Browsing by Author "Kyewalyanga, Margareth S."

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    Coastal upwelling and seasonal variation in phytoplankton biomass in the Pemba Channel
    (WIOMSA, 2020) Kyewalyanga, Margareth S.; Peter, Nyamisi; Semba, M.; Mahongo, S.B.
    This study was conducted in the Pemba Channel off Tanga Region in northern Tanzania to investigate physical and chemical factors that drive changes in phytoplankton biomass. Three transects off Mwaboza, Vyeru and Sahare were selected. For each transect, ten stations were sampled. Phytoplankton biomass was determined as chlorophyll-a (Chl-a) concentration. Similarly, physico-chemical variables (temperature, salinity, dissolved oxygen, pH and nutri ents) were determined. It was observed that the Chl-a concentration was significantly higher during the northeast monsoon (median 1.44 mg m-3) as compared to the southeast monsoon (median 1.19 mg m-3; W = 2216, p = 0.029). The higher productivity during the northeast monsoon is attributed to the presence of high-nutrient water caused by coastal upwelling. It is concluded that indication of upwelling, observed through relatively low temperatures during the northeast monsoon season, could be responsible for bringing nutrient-rich waters to the surface, which in turn stimulated the increase in Chl-a concentration.
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    Health problems related to algal bloom among seaweed farmers in coastal areas of Tanzania
    (Academic Journals, 2018-08) Said, Aziza H.; Msuya, Flower E.; Kyewalyanga, Margareth S.; Mmochi, Aviti J.; Mwihia, Evalyn W.; Skjerve, Eystein; Ngowi, Helena A.; Lyche, Jan 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 crosssectional 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.
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    The performance of the seaweed Ulva reticulata as a biofilter in a low-tech, low-cost, gravity generatedwater flow regime in Zanzibar, Tanzania
    (Elsevier, 2006) Msuya, Flower E.; Kyewalyanga, Margareth S.; Salum, Dotto
    In most land-based mariculture, seaweeds have been cultured using expensive ponds and electrical pumps to aerate the seaweeds, methods that can be expensive and not applicable to areas where electricity is lacking. In this study, a low-tech, low-cost, gravity-generated water flow regime was used in earthen ponds in Zanzibar, Tanzania. The seaweed Ulva reticulata was cultured suspended in 2 m−2 fishnet cages (units) in channels located at the outflow of fishponds as treatment and at the channel leading water to the fishponds as control, in a fish-seaweed integrated system. The seaweed grew at an average of 4.0% per day at the treatment (fishpond outflow channel) with a biomass yield averaging 46 g m−2 day−1, compared with 2.5% and 27 gm−2 day−1 at the control (fishpond inflow channel). Likewise, the seaweed removed a significant amount of areal total ammonia nitrogen (TAN) averaging 6.5 g Nm−2 day−1 with 65% removal efficiency and 0.3 g Pm−2 day−1 of soluble reactive phosphate (SRP) with 33% efficiency, from a TAN load of 10.6 g m−2 day−1 and phosphate load of 0.7 g m−2 day−1. In the control, only 1.9 g Nm−2 day−1 (44% efficiency) TAN and 0.3 g Pm−2 day−1 (33% efficiency) SRP were removed from TAN and phosphate loads of 4.8 and 0.8 g m−2 day−1, respectively. Through its photosynthetic activity, the seaweed significantly (pb0.001) raised the oxygen concentration and pH of the fishpond outflow water (from 5.6 to 13.4 mg l−1 and 7.8 to 8.4, respectively). It is therefore concluded that seaweeds can be cultured in fishpond outflow channels, in a low-tech, low energy, gravitygenerated water flow regime and function as effective biofilters of fishpond effluent water. © 2005 Elsevier B.V. All rights reserved.
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    Seasonal variation in growth rates and carrageenan properties of Kappaphycus alvarezii and Eucheuma denticulatum cultivated with and without additionnutrients, in Uroa, Zanzibar, Tanzaniaal
    (Tanzania Journal of Natural and Applied Sciences, 2012) Msuya, Flower E.; Kyewalyanga, Margareth S.; Bleicher-Llhonneur, Genevieve; Lampin, Tatiana; Lhonneur, Jean-Pierre; Mazoyer, Jacques; Critchley, Alan T.
    Kappaphycus alvarezii and Eucheuma denticulatum were cultivated under two treatments: with & without additional nutrients in Uroa, Zanzibar. The seaweeds were cultivated for 8 weeks (total of 15 weeks) in contrast to the 4-6 weeks normally used by farmers. Water column nutrients were 8-17μM total ammonia nitrogen & 2-38 μM soluble reactive phosphate. There were no significant differences in specific growth rates of fertilised & unfertilised seaweeds (P>0.05). However, during heavy rains & high surface seawater temperatures there were significant differences between the two treatments for both species (P<0.05). Whereas seaweed growth rates seemed to be affected by protracted periods of rain and a hot season of 31 0C maximum, fertilised K. alvarezii was more affected by the hot season than the unfertilised plant. For short rains and cooler months (27 0C maximum) both treatments showed similar rates. No significant differences (P>0.05) were found in carrageenan yield, dry matter, iota carrageenan percentage, and viscosity between fertilised and unfertilised treatments. Seasonal variations showed lower carrageenan yield & dry matter during heavy rains and higher values at the end of rainy season. Seaweed farmers in Tanzania could use a lower stocking density for higher seaweed biomass production & cultivate seaweeds for longer periods to satisfy customers in the carrageenan industry if so desired.
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    Supplementing wastewater with NPK fertilizer as a cheap source of nutrients in cultivating live food (Chlorella vulgaris)
    (SPRINGER NATURE, 2021) Mtaki, Kulwa; Kyewalyanga, Margareth S.; Mtolera, Matern S.P.
    Introduction: The decline in fishery resources from the wild has led to an ever increasing focus on aquaculture in recent years. With increasing aquaculture of animal species, there is an increasing need for suitable microalgae in the production of these animals. However, cultivation of microalgae in expensive pure chemical media is one of the major challenges facing large-scale cultivation of microalgae. Purpose: The present study investigated the suitability of aquaculture wastewater (AWW) supplemented with NPK (nitrogen:phosphorus:potassium) fertilizer as a cheap source of nutrient to cultivate a microalga Chlorella vulgaris (C. vulgaris). Methods: C. vulgaris with an initial cell density of 0.8 × 106 cells/mL was batch cultured in AWW supplemented with NPK at 0.1, 0.5, 1.0 g/L and BBM for 20 days under laboratory conditions using 2000 mL Erlenmeyer flasks. The proximate composition, chlorophyll, minerals, and vitamins analysis of C. vulgaris biomass were done using standard analytical methods. Results: The highest values in optical density (4.872 ± 0.025), dry cell weight (2.858 ± 0.015 g/L), specific growth rate (0.2097 ± 0.0038 day–1), and biomass productivity (0.1701 ± 0.0007 g/L/day) were obtained in C. vulgaris grown in AWW + 1.0 NPK medium. The total chlorophyll, protein, lipid, and carbohydrate content of the microalgae biomass were in the range of 0.05–0.862%, 44.062–57.089%, 17.064–23.260%, and 15.217–21.896%, respectively. Furthermore, microalgae grown in AWW + 1.0 NPK showed good vitamin and mineral content compared to BBM grown alga. Conclusion: These findings indicated that the AWW + 0.1 NPK, AWW + 0.5 NPK, and AWW + 1.0 NPK are potential growth media for C. vulgaris cultivation and can replace the BBM medium, which is very expensive and less accessible to users.