Browsing by Author "Mtolera, Matern S. P."
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Item Assessment of changes in the seagrass-dominated submerged vegetation of tropical Chwaka Bay (Zanzibar) using satellite remote sensing. Estuar Coast Shelf S(Elsevier, 2006-02-15) Gullström, Martin; Lundén, Bengt Axel; Bodin, Maria; Kangwe, Juma; Öhman, Marcus C.; Mtolera, Matern S. P.; Björk, MatsSpatial and temporal dynamics of submerged aquatic vegetation (SAV) cover were studied in the relatively pristine and seagrass-dominated area of Chwaka Bay, Zanzibar (Tanzania) by using satellite remote sensing. Through complementary field work the potential of the technique for change detection was verified. The general changes in SAV cover were examined using Landsat images from 1986, 1987, 1998, 2001 and 2003. Two of these images, from 1987 (Landsat TM) and 2003 (Landsat ETM+), were specifically analysed to create a map of the change in SAV cover. Overall, the general distribution of SAV stayed fairly stable over the period investigated, but the result also showed regions where significant alterations, both losses and gains, had occurred between the two years. Based on our findings and anecdotal information from local fishermen and seaweed farmers potential causative factors are discussed. It was concluded that a repeated mapping with satellite remote sensing is a suitable tool to monitor changes of seagrass and seaweed distribution in shallow tropical environments.Item The Effect of Seasons on Yield And Quality of Carrageenan from Tanzanian Red Alga Eucheuma Denticulatum (Gigartinales, Rhodophyta)(Elsevier, 2001-09) Buriyo, Amelia S.; Semesi, A. K.; Mtolera, Matern S. P.Samples were collected monthly from Oyster Bay, Dar es Salaam. Light, temperature, salinity, pH, seawater nitrogen and phosphorus were determined on each sampling period. Mean carrageenan yield was significanlly higher during the SE monsoon period (t = 6.15, P<0.05). Gef strength was significantly higher during NE monsoon period (t = 2.61, P<0.05) and lower during the start of the rainy season particularly in March.Item Macroalgae as Biofilters of Dissolved Inorganic Nutrients in an Integrated Mariculture Tank System in Zanzibar(2001) Mwandya, Augustine W.; Mtolera, Matern S. P.; Pratap, Harish B.; Jiddawi, Narriman S.A laboratory experiment was conducted to determine the capacity of themacroalgae Eucheuma denticulatum, Gracilaria crassa and Ulva reticulatato remove dissolved inorganic nutrients from finfish effluents in seriallyarranged tank systems. The aim was to determine the capacity ofmacroalgae which could be used in an integrated maricultre pond systemat Makoba, Zanzibar. Seawater from the reservoir entered the finfish tanksfirst, then drained through plastic pipes into the shellfish units and finallyinto the macroalgae units before being discharged back into the sea. Thewater residence time in each tank was 4 days. The performance of each ofthe different units was assessed in terms of total ammonia-N, phosphate-P and nitrate-N produced by finfish, and then, the removal of these nutrientsby shellfish and macroalgae biofilters. The levels of dissolved inorganicnutrients were highest in the finfish units and lowest in the macroalgaeunits. Increase in stocking density of macroalgae from 1g/l to 2g/l wasrelated to their increase in daily growth rates, specific growth rates andinorganic nutrient uptake rates. However optimum stocking densities werenot reached. Of the three inorganic nutrients, ammonia-N and phosphate-P was taken up by the macroalgae much more than nitrate-N. Ammonia-N removal efficiency in the system reached a maximum of about 63% at2g/l of Ulva reticulata whereas, phosphate-P and nitrate-N maximumremoval capacity were 58 and 54% respectively. Among the three species ofmacroalgae, Ulva reticulata seems to be the most efficient biofilter. It isconcluded that locally available macroalgae are good bioregulators of waterquality, thus can be applied in small scale mariculture activities and canalso generate income.Item Photosynthetic Responses to Submergence in Mangrove Seedlings(CSIRO, 2014-03-27) Mangora, Mwita M.; Mtolera, Matern S. P.; Björk, MatsFlooding and salinity fluctuations are common in mangrove systems. Sometimes these events are long-lasting, persisting several months. With an increased frequency of heavy rainfalls and terrestrial run-off, subsequent floods have been associated with massive mangrove mortality and failure to regenerate in the region. Owing to climate change, these events are expected to be more common in the future. We investigated how three weeks of submergence in water of different salinities affected the photosynthetic rates in seedlings of three common mangroves: Bruguiera gymnorrhiza (L.) Lamk.; Avicennia marina (Forssk.) Vierh.; and Heritiera littoralis Dryand. We found that photosynthesis and survival rates declined with increasing salinity and submergence time for all species. Prolonged submergence caused a significant decline in photosynthetic rates (as electron transport rate – ETR) for B. gymnorrhiza (P = 0.021) and H. littoralis (P = 0.002), whereas significant effects of both salinity (P = 0.003) and submergence (P = 0.023) were observed between species. Maximum diurnal values of ETR declined in the order of A. marina > B. gymnorrhiza > H. littoralis. After submergence, survived seedlings were tended normally, watered twice a day with freshwater. Three seedlings of B. gymnorrhiza from freshwater and 33% seawater treatments and of A. marina from freshwater treatment displayed signs of recovery for the first 3–5 days, but after that they died. We conclude that submergence time and water salinity will affect the performance of mangrove areas, such that areas experiencing prolonged submergence with flooding dominated by saline water might be most severely impacted.Item Studies on Tanzanian Hypneaceae: Seasonal Variation in Content and Quality of Kappa-Carrageenan from Hypnea musciformis (Gigartinales : Rhodophyta)(Western Indian Ocean Journal Marine Sciences, 2004) Mtolera, Matern S. P.; Buriyo, Amelia S.Seasonal effects on yield and quality of kappa-carrageenan from the red alga Hypnea musciformis were investigated in samples collected from natural populations in Oyster Bay, Dar es Salaam during June 1996–May 1997. The mean annual carrageenan yield, gel strength (after treatment with 0.1 M KCl) gelling and melting temperature (± standard deviation) were 25.24 ± 4.44 % dry weight, 171.72 ± 41.42 g/cm2, 54.66 ± 3.12 ºC and 68.62 ± 0.60 ºC, respectively. Carrageenan yield and quality (gel strength) during the SE and NE monsoon seasons were not significantly different (t = 0.55, p > 0.05) and (t = 1.91, p > 0.05), respectively. The reported carrageenan yield and gel strength values were, respectively, about 50% and 40% those of carrageenan from Kappaphycus alvarezii. Although the carrageenan properties from H. musciformis were promising, its natural populations are generally insufficient to sustain the pressure of economic harvesting. Moreover, the extent to which its carrageenan yield and properties could be improved is not known. Suitable methods for mariculture are therefore needed before the resource can be exploited economically.Item Studies on Tanzanian Hypneaceae: Seasonal Variation in Content and Quality of Kappa-Carrageenan from Hypnea musciformis (Gigartinales : Rhodophyta)(2005) Mtolera, Matern S. P.; Buriyo, Amelia S.Seasonal effects on yield and quality of kappa-carrageenan from the red alga Hypnea musciformis were investigated in samples collected from natural populations in Oyster Bay, Dar es Salaam during June 1996May 1997. The mean annual carrageenan yield, gel strength (after treatment with 0.1 M KCl) gelling and melting temperature (±standard deviation) were 25.24 ±4.44 % dry weight, 171.72 ±41.42 g/cm2, 54.66 ±3.12 C and 68.62 ±0.60 C, respectively. Carrageenan yield and quality (gel strength) during the SE and NE monsoon seasons were not significantly different (t = 0.55, p > 0.05) and (t = 1.91, p > 0.05), respectively. The reported carrageenan yield and gel strength values were, respectively, about 50% and 40% those of carrageenan from Kappaphycus alvarezii. Although the carrageenan properties from H. musciformis were promising, its natural populations are generally insufficient to sustain the pressure of economic harvesting. Moreover, the extent to which its carrageenan yield and properties could be improved is not known. Suitable methods for mariculture are therefore needed before the resource can be exploited economically.Item Survival and Growth of Tilapia zillii and Oreochromis urolepis urolepis (Order Perciformes; Family Cichlidae) in Seawater(wiomsa, 2014) Nehemia, Alex; Mmochi, Aviti J.; Mtolera, Matern S. P.Abstract—The potential for Tilapia zillii and Oreochromis urolepis urolepis culture in seawater was evaluated by determining their survival and growth in seawater at 35‰. Fingerlings were collected from Pangani River using seine nets and reared in 1 m3 concrete ponds after acclimatization from salinity of 2‰ to 35‰. Fingerlings were also reared in freshwater as controls. Fingerlings were fed twice daily using commercial fish feeds (White Rose floating pellets), initially at a rate of 5% of their total body weight (TBW) and 10% of their TBW after two weeks. Their growth rate (length and weight) was recorded weekly except controls for handling, their growth being recorded at the beginning and end of the experiment. The average weight gain (g.week-1), percentage weights gain (week-1) and specific growth rate (SGR, %.day-1) were determined in freshwater and seawater. There was no significance difference (p >0.05) in the SGR between the two species in seawater. The survival rates of O. urolepis urolepis were 100% in freshwater and seawater and 89% and 96% respectively for T. zillii. This study showed that T. zillii and O. urolepis urolepis can survive and grow in seawater but the former is a better candidate for mariculture