Growth rate of African catfish (Clarias Gariepinus) and plankton diversity in ponds under organic and inorganic fertilization

Aquaculture offers the opportunity for safeguarding local and global food security in the face of declining capture fisheries. However, the form of aquaculture that is commonly practised in Kenya is characterized by the use of agrochemicals such as fertilizers that negatively impact biodiversity especially when effluents from fish ponds drain into water bodies. This study aimed to determine differences in growth rate of Clarias gariepinus, an important aquaculture fish in Kenya, to assess plankton diversity, and to identify phytoplankton species associated with pollution under organic and inorganic fertilization regimens using chicken manure, Diammonium phosphate and urea, respectively. Average growth rate calculated per day was higher in the organically-fertilized ponds at 0.06 cm/day, followed by inorganically-fertilized ponds at 0.05cm/day and then, the control at 0.04 cm/day. Average weight gain was higher in organically-fertilized ponds at 0.08 g/day followed by ponds fertilized with inorganic fertilizer at 0.07 g/day and the control, at 0.06g/day. There were significant differences in growth rate across fertilization regimens (length: F2, 264 = 24.06, p = 0.0399; weight: F2, 264 = 20.89, p = 0. 0457). Specifically, although differences in growth rate of fish in organically and inorganically fertilized ponds were not significant, fish in fertilized ponds were on average, longer and weighed more than those in the control pond. Jaccard’s similarity index for phytoplankton was highest (0.38) between organically fertilized ponds and control but lowest (0.25) between inorganically-fertilized ponds and control. Use of chicken manure produced the highest diversity of zooplankton (Shannon-Weiner’s H in organically-fertilized pond = 1.886; inorganic = 1.044, and control = 0.935). The use of DAP and urea produced the highest proportion of phytoplankton species associated with pollution. These results do not support the commonly reported notion that ponds fertilized using inorganic fertilizers are more productive. Findings suggest that the use of inorganic fertilizers may threaten biodiversity in aquatic ecosystems through the production of toxic algae

Co2 exchange and biomass development of the herbaceous vegetation in the portuguese montado ecosystem during spring

Montado are spatially heterogeneous ecosystems that are economically important for the production of cork and herbaceous biomass that provide fodder for animals. Understanding of how trees and the herbaceous layer interact to determine pasture yield and the overall CO2 exchange of the herbaceous layer is crucial. Portable chamberswere used to study CO2 exchange by the herbaceous layer component of the montado ecosystem in southern Portugal. Biomass, Net herbaceous layer CO2 exchange (NEE) and respiration (Reco) were measured in the open and understory locations between March and May, during the active growing period. Parameter fits on the NEE data were performed using empirical hyperbolic light response model, while ecosystem respiration (Reco) data were fitted with a two-parameter exponential model. Annual green biomass productions were 405.8 9.0 and 250.6 6.3 g m 2 in the open and the understory, respectively. The respective maximum NEE during the day were 24.0 2.9 and 9.6 2.2 mmol m 2 s 1 while maximum Reco were 20.6 2.2 and 10.0 1.6 mmol m 2 s 1, occurring in April. Photosynthetic photon flux density (PPFD) explained more that 70% of variations in daytime NEE while soil temperature at 10 cm depth (Tsoil) explained >50% of the variations in Reco under non-limiting soil moisture conditions. Both the herbaceous layer communities shared similar plant functional types and no significant difference in nutrient nitrogen (N) occurred between them. The two herbaceous layer components shared similar physiological characteristics and differences that arose in their CO2 uptake capacities and green biomass production were the result of microclimatic differences created by tree shadin

Socio-cultural determinants of sexual debut among in-school adolescents in Nyamira county

Background: One’s socialization greatly impacts their sexual behavior. Young people’s understanding of sex is influenced by prescribed social scripts which are learnt from peers, parents, media, among other sources. Nyamira County has the fourth highest burden of teenage pregnancy and motherhood in Kenya, standing at 28% against a national average of 18%. It’s therefore very important to understand the drivers of sexual debut among adolescents in Nyamira County.Objective: To establish the socio-cultural determinants of sexual debut among in-school adolescents in Nyamira County through the lens of the Social Learning theory.Design: A mixed method study design employing the collection of both quantitative and qualitative data.Setting: Mixed day, girls-only boarding and boys-only boarding secondary schools in Nyamira county.Study participants: These included 400 respondents, 200 males and 200 females, aged 14-18 years from mixed-day secondary schools and single-sex boarding secondary schools. Twenty-four key informants were also interviewed.Results: Of the 400 students, 61% had ever had sex. More students (63.5%) in mixed day schools had ever had sex compared to single sex schools (58.5%). Gender, age, marital status and coming from polygamous homes were found to be associated with ever having sex. Older sexual partners were seen to provide parental love. Peer pressure was reported by most male students as a driver towards initiating sex, while most female students reported poverty.Conclusion: Polygamous upbringing, peer pressure and watching pornography came out as strong determinants of sexual debut among in-school adolescents in Nyamira County

Molecular characterization of wood ear mushrooms (Auricularia sp) from Kakamega forest in western Kenya

Tanzania natural forests harbor several indigenous edible mushrooms that are meagerly exploited due to various reasons including unawareness on their potential values. This study establishes antioxidant potentials of seven wild edible mushroom species, and their two domesticated forms. The investigation used mushroom methanolic extract for antioxidant activities’ determination. A DPPH (1, 1-diphenyl-2-picrylhydrazyl) radical was used as a substrate to determine radical scavenging abilities whereas ferrozine was employed to determine ferrous ion chelating abilities. Additionally, quantitative analyses for β-carotene, lycopene, flavonoids, and total phenolic compounds were done using spectrophotometric assay. Mushrooms analysed displayed amazing antioxidant potentials which varied between different species and between the wild and domesticated forms of the same species. The range of EC50 values for DPPH free radical scavenging activity (DRSA) was 0.075 ̶ >0.3 mg/mL, with the strongest and weakest EC50 recorded from P. tenuiculus and the wild Amylosporus sp. IJ-2014, respectively. The range of EC50 values for ferrous ion chelating activity (FICA) was <0.1 ̶ 0.455 mg/mL, with the strongest and weakest EC50 noted in domesticated Amylosporus sp. IJ-2014 and L. sajor-caju, correspondingly. The maximum and minimum total phenolic content (TPC) recorded were 537.39 and 160.97 mg GAE/100g, from domesticated Amylosporus sp. IJ-2014 and Laetiporus sp. IJ-2014, respectively. The highest and least quantities of β-carotene (BC) recorded were 48.59 and 5.56 mg/100g, from P. tenuiculus/wild Amylosporus sp. IJ-2014 and P. cystidiosus, respectively. Lycopene contents (LC) ranged from 2.24 to 18.95 mg/100g, with P. cystidiosus and P. tenuiculus having the slightest and peak values, correspondingly. Maximum value for total flavonoid contents (TFl) recorded was 25.27 mg QE/100g from P. tenuiculus whereas the minimum value was 3.71 mg QE/100g from P. cystidiosus. Due to the antioxidant potentials of these mushrooms, people are advised to maximally exploit them for improved nutrition and health

Identification and synthesis of sordidin, a male pheromone emitted by Cosmopolites sordidus

International audienc

Herbaceous layer development during spring does not deplete soil nitrogen in the portuguese montado

Available at ScienceDirectNitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of 2004e2006 to determine how the herbaceous layer development influences soil N availability in the montado ecosystem of southern Portugal. Highest (246.6 52.7 g m 2) and lowest (123.2 89.5 g m 2) peak biomass occurred in 2006 and 2005 respectively. Total soilNwithin the top 20 cmsoil profile ranged between 0.2 0.1% in February and 0.41 0.2% inMay,while available soil N was lowest (5 2 mg g 1soil) in February but increased three-to-five fold in March and was >17.5 mg g 1soil at senescence in May. Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May. There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical component of the montado that contributes to N recharge and cycling within the ecosyste