean water, heavy meta

UPDATE OF ICHTHYOFAUNA AND ITS CONSERVATION STATUS IN THE AGHIEN LAGOON, CÔTE D’IVOIRE

Istraživanje se usredotočilo na raznolikost ihtiofaune te njen status očuvanja i osjetljivosti u slatkovodnoj laguni Aghien (jugoistočno od Obale Slonovače). Za prikupljanje podataka o ribama korištena su dvapristupa uzorkovanja: eksperimentalni i tradicionalni ribolov. Kao rezultat, 80 vrsta zabilježenih u laguni raspoređeno je u 55 rodova, 27 porodica i 10 redova. Najčešće zastupljeni redovi su Perciformes, Siluriformes, Osteoglossiformes, Characiformes, Cyprusinodontiformes i Pleuronectiformes. Cichlidae, Mormyridae i Clupeidae predstavljale su najraznolikije porodice. Sa pojavnošćuod 100%, najčeste vrste su bile: Brycinus longipinnis, Chrysichthys nigrodigitatus, Pellonula leonensis, Schilbe intermedius i S. mandibularis. U ukupnoj ribljoj populaciji, aprema IUCN crvenoj listi, četiri vrste su opisane kao „skoro ugrožene“ (Coptodon walteri, Marcusenius furcidens, Galeoides decadactylus i Cynoglossus senegalensis), četiri su zabilježene kao „osjetljive“ (B. brevis, Rhexipanchax nimbaensis, Enteromius raimbaulti i Tilapia busumana) i jedna vrsta kao „ugrožena“ (Pseudotolithus senegalensis).Kategorije vrsta koje imaju interes za očuvanje prema IUCN crvenoj listi predstavljaju 10,26% od cjelokupne populacije. Populacija ribe u Aghien laguni podijeljena je u sedam klasa u rasponu od „niske“ do „vrlo visoke“ osjetljivosti, u pogledu osjetljivosti na stres i ribolovni pritisak.This study focused on the diversity of fish fauna, its conservation status and its vulnerability in the Aghien freshwater lagoon (southeast of Côte d\u27Ivoire). For the fish data collection, two sampling approaches were used: experimental fishing and artisanal fishing. As a result, 80 species observed in this lagoon are distributed into 55 genera, 27 families and 10 orders. The best represented orders are the Perciformes, Siluriformes, Osteoglossiformes, Characiformes, Cyprinodontiformes and Pleuronectiformes. The Cichlidae, Mormyridae and Clupeidae represented the best diversified family. With an occurrence of 100%, the most frequent species are: Brycinus longipinnis, Chrysichthys nigrodigitatus, Pellonula leonensis, Schilbe intermedius and S. mandibularis. In the whole fish population, according to IUCN red list, four species where described as Near Threatened (Coptodon walteri, Marcusenius furcidens, Galeoides decadactylus and Cynoglossus senegalensis), four as Vulnerable (B. brevis, Rhexipanchax nimbaensis, Enteromius raimbaulti and Tilapia busumana)and one as Endangered species (Pseudotolithus senegalensis). These categories of species that have a conservation interest according to theIUCN Red List represent respectively 10.26% of the whole population. Fish population of the Aghien Lagoon are divided into seven classes ranging from "low" to "very high" vulnerability, regarding the vulnerability to stress due to fishing pressure

Evaluation de la Contamination Chimique des Eaux Souterraines par les Activités Anthropiques : Cas de la Zone d'Ity-Floleu Sous-Préfecture de Zouan- Hounien, Ouest de la Côte d'Ivoire

L’objectif de cette étude vise à évaluer la qualité saisonnière des eaux souterraines afin d’expliquer l’origine de leur pollution dans le département Zouan-Hounien. Les paramètres physico-chimiques in situ (température, conductivité, total des sels dissous, salinité, pH, potentiel redox, turbidité et oxygène dissous), les concentrations en éléments nutritifs (NO3-, NO2-, NH4+, PO43-, SO42-), majeurs (Ca, Fe, K, Mg, Mn et Na) et traces (As, Cd, Cu, Ni, Pb et Zn) ont été mesurés sur deux années successives. Les analyses physico-chimiques faites avec un multiparamètre montrent que les eaux sont acides avec un pH moyen de 4,96 en saison sèche et de 4,14 en saison pluvieuse; la conductivité électrique moyenne est de 78,14 μS.cm-1 en saison sèche et 48,43 μS.cm-1 en saison pluvieuse. La turbidité avec une valeur moyenne de 4,14 NTU en saison sèche et de 29 NTU en saison pluvieuse affecte beaucoup la qualité de ces eaux de consommation surtout en saison pluvieuse. Les teneurs en nitrates dans toutes les stations ne respectent pas les normes OMS en toute saison et celles des phosphates pendant la saison sèche. Les concentrations de Fe et du Pb sont généralement supérieures aux normes OMS alors que celles des autres éléments le sont parfois. Le calcul de l’indice de qualité (WQI) a montré que pendant la saison sèche 85,7% des eaux étudiées sont impropre à la boisson et pendant la saison pluvieuse 28,6%. Les analyses en Classification Hiérarchique Ascendante (CHA) et en composante principale (ACP) montrent que la pollution est due aux activités anthropiques. The objective of this study is to assess the seasonal quality of groundwater in order to explain the origin of its pollution in the Zouan- Hounien department. In-situ physico-chemical parameters (temperature, conductivity, total dissolved salts, salinity, pH, redox potential, turbidity and dissolved oxygen), nutrient concentrations (NO3 - , NO2 -, NH4 +, PO4 3-, SO4 2-), major (Ca, Fe, K, Mg, Mn and Na) and traces (As, Cd, Cu, Ni, Pb and Zn) were measured over two successive years. The physico-chemical analyses made with a multiparameter show that the waters are acidic with an average pH of 4.96 in the dry season and 4.14 in the rainy season; the average electrical conductivity is 78.14 μS.cm-1 in the dry season and 48.43 μS.cm-1 in the rainy season. Turbidity with an average value of 4.14 NTU in the dry season and 29 NTU in the wet season greatly affects the quality of this drinking water, especially in the wet season. Nitrate levels in all stations do not meet WHO standards in all seasons and phosphate levels in the dry season. The concentrations of Fe and Pb are generally higher than WHO standards, while those of other elements are sometimes higher. Calculation of the quality index (WQI) showed that during the dry season 85.7% of the water studied is unfit for drinking and during the rainy season 28.6%. The analyses in Ascending Hierarchical Classification (AHC) and Principal Component Analysis (PCA) show that the pollution is due to anthropogenic activities

Physico-chemical characterization of liquid waste from sugar production unit labs in Zuenoula, Côte d'Ivoire

Managing liquid waste from the laboratories of Integrated Agricultural Unit (IAU) of Zuénoula (Côte d´Ivoire) is a major concern for the decision-makers of the company, who are working to solve this problem in their sustainable development policy. This work aims at quantifying liquid waste from the agronomic laboratories and factory of IAU of Zuénoula and to assess their level of pollution. The quantities of waste produced daily are estimated at 28.5 L, 52.6 L and 2600 L respectively for waste from the agronomy laboratory, the factory laboratory and from the rinsing water from latter's glassware. The following parameters were analyzed, temperature, pH, conductivity, turbidity, total suspended solids, COD, BOD5, total nitrogen, total phosphorus, zinc, copper, lead and mercury. The results of these analyzes generally showed that waste produced did not comply with national standards. In particular, the level of lead was very high in these liquid wastes and reached 160 times the standard value. These results require a waste treatment system, which would reduce all the parameters, in particular those of the most noxious metals (lead and mercury).Keywords: Heavy metals, Pollution, Industrial unit, Ivorian standards, Wastewater

Évaluation de la diversité et de la charge parasitaire des lacs de la ville de Yamoussoukro en Côte d’Ivoire

Objectif: Cette étude vise à caractériser les parasites des eaux des lacs de Yamoussoukro et d’étudier les risques sanitaires dans la réutilisation de ces eaux usées afin d'en tirer les conséquences épidémiologiques.Méthodologie et résultats : Vingt-huit échantillons d’eaux résiduaires ont été collectés dans huit lacs de Yamoussoukro à partir de récipients stériles. La méthode de Bailenger a été utilisée pour la mise en évidence des parasites. La reconnaissance spécifique et le dénombrement des parasites ont été faits à l’aide d’un microscope optique. Les prévalences observées ont été comparées entre lacs et par espèce de parasite.Au total, 13 espèces de parasites: Ankylostoma sp., Strongyloïde sp., Ascaris sp., Nematodirus sp., Trichuris sp., Toxocara sp., Capillaria sp., Ascaridia galli, Enterobius vermicularis, Taenia sp., Hymenolepis diminuta., Entamoeba coli., Entamoeba histolytica et les larves de Strongles ont été détectées dans les eaux des huit lacs investigués à Yamoussoukro. Les oeufs d’helminthes sont quasi-présents dans tous les lacs investigués avec des charges parasitaires variables. Trois espèces ont donné des charges parasitaires très élevées : L’espèce Ankylostoma sp a été retrouvée dans tous les lacs. Les Strongyloïdes et les Ascaris sp présentaient des prévalences de 100 % et 87,5 % respectivement. Au niveau des lacs investigués, lacs, le lac N° 5 était le plus parasité avec une prévalence de 100 % sur l’ensemble des parasites, ensuite viennent les lacs N°1, 6 et 8 (69,2 %) puis les lacs G0, 9 et 10 (53,8 %).Conclusion et application des résultats: Les analyses parasitologiques montrent que les lacs de Yamoussoukro sont contaminés par des parasites d’importances médicales. L’infestation de ces eaux en agents pathogènes interdit leur usage en agriculture ce qui n’est pas couramment observé sur le terrain.Mots clés: Parasites, lacs, eaux résiduaires, Yamoussoukro, Côte d’IvoireEnglish AbstractObjectives: Water, source of life is essential for all living beings. After its use, the water is loaded in various elements modifying its physical, chemical and biological characteristics. One of the most serious environmental problems is the problem of sanitation. Indeed, human activity leads to the production of wastewater discharged daily into the wild.Methodology and results: Twenty-eight waste water samples were collected from eight Yamoussoukro lakes from sterile containers. The method of Bailenger was used for the detection of parasites. The specific recognition and enumeration of the parasites was done using an optical microscope Prevalences observed were compared between lakes and by parasite species. A total of 13 species of parasites: Ankylostoma sp., Strongyloïd sp., Ascaris sp., Nematodirus sp., Trichuris sp., Toxocara sp., Capillaria sp., Ascaridia galli, Enterobius vermicularis, Taenia sp., Hymenolepis diminuta., Entamoeba coli., Entamoeba histolytica et les larves de Strongles were detected in the waters of Yamoussoukro lakes. Helminth eggs are almost present in all investigated lakes with variable parasite loads. Three species gave very high parasite loads: The species Ankylostoma sp was found in all lakes. Strongyloids and Ascaris sp had prevalence rates of 100 % and 87.5 %, respectively. At the level of the parasite load of the lakes, Lake N ° 5 was the most parasitized with a prevalence of 100 % on all the parasites, then the lakes N ° 1, 6 and 8 (69,2 %) then the Lakes G0, 9 and 10 (53.8 %).Conclusion and application of results: Parasitological analysis show that Yamoussoukro lakes are contaminated by parasites of medical importance. The infestation of these waters with pathogens prohibits their use in agriculture, which is not commonly observed in the field.Keywords: Parasites, lakes, wastewater, Yamoussoukro, Côte d’Ivoir

Genetic Adaptability of Sarotherodon Melanotheron to Polycyclic Aromatic Hydrocarbons (PAHs) in Some Senegal Hydrosystems

The objective of this study is to evaluate the level of Polycyclic Aromatic Hydrocarbons (PAH) contamination at the Sine-Saloum (Foundiougne, Kaolack and Missirah), Hann Bay and Niayes (1 and 2) sites in Sénégal and genetic ecotoxicology of Sarotherodon melanotheron specimens from these sites.The genes of the specimens were studied by the enzymatic electrophoresis technique. Seven enzymatic systems (ADH, AAT, IDHP, MDH, PGM, GPI and EST) were analyzed. The analysis of the PAHs was carried out by gas chromatography coupled to mass spectrometry (GCMS). Populations of Sarotherodon melanotheron and sediments used for PAH measurements were sampled in 2009. Chemical characterization of the sampling sites revealed a high concentration of PAHs at Foundiougne and Hann Bay. The high pollution of environment is characterized by PAH napht (Foundiougne (14 378 ng/g) ; Hann Bay (5856 ng/g). The analysis of allelic variability showed the existence of an adaptive polymorphism at the PGM locus in S. melanotheron. The particularly low frequencies of the PGM * 105 allele in populations of disturbed environment (Foundiougne, Kaolack, Hann Bay, Niayes 1 and Niayes 2) suggest its involvement in the response to environmental stress. A negative correlation was observed between the PGM, IDHP and MDH-1 locus and PAH. The presence of PAHs in the environmentcauses to a decrease in the frequency of the PGM * 105 alleleatS. melanotheronspecimens

PREDVIĐANJE ČIMBENIKA KOJI UTJEČU NA SASTAV STRUKTURA RIBA U ČETIRI OBALNE RIJEKE (JUGOISTOČNA OBALA BJELOKOSTI) POMOĆU UMJETNIH NEURONSKIH MREŽA

The present study is focused on small coastal rivers in southeast Ivory Coast, aimed to predict species richness of fish guilds and to test contribution of environmental variables for explaining guild structure with Self- Organizing Map (SOM) and Backpropagation (BP) algorithms. The former method was applied to pattern the samples based on the richness of six major fish guilds observed (benthivores, invertivores, detritivores, piscivores, herbivores and omnivores). Four clusters were identified: cluster I was characterised by benthivores, cluster II was distinguished by invertivores, detritivores, piscivores and omnivores, cluster III had high richness of benthivores, invertivores and herbivores, and cluster IV had high numbers of omnivore, detritivore and piscivore species. The BP showed high predictability (0.89 for benthivores, 0.85 for omnivores and Odonata, 0.84 for herbivores). There was high correlation between observed and estimated values for piscivores (0.77) and detritivores (0.72); the poorest fit was for invertivores (0.63). The frequency histogram of residuals showed that most residuals lie around zero for all guilds. The most contributing variables in predicting the six fish trophic guilds were water temperature, conductivity, total dissolved solids, dissolved oxygen, depth, width, canopy and distance from source. This underlines the crucial influence of both instream characteristics and riparian environment.Ovo je istraživanje usmjereno prema malim obalnim rijekama na jugoistočnoj Obali Bjelokosti s ciljem predviđanja bogatstva vrsta riba i testiranjem doprinosa varijabli iz okolice kako bi se objasnila struktura populacija pomoću samoorganiziranih karata (SOM) i povratnih (BP) algoritama. Metoda je primijenjena na uzorku temeljenim na bogatstvu šest glavnih zabilježenih tipova ishrane (bentivori, invertivori, detrivori, piscivori, herbivori i omnivori). Identificirane su četiri skupine: klaster I je karakteriziran bentivorima, klaster II se odlikuje invertivorima, detrivorima, piscivorima i omnivorima, klaster III je bogat bentivorima, invertivorima i herbivorima, a klaster IV je imao visok broj omnivora, detrivora i piscivora. BP je pokazao visoku predvidljivost (0,89 za bentivore, 0,85 za omnivore i Odonata, 0,84 za herbivore). Visoka korelacija je zamijećena između promatranih i procijenjenih vrijednosti za piscivore (0,77) i detrivore (0,72), a najmanja za invertivore (0,63). Histogram pokazuje da se većina ostataka kreće oko nule za sve osobine. Varijable koje su najviše doprinijele predviđanju šest trofičkih ribljih struktura su temperatura vode, provodljivost, ukupno otopljene tvari, otopljeni kisik, dubina, širina, zasjenjenost i udaljenost od izvora. To naglašava presudan utjecaj karakteristika vodotoka i priobalnog okoliša

Phytoplankton Composition and trophic state of Guessabo lake (Upstream in Buyo lake, Ivory Coast)

Objectives: The trophic quality of Guessabo Lake (Ivory Coast) under the influence of fishing and agriculture was analysed starting according from the phytoplankton composition. Methodology and results: Sampling spatio-temporal in pelagic zone were made from a plankton net and supplemented with an integrated sampler. A total of three hundred and forty six species were identified. The groups, by orders of prevalence are, Chlorophyta with 164 species (48 %), Euglenophyta with 64 species (19 %), Cyanobacteria represented by 53 species (16 %), Bacillariophyta with 50 species (15 %) and, the other groups (Pyrrophyta, Chrysophyta and Xanthophyta) represented by 15 species (4 %). On the level of sampling stations of Guessabo Lake, 239 species were identified in Guemon sector against 231 and 257 species respectively in bed of the lake and Haut Sassandra sector. Concerning Guemon sector, 181 species were recorded at station G1 and 192 at station G5. In bed of lake (Channel), 154 species were listed at station G2, whereas 157 and 168 species were observed respectively at stations G4 and G6. For Haut Sassandra, stations G3 and G7 respectively presents 208 and 211 species. During this study, 103 species constant were listed against 66 species additional and 170 species accidental. In the floristic list, 73 species are common to all sampling stations. Sorensen index showed a similarity between the sectors and sampling stations. Trophic index based on Phytoplankton composition indicated that lake is from mesotrophy to eutrophy state. Key words: Phytoplankton, lake, mesotrophy, eutrophy; Ivory Coast

Spatio-temporal patterns of fish assemblages in coastal West African rivers: a self-organizing map approach

We investigated spatio-temporal patterns of fish assemblages in four small coastal rivers in South-East Ivory Coast. The samples were collected between July 2003 and March 2005 at 8 sampling sites (2 per river: 1 upstream and 1 downstream). A total of 59 fish species belonging to 39 genera, 23 families and 11 orders were captured. Perciforms (30% of the families and 33% of the species), followed by Siluriforms (22% and 22%), Osteoglossiforms (13% and 17%), Characiforms (9% and 10%) and Pleuronectiforms (9% and 3%) were the most abundant orders. Among the families sampled, Cichlidae (20% of the species), Mormyridae (13%), Clariidae (10%), Cyprinidae (10%) and Characidae (8%) were largely represented. Among the 59 fish species captured, we identified fifteen marine/brackish species and two introduced species. To analyse patterns of fish assemblages, we used a non-linear clustering technique, the self-organizing map (SOM). Using SOM, samples were classified into 4 clusters, mainly related to the spatial location of the sampling sites. Except for the distance from the source of the river, environmental variables (width, depth, current velocity) did not show a clear distribution gradient on the SOM map. This pattern was explained by the abundance of estuarine/marine species (i.e. 25% of the species) characterizing the lower course of the rivers studied. Such a distribution of estuarine/marine species colonizing the lower and middle course of the rivers was explained by the absence of dams and contrasts with the patterns observed in more fragmented rivers of Ivory Coast. Therefore, we suggest that these small streams should be preserved in order to permit estuarine/marine species to migrate between streams and the Aby lagoon, thus allowing their large distribution and their reproduction in favourable habitats. We suggest particular attention be given to the Soumié River basin which represents the only preserved stream ecosystem within the Bia River basin