Institute of Marine Sciences

Permanent URI for this community

http://192.168.13.253:4000/handle/123456789/3543

Back to the main page

Browse

Now showing 1 - 20 of 46

The reproductive biology of the squid, sepioteuthis lessoniana ( lesson, 1830 ) in the coastal waters of Zanzibar.
(University of Dar es Salaam, 1997) Mhitu, Hassan Ahmed
A study on the reproductive biology of the bigfin reef squid, Sepioteuthis lessoniana f Lesson, 1830) in the coastal waters of Zanzibar, was conducted with a view to obtaining basic information that will be relevant to proper management of the squid fishery in the area. Data collection involved field sampling and laboratory work. A total of 664 specimens of the species were collected from artisanal fisheries at Chwaka, Zanzibar during 1994/1995. The body weight and the morphometric length measurements (DML, FW and FT) of S. lessoniana taken before and after freezing had no significant difference (P>0.05). However, the difference between the measurements made on 20 specimens while fresh and after freezing was less than 4%. The maximum size of S. lessoniana was 347 mm DML and 277 mm DML for males and females, respectively. The minimum size for males was 63 mm DML and 72 mm DML for females. The maximum weight was 1617.3 g for males and 969 g for females whereas the minimum weights were 20.8 g and 26.3 g for males and females, respectively. Mature squids migrate from the coastal waters from July to offshore waters to spawn. The length-weight regression equations were: Males W=0.0005L2547 , Females W=0.0004L2576 and Combined W=0.0005L2 555. The slopes for length-weight regression lines for both males and females showed no significant difference (P>0.001) when compared. Both male and female S. lessoniana exhibited allometric growth. The mean condition factor was generally higher for females than for males in all months except for August. Females were therefore heavier than males. Sexual dimorphism was evident in this species where 344 females and 320 males were identified. Sex ratio in S. lessoniana was not significantly different from 1:1 throughout the year except in May, June and November. Two maturity indices, the gonadosomatic index (GSI) for both sexes, and the ratio of nidamental gland length to dorsal mantle length (NGL/DML ratio) for females coincided in their peaks in July. This coincidence may imply that, the individuals were mature and were ready to spawn. Statistical and graphical methods were used to determine size at maturity. Size at maturity for S. lessoniana was 138.9 ± 6.4 mm DML for males and 162.9 ± 4.3 mm DML for females through the statistical method. The graphical method yielded 149.5 mm DML and 162.8 mm DML for males and females, respectively. The estimated fecundity for female S. lessoniana from Zanzibar ranged from 450 to 1180 with a mean of680 eggs for individuals of 140 mm to 249 mm DML. The number of eggs in a capsule was 6 and mean size of the eggs was 6 mm in length and 4.5 mm in breadth. Fecundity was related to the size of the female.
Ecology of the intertidal zone of selected sandy/muddy shores in the Dar es salaam area
(University of Dar es Salaam, 2000) Mlay, Angela Peter
An ecological study was conducted on four shores in the Dar es Salaam area, Kunduchi, Ocean Road, Mjimwema/Kendwa, and Mtoni. The following were determined monthly for a period of one year: particle size, organic matter content, and percent pore water of the substrate; depth of the hydrogen sulphide layer; temperature; salinity; dissolved oxygen concentration in tidal pool water; and density, biomass, and species diversity of benthic macrofauna. In a comparison of the four shores, there was a very significant difference in density (randomized block analysis of variance, F = 22.751, p = 3.609 x 10"8), and biomass (Friedman’s test, Chi-square = 23.900, p = 2.576 x 105). Kunduchi and Ocean Road were similar in all the abiotic factors measured. Both shores had moderate species diversity, but low density and biomass of macrofauna. Besides being under environmental stress due to desiccation, these shores have been exposed to anthropogenic impacts due to excessive movement of boats and people, destructive fishing methods and pollution. In comparison with Kunduchi and Ocean Road, Mjimwema/Kendwa had higher percent pore water, lower organic matter content, thinner hydrogen sulphide layer, but approximately the same dissolved oxygen and salinity levels. Due to the physical contours of the surrounding area, this shore never completely drains and there are relatively few anthropogenic effects. Compared to the other three shores, Mjimwema/Kendwa had the highest biomass and species diversity of macrofauna. It also had high density. At Mtoni, the substrate was determined to be very fine silt, poorly sorted, with very low percent pore water, a high build up of organic matter, and a thick hydrogen suphide layer. Since it is in an estuary, salinity was lower than on the other shores and showed the greatest drop during the rainy season. Compared to the other three shores, Mtoni had the lowest species diversity, lowest biomass, yet highest density. This was due to the high density of two species of very small organisms that seem to be adapted to that stressful environment, i.e., Arcuatula arcuatula and Modiolus sp Mtoni had greater biomass of bivalves, crabs, and polychaetes than on the other shores. Gastropods were found in the greatest biomass at Mjimwema and were not observed at all at Mtoni. Total macrofauna, bivalve, and polychaete biomass were highest during the principal and secondary rainy seasons at Mjimwema/Kendwa. Crabs had greater biomass during the principal rainy season at both Ocean Road and Mjimwema/Kendwa. Kunduchi and Ocean Road showed the greatest biomass on the lower part of the shore, while Mjimwema and Mtoni showed the greatest biomass in the middle of the shore. All shores showed the lowest biomass on the upper part of the shore, which was dominated by crabs. In this zone, Dotilla fenestrata was dominant on all shores along with either Ocypode spp. (Kunduchi, Ocean Road and Mjimwema) or Uca spp. (Mtoni). At Kunduchi and Ocean Road, midshore was dominated by a variety of polychaetes, sipunculids, bivalves and crabs, while holothurians dominated the lower shore. At Mjimwema/Kendwa, midshore was dominated by a variety of gastropods, bivalves, sponges, holothurians, sea urchins, and brittle stars.
Phytoplankton diversity and productivity wiht emphasis on the bloom dymamics of the potentially toxic cynobacterrium arthrospira fusiformis in Momela lake,Arusha, Tanzania
(University of Dar es Salaam, 2007) Kaaya, Lulu Tunu
Limnological studies were conducted in Momela lakes ( Small Moinela, Big momela and Tulusia)for analysis of phyloplankton species composition, abudance, and biomass ( chlorophyll ‘’a’’) and environmental parameters (TSS, alkalinity, Ph salinity). transparency, water temperature and hardness and inorganic nutrients) as well estimamtions of primary production and nitrogen fixation rates, sampling was conducted once per month for a period of one year ( May 2005 to April 2006) .Calculated Shannon-weaver diversity indicates were higher in lake Small momela compared to lake big momela and Tulusia. Arthaspira fusiformis was the most dominant species in lake big (up to 1840 filaments/m1) while it existed at background concentrations in Lake Small Momela (maximum of 9 filaments/m1). Phytoplankton biomass was significantly and consistently low in Lake Small Momela compared to Lake Big Momela and Tulusia. However, there were no significant seasonal variations in phytoplankton biomass and abundance of a fusiformis. Environmental parameters were fairly stable showing insignificant temporal variations during the study period. However significant spatial variations in salinity and alkalinity among the hikes were noted. Lake Small Momela had significantly less, salinity and alkalinity levels compared to Lake Big Momela and Tulusia. Also, there were no significant differences in the rates of gross- and net-primary productivity as well as nitrogen fixation among the lakes and between seasons. In general, limnological parameters in Momela lakes did not vary much between seasons but much variation were observed among the lakes.
Levels and distribution polycyclic aromatic hydrocarbons (PAHs) in interstitial water, surface sediments and Oysters from the intertidal areas of Dar es Salaam, Tanzania
(University of Dar es salaam, 2007) Gaspare, Lydia
Interstitial water, surface sediment and oyster samples from the intertidal areas of Dar es Salaam, Tanzania were analysed to determine the level and distribution of PAHs. Samples were extracted using shaking and Accelerated Solvent Extraction methods and cleaned up using column chromatography. Samples were analysed using GC/MS. The concentration of PAHs in interstitial water ranged from 47.15 ng/1 and in sediment ranged from 56.41 ng/g dry weight (dw) to 14815.84 ng/g dw. The concentration between sediment PAHs concentration was positively correlated to sediment fine grain size of <63 um (r=0.68, n= 18, p<0.05). the concentration of PAHs in oysters ranged from 16.82 ng/g dw. Oyster samples were enriched with 2-3 ring PAHs by 40 % of total PAHs at all sampling stations except at Ocean Road which had 31.4 % 2-3 ring PAHs. The results showed that Ocean Road was highly polluted by PAHs followed by Mzinga creek. Lowest levels of PAHs were found at Kunduchi and Tegeta. Analysis of the possible sources of PAHs suggests petrogenis and pyrolyic dominated PAHs origins. It was concluded that sediment bound PAHs were not readily bioavailable to oysters and it is recommended that monitoring program be established for PAHs, so that any exceedance in concentration overenvironmental quality standards can be detected and appropriate actions be taken.
Dynamics in Shirati Bay, Lake Victoria Tanzania With Special Zooplankton Emphasis on the Copepods
(University of Dar es Salaam, 2008) Waya, Revania Kiduduye
The population of dynamics of zooplankton with emphasis on the copepods were studied Shirati Bay, Lake Victoria, between March 2005 and March 2006. The study revealed spatio-temporal variations in zooplankton distribution and the factors influencing their distribution, abundance and composition. Factors affecting zooplankton density, biomass and distribution in Shirat Bay were found to include food condition, predation, temperature, wind, light and transparency. There was significant correlation between zooplankton abundance and the bacillariophytes (r = 0.9454,n=13,p<0.0001),Rotifera biomass and cyanophytes (r=08264, n =13,p<0.0001)there was a significant association between abundance of fish and zooplankton (Matel test: Standard normal Variate g(1,1000)=7.0834, p=0.009,r=0405, and abundance of haplochromines and zooplankton (g 1,1000) = 6.348, p=0.001,r = 0.888). also the linear correlation analysis revealed significant correlation between temperature and number of ovigerous female copepod (r= -05585, n=13, p=0.0473). three groups of zooplankton were recorded namely, Copepoda, Rotifera, and Cladocera. A total of 44 species were recorded, Rotifera showed highest diversity index (H’) of 2.321. Copepoda was the most important group in terms of abundance and biomass among them cyclopoid copepod dominated the zooplankton community throughout the study period. Nauplius and Cyclpopoid Copepodites in Shirati Bay During March 2005 –March2006 0 MAR-05 APR 05 MAY 05 JUN 05 JUL 05 AUG 05 SEP 05 0CT 05 N0V 05 MAR O5 0.000 0.741 0.647 0.816 0.789 0.800 0.989 0.929 APR 05 2.770 0.000 1.000 1.000 1.000 1.000 1.000 1.000 MAY 05 3.010 0.240 0.000 1.000 1.000 1.000 0.997 1.000 JUN 05 2.558 0.212 0.451 0.000 1.000 1.000 1.000 1.000 JUL 05 2.639 0.131 0.371 0.081 0.000 1.000 1.000 1.000 AUG05 2.606 0.164 0.404 0.048 0.033 0.000 1.000 1.000 SEP 05 1.624 1.146 1.386 0.935 1.015 0.983 0.000 1.000 OCT 05 2.139 0.631 0.871 0.419 0.500 0.467 0.515 0.000 NOV 05 1.324 1.446 1.686 1.234 1.315 1.282 0300 0.815 DEC O5 2.807 0.037 0.203 0.249 0.168 0.201 1.183 0.668 JSN 05 0.220 2.550 2.790 2.339 2.419 2.386 1.404 1.919 FEB 06 3.755 6.525 6.765 6.313 6.394 6.361 5.378 5.894 MAR 06 1.754 4.524 4.764 4.312 4.393 4.360 3.378 3.893 Values in bold indicate significant differences among months.
Photophysiological responses of thermally stressed symbiodium harboured by reef building corals common to Tanzania and Mauritius
(University of Dar es Salaam, 2011) Maurice, Ravina Joseph Jean
The study aimed at comparing the photosynthetic responses of selected different reef building corals common to Tanzanian and Mauritian water. Equally of interest was to determine whether there has a significant difference in photosynthetic response between isolated Symbiodinium common to Mauritius and Tanzania. A Diving-PAM (Walz; Germany) was used to measure the maximum quantum yield (dark-adapted Fv/Fm) of lsolated and in hospite Symbiodinium from Acropora muricata, Galaxia fascicularis, Pocillopora verrucosa, and Porites cylindrica. The use of chlorophyll fluorescence showed no significant variation in isolated Symbiodinium PSll responses to thermal (28, 30 and 33 0C) and/ or light (170 and 750 µmol quanta m2s -1) between Zanzibar and Mauritius samples. Significant variation (p<0.001 ) was observed in photosynthetic yield of isolated Symbiodinium from the coral species investigated. Significant variation (P<0.01) in in-hospite Symbiodinium PSll responses to thermal and light stresses were observed between the four candidate coral species collected in Tanzania. Poritescylindrical and Galaxea fascicularis were more resilient to high light and high heat stresses in both Tanzania and Mauritius. The in hospite Symbiodinium from Galaxea fascicularis, Porities cylindrical, Aeropora muricata, Pocillopora verrucosa occur in order of most to less tolerant ones in Tanzania.
Survival and growth rates of Pangani River’s tilapia in sea water for mariculture development
(University of Dar es Salaam, 2011) Nehemia, Alex
The potential for Tilapia zillii and Oreochromis urolepis culture in marinewaters was evaluated by determination of the survival and growth rates in full strength sea water (FSSW) at 35%o. For the study fingerlings were collected from Pangani by using seine nets and reared in 1m 3 concrete ponds where salinity for their growth media was changed to 35%o at the rate of about 2%o per day. Fingerlings were fed twice daily using commercial fish feeds (White Rose floating type), initially at a rate of 5% af their total body weight (TBW) and two weeks later at 10% of their TBW. The growth rate was recorded once a week except for handling control fingerlings which were recorded at the beginning and at the end of the experiment. The average Height gain (g/week), percentage weight gain (%/week) and specific growth rate (SGR, %/day) during acclimatization period in fresh water (FW) and acclimatization saline Hater (SW) in the bracket for O. urolepis urolepis were found to be 1.06 (2.5), 24.6 (6.98) and 2.86 (0.93) respectively and in T zillii 1.59 (2.30), 19.11 (13.50) and 2.47(1.77) respectively. After acclimatization in freshwater (FW) and full strength sea water (FSSW) at 35%o (in bracket) for O. urolepis urolepis were found to be 1.88 (1.86), 22.96(4.09) and 2.92(0.58) and for T. zillii 0.66(1.32), 5.09 (5.44) and 0.71 (0.75), respectively. There was no signifcance difference (p >0.05) in SGR between the two species in FSSW at 35%o. The survival rates in FW and FSSW at 35%o (in bracket) for O. urolepis urolepis and T. zillii were 100% (100%) and 89% (96%), respectively. This study shows that if managed well T. zillii and 0. urolepis urolepis can survive and grow in FSSW at 35%o.
Comparative study of genetic diversity and distribution of symbiodinium harboured by reef building corals common to Tanzania and Mauritius
(University of Dar es Salaam, 2011) Chumun, Pramod Kumar
The symbiosis of dinoflagellate micro-algae, zooxanthellae (genus Symbiodinium) with corals is vital for the survival and ecology of reef-building corals. Nevertheless, extremes of climate change induced factors e.g. temperature and irradiance may crumble the association if intolerant zooxanthellac clades are involved. This research aims at establishing the genetic diversity of Symbiodinium in coral species found in selected sites in Mauritius and Zanzibar that experience differing factors such as biogeography, temperature and irradiance levels throughout the year with the view to understand the possible environments such corals are exposed to. Molecular work was performed on five coral species named Galaxea fascicularis (n=51), Acropora muricata (n=49), Pocillopra damicornis (n=30) Porites cylindrical (n=44) and Pocillopora verrucusa (n=31)) in order to classify their different Symbiodinium genetic clades. The 18S- ribosomal DNA of the endosymbiont, which is a highly conserved region, was amplified using zooxanthellae specific primers and the clades were classified by RFLP method. Taq 1 and Hha 1 restriction enzyme were used for the digestion of the PCR product. It was found that zooxanthellae clades A, C and D were present among the studied coral species in both countries but in different proportions. In Zanzibar, clade D was dominant among A. muricata (8 1%) and G. fascicularis (88%) but higher proportion (76% and 68%) of clade C was found in respective Mauritian coral species. P. verrucusa associated more with clade A in Zanzibar (80%) compared to Mauritius (29%) This difference in proportion may be due to varying environmental factors like temperature and light prevailing in the two studied regions or due to stress from climatic changes resulting in coral bleaching. Results obtained can peeve the way for a better understanding of zooxanthellae clade dominance among coral species in the Western Indian Ocean (WIO) region and thus contribute in the long-term management of coral reefs.
Assessment of ecological differences between conserved and unconserved mangrove forests of Zanzibar, Tanzania
(University of Dar es Salaam, 2011) Monga, Elinasi
While exploitation pressure is mounting in mangrove forests in Zanzibar, the ecological consequences are not well understood. This study, aimed to establish whether there are ecological differences between the conserved mangrove forest of Jozani and unconserved mangrove forest of Pete in Zanzibar, Tanzania. Ecological parameters of mangrove tree density, basal area, above ground biomass (AGB) and crab diversity and abundance were assessed and compared. The ABG (kg/ha) were found to decrease from the lower to the upper zones in both forests with higher values recorded in Jozani forest. Tree density was higher in Jozani than Pete, with the density decreasing from the upper zone to the lower zone in Jozani while at Pete it was even across the zones. Similarly, Jozani forest had higher seedlings density than Pete forest, with a decreasing trend from the lower to upper zone while an increasing trend was observed in the Pete forest. For saplings, Pete forest had higher density than Jozani forest, with an even distribution across the three zones in both forests. The number of cut stumps increased across the zones from lower to upper with higher densities recorded in Pete forest. Crab densitiesdecreased from the lower zone to the upper zone in both forests with highest densities recorded in Pete forest. The physical observation in Pete was that almost all mature treeswere cleared and the stand comprised of new successional regeneration. These results indicate promising ecological returns of conservation for Jozani, and it calls for strictforest conservation measures particularly that of Pete. Public education and capacity building to forest guards are proposed for restoration and sustainability of the ecosystem.
Mapping and characterization of fish landing sites and related infrastructures along the coast of Kinondoni and Bagamoyo Districts, Tanzania
(University of Dar es Salaam, 2011) Semba, Masumbuko
Mapping artisanal fisheries activities for Bagamoyo and Kinondoni Districts based on spatial patterns of landing sites was carried out in a Geographic Information System (GIS) environment. Spatial attributes of the fish landing sites from fisheries frame survey database and field collected data was analyzed. The spat ial distribution of the fish landing sites was weighted using average nearest neighbour tool (ANNT. The ANNT revealed that fish landing sites were not scattered but statistically spatially dispersed (P<0.01) in the study area, and the hierarchy for the relative importance of the landing sites in the area was established. Msasani, Kunduchi and Custom were the most prominent ones. Moran I tool (MIT) showed a significantly high number of fishing vessels for fish landing sites at Kinondoni district (P<0.01). Analysis of the value of fish landing sites based on the price of filling vessels showed that Kunduchi had the highest investment value (532.65 Tsh Million), and was dominated by expensive fishing vessels (Boats), which constituted more than 52% of its total fishing vessel. Kunduchi was followed by Mlingotini (256.9 Tsh Million), and Msasani (152.05 Tsli Million), Nchipana(128.8 Tsh Million) and Custom (121.2 Tsh Million). It is important to highlight that price value of fishing vessels come from in situ data, while the number of fishing vessels come from fisheries frame survey database. Although, the number of fisheries records used for only ten fish landing sites, the study attempts to provide new insight on the spatial distribution, characteristic and investment value of landing sites, however, further studies will be needed to cover the whole coastline.
Acclimatization, survival and growth. Rates of Pangani tilapia (oreochromis pangani) in different salinities.
(University of Dar es Salaam, 2011) Hassan, Aziza
Coastal communities depend on fisheries activities as their main source of income. With the fast rising coastal population and technological advancement, pressure on the wild marine resources is increasing leading to overexploitation. Aquaculture sees as a possible livelihood alternative that will provide the coastal people with an alternative source of income. Some species of tilapia are known to survive and grow in estuarine and marine environment. The aim of this study is to determine the Acclimatization survival and growth of Oreacbromis pangani in four different salinities. Pangani species was collected from Pangani River and acclimatized for 17 days by raising the salinity by 2 PPt /day. The fingerlings weighing between 1 .3g-3 1 .4g were cultured at 0, 15, 25 and 35 ppt in 1 m 3 concrete ponds. Environmental parameters in the ponds were monitored once a day. Water exchange was done at 15% per day throughout the experiment while fecal matter, feeds remains were removed weekly by flushing. The mean growth rates per week were 2.25 ± 2.0 g, 2.77 ± 1.55 g, 2.34 ±1.38 g, and 1.86 g ± 0.16 at salinity level of 0, 15, 25, 35 ppt respectively. The growth rates were not statistically different among salinity levels (1- ANOVA, F =1.129, DF = 55, P > 0.05). Also from one way ANOVA results shows that, there was no significance difference in growth rates between treatments ponds and control ponds for 0, 15 and 25 ppt. However, at 35 ppt stress had impact on growth rate (t, 8.85, P= 0.006). Nevertheless, the results of the study have shown O. pangani to grow better on salinity level of 15. The overall survival rate was 96.46% and that of the different salinities were 100,95,95 and 90 for O, 15, 25 and 35 ppt respectively.
Molecular ecology and photo—physiology of symbiodinium harboured by Tanzania reef Building coral
(University of Dar es Salaam,, 2012) Chauka, Leonard Jones
Establishment of symbiosis with thermal tolerant Symbiodinium type is widely believed to be amongst the functional adaptation mechanism employed by reef-building corals (RBCs) to bleaching. In this study, Symbiodinium types found in 66 most common RBC species have been studied together with photo-physiology of the selected corals and their respective Symbiodinium with a view to evaluate Tanzanian reefs' capacity to adapt to current trends of climate change. Internal transcribed spacer two (ITS-2) regions of nuclear ribosomal DNA genes (rDNA) was used to identify the symbiont types. In addition, changes in photosynthetic pigment concentrations and ratios, synthesis of ultra violet absorbing substances, changes in Symbiodinium types and abundances, maximum quantum yield (Fv/Fm) and excitation pressure on PS II (Qm) were used to assess responses of corals and/or their associated Symbiodinium types to both thermal and photo-radiations in situ and/or ex-situ. It was found that, Symbiodinium cells harboured by RBC from Tanzania do not constitute a distinct genetic group from those in other parts of the world. Although they were found to be thermal and irradiance susceptible, Symbiodinium C3u and C3z dominate in Tanzanian reef-building corals. Shuffling of algal symbionts that hypothetically provide corals with thermal resistance is limited to few Tanzanian RBCs. The renown high bleaching resistance of Porites cylindrica as compared with other species was found to -be contributed by its Symbiodinium C15's ability to synthesize significantly higher concentrations of both carotenoids and UV-absorbing compounds. Besides, this study recognizes the contribution of the host to this ability. It is generally concluded that the rate at which Tanzanian RBC develop adaptations to current trends of climate change is not enough to survive from devastating effects of bleaching. Because a reverse of current trends of climate change is not a possibility, this thesis recommends useful management information and an urgent need of alleviating local anthropogenic threats on Tanzanian coral reef ecosystems to enhance their resilience.
Modelling coral-corallimorpharia interaction under varying anthropogenic inputs along the coast of Tanzania
(University of Dar es Salaam,, 2012) Rushingisha, George
Coral reefs are valuable resources for humanity, but are increasingly threatened by natural and anthropogenic stresses. The increased corallimorpharian abundance on reefs located close to urban centers is alarming as it appears to outcompete and inhibit recruitment of corals. This study investigated the interaction between corals and corallimorpharians under varying anthropogenic inputs using observational, experimental and modelling approaches. The Line Intercept Transect method (LIT) was used to determine changes on corals, corallimorpharians, macro-algae, turf-algae and coral rubble and the changes were correlated to (a) water visibility (b) phosphate and (c) nitrate concentrations. Nutrients and iron were enriched within Porites and Rhodactis rhodostoma interactin plots. A cellular automata (CA) model was applied to investigate the interaction between corals and corallimorpharians under a nutrient gradient. Results indicated no significant changes on corals, corallimorpharians, turf-algae and coral rubble covers during the study period. Porites and Galaxea genera were found to be susceptible and not susceptible to corallimorpharians overgrowth, respectively. Corallimorpharians cover correlated positively to phosphate and nitrate concentrations but negatively to water visibility. The experimental results indicated higher R. rhodostoma growth rate in nutrient enriched plots (1.7cm/month) than controls with and without iron nail (0.5cm/month). The model showed that corallimorpharians spread was faster and their cover was higher on high nutrient zone. The study suggests nutrient as the major factor facilitating corallimorpharians overgrowth on corals. Therefore, coexistence between corals and corallimorpharians is only possible under low nutrient conditions.
Ecophysiology of mangrove seedlings: Responses to Waterlogging, Salinity, Light and Nutrient Enrichment
(University of Dar es Salaam,, 2012) Mangora, Mwita Marwa
Although flooding and salinity variations occur commonly in mangrove systems, their frequency and severity have, however, been increasing with increased global warming (GW) to an extent that GW induced phenomenon such as heavy rainfall and subsequent floods, increased terrestrial runoff, and sea level rise are frequently associated with massive mangrove mortality and/or failure to regenerate. Manipulative mesocosm experiments were therefore set to assess the interactive stress effects of mimicked waterlogging/submergence, salinity, light and nutrient enrichment on growth and photosynthesis of seedlings of the mangroves Avicennia marina (Forssk.) Vierh., Bruguiera gymnorrhiza (L.) Lamarck and Heritiera littoralis Dryand. Three main experiments were conducted: (i) interactive effect of waterlogging, salinity and light, (ii) interactive effect of waterlogging, salinity and nutrient enrichment and (iii) underwater photosynthesis in varied salinities. Growth was assessed through structural and biomass traits, and photosynthesis through assessment of photosynthetic yield and leaf chlorophyll content. It was found that H. littoralis growth was drastically suppressed and its photosynthetic yield significantly declined during prolonged waterlogging and submergence, increased salinity, and when shifted from shade to light. Comparably, B. gymnorrhiza seedlings maintained high tolerance across the variably interactive stresses than A marina and H. littoralis. Nutrient enrichment did not provide enhancing effect to override the stressful conditions of waterlogging and elevated salinities. The varying ability of B. gymnorrhiza and A. marina to acclimatisation and the inability of H. littoralis to withstand the stresses suggest possible disruptions in mangrove forests regeneration in conditions of prolonged inundations due to flooding or sea-level rise. Results of the present study demonstrated that climate change driven environmental conditions may influence the performance of seedlings. They are useful in explaining the phenomenon of retarded natural regeneration in mangrove stands in major river estuaries of the region following flooding events, like that of 1997/98 El Nino. They are also useful in guiding management decisions on mitigation and adaptive mangrove restoration and management especially where reforestation and afforestation may be necessary.
Phytochemical investigations and antimicrobial analysis of caesalpinia bonduc (l.) roxb
(University of Dar Es Salaam, 2013) Hanolo, Stephano
This thesis reports phytochemical investigations, antimycobacterial, antibacterial and antiviral analysis of extracts from Caesalpinia bonduc (L.) Roxb. Phytochemical analysis of Caesalpinia bonduc furnished 2-acetoxycaesaldekarin E and 7,3′,4′-trihydroxyisoflavan-(6′→6′′′)-7′′,3′′′,4′′′-trihydroxyisoflavan from the extracts of leaves and stem wood respectively. The former compound is new from the species and late compound is new in nature. The structure of compounds was established based on the 1D NMR, 2D NMR, IR and MS data. Methanol, chloroform and n-hexane extracts from stem wood, stem bark and leaves of Caesalpinia bonduc were evaluated for antibacterial and antimycobacterial activity. Antibacterial activity was performed against the three species namely Staphylococcus aureus (ATCC25923), Escherichia coli (ATCC29953) and Pseudomonas aeruginosa (ATCC25922). Antimycobacterial activity was performed against two non-pathogenic mycobacteria species namely Mycobacteria indicus pranii and Mycobacteria madagascariense. The two-fold serial dilution method was used to evaluate MIC for antimicrobial activities. Extracts with high activity had MIC of 2.5 mg/mL while those with low activity had MIC of 5.0 mg/mL. Also, Caesalpinia bonduc extracts were evaluated for antiviral activities. The Newcastle diseases virus (NDV) was used for bioassay experiments. The antiviral activities of extracts against NDV were observed at HA titre of for high activity and HA titre of for low activity. Antimicrobial activity exhibited by extracts indicated that, Caesalpinia bonduc is a potential source of bioactive metabolites which can be used as leads for the development of broad spectrum antimicrobial agents.
Effect of different dietary protein sources on growth performance of rufiji tilapia, oreochromis urolepis urolepis (Norman, 1922)
(University of Dar es Salaam, 2015) John, Maria
One of the challenges facing intensive tilapia aquaculture development in developing countries is finding suitable alternatives to fishmeal (FM) from easily available and cheap local dietary protein sources. A 56 days experiment was therefore conducted in 80-liter plastic containers to investigate the suitability of blood meal (BM), sunflower meal (SFM) and Azola meal (AM) as alternative dietary protein sources on growth performance and feed utilization of the Rufiji tilapia, Oreochromis urolepis urolepis Norman (1922). Dry pelleted BM, SFM and AM containing 35% crude protein and 10% lipid were used as a protein sources and FM was used as a control in feeding two sets each containing 10 fingerlings with an average weight of 0.92±0.They were fed twice a day at a daily ration of 5% of the body weight. Water parameters monitored during the study were pH, temperature, salinity and dissolved oxygen concentration. No significant differences (P > 0.05) were found in growth performance and feed utilization in terms of weight gain, protein efficiency ratio, feed conversion ratio, feed intake and specific growth rate in all the three diets used. From the results of the present study fish meal can be replaced up to 15%, 45% and 60% with Azolla, sunflower and blood meals respectively without affecting the general growth performance of the experimental fish. Cost analysis showed that fish feeding on BM was most cost effective followed by AM then SFM.
Potential of mangrove forests for carbon market for Geza and Mtimbwani communities in Tanga, Tanzania
(University of Dar es Salaam, 2015) Alavaisha, Edmond
Mangroves offer important goods and services, including mitigation of climate change due to their high capacity for carbon sequestration and stocking. However, they are one of the most threatened ecosystems facing rapid degradation. Socio-economic and ecological surveys were done to assess the socio-ecological aspects of mangroves in Geza and Mtimbwani communities of Tanga, Tanzania to define their potential for carbon projects. Socio-economic surveys involved use of key informant interviews, focus group discussions and household questionnaires. Inventory of mangrove forests was conducted in Bongoa and Ngole River estuarine mangroves in Geza and Mtimbwani respectively to characterise forest stand structure and estimate carbon pools. Content analysis and multiple linear regression were used to establish the influence of socio-economic factors on exploitation of mangrove resources. Forest structure and carbon pools were estimated using available mangrove forest inventory protocols and laboratory procedures. Results indicated that major threats to mangroves are cutting for firewood and building poles. Key socio-economic factors that significantly (p<0.05) influenced exploitation of mangrove resources were income, age and level of education for Geza, and proximity from the resources and income for Mtimbwani. Six common mangrove species were identified with Avicennia marina (Forsk.) Vierh and Rhizophora mucronata Lamarck dominating in all sites. Forest stand density and basal area were 1740 stems ha-1 and 17.21 m2 for Geza and 2334 stems ha-1 and 30.27 m2 for Mtimbwani. Total ecosystem carbon stocks were 414.64 Mg C ha-1 for Geza and 684.99 Mg C ha-1 for Mtimbwani. These findings indicate that the two mangrove forest communities would be suitable for carbon projects as a conservation strategy because of their potential for high carbon stocks. Obtained data provide the needed baseline for monitoring, reporting and verification (MRV) to support the carbon projects.
Mapping anthropogenic impacts on Peri-urban mangroves of Kunduchi and Mbweni in Dar es Salaam, Tanzania
(University of Dar es Salaam, 2015) Mabula, Makemie Jumanne
Increasing demand for socio-economic services and infrastructure developments, exert multiple pressures on coastal and marine resources, especially mangroves that occur in the outskirts of Dar es Salaam cityfThe aim of this study was to assess and map the anthropogenic threats on and vulnerability of mangroves at Kunduchi and Mbweni. The threats were identified and validated through field observations before they were mapped. Google Earth (GE) images were used to map the anthropogenic threats and mangrove areas. Major threats were ranked on the basis of their persistence and proportional area of mangrove forest modified. The mangroves were also ranked on the basis of their proximity to the major threats. These threats and mangrove ranks were then spatially integrated in ArcGIS to develop mangrove vulnerability maps. Normalized Vegetation Index (NDVI), as a proxy indicator for mangrove vegetation health was analysed from 2014 Landsat 8 images in QGIS. GE images of 2003 and 2014 were analysed in ArcGIS for mangrove area change detection. The major human threats at Kunduchi were the salt works and settlement, whereas at Mbweni were settlement and trampling. Analysis of the 2014 GE images indicated that Kunduchi and Mbweni had 157.3 and 42.1 ha of mangroves, respectively. About 40% and 31% of the mangroves at Kunduchi and Mbweni respectively, were vulnerable to anthropogenic pressures. There was a net gain of 12.0 ha at Kunduchi and 0.7 ha at Mbweni during the period of 2003-2014. Effective control measures are required to regulate human pressures and protect these mangroves. Promotion of incentive-based conservation schemes like community-based payment for ecosystem services is one of the plausible options to explore.
Levels, distribution and fate of pollutants in the coastal waters off Zanzibar town
(University of Dar es Salaam, 2015) Nyanda, Frank
Biofiltration performances of native microorganisms concentrated on East African Doum Palm Fronds (EADPF), Hyphaene compressa (H. Windl. 1878) and Effective Microorganisms (EM) consortium were assessed. Triplicate polyculture tanks (1 m3) with Orechromis urolepis urolepis (Norman, 1922) and Mugil cephalus (Linnaeus, 1758) were used. Seawater treated EADPF (EADPF-F), untreated EADPF (EADPF-U), EM on Polyvinyl Chloride sheets (PVC-EM), EM consortium without media (EM) and Polyvinyl Chloride without EM (PVC) were used except in the control (CONTROL) tanks. PVC-EM, PVC, EADPF-F and EM systems had better ammonia biofiltration efficiency of 83.7 ± 3.13%, 80.9 ± 3.13%, 73.2 ± 5.36% and 66.7 ± 3.23% respectively while EADPF-U had the least (38.4 ± 7.09%). Total suspended solids levels were relatively little in PVC-EM, PVC and EM but high in EADPF-F and EADPF-U systems. Of the two finfish, O. urolepis urolepis had relatively higher specific growth rate (SGR) and survival rate (SR), with EM and EADPF-F systems providing the best SGR (3.41%) and SR (55.6 ± 9.0%) while the CONTROL and EADPF-U provided the least SGR (2.45±0.03%) and SR (27.9 ± 14.7%), respectively. The results showed that EM, PVC-EM and PVC were effective in enhancing both, the effluents biofiltration and growth of O. urolepis urolepis. Higher values in EM and PVC-EM were attributed to both the regenerative characteristics of EM consortium and ability to fix ammonia while excess heterotrophic activities explained the low values in EADPF-U. The EADPF-F, providing the best SR and run-up SGR of 3.17±06 similar to PVC-EM (3.17±04) was revealed as a potential biofilter media and enhancer of periphyton or bioflocs in mariculture system.
Sustainability and suitability of marine small pelagic fish processing techniques in Unguja Island, Tanzania
(University of Dar es Salaam, 2015) Mataba, Cesilia
This study examined the trends, environmental sustainability and suitability of the processing techniques of marine small pelagic fish in Unguja Island. Two sites in Unguja were selected for the study. Interview schedules, field observations and focus group discussions were used to collect socio economic and environmental data. Fresh, boiled and sundried small pelagic fish were collected at the sites for nutritional composition analysis which was conducted at the Sokoine University of Agriculture (SUA) in Morogoro. The small pelagic fish processed mainly were the large anchovies (Stoleophoruscommersonnii) and the small anchovies (Stoleophorusheterolobus). The study revealed an increasing trend for processing of small pelagics both in number of sites and quantities processed. The most popular pelagic fish processing technique was boiling followed by direct sun drying. The customers of the processed products highly influenced the processing technique which was largely adopted by the fish processors. The important environmental impacts associated with small pelagic fish processing techniques include cutting down of trees for firewood collection, environmental pollution around the processing sites due to absence of clean water, latrines, and disposal of hot fish soup. Statistically the nutritional values (crude protein, moisture content and ether extract-fat) between fresh, boiled and sundried small pelagic fish were found to be significantly different (P<0.05). However post hoc test shows small mean differences in crude protein between the sundried fish and boiled fish. Better management strategies to make this activity sustainable are suggested. The major constraints are the poor financial capability and inadequate institutional and legal framework to ensure sustainability of these processing techniques.

Browse

Browsing Institute of Marine Sciences by Issue Date

Results Per Page

Sort Options