Adama Oueda

Using macroinvertebrates for ecosystem health assessment in semi-arid streams of Burkina Faso

Efficient monitoring tools for the assessment of stream ecosystem response to urbanization and agricultural land use are urgently needed but still lacking in West Africa. This study investigated taxonomic and functional composition of macroinvertebrate communities at 29 sites, each exhibiting one of four disturbance levels [‘protected’ (P), ‘extensive agriculture’, ‘intensive agriculture’ (IA) and ‘urban’ (U)] in Burkina Faso and explored their potential for bioassessment. We recorded a total of 100 taxa belonging to 58 families, with the highest richness (16.9 taxa per site) observed in the sites with IA and lowest (3.4 taxa) in U sites. We found a gradual decrease of sensitive Ephemeroptera, Plecoptera and Trichoptera taxa and of collector-filterers feeding guild between P, agricultural and U sites accompanied by an increase in the relative abundance of tolerant dipteran taxa. Measures of overall taxonomic richness and diversity were mostly efficient in detecting the high impoverishment of the U sites, while FFG ratios did not deliver consistent results. Finally, all four land use types were successfully distinguished by identifying indicator taxa through hierarchical clustering and indicator value index. This work produced an unprecedented faunal inventory of Burkina Faso streams and laid the basis for the development of urgently needed stream assessment tools.

Physicochemical and parasitological quality of vegetables irrigation water in Ouagadougou city, Burkina-Faso

The quality of irrigation water from different sources used by urban vegetable producers, the watered soils and vegetables in Ouagadougou was investigated. From December 2012 to December 2013, samples of water (97), lettuces heads (20), manure (10) and soil (9) were collected and analyzed for their parasitological quality using modified Bailenger methods. The result shows that parasites concentration in samples (1 to 11 egg/L in water, 0.45 egg/g on lettuce and 0.48 egg/g in soil) are above the threshold levels set by WHO/FAO for unrestricted irrigation. Different protozoa and helminthes belonging to 9 species were identified in the samples analyzed. These include Ankylostoma duodenalis, Hymenolepis nana, Ascaris lombricoides, Taenias ssp., Strongyloides stercoralis, Entamoeba histolytica, Giardia lamblia and Entamoeba coli. Despite variation in isolated parasites, eggs of A. lumbricoides and A. duodenalis were common in all water, soil and vegetables. Furthermore 14.87% of collected eggs have proven to be viable with predominance of helminthes eggs. As a result, farmers appear to be the most exposed group to helminthiasis. Key words: Waterborne parasites, vegetables, urban-farming, Ouagadougou.

Developing reference criteria for the ecological status of West African rivers

Awareness of sustainable management of water and its biological resources is rising in West Africa, but application of effective tools for biomonitoring and detecting habitats at risk in aquatic ecosystems is limited. In this study, we provide key environmental descriptors to characterize reference sites by applying the following “a priori criteria” (physical and chemical, hydro-morphological, and land use parameters) by exploring their potential to determine suitable reference sites. Using data collected from 44 sites, we identified 37 criteria that reliably identify reference conditions in semi-arid rivers by reflecting the impacts of multiple pressures ranging from low to very high intensity of human uses and impairments. We integrated all these impacts in an overall pressures index, which showed that protected areas can reasonably be considered as credible reference sites as far as they show low overall impact levels from cumulative pressures. We recommend that development of bio-indicator standards should be based on the collection and integration of all the available information, especially quantitative, spatially-explicit data, from benthic macroinvertebrates and fish. Rigorous standardization of bio-indicator protocols will make them more easily applicable for management and conservation of aquatic ecosystem resources in semi-arid zones of Africa.

Assessment of benthic molluscs diversity and distribution in urban reservoirs (Ouagadougou, Burkina Faso)

The urban reservoirs n° 2 and n°3 of Ouagadougou, located in the middle of the city are subject to multiple anthropogenic pressures which threaten the diversity of benthic macroinvertebrates community group like molluscs. This study was initiated to assess the diversity and distribution of benthic molluscs in these reservoirs. Molluscs samples were collected monthly using an Eckman grab (12 x 20 cm 2 ) between September 2011 and February 2012 in 24 sampling points defined on each reservoir. In parallel, physicochemical variables and water colon depth were measured. After sampling, molluscs were transported to the laboratory for identification. A total of 328 specimens were collected of which 5 species were identified: three species of Gastropods ( Bellamya unicolor , Cleopatra bulimoides , Lanistes ovum ) and two species of Bivalves ( Coelatura aegyptiaca , Mutela rostrata ). B. unicolor was the most abundant species with 71% of the collected molluscs and preferentially occupied the edges of the reservoir. It was followed by C. aegyptiaca (27%) which was abundant in the central axis of the reservoir. Physicochemical variables influence the distribution of species. For all measured physicochemical factors, B. unicolor was more tolerant than C. aegyptiaca on the occupation of available habitat.

Occurrence of Tetracampos ciliotheca (Cestoda: Bothriocephalidea) in the gall bladder of Clarias anguillaris in Burkina Faso

The presence of the bothriocephalidean cestode Tetracampos ciliotheca Wedl, 1861 is reported from the gall bladders of the catfish Clarias anguillaris from Loumbila and Ziga reservoirs, Burkina Faso, in 2010–2011. Of the 159 specimens examined, 47 were infected. Mean intensity of infection was 4.3 parasites per infected host, the maximum was 22 tapeworms in the gall bladder and the mean abundance was 1.3 parasites. There was no significant difference between males and females or between the two localities. There was a positive relationship between fish size and the number of parasites in the gall bladder. This study provides further evidence of the presence of T. ciliotheca in the gall bladder, in which most tapeworms found were localised. Tapeworms were also found in the stomach and intestine, with prevalences of 1% and 16%, and mean infection intensities of 1 and 5.3, respectively.