Browsing by Author "Kyewalyanga, M.S."
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Item Antioxidants activity of the cyanobacterium, Arthrospira (Spirulina) fusiformis cultivated in a low-cost medium(ACADEMIC JOURNAL, 2018-08) Michael, A.; Kyewalyanga, M.S.; Mtolera, M.S.; Lugomela, C.V.Spirulina species are known to have a good nutritional profile and antioxidant properties against reactive oxygen species. However, little is known about the antioxidant contents and the scavenging ability of Arthrospira fusiformis, cultivated under various conditions. This study aimed at evaluating the content of antioxidants (total phenols, total flavonoids, β-carotene, and lycopene) and the activity of A.fusiformis produced using low-cost culture (LCMA) and standard culture (Zarrouk) media. The results revealed that A. fusiformis is rich in antioxidants and it possesses high scavenging and chelating activities. Interestingly, the LCMA was superior over the Zarrouk medium as it resulted in spirulina with a higher amount of antioxidants and lower EC50 values. In this context, production of natural antioxidants can be maximized through the use of cost-saving, inorganic culture medium.Item Biomass and nutritive value of Spirulina (Arthrospira fusiformis) cultivated in a cost-effective medium(SPRINGER NATURE, 2019-12-23) Michael, A.; Kyewalyanga, M.S.; Lugomela, C.V.Introduction Cultivation of spirulina at commercial-scales relies on analytical grade–based media, which are expensive and so are the product. Purpose This study assessed the biomass, proximate composition, and other useful compounds in Spirulina (Arthrospira fusiformis) produced with a cost-effective culture medium (LCMA), and the results were compared with those from a standard Zarrouk medium–grown spirulina. Methods The LCMA medium was formulated by using a commercial NPK10-20-20 fertilizer as a source of the three major nutrients for spirulina growth, and other three ingredients from Zarrouk medium. The experiment was conducted for 28 days in the glass aquaria under indoor conditions. Standard analytical methods were applied for the determination of proximate composition, chlorophyll, minerals, and vitamins in the spirulina biomass. Result The LCMA medium showed the best growth conditions by accumulating higher chlorophyll content (0.99 ± 0.02%) and dry weight (0.75 ± 0.01 g/100 ml) as well as attaining higher optical density (2.06 at day 15) earlier than the Zarrouk medium. The results of the proximate analysis for spirulina cultured in the LCMA medium were of good quality, with the protein contributing more than 50% of its dry matter. It was further noticed that the LCMA was an ideal medium for optimization of vitamins and some minerals since it recorded a significant amount of most of the analyzed vitamins together with the minerals sodium and potassium compared with the Zarrouk medium. Conclusion It is suggested that LCMA medium could be used as the alternative and cheap medium for maximization of biomass and production of useful biochemical compounds in spirulina species.Item Employing multivariate analysis to determine the drivers of productivity on the North Kenya Bank and in Kenyan territorial waters(WIOMSA, 2020) Kamau, J.; Ochala, O.; Ohowa, B.; Mitto, C.; Magori, C.; Osore, M.; Mahongo, S.B.; Kyewalyanga, M.S.A complex mix of natural processes exist in nearshore and offshore waters which influence coastal and marine ecosystem productivity. An understanding of the biogeochemical processes involved is a key element in interdis ciplinary studies of primary production, oceanic flux and storage of carbon dioxide. Water circulation in the East African region is influenced by coastal currents driven by monsoon winds. There are four oceanic currents influenc ing Kenya’s coastal waters; namely the East African Coastal Current, the Somali Current, the Southern Equatorial Current and the Equatorial Counter Current. The Kenyan fishing industry is slowly embracing offshore fishing grounds, and the North Kenya Bank is emerging as the next fishery frontier. This study aims to provide insight on the processes driving the productivity of Kenya’s territorial waters. The variable Si* (the difference between available silicate [Si(OH)4] and nitrate [NO3- ]) was employed as a proxy of upwelling. It was highly positively correlated to chlorophyll-a, indicating that upwelling is a major phenomenon driving productivity in Kenyan territorial waters. Particulate Organic Carbon (POC) and Dissolved Oxygen (DO) exhibited a lesser positive correlation with chloro phyll-a, implying that remineralization also has some influence in the productivity of the area.Item Health problems related to algal bloom among seaweed farmers in coastal areas of Tanzania(ACADEMIC JOURNAL, 2018-08) Said, A.H.; Msuya, F.E.; Kyewalyanga, M.S.; Mmochi, A.J.; Mwihia, E.W.; Skjerve, E.; Ngowi, H.A.; Lyche, J.L.There is a scarcity of research-based data on the factors associated with skin irritation due to algal blooms in seaweed farming. Changes in temperature with an increase in nutrients levels lead to the growth of harmful algal blooms, which produce many active metabolites, some of which induce toxic responses in human including skin irritation. The objective of this study was to identify health problems experienced by seaweed farmers and the seasons when they occur, and how these are treated. A cross sectional study design was used to gather data using structured questionnaire, focus group discussions and key informant interviews. The study was conducted between June and August 2015, in six villages, two from Mainland, and four from Zanzibar Islands, Tanzania. Study revealed that seaweed more than 50% of farmers experienced skin irritation problem, followed by 30.4% who had eye related problems, and only 19.6% had respiratory disorders as the most serious. Hot season, which is associated with algal blooms, was the period with the highest occurrence of skin irritation. No specific medication was used to treat the health problems reported. In some severely affected areas, farmers could not tend to their farms for months, a situation which affected their income. It is suggested that the findings from this study would reduce this knowledge gap and motivate stakeholders especially the policy makers to implement measures, which reduce the health problems observed due to algal blooms in the seaweed farmers.Item The influence of physical-chemical variables on the spatial and seasonal variation of Chlorophyll-a in coastal waters of Unguja, Zanzibar, Tanzania(WIOMSA, 2018) Peter, N.; Semba, M.; Lugomela, C.; Kyewalyanga, M.S.Chlorophyll-a (Chl-a) concentrations were measured at four sites around Unguja, Zanzibar during the northeast (NE) and southeast (SE) monsoon seasons. Data for Chl-a, nitrate, phosphate, ammonia, dissolved oxygen, sea sur face temperature, pH and salinity were collected once a month from March 2008 to March 2009. The SE monsoon had insignificantly higher Chl-a compared to the NE monsoon season when Chl-a for Bawe, Chumbe, Pongwe and Mnemba were combined (W = 234, p = 0.93). The drivers of high Chl-a during the SE monsoon were ammonia and nitrate. Results from individual sites showed that Pongwe and Mnemba had higher median Chl-a during the SE than the NE monsoon season. Temperature, dissolved oxygen and ammonia were the major factors that influenced high Chl-a at these sites. In contrast, Chumbe and Bawe had higher median Chl-a during the NE- than the SE mon soon season. The major factors influencing high Chl-a in the NE at Chumbe and Bawe were high levels of nutrients, mainly from sewage effluent and various human activities around the coast in Zanzibar town. The interaction of Chl-a between monsoon seasons (NE and SE) and sites (Bawe, Chumbe, Pongwe and Mnemba) was insignificant (F(1,3) = 1.3144, p = 0.2949). The principal component analysis revealed that different physical and chemical environmental variables affect Chl-a concentration over time and location.Item Isolation of the Tephrosia vogelii extract and rotenoids and their toxicity in the RTgill-W1 trout cell line and in zebrafish embryos(ELSEVIER, 2020-05-23) Said, A.H.; Solhaug, A.; Sandvik, M.; Msuya, F.E.; Kyewalyanga, M.S.; Mmochi, A.J.; Lyche, J.L.; Hurem, S.This study focused on identifying the rotenoids from the Tephrosia vogelli plant (fish-poison-bean), investigating the toxic potency of a crude T. vogelii extract and individual rotenoids (tephrosin, deguelin and rotenone) in vitro and in vivo and assessing the mode of action. A trout (Onychorynhis mykiss) gill epithelial cell line (RTgill-W1) was used to determine the cytotoxicity of rotenoids and effects on cell metabolism. Zebrafish (Danio rerio) aged from 3 h post fertilization (hpf) to 72 hpf were used for testing the developmental toxicity. The crude T. vogelii plant extract significantly decreased the cellular metabolic activity and was cytotoxic at lower concentrations (5 and 10 nM, respectively), while tephrosin, deguelin and rotenone showed these effects at concentrations � 50 nM. The crude T. Vogelli extract had the highest toxic potency and induced adverse health effects in zebrafish including deformities and mortality at the lowest concentration (5 nM) compared to rotenone (10 nM) and deguelin and tephrosin (50 nM). These results indicate that the crude T. Vogelii extracts are highly potent and the bioactivity of these extracts warrant further investigation for their potential use to treat parasites in human and veterinary medicine and as a natural alternative to pesticides.Item Variability of Mackerel fish catch and remotely-sensed biophysical control in the eastern Pemba Channel(ELSEVIER, 2021-03-11) Kizenga, H.J.; Jebri, F.; Shaghude, Y.; Raitsos, D.E.; Srokosz, M.; Jacobs, Z.L.; Nencioli, F.; Shalli, M.; Kyewalyanga, M.S.; Popova, E.Advances in satellite remote sensing of environmental perturbations have become important in understanding variations of ocean productivity and small pelagic fish catches. This marine resource is vital for coastal populations dependent on artisanal fishing for their income and food security, such as in coastal East Africa. In this region, the eastern Pemba Channel (Tanzania) represents a hotspot area, for a variety of marine species including small pelagics and coral reef associated species. This study examines the links between mackerel fish catch, one of the important small pelagic fish for direct consumption in the region, and changes in environmental oceanographic parameters over the period 2012–2018. The fisheries catch data is a rare local dataset, consisting of daily mackerel landings (from 2012 onwards) and supplemented by qualitative information on the mackerel fishery obtained through interviews with local stakeholders. The physical factors influencing phytoplankton biomass, and in turn, mackerel fisheries yield is investigated, using remotely-sensed chlorophyll-a (Chl-a) and Sea Surface Temperature (SST), together with Mixed Layer Depth (MLD) data from the high-resolution ocean model NEMO. We show that seasonal variations in mackerel landings are positively (negatively) correlated with Chl-a (SST) with a 1-month time lag (i.e., biophysical factors change first, mackerel stocks follow one month later). On the eastern side of the Pemba Channel, cooler SST and higher Chl-a are observed during the Southeast monsoon accompanied by increased mackerel landings, suggestive of enhanced productivity. Interannually, these relationships remain valid both for monthly and annual means, which confirms the close link between the variations of mackerel and biophysical conditions. Analysis of the Chl-a and MLD anomalies, relative to the mean, reveals that the phytoplankton blooms observed on the eastern side of the Pemba Channel, during the Southeast monsoon, are likely due to the deepening of the mixed layer, which tends to entrain cold and nutrient rich waters from greater depths to the surface. We conclude that upper ocean mixing contributes to the observed enhanced productivity along with other environmental factors. Additionally, we show how our results can be applied in the management of the mackerel resource in the Pemba Channel.