Valorisation of organic waste through larval feeding activity of the Black Soldier Fly (BSF), Hermetia illucens, constitutes a potential benefit for low-and middle-income countries. BSF larvae feed on organic waste while building their body composition of protein and fat. As a response to the escalating demand for protein in livestock feed, their protein can be used to replace fishmeal in monogastric animals' diet. Experiments were carry out to evaluate the feasibility of Black Soldier Fly (BSF) Hermetia illucens Linnaeus larvae to digest and degrade organic waste in a small-scale. Organic wastes (pig and chicken manures and kitchen wastes) were introduced in basins with 2000 young larvae (3-5 day-old) per basin for 15 days in batch and continuous feeding. We achieved an average pre-pupae production 830.1 and 694.0 g/m 2 (wet weight) under favourable conditions respectively in continuous and in batch feedings. Larvae fed every three days with waste materials developed into significantly larger larvae and pre-pupae than those fed at once. Waste reduction ranged from 53 to 80% depending on the daily amount of waste added to the experimental unit. The bioconversion rates were 12.8%, 10.7% and 6.5% respectively for chicken manure, pig manure and kitchen at the feeding ratio of 220 mg/day/larvae in continuous feeding. This study confirmed the great potential of BSF as a component of waste management in low and middle-income countries. If applied in organic waste management chain, the process could contribute to generate biofuel energy as well as sustainable protein provision to the animal industries. It could further reduce waste amounts significantly, minimizing possible pollution and improving environmental sanitation.

Various configurations of vegetated bed systems with a variety of macrophytes have been tested experimentally in Cameroon, for the treatment of domestic wastewater. The aim of this work was to assess the growth and biomass production of Fuirena umbellata (Cyperaceae) and its potentials in the removal of faecal bacteria and nutrients from primarily treated domestic effluent. A wetland vegetated with this macrophyte and a non-vegetated wetland (control) were continuously fed with primarily treated domestic wastewater at an estimated loading rate of 205 Litres/day in dry and rainy seasons for two consecutive years. Physicochemical and microbiological parameters of the effluent were monitored at the inflow and outflows of the wetlands alongside with the growth and productivity attributes of the young plants during each season. The density of plants ranged in the wetland from 17 -185 plants/ m 2 and from 11 -146 plants/m 2 respectively during the first and the second years. More biomasses were instead produced in the dry seasons than in the rainy seasons but with no significant differences observed. As for nutrients removal, higher efficiencies were observed in the vegetated wetland (45% -73%) compared to the non-vegetated control (17% -66%). Similar trends were observed for the faecal bacteria but with no significant differences between the seasons. However, the vegetated beds were significantly more efficient than the non-vegetated control in the reduction of many physicochemical parameters and faecal bacteria. This varied with the seasons.

Effet du stress salin sur la croissance des légumineusesAgronomie RESUMELes effets de la salinité sur la croissance des organes de cinq espèces légumineuses ont été évalués afin d'identifier celles susceptibles d'être cultivées sur des terres plus ou moins salées. 4 niveaux de salinité (0, 50, 100 et 200 mM de NaCl) ont été testés. Ainsi, l'augmentation de la salinité entraîne chez Glycine max et Phaseolus vulgaris (glycophytes sensibles) la baisse de la biomasse sèche dès 50 mM de NaCl. Chez Mucuna poggei (halophyte facultative) et Vigna unguiculata (glycophyte moyennement tolérante) cette baisse s'observe dès 100 mM de NaCl. L'inhibition de la croissance des glycophytes sensibles est liée à une diminution de la consommation d'eau en milieu salé. Le blocage de Na + dans les racines représente le principal facteur responsable du déficit hydrique des feuilles. Chez Phaseolus adenanthus (halophyte), la production de matière sèche foliaire est peu affectée par la salinité. La résistance de cette espèce à NaCl s'explique par un bon cheminement du flux hydrique vers les feuilles, facilité par une augmentation des teneurs en Na + et K + dans le sens racines, tiges et feuilles. Par ailleurs, au niveau des feuilles la déficience en K + est liée à la salinité du milieu, qui limite la croissance chez les espèces étudiées. La tolérance de V. unguiculata, M. poggei, et P. adenanthus vis-à-vis du sel permet d'envisager leur utilisation sur des terres marginales plus ou moins salées.Mots clés : stress salin, légumineuses, croissance, distribution ionique, Cameroun. ABSTRACT SALT STRESS RESPONSE VARIATION IN FIVE LEGUMINOUS PLANTS In order to determine leguminous plants able to be used as pioneer plant species on more or less saline areas, effects of NaCl concentrations on the growth of organs of five leguminous wild or cultivated plants were evaluated. Plants were submitted to 4 levels of salt stress at the roots (0, 50, 100 and 200 mM of NaCl). The increase in salt concentration greatly reduces the production of dry mater at 50 mM of NaCl in Glycine max and Phaseolus vulgaris (sensitive glycophytes). In Mucuna poggei (facultative halophyte) and

The aim of this study was to evaluate the removal of faecal bacteria and nutrients from domestic wastewater, in surface flow wetlands vegetated with Echinochloa pyramidalis. Horizontal surface flow (HSF) wetlands were fed with primarily treated domestic wastewater at organic loading rates varying from 20.74 to 27.15 g BOD/m 2 /day for two consecutive years. Water samples were collected at two weeks interval from the inflow and the outflow of the treatment wetlands for physicochemical and faecal bacteria analyses. Physicochemical parameters with highest removal rates were total suspended solids (TSS, 62-80%), Nitrates (57-73 %) and PO 4-3 (57-84 %). Faecal indicators reductions of 1.4 and 0.3 log units (1 st year) and 1.15 and 0.65 log units (2 nd year) were respectively recorded in the vegetated and the control wetlands. Reductions of total coliforms, faecal coliforms and faecal streptococci were significantly higher in the vegetated wetland than in the non-vegetated control in both seasons of the first year. In the contrary, there was no significant difference in the removal rates of faecal indicators between vegetated wetland and the non-vegetated control during the dry season of the second year. Wetlands vegetated with E. pyramidalis was proven to be continuously efficient in the removal of faecal indicators for the two years of study, with no significant differences between the seasons of the year and between the years.

Concentrations of cadmium (Cd), copper (Cu), zinc (Zn) and lead (Pb) in water, sediments, fish organs and plants from two ponds of the Olezoa wetland complex were analyzed. Plants investigated were Cyperus papyrus, Enydra fluctuans, Ipomoea aquatica and Echinocloa pyramidalis. The fish species studied was the walking catfish Clarias lazera and the heavy metal concentrations were measured in the digestive tract, gills, flesh and liver. Average concentrations in water were 6 x 10 -2 ppm for Cd, 14.53 ppm for Cu, 2.88 ppm for Zn and 17.69 ppm for Pb. These values were low compared to those recorded in the sediments, plants and fish organs. Results revealed an increase of heavy metal concentrations from water to plants and fish organs, with magnification factors ranging from 580 to 5700 and from 577 to 8173, respectively. In the sediments and the floating mat of the eutrophic fish ponds, these factors ranged from 491 to 1065 and 624 to 758, respectively. In the fish organs, particularly, the following accumulation gradients were foreseen: gills → flesh → digestive tract → liver for Cd and Pb; and flesh → gills → digestive tract → liver for Cu and Zn. The four plants studied appeared to be good candidates for phytoremediation of water metal pollution. The quantity of heavy metals in this wetland complex is considerable and will constitute a potential hazard for biota.

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Cloud cover constitutes a major obstacle to land cover classification in the humid tropical regions when using optical remote sensing such as Landsat imagery. The advent of freely available Sentinel-1 C band synthetic aperture radar (SAR) imagery offers new opportunities for land cover classification in frequently cloud covered environments. In this study, we investigated the utility of Sentinel-1 for extracting land use land cover (LULC) information in the coastal low lying strip of Douala, Cameroon when compared with Landsat enhanced thematic mapper (TM). We also assessed the potential of integrating Sentinel-1 and Landsat. The major LULC classes in the region included water, settlement, bare ground, dark mangroves, green mangroves, swampy vegetation, rubber, coastal forest and other vegetation and palms. Textural variables including mean, correlation, contrast and entropy were derived from the Sentinel-1 C band. Various conventional image processing techniques and the support vector machine (SVM) algorithm were applied. Only four * Corresponding author. M. L. Fonteh et al. 496 land cover classes (settlement, water, mangroves and other vegetation and rubber) could be calibrated and validated using SAR imagery due to speckles. The Sentinel-1 only classification yielded a lower overall classification accuracy (67.65% when compared to all Landsat bands (88.7%)). The integrated Sentinel-1 and Landsat data showed no significant differences in overall accuracy assessment (88.71% and 88.59%, respectively). The three best spectral bands (5, 6, 7) of Landsat imagery yielded the highest overall accuracy assessment (91.96%). in the study. These results demonstrate a lower potential of Sentinel-1 for land cover classification in the Douala estuary when compared with cloud free Landsat images. However, comparable results were obtained when only broad classes were considered.