Research Repository :: Browsing by Author "Mvungi, Esther F."

Browsing by Author "Mvungi, Esther F."

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. Abundance and diversity of seagrass and macrofauna in the inter-tidal areas with and without seaweed farming activities in the east coast of Zanzibar
(2008) Lyimo, Thomas J.; Mvungi, Esther F.; Mgaya, Yunus D.
The diversity and abundance of seagrass and associated macrofauna were studied in transects with and without seaweed farms at Chwaka Bay and Jambiani, in the East Coast of Zanzibar. Eight seagrass species, namely Cymodocea rotundata, Cymodocea serrulata, Thalassia hemprichii, Thalassodendron ciliatum, Syringodium isoetifolium, Halodule uninervis, Halophila ovalis and Enhalus acoroides were recorded in the transects. The mean total biomass of seagrass at Chwaka Bay ranged from 142.4 ± 70.71 to 1652 ± 772.7 g dw/m2 and 212.9 ± 146.2 to 1829 ± 1692 g dw/m2 in station with and without seaweed farms, respectively. At Jambiani, the mean total biomass ranged from 880.4 ± 336.8 to 3467 ± 549.9 and 203.4 ± 102.4 to 3810 ± 2770 g dw/m2 in station with and without seaweed farms, respectively. The overall total biomass of seagrass was significantly lower (KW = 108.7, p < 0.0001) in station with seaweed farms than in stations without seaweed farms. A total of 93 macrofauna species representing 60 families were encountered and the mean density ranged from 910 to 6990 individuals/m2 at Chwaka Bay and Jambiani in stations with and without seaweed farms respectively. The most common macrofauna species were Codakia punctata, Meropesta nicobarica, Echinometra mathaei, Pinna muricata and Clibanarius emystemus. It was shown that the macrofauna abundance and diversity was higher in stations without seaweed farms than in the stations with seaweed farms, which could be due to activities associated with seaweed farming which contributed to the loss of diversity and biomass of flora and macrofauna of the seagrass meadows.
Abundance and Diversity of Seagrass and Macrofauna in the Intertidal Areas with and Without Seaweed Farming Activities in the East Coast of Zanzibar
(Tanzania Journal of Science, 2009-07) Lyimo, Thomas J.; Mvungi, Esther F.; Mgaya, Yunus D.
The diversity and abundance of seagrass and associated macrofauna were studied in transects with and without seaweed farms at Chwaka Bay and Jambiani, in the East Coast of Zanzibar. Eight seagrass species, namely Cymodocea rotundata, Cymodocea serrulata, Thalassia hemprichii,Thalassodendron ciliatum, Syringodium isoetifolium, Halodule uninervis, Halophila ovalis and Enhalus acoroides were recorded in the transects. The mean total biomass of seagrass at Chwaka Bay ranged from 142.4 ± 70.71 to 1652 ± 772.7 g dw/m2 and 212.9 ± 146.2 to 1829 ± 1692 gdw/m2 in station with and without seaweed farms, respectively. At Jambiani, the mean total biomass ranged from 880.4 ± 336.8 to 3467 ± 549.9 and 203.4 ± 102.4 to 3810 ± 2770 g dw/m2 in station with and without seaweed farms, respectively. The overall total biomass of seagrasswas significantly lower (KW = 108.7, p < 0.0001) in station with seaweed farms than in stations without seaweed farms. A total of 93 macrofauna species representing 60 families were encountered and the mean density ranged from 910 to 6990 individuals/m2 at Chwaka Bay andJambiani in stations with and without seaweed farms respectively. The most common macrofauna species were Codakia punctata, Meropesta nicobarica, Echinometra mathaei, Pinna muricata and Clibanarius emystemus. It was shown that the macrofauna abundance and diversity was higher in stations without seaweed farms than in the stations with seaweed farms, which could be due to activities associated with seaweed farming which contributed to the loss of diversity and biomass of flora and macrofauna of the seagrass meadows.
Photosynthetic performance, epiphyte biomass and nutrient content of two seagrass species in two areas with different level of nutrients along the Dar es Salaam coast
(African Journal of Marine Science, 2001-10) Mvungi, Esther F.; Mamboya, Florence A.
Heavy nutrient loads in coastal waters often lead to excessive growth of microalgal and macroalgal epiphytes on seagrass leaves, with varying effects on the underlying seagrasses. This study evaluates the photosynthetic performance, epiphytic biomass and tissue nutrient content of two tropical seagrasses, Cymodocea serrulata and Thalassia hemprichii, in two intertidal areas along the Dar es Salaam coast in the Indian Ocean, a nutrient-rich region at Ocean Road (near the city centre), and a nutrient-poor region at Mjimwema (south of the city centre). Epiphyte biomass was significantly higher at the nutrient-rich site, and epiphytes were associated with reduced photosynthetic performance in both seagrass species at both sites. Likewise, nitrogen and phosphorus tissue content was higher in both species at the nutrient-rich site than at the nutrient-poor site. Epiphytic species composition on the seagrass leaves varied between seagrass species and between sites. Cymodocea serrulata had a higher number of epiphytic species at Mjimwema than at Ocean Road, whereas Thalassia hemprichii had more epiphytic species at Ocean Road than at Mjimwema. Seagrass photosynthetic performance, epiphytic biomass and nutrient content of the seagrasses were shown to be affected by nutrient concentration in the water column. Thus, for the future monitoring of the seagrass meadow, we recommend the use of combined measures such as seagrass performance, epiphytic biomass, nutrient contents and nutrient concentration levels in the water column.
Seagrass - Sea urchin interaction in shallow littoral zones of Dar es Salaam, Tanzania
(Wiley Online Library, 2008-07) Mamboya, Florence; Lugomela, Charles; Mvungi, Esther F.; Hamisi, Mariam; Kamukuru, Albogast T.; Lyimo, Thomas J.
Seagrasses biomass, canopy height, shoot density, percentage cover, and sea urchin abundance wereintermittently (between July and November 2007) studied at four littoral sites in the Dar es Salaam area(Mjimwema, Mbweni, Bongoyo Island and Mbudya Island) in order to investigate the seagrass–sea urchinassociation.2. Seagrass biomass ranged from 126.7765.62 g dwt m2in the upper sub-tidal area at Bongoyo Island to508.17133.4 g dwt m2in the upper sub-littoral area at Mbudya Island. Canopy height ranged from6.5172.76 cm in the mid-littoral zone at Mjimwema to 23.878.93 cm in the upper sub-littoral zone atMbudya Island. Shoot densities ranged from 363.67268.9 shoots m2in the mid-littoral zone at Mjimwema to744.07466.9 shoots m2in the lower littoral zone at Mbudya Island.3. Seagrass biomass, canopy height and percentage cover differed signiﬁcantly among study sites (P 5 0.001,0.0001, 0.008 respectively). However, there was no signiﬁcant difference in shoot density among the sites(P 5 0.376).4. Ten species of sea urchins were recorded, Echinometra mathaei being the most abundant followed byTripneustes gratilla. Total sea urchin abundance was signiﬁcantly different among the study sites (P 5 0.001).Seagrass–sea urchin interaction was depicted by signiﬁcant negative correlations between sea urchin densitieswith seagrass biomass, canopy height, shoot density and percentage cover. This suggests that grazing by seaurchins might have contributed to the reduction of above ground seagrass biomass in locations with higher seaurchin densities. However, further studies are required to corroborate the present results and assess effects ofother factors (e.g. light, nutrients and currents), which also inﬂuence seagrass growth.
Seagrass Biomass and Productivity in Seaweed and Non- Seaweed Farming Areas in the East Coast of Zanzibar, Tanzania
(2006-01) Lyimo, Thomas J.; Mvungi, Esther F.; Lugomela, Charles; Björk, Mats
Seagrass beds are often subjected to stress resulting from natural and human activities. In this study, the shoot density, biomass and growth characteristics of Thalassia hemprichii and Enhalus acoroides were measured to assess the impact of seaweed farming activities on seagrass meadows at Marumbi, Chwaka Bay and Jambiani in the East Coast of Zanzibar. There was significantly higher T. hemprichii shoot density in non-seaweed areas compared to seaweed farmed areas. However, there were no significant differences in E. acoroides shoot density between seaweed and non-seaweed areas and between the two sites. Also, there was significantly higher total biomass of T. hemprichii in non-seaweed areas compared to seaweed areas. However, there were no significant differences in the total biomass of E. acoroides between seaweed and non-seaweed areas and among the sites. The growth and photosynthetic (ETR and Fv/Fm ratios) characteristics of both T. hemprichii and E. acoroides varied inconsistently between seaweed and non seaweed areas suggesting that there is no effect on seaweed farming to the growth rate of the seagrasses. Thus, the reduced seagrass shoot density and biomass in seaweed farms compared to non-seaweed areas observed in this particular study is most likely to be due to physical disturbances in the farms such as bioturbation or deliberate removal of seagrasses by farmers.
Seagrass Biomass and Productivity in Seaweed and Non-Seaweed Farming Areas in the East Coast of Zanzibar
(Western Indian Ocean Journal of Marine Science, 2006-01) Lyimo, Thomas J.; Mvungi, Esther F.; Lugomela, Charles K.; Björk, Mats
Seagrass beds are often subjected to stress resulting from natural and human activities. In this study, the shoot density, biomass and growth characteristics of Thalassia hemprichii and Enhalus acoroides were measured to assess the impact of seaweed farming activities on seagrass meadows at Marumbi, Chwaka Bay and Jambiani in the East Coast of Zanzibar. There was significantly higher T. hemprichii shoot density in non-seaweed areas compared to seaweed farmed areas. However, there were no significant differences in E. acoroides shoot density between seaweed and non-seaweed areas and between the two sites. Also, there was significantly higher total biomass of T. hemprichii in non-seaweed areas compared to seaweed areas. However, there were no significant differences in the total biomass of E. acoroides between seaweed and non-seaweed areas and among the sites. The growth and photosynthetic (ETR and Fv/Fm ratios) characteristics of both T. hemprichii and E. acoroides varied inconsistently between seaweed and non seaweed areas suggesting that there is no effect on seaweed farming to the growth rate of the seagrasses. Thus, the reduced seagrass shoot density and biomass in seaweed farms compared to non-seaweed areas observed in this particular study is most likely to be due to physical disturbances in the farms such as bioturbation or deliberate removal of seagrasses by farmers.
Towards a Phylogeny for Coffea (Rubiaceae): Identifying Well-supported Lineages Based on Nuclear and Plastid DNA Sequences
(Oxford University Press, 2008-01) Maurin, Olivier; Davis, Aaron P.; Chester, Michael; Mvungi, Esther F.; Jaufeerally-Fakim, Yasmina; Fay, Michael F.
†Background and AimsThe phylogenetic relationships between species ofCoffeaandPsilanthusremain poorlyunderstood, owing to low levels of sequence variation recovered in previous studies, coupled with relativelylimited species sampling. In this study, the relationships betweenCoffeaandPsilanthusspecies are assessedbased on substantially increased molecular sequence data and greatly improved species sampling.†MethodsPhylogenetic relationships are assessed using parsimony, with sequence data from four plastid regions[trnL – Fintron,trnL – Fintergenic spacer (IGS),rpl16intron andaccD – psa1IGS], and the internal transcribedspacer (ITS) region of nuclear rDNA (ITS 1/5.8S/ITS 2). Supported lineages inCoffeaare discussed within thecontext of geographical correspondence, biogeography, morphology and systematics.†Key ResultsSeveral major lineages with geographical coherence, as identified in previous studies based on smallerdata sets, are supported. Other lineages with either geographical or ecological correspondence are recognized for thefirst time.CoffeasubgenusBaracoffeais shown to be monophyletic, butCoffeasubgenusCoffeais paraphyletic.Sequence data do not substantiate the monophyly of eitherCoffeaorPsilanthus. Low levels of sequence divergencedo not allow detailed resolution of relationships withinCoffea, most notably for species ofCoffeasubgenusCoffeaoccurring in Madagascar. The origin ofC. arabicaby recent hybridization betweenC. canephoraandC. eugenioidesis supported. Phylogenetic separation resulting from the presence of the Dahomey Gap is inferredbased on sequence data fromCoffea.
Two new endangered species of Coffea (Rubiaceae) from the Eastern Arc Mountains (Tanzania) and notes on associated conservation issues
(Wiley Online Library, 2004-10) Davis, Aaron P.; Mvungi, Esther F.
Coffea bridsoniae and C. kihansiensis are described as new species from the Eastern Arc Mountains, Tanzania. Full descriptions and conservation assessments are given, and affinities with other East African Coffea species are discussed. Supplementary taxonomic notes on Tanzanian Coffea are given, including a concise species checklist. Conservation issues concerning Tanzanian Coffea and the Kihansi River Gorge are briefly covered.
When Zostera marina is Intermixed with Ulva, its Photosynthesis is Reduced by increased pH and Lower light, but not by changes in Light Quality
(2012-09) Mvungi, Esther F.; Lyimo, Thomas J.; Björk, Mats
To evaluate the effects of Ulva on the photosynthetic capacities of the temperate seagrass Zostera marina,we compared it in the laboratory under normal light and light ﬁltered through layers of Ulva intesti-nalis, and repeated the experiments with the addition of pH-induced changes in carbon speciation andavailability. One thallus of Ulva reduced photosynthetically available irradiance to underlying seagrassby about 50% and shifted the quality of remaining light towards the green part of the spectrum (approx-imately 520–570 nm). There was no signiﬁcant difference in photosynthetic performance between Z.marina under normal light and under Ulva-ﬁltered light when adjusted to the same irradiance as for thecontrol plants, indicating that the green spectrum transmitted through Ulva layers was being absorbedby the seagrass and was as efﬁcient in driving photosynthesis as was the normal light. On the otherhand, algae-generated pH shifts which could extend up to pH 10 had signiﬁcant negative effects onphotosynthesis of the seagrass, reducing the electron transport rates with up to 75%

Browsing by Author "Mvungi, Esther F."

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