Research Repository :: Browsing by Author "Lyimo, Thomas J."

Browsing by Author "Lyimo, Thomas J."

Now showing 1 - 20 of 35

. 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.
Academic Journals Food Preference of the Sea Urchin Tripneustes Gratilla (Linnaeus, 1758) In Tropical Seagrass Habitats at Dar Es Salaam, Tanzania
(2010-12) Lyimo, Thomas J.; Mamboya, Florence; Hamisi, Mariam; Lugomela, Charles
The sea urchin Tripneustes gratilla is the most well-known seagrass grazer in the Western Indian Ocean and a few cases of overgrazing have been reported. However, few studies on their feeding preference have been performed in this region. In this study, the food items in the gut contents of T. gratilla collected from seagrass beds and in a bare sediment in intertidal areas of Dar es Salaam, Tanzania, were analysed and compared to their availability in the surrounding environment. A total of 59 micro and macro-algae species were identified from the environment and the guts of T. gratilla, of which 48 were found in both gut contents and the environment. Gut contents of T. gratilla collected from mono specific seagrass habitats were dominated by the species in which they were found. In a mixture of four different seagrass species, Syringodium isoetifolium was preferred (with electivity indices (E*) of +0.36) while Cymodocea rotundata, Halodule uninervis and Thalassia hemprichii were slightly avoided (E* = -0.24, -0.22 and -0.22, respectively). We concluded that T. gratilla generally feeds on available seagrass species. However, in the presence of different types of seagrasses it showed preference to S. isoetifolium possibly due to presence of high epiphyte load which may increase its palatability.
Anaerobic Oxidation f Dimethylsul¢De AndmethanethiolIn Mangrove Sediments s Dominated By Sulfate-Reducing Bacteria
(2009-08) Lyimo, Thomas J.; Pol, Arjan; Harhangi, Harry R.; Jetten, Mike S. M.; Op den Camp, Huub J. M.
The oxidation of dimethylsulfide and methanethiol by sulfate-reducing bacteria (SRB) was investigated in Tanzanian mangrove sediments. The rate of dimethylsulfide and methanethiol accumulation in nonamended sediment slurry (control) incubations was very low while in the presence of the inhibitors tungstate and bromoethanesulfonic acid (BES), the accumulation rates ranged from 0.02-0.34 to 0.2-0.4 nmol g FW sediment(-1) h(-1), respectively. Degradation rates of methanethiol and dimethylsulfide added were 2-10-fold higher. These results point to a balance of production and degradation. Degradation was inhibited much stronger by tungstate than by BES, which implied that SRB were more important. In addition, a new species of SRB, designated strain SD1, was isolated. The isolate was a short rod able to utilize a narrow range of substrates including dimethylsulfide, methanethiol, pyruvate and butyrate. Strain SD1 oxidized dimethylsulfide and methanethiol to carbon dioxide and hydrogen sulfide with sulfate as the electron acceptor and exhibited a low specific growth rate of 0.010 +/- 0.002 h(-1), but a high affinity for its substrates. The isolated microorganism could be placed in the genus Desulfosarcina (the most closely related cultured species was Desulfosarcina variabilis, 97% identity). Strain SD1 represents a member of the dimethylsulfide/methanethiol-consuming SRB population in mangrove sediments.
Assessment of Faecal Bacteria Contamination in Selected Coastal Waters of Tanzania
(2013-03) Mwakalobo, Samson L.; Namkinga, Lucy; Lyimo, Thomas J.; Lugomela, Charles
Coastal communities of Tanzania use natural water systems such as rivers, estuaries and marine for various activities like drinking, fishing, washing and bathing. However, there is scanty information on the safety for these water bodies for the various uses. In this study faecal indicator bacteria were assessed in three sites along the coast of Tanzania (i.e. Pangani Estuary in Tanga Region, Ruvu Estuary in Pwani Region and Mzinga Creek in Dar Es Salaam Region). At each site, three sampling stations covering fresh, brackish and marine waters were selected for monthly sampling between July 2009 and June 2010. Faecal bacterial indicators were generally higher in Mzinga Creek compared to the rest of the study sites with significant differences between Mzinga Creek and Pangani Estuary for total coliforms (TC) and faecal coliforms (FC) (P < 0.05). All faecal indicator bacteria were significantly higher in fresh waters compared to brackish and marine waters (P = 0.0001), for TC and FC and P = 0.001 for Enterococcus (ENT). The faecal indicator bacteria correlated positive to each other and negatively to some environmental parameters namely pH and Salinity. Results suggest allochthonous sources of contamination and the influence of environmental factors. Generally the faecal bacterial indicators in the studied waters along the coast of Tanzania were within the acceptable standards according to WHO and USEPA indicating low risks situation for recreational purposes. However, these levels of faecal bacteria does not warrant the use in the studied estuaries for shellfish harvesting and the fresh water is not suitable for direct drinking. Further studies and monitoring programs are recommended to substantiate the current results.
Assessment of Faecal Bacteria Contamination in Selected Coastal Waters of Tanzania
(Macrothink Institute, 2013) Lazaro, Samson; Mwakalobo, Samson; Thomas, Jacob; Lyimo, Thomas J.; Lugomela, Charles
Coastal communities of Tanzania use natural water systems such as rivers, estuaries and 64 marine for various activities like drinking, fishing, washing and bathing. However, there is scanty information on the safety for these water bodies for the various uses. In this study faecal indicator bacteria were assessed in three sites along the coast of Tanzania (i.e. Pangani Estuary in Tanga Region, Ruvu Estuary in Pwani Region and Mzinga Creek in Dar Es Salaam Region). At each site, three sampling stations covering fresh, brackish and marine waters were selected for monthly sampling between July 2009 and June 2010. Faecal bacterial indicators were generally higher in Mzinga Creek compared to the rest of the study sites with significant differences between Mzinga Creek and Pangani Estuary for total coliforms (TC) and faecal coliforms (FC) (P < 0.05). All faecal indicator bacteria were significantly higher in fresh waters compared to brackish and marine waters (P = 0.0001), for TC and FC and P = 0.001 for Enterococcus (ENT). The faecal indicator bacteria correlated positive to each other and negatively to some environmental parameters namely pH and Salinity. Results suggest allochthonous sources of contamination and the influence of environmental factors. Generally the faecal bacterial indicators in the studied waters along the coast of Tanzania were within the acceptable standards according to WHO and USEPA indicating low risks situation for recreational purposes. However, these levels of faecal bacteria does not warrant the use in the studied estuaries for shellfish harvesting and the fresh water is not suitable for direct drinking. Further studies and monitoring programs are recommended to substantiate the current results.
Assessment of fecal bacteria contamination in sewage and non-sewage impacted mangrove ecosystems along the coast of Dar es salaam
(2009-07) Abbu, A. A.; Lyimo, Thomas J.
Microbiological quality of the intertidal pool water was evaluated in sewage impacted (Mtoni Kijichi) and non-sewage impacted (Rasi Dege) mangrove forest sites along the coast of Dar es Salaam, Tanzania. The Most Probable Number method was used for estimating the total coliform (TC), fecal coliform (FC) and fecal enterococci (ENT) levels. In addition, physicochemical parameters (temperature, pH, salinity and nutrients) were measured. The results for microbial fecal indicators were compared to the World Health Organisation (WHO) and United States Environmental Protection Agency (USEPA) guidelines for marine recreational and shellfish harvesting waters. Fecal bacteria contamination was significantly higher at Mtoni Kijichi than at Rasi Dege mangroves Nutrient levels were also significantly higher at Mtoni Kijichi than Rasi Dege). No significant variation was noted on the values of temperature, pH and salinity. A significant correlation between the levels of fecal bacteria indicators and nutrient concentrations was observed at both sites. Regarding compliance to WHO and USEPA guidelines, only one station at Mtoni Kijichi was found to have levels exceeding the recommended thresholds for marine recreational waters. The high level of fecal bacteria contamination and nutrients was attributed to anthropogenic activities. Further studies and education of the users of these ecosystems is recommended.
Co-variation of Cholera with Climatic and Environmental Parameters in Coastal Regions of Tanzania
(2014-01) Lugomela, Charles; Lyimo, Thomas J.; Namkinga, Lucy A; Moyo, Sabrina; Goerricke, Ralf; Sjöling, Sara
The bacterium causing cholera, Vibrio cholerae, is essentially a marine organism and its ecological dynamics have been linked to oceanographic conditions and climate. We used autoregressive models with external inputs to identify potential relationships between the number of cholera cases in the coastal regions of mainland Tanzania with climatic and environmental indices (maximum air temperature, sea surface temperature, wind speed and chlorophyll a). Results revealed that, between 2004 and 2010, coastal regions of mainland Tanzania inhabited by approximately 21% of the total population accounted for approximately 50% of the cholera cases and 40% of the total mortality. Significant co-variations were found between seasonally adjusted cholera cases and coastal ocean chlorophyll a and, to some degree, sea surface temperature, the outbreaks lagging behind by one to four months. Cholera cases in Dar es Salaam were also weakly related to the Indian Ocean Dipole Mode Index, lagging by five months, suggesting that it may be possible to predict cholera outbreaks for Dar es Salaam this period ahead. The results also suggest that the severity of cholera in coastal regions can be predicted by ocean conditions and that longer-term environmental and climate parameters may be used to predict cholera outbreaks along the coastal regions.
Community Awareness on Microbial Water Pollution and Its Effects On Health Development in Urban Tanzania: A Case Study of Tabata and Kiwalani Wards in Ilala District in Dar es Salaam Region
(2009-11) Lyimo, C. W.; Shayo, R.; Lyimo, Thomas J.
This article is based on a study that investigated community awareness on the problem of water pollution and established its relationship to socio-economic development in urban Tanzania, with a focus on a case study of Ilala Municipality in Dar es Salaam region. A sample of 160 respondents (men and women) from Tabata and Kiwalani wards in Ilala district were randomly selected and interviewed. Data was collected through questionnaire, focus group discussions, participant observation, and documentary reviews. Findings revealed that water pollution has been a major problem confronting most of Dar es Salaam residents. Ignorance on effects of microbial water pollution has resulted in tremendous ill health, which, in turn, has had negative consequences on socio-economic development. Indeed, frequent endemic water-borne diseases in the studied area were found to be a result of lack of awareness on water pollution. The majority of respondents 156 (97.5%) rely on dug wells that are very close to pit latrines, and drink water without boiling. In addition, 54 respondents (33.8%) had little knowledge on what causes water pollution. Although some respondents were aware of the possibility of acquiring diseases from untreated water, they continue using water from wells and boreholes due to the lack of safe tap water and poverty (ability to boil water). In addition, many of the respondents did not know the status of their water, although there are many scientific reports indicating that most of the well water in this area is faecal-polluted. As such, knowledge on water pollution is lacking. The study recommends government intervention by supplying safe-water and educating people in order to avoid occurrence of gastro-intestinal diseases. In addition, there is a need to give feedback of scientific results obtained from scientific research to the society.
Cyanobacterial Occurrence and Diversity in Seagrass Meadows in Coastal Tanzania
(2007) Hamisi, Mariam; Lyimo, Thomas J.; Muruke, Masoud S. H.
We report on the occurrence and diversity of cyanobacteria in intertidal seagrass meadows at Ocean Road and Mjimwema, Dar es Salaam, Tanzania. Nutrients, temperature and salinity were measured as comparative environmental factors. A total of 19 different cyanobacteria taxa were encountered, out of which eight were found exclusively in Mjimwema, four exclusively in Ocean Road and seven were common to both sites. Oscillatoria, Lyngbya and Spirulina were the dominant cyanobacterial genera. Cyanobacterial coverage was higher in Mjimwema (31–100%) than in Ocean Road (0–60%). The levels of nutrients in tidal pool waters at Ocean Road ranged from 0.45–1.03 μmol NO3 -N/l, 0.19–0.27 μmol NO2 -N/l and 0.03–0.09 μmol PO4 -P/l. At Mjimwema the nutrient concentration ranges were 0.14–0.93 μmol NO3 -N/l, 0.20–0.30 μmol NO2 -N/l and 0.01-0.07 μmol PO4 -P/l . The nutrient levels were significantly higher at Ocean Road than at Mjimwema (P = 0.001 for nitrate and P = 0.025 for phosphate). There was no significant difference in nitrite levels between the study sites (P = 0.83). The low cyanobacterial diversity and coverage in Ocean Road is related to the high levels of nutrients and physical disturbance from sewage discharge and the harbour in the area.
Distribution and Abundance of the Cyanobacterium Richelia Intracellularis in the Coastal Waters of Tanzania
(2011-03) Lyimo, Thomas J.
The filamentous heterocystous cyanobacterium, Richelia intracellularis Schmidt have been suggested to be among the most important nitrogen fixing cyanobacteria in tropical and subtropical waters, but they are less studied in the tropical Western Indian Ocean waters. The spatial and temporal distribution of this cyanobacterium was studied in the coastal waters of Zanzibar and Dar es Salaam, Tanzania. The Richelia sp. was found as an endosymbiont within five species of diatom Rhizosolenia spp., two Hemiaulus species and rarely as epiphyte to Chaetocerus spp. or freely in waters. The morphology and sizes of Richelia sp. did not show big variations but the number of vegetative cells per filament ranged from 4 to 14 cells. Abundance of Richelia sp. ranged from zero in some samples to mean maximum of 428 ± 105 filaments l −1 . The diatom–diazotroph associations were found throughout the year peaking during southeast monsoon. Blooms (up to 1554 filament l -1) of Richelia sp. were recorded in July to August 1993. High rates of nitrogen fixation occurred during northeast monsoon with maximum value (2.75 ± 0.03 nmol N h -1 l -1) in February corresponding to high numbers of Trichodemium spp. Lower values were obtained during southeast monsoon with the lowest value (0.03 ± 0.005 nmol N h -1 l -1) recorded in August when the number and type of cyanobacteria including Richelia sp. was very low. The results clearly indicate that Richelia sp. may contribute significantly to the productivity of the studied waters through its ability t
Epiphytic Cyanobacteria of the Seagrass Cymodocea Rotundata: Diversity, Diel Nifh Expression and Nitrogenase Activity
(Wiley, 2013-05) Hamisi, Mariam; Diez, Beatriz; Lyimo, Thomas J.; Ininbergs, Karolina; Bergman, Birgitta
Epiphytic cyanobacteria of the seagrass Cymodocearotundata: diversity, diel nifH expression andnitrogenase activityMariam Hamisi,1* Beatriz Díez,2†Thomas Lyimo,3Karolina Ininbergs2and Birgitta Bergman21College of Natural & Mathematical Sciences, TheUniversity of Dodoma, P.O. Box 338, Dodoma,Tanzania.2Department of Ecology, Environment and PlantSciences, Stockholm University, Lilla Frescati, SE-10691 Stockholm, Sweden.3Department of Molecular Biology & Biotechnology, Dares Salaam University, P.O. Box 35179, Dar es Salaam,Tanzania.SummarySeagrasses are photoautotrophic, ecologically im-portant components of many globally widespreadcoastal ecosystems, in which combined nitrogen maylimit their production. We examined the biodiversityand diazotrophic capacity of microbial epiphytesassociated with the phyllosphere of the seagrassCymodocea rotundata of the Western Indian Ocean.Light microscopy, 16S rRNA and nifH gene analysisrevealed the dominance of cyanobacteria in the epi-phytic microbial community. Most phylotypes wererelated to free-living uncultured benthic cyanobacte-ria, while some to cyanobacterial endosymbionts ofmarine diatoms. Novel and potentially diazotrophicspecies, some of known pantropical distribution,were also discovered. Signiﬁcant diel nitrogenaseactivities (acetylene reduction assay) were recorded(up to 358 ⫾ 232 nmol C2H4g-1of seagrass FW h-1).The nifH gene expression patterns showed that het-erocystous phylotypes may be the dominant diazo-trophs during the day and non-heterocystous atnight. These data show that C. rotundata is colonizedby diverse diazotrophic cyanobacteria species andsuggest that these may be beneﬁcial partners of
Food Preference of the Sea Urchin Tripneustes Gratilla (Linnaeus, 1758) In Tropical Seagrass Habitats at Dar Es Salaam, Tanzania
(2011) Lyimo, Thomas J.; Mamboya, Florence; Hamisi, Mariam; Lugomela, Charles
The sea urchin Tripneustes gratilla is the most well-known seagrass grazer in the Western Indian Ocean and a few cases of overgrazing have been reported. However, few studies on their feeding preference have been performed in this region. In this study, the food items in the gut contents of T. gratilla collected from seagrass beds and in a bare sediment in intertidal areas of Dar es Salaam, Tanzania, were analysed and compared to their availability in the surrounding environment. A total of 59 micro and macro-algae species were identified from the environment and the guts of T. gratilla, of which 48 were found in both gut contents and the environment. Gut contents of T. gratilla collected from mono specific seagrass habitats were dominated by the species in which they were found. In a mixture of four different seagrass species, Syringodium isoetifolium was preferred (with electivity indices (E*) of +0.36) while Cymodocea rotundata, Halodule uninervis and Thalassia hemprichii were slightly avoided (E* = - 0.24, -0.22 and -0.22, respectively). We concluded that T. gratilla generally feeds on available seagrass species. However, in the presence of different types of seagrasses it showed preference to S. isoetifolium possibly due to presence of high epiphyte load which may increase its palatability.
Genetic Relationship between Clinical and Environmental Vibrio Cholera Isolates in Tanzania: A Comparison Using Repetitive Extragenic Palindromic (REP) and Enterobacterial Repetitive Intergenic Consensus (ERIC) Fingerprinting Approach
(2015) Dalusi, Lucy; Saarenheimo, Jatta; Lyimo, Thomas J.; Lugomela, Charles
The bacterium causing cholera, Vibrio cholerae, is a marine organism and coastal waters are important reservoirs of the organism. There are more than 200 serogroups of V. cholerae, of which serogroups O1 and O139 are known to be the causative agent of the cholera. The main virulent factor in V. cholerae is cholera toxin gene (ctx) that is found from the epidemic O1 and O139 strains, but may also be found in some strains other than O1 and O139 (non-O1 and non-O139). In this study, 48 V. cholerae strains isolated from three estuaries of Tanzania and 20 stool isolates were characterized in terms of their serogroups and possession of ctx gene and then compared using two PCR based fingerprinting methods: Enterobacterial repetitive intergenic consensus (ERIC) sequences and repetitive extragenic palindromic (REP) sequences. All the stool isolates and twelve of the environmental isolates belonged to serogroup O1 while the remaining 36 environmental isolates were defined as non-O1/O139. The entire stool isolates and 21 of the environmental isolates had the cholera toxin gene (ctxA). Both ERIC and REP methods gave almost unique fingerprints for each strain and confirmed high genetic heterogeneity among the different cholera strains. Higher similarity was observed in REP-PCR (70-100%) than in ERIC-PCR (62-100%), indicating different discriminative power of these methods. Environmental isolates clustered together with clinical isolates at ≥90% similarity level suggesting their great potential of producing pathogenic strains that may be the causative agents for the frequent observed cholera outbreaks particularly along the coast
Genetic Relationship Between Clinical and Environmental Vibrio Cholera Isolates in Tanzania: A Comparison Using Repetitive Extragenic Palindromic (REP) and Enterobacterial Repetitive Intergenic Consensus (ERIC) Fingerprinting Approach
(Academic Journals, 2015-02) Dalusi, Lucy; Saarenheimo, Jatta; Lyimo, Thomas J.; Lugomela, Charles
The bacterium causing cholera, Vibrio cholerae, is a marine organism and coastal waters are important reservoirs of the organism. There are more than 200 serogroups of V. cholerae, of which serogroups O1 and O139 are known to be the causative agent of the cholera. The main virulent factor in V. cholerae is cholera toxin gene (ctx) that is found from the epidemic O1 and O139 strains, but may also be found in some strains other than O1 and O139 (non-O1 and non-O139). In this study, 48 V. cholerae strains isolated from three estuaries of Tanzania and 20 stool isolates were characterized in terms of their serogroups and possession of ctx gene and then compared using two PCR based fingerprinting methods: Enterobacterial repetitive intergenic consensus (ERIC) sequences and repetitive extragenic palindromic (REP) sequences. All the stool isolates and twelve of the environmental isolates belonged to serogroup O1 while the remaining 36 environmental isolates were defined as non-O1/O139. The entire stool isolates and 21 of the environmental isolates had the cholera toxin gene (ctxA). Both ERIC and REP methods gave almost unique fingerprints for each strain and confirmed high genetic heterogeneity among the different cholera strains. Higher similarity was observed in REP-PCR (70- 100%) than in ERIC-PCR (62-100%), indicating different discriminative power of these methods. Environmental isolates clustered together with clinical isolates at ≥90% similarity level suggesting their great potential of producing pathogenic strains that may be the causative agents for the frequent observed cholera outbreaks particularly along the coast.
Influence of Combined Changes in Salinity and Copper Modulation on Growth and Copper Uptake in The Tropical Green Macroalga Ulva Reticulate. Estuar Coast Shelfs
(Elsevier, 2009-08) Mamboya, Florence; Lyimo, Thomas J.; Landberg, Tommy; Björk, Mats
The influence of salinity on growth and Cu uptake in the green macroalga Ulva reticulata collected from the intertidal area in the Western Indian Ocean was studied under controlled laboratory conditions. Exposure concentrations ranged from 5 to 500 μg Cu l−1 at five salinities (ranging 20–40). The accumulation of Cu increased with decreasing salinity, so that the uptake at 500 μg Cu l−1 was approximately 2.7, 2.4 and 2.0 times higher at salinities of 20, 25, and 30 respectively, than uptake at salinity of 35, and with uptake being lowest at salinity of 40. Ulva maintained a positive growth rate over the whole salinity range (20–40), with highest rates at salinity of 35. When exposing to Cu at low salinities (20 and 25), the growth rate of Ulva was strongly inhibited suggesting an increase in toxicity of Cu with decreasing salinity. EC50 and NOEC increased with increase in salinity, implying a reduced Cu toxicity at high salinities. It was concluded that salinity needs to be considered when using macroalgae, such as U. reticulata, as a bioindicator of heavy metals in areas with heavy rainfall, underground fresh water intrusion or in estuaries, as
Influence of Flow Velocity on The Removal f Faecal Coliforms in Horizontal Subsurface Flow Constructed Wetland
(2012-09) Lohay, W. S.; Lyimo, Thomas J.; Njau, Karoli N.
In order to determine the influence of flow velocity on the removal of faecal coliforms (FC) in constructed wetlands (CWs), removal rate constants of FC (k(FC)) were studied at various flow velocities (u). Membrane filtration technique was used during analysis. Values of k(FC) were determined using Reed's equation of pathogen removal; the results were compared with the plug flow equation. According to Reed's equation, k(FC) values ranged from 1.6 day(-1) at a velocity of 4 m/day to 34.5 day(-1) at a velocity of 42.9 m/day. The removal rates correlated positively with flow velocity (r = 0.84, p < 0.05). On assuming a plug flow equation, removal rates constants ranged from 0.77 to 11.69 day(-1); a more positive correlation (r = 0.93, p < 0.05) was observed. Optimum removal rate constants were observed for the velocity ranging 36 to 43 m/day. Generally, the increase of flow velocity improved FC removal rate constants: implying that pathogen removals are influenced by diffusion of the microorganisms into the biofilms on CW media. The velocity dependent approach together with the plug flow equation is therefore proposed for incorporation in the design of CW in a tropical climate where temperature variations are minor.
Involvement of Methyltransferases Enzymes During the Energy Metabolism of the Anaerobic Archaeon Methanosarcina Semesiae Sp. Nov.
(2009-07) Lyimo, Thomas J.
The methyl group transfer from dimethylsulfide (DMS), trimethylamine and methanol to 2-mercaptoethanesulfonic acid (coenzyme M) were investigated from cell extracts of Methanosarcina semesiae sp. nov. to evaluate whether the enzyme systems involved were constitutive or inductive. The extracts from cells grown on DMS exhibited methanogenic activity exclusively with DMS and methanethiol. Likewise when cells were pre-grown on trimethylamine or methanol the extracts only produced methane from the respective metaboilic substrate. Dimethylsulfide:methyl-coenzyme M transferase activity was dependent on ATP, but hydrogen did not stimulate activity. The fact that ATP could be replaced by the reductant Ti(III)-citrate indicates that reductive activation of methyl transfer reaction in DMS conversion proceeds in a manner similar to methyltransferasesinvolved in methanol and trimethylamine conversion, but with a different reduction source. This source appears to be limited since sometimes the cell extracts were totally inactive in the presence of ATP, while still being activated with Ti(III)-citrate. It was concluded that enzymes involved inmethyl transfer reactions are specific for each substrate; DMS, trimethylamine and methanol and have to be induced. Further investigations are recommended to corroborate the current study.
Nitrogen Fixation by Epiphytic and Epibenthic Diazotrophs Associated with Seagrass Meadows along the Tanzanian Coast, Western Indian Ocean. Aquat Microb Ecol
(2009-09) Hamisi, Mariam; Lyimo, Thomas J.; Muruke, M . H. S.; Bergman, Birgitta
Seasonal, diurnal, and age-dependent variations in nitrogen fixation (nitrogenase activity) by epiphytic diazotrophs colonizing the seagrasses Halodule uninervis, Cymodocea rotundata, Thalassodendron ciliatum, and Thalassia hemprichii, and by epibenthic diazotrophs associated with seagrass-vegetated and nonvegetated sediments, were estimated at 2 sites along the Tanzanian coast, Western Indian Ocean. Acetylene reduction-gas chromatography showed that nitrogenase activity values were significantly higher (p = 0.0004) at the site with low nutrient levels (Mjimwema) than at the site with higher nutrient levels (Ocean Road). The nitrogenase activity ranged from 10 to 192 nmol N g(-1) h(-1) for H. uninervis, 7 to 80 nmol N g(-1) h(-1) for C. rotundata, 10 to 75 nmol N g(-1)h(-1) for Thalassia hemprichii, and from 4 to 61 nmol N g(-1) h(-1) for Thalassodendron ciliatum. Nitrogenase activity values in sediments covered by seagrasses were significantly higher than in surrounding nonvegetated sediments (t = 4.021, p = 0.0005). Significant variations in nitrogenase activity were apparent depending on leaf age and season, with highest activity being found in mid-aged leaves during the northeastern monsoon (NEM), and in older leaves during the southeastern monsoon (SEM). Daytime nitrogenase activity was appreciable on above-ground seagrass parts, while rhizosphere activity peaked at night-time. Collectively our data show that diazotrophs (cyanobacteria and other bacteria) are associated with seagrasses (leaves and roots), and potentially constitute an integral part of the ecosystem. They show highly dynamic nitrogenase activity and a succession in seagrass colonization, and we concluded that their presence may contribute to the productivity of the seagrass beds.
Nitrogenase Activity in Intertidal Sediment Along the Tanzanian Coast, Western Indian Ocean
(2006) Lyimo, Thomas J.; Lugomela, Charles
Nitrogenase activity was determined using the acetylene reduction assay in the littoral areas near Tanga, Dar es Salaam and Mafia with the aim of investigating its spatial and temporal distribution along the Tanzanian coastal line. Ethylene (C2H4) production rates ranged from 0.07 - 13.5 nmol C2H4 cm-2h-1 in Tanga area, 0.30 - 5.43 nmol C2H4 cm-2h-1 in Dar es Salaam and from 0.10 - 6.25 nmol C2H4 cm-2h-1 in Mafia. Significantly higher rates of nitrogenase activity were measured during night-incubated samples compared to daytime incubated samples suggesting that the sediments were mostly composed of non-heterocystous diazotrophic organisms. However, there were no significant differences in rates of nitrogenase activity between the rainy and dry season and between the sandy and muddy beaches. Also, there were no significant differences in nitrogenase activity between the upper, mid and lower littoral zones, and between the three sampling locations, i.e. Tanga, Dar es Salaam and Mafia. A nitrogen fixation rate of 38 mmol N m-2y-1 was estimated. We conclude that diazotrophs contribute a substantial amount of nitrogen input to the Tanzania coastal ecosystems.

Browsing by Author "Lyimo, Thomas J."

Results Per Page

Sort Options