Browsing by Author "Tamatamah, Rashid A."
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Item The Atmospheric Deposition of Phosphorus in Lake Victoria (East Africa)(Springer Link, 2005) Tamatamah, Rashid A.; Hecky, Robert E.; Duthie, H. C.Wet and dry atmospheric fluxes of total phosphorus (TP) and soluble reactive phosphorus (SRP) measured at four sites over a 12-month period were used to estimate lake-wide atmospheric phosphorus (P) deposition to Lake Victoria, East Africa. Atmospheric samples were collected in plastic buckets with top diameter of 25.5 cm by 30 cm deep. The highest P loading rates of 2.7 (TP) and 0.8 (SRP) kg ha 2 year 1 were measured at Mwanza compared to less than 1.9 (TP) and 0.65 (SRP) kg ha 2 year 1 measured in other three sites. By applying these loading rates to the lake surface, it was estimated that 13.5 ktons (13.5 · 103 kg) of TP were deposited annually into the lake from the atmosphere. Thirty-two percent of the total was found to be in the SRP form. Dryfall, a component ignored in previous studies exceeded wet deposition by contributing 75% of the total P input. However, materials deposited by dryfall made a lesser contribution to soluble form of phosphorus, as SRP concentrations in the wet samples were 2–3 times higher than SRP concentrations in dry samples. The annual fluxes of phosphorus measured on the south and western shores of Lake Victoria (1.8–2.7 kg ha 2 year 1 ) are near the upper range of similar fluxes measured in the tropics. In comparison with the existing estimates of municipal and runoff P inputs from other studies, it is estimated that atmospheric deposition represent 55% of the total phosphorus input to the Lake Victoria. The four sampling sites were fairly clustered and wet and dry P deposition data were collected from shore/land stations and applied to open lake areas to estimate lake-wide P deposition. In this regard, the estimates determined here should be viewed as a first order approximation of actual P load deposited into the lake.Item Century-Long Warming Trends in the Upper Water Column of Lake Tanganyika(2015) Kraemer, Benjamin M.; Hook, Simon J.; Huttula, Timo H.; Kotilainen, Pekka; O’Reilly, Catherine M.; Peltonen, Anu; Plisnier, Pierre D.; Sarvala, Jouko; Tamatamah, Rashid A.; Vadeboncoeur, Yvonne; Wehrli, Bernhard; McIntyre, Peter B.Lake Tanganyika, the deepest and most voluminous lake in Africa, has warmed over the last century in response to climate change. Separate analyses of surface warming rates estimated from in situ instruments, satellites, and a paleolimnological temperature proxy (TEX86) disagree, leaving uncertainty about the thermal sensitivity of Lake Tanganyika to climate change. Here, we use a comprehensive database of in situ temperature data from the top 100 meters of the water column that span the lake’s seasonal range and lateral extent to demonstrate that long-term temperature trends in Lake Tanganyika depend strongly on depth, season, and latitude. The observed spatiotemporal variation in surface warming rates accounts for small differences between warming rate estimates from in situ instruments and satellite data. However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements. Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously. Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.Item Comparing Flow Regime, Channel Hydraulics and Biological Communities to Infer Flow-Ecology Relationships in the Mara River of Kenya and Tanzania(2014) McClain, Michael E.; Subalusky, Amanda L.; Anderson, E.; Dessu, Shimelis B.; Melesse, Assefa M.; Ndomba, Preksedis M.; Mtamba, Joseph O. D.; Tamatamah, Rashid A.; Mligo, CosmasEquatorial rivers of East Africa exhibit unusually complex seasonal and inter-annual flow regimes, and aquatic and adjacent terrestrial organisms have adapted to cope with this flow variability. This study examined the annual flow regime over the past 40 years for three gauging stations on the Mara River in Kenya and Tanzania, which is of international importance because it is the only perennial river traversing the MaraSerengeti ecoregion. Select environmental flow components were quantified and converted to ecologically relevant hydraulic variables. Vegetation, macroinvertebrates, and fish were collected and identified at target study sites during low and high flows. The results were compared with available knowledge of the life histories and flow sensitivities of the riverine communities to infer flow–ecology relationships. Management implications are discussed, including the need to preserve a dynamic environmental flow regime to protect ecosystems in the region. The results for the Mara may serve as a useful model for river basins of the wider equatorial East Africa region.Item The Distribution, Biological Characteristics and Vulnerability of the Giant Sea Catfish, Arius thalassinus (Rüppell, 1837), to Fishing at Mafia Island, Tanzania(2015) Kamukuru, Albogast T.; Tamatamah, Rashid A.The distribution and some biological characteristics of commercially important giant sea catfish, Arius thalassinus (Rüppell, 1837) were studied at Mafia Island. Artisanal fishing catches were sampled, caught mainly with longlines, shark nets and ring nets. These yielded a total of 2 723 kg of A. thalassinus, comprising 756 individuals, the largest measuring 1 000 mm TL. Arius thalassinus occurred only on the western coast of Mafia Island and the highest catch rate was 19.3 kg.fisher-1.day-1 in March when murky water was predominant. The reproductive biology of A. thalassinus was investigated to assess its vulnerability to fishing. Arius thalassinus reached a size at first maturity (LM50) of 520 mm TL and exhibited a low mean (±SE) fecundity of 65.6 ± 3.37 eggs per female within the size range of 605-970 mm TL. The hydrated oocytes were large (mean diameter ±SE = 15.2±0.12 mm). Arius thalassinus spawned once in the study year during February and April, during heavy precipitation (124-499 mm). We therefore conclude that its restricted distribution, large size, low fecundity, late maturation and its reported high trophic level indicate that it would be vulnerable to fishing pressure. It is therefore recommended that fishing for A. thalassinus be restricted during its spawning season to ensure its sustainabilityItem Ichthyofaunal Survey of the Rivers of the Eastern Arc Mountains in Tanzania (poster presentation)(2008-11) Tamatamah, Rashid A.; Vigliotta, Thomas R.; Friel, John P.; Thomson, AlfredItem Length Frequency Distribution, Mortality Rate and Reproductive Biology of Kawakawa (Euthynnus affinis-Cantor, 1849) in the Coastal Waters of Tanzania(2013) Johnson, M. G.; Tamatamah, Rashid A.This study explored important aspect of the basis for the highly complex population of kawakawa (Euthynnus affinis) within the coastal waters of Tanzania; by investigating length frequency distribution, mortality rate and reproductive characteristics. This information is essential for the sustainable management of the regionally-important recreational and economic E. affinis fishery. Fish were sampled on a monthly basis for two monsoon seasons using a ring net and artisanal fishermen boat. Maximum and minimum total length was 85 and 31 cm, respectively. Nonlinear least square fitting provided a complete set of von Bertalanffy growth estimates: L8 = 89.25 cm total length and K = 0.78. The estimated value of total mortality based on length converted catch curve using these growth parameters is Z = 1.78 year(-1). Natural mortality based on growth parameters and mean environmental temperature (T = 26.9 degrees C) is M = 1.09 year(-1). The estimated annual instantaneous fishing mortality (F = 0.69 year(-1)) was considerably grater than the target (Fopt = 0.43 year(-1)) and limit (Flimit = 0.58 year(-1)) biological reference point indicating that E. affinis is heavily overexploited. Reproductive aspects were assessed whereby female E. affinis was reported to reach maturity earlier than males which is an indication of phenotypic response toward a decline in population. Two peaks was revealed by the use of Gonad-Somatic Index (GSI), however an extended spawning period was noticed in a period between November to February following an increased water temperature. Although, these findings presents a snapshot concerning population structure and reproduction of E. affinis, further studies covering the entire coastal waters of Tanzania are recommended to aid the management and conservation strategiesItem Morphometry and Average Temperature Affect Lake Stratification Responses to Climate Change: Lake Stratification Responses to Climate(Wiley, 2015-05) Kraemer, Benjamin M.; Anneville, Orlane; Chandra, Sudeep; Dix, Margaret; Kuusisto, Esko; Livingstone, David M.; Rimmer, Alon; Schladow, Geoffrey S.; Silow, Eugene; Sitoki, Lewis M.; Tamatamah, Rashid A.; Vadeboncoeur, Yvonne; McIntyre, Peter B.Climate change is affecting lake stratification with consequences for water quality and the benefits that lakes provide to society. Here we use long-term temperature data (1970–2010) from 26 lakes around the world to show that climate change has altered lake stratification globally and that the magnitudes of lake stratification changes are primarily controlled by lake morphometry (mean depth, surface area, and volume) and mean lake temperature. Deep lakes and lakes with high average temperatures have experienced the largest changes in lake stratification even though their surface temperatures tend to be warming more slowly. These results confirm that the nonlinear relationship between water density and water temperature and the strong dependence of lake stratification on lake morphometry makes lake temperature trends relatively poor predictors of lake stratification trends.Item Phosphorus and Suspended Sediment Loading from Two Rivers Flowing Into Lake Victoria in Tanzania.(2006-01) Tamatamah, Rashid A.; Hecky, R. E.; Duthie, H. C.Item Phosphorus Sorption Characteristics of Sediment in the Simiyu and Kagera River Basins: Implications for Phosphorus Loading Into Lake Victoria(Taylor and Francis, 2004) Tamatamah, Rashid A.As part of a larger study to assess the influence of land use on riverine and atmospheric phosphorus (P) loading to Lake Victoria, P sorption characteristics of eight composite bottom sediment samples from the Simiyu and Kagera rivers were determined using the Langmuir equation. The samples had low to medium Langmuir adsorption maxima (Γm) ranging from 107 to 201μg g-1. Langmuir binding energy co-efficient (K) ranged from 60 to 181μg l-1 and the equilibrium P concentration at zero sorption (EPC0) from 0.1 to 2.75μg g-1. By using Langmuir co-efficients derived from P sorption experiments and soluble reactive phosphorus (SRP) concentrations measured in rivers as well as the in-shore waters of Lake Victoria, it was possible to determine the potential release of SRP into the lake by sediment from the two catchments. For the 2000 water-year, it was estimated that about 28.65 ± 0.89 (mean ± SD) and 66 ± 6.76 tons of SRP were released into Lake Victoria by sediment deposited by the Simiyu and Kagera rivers, respectively. The implications of these results to future management of cultural eutrophication in Lake Victoria are also discussed.Item Phosphorus Sorption in Relation to Soil Grain Size and Geochemical Composition in the Simiyu and Kagera River Basins, Tanzania(2005) Tamatamah, Rashid A.The phosphorus sorption characteristics of eight surface soil samples representative of the land use and landscape in the Simiyu and Kagera River basins were determined using the Langmuir equation. The Langmuir P adsorption maximum (Cmax) ranged from 109 to 802 mg kg-1 , while Langmuir coefficient (K) ranged from 59 to 736 mg L-1 . Cmax and were positively correlated to clay content, aluminium (Al), and iron (Fe) and negatively correlated to calcium (Ca). By using stepwise regression, the combination of Al, Fe, clay and Ca predicted more than 94% of the variation in the P sorption capacity of soils samples from Simiyu and Kagera basins. These four soil properties, which are strongly related to P sorption, could therefore be used as quick tests for predicting the P sorption capacity of soils in the two basinsItem Refining Environmental Flows for the Mara River, Kenya and Tanzania: Report on Fish Ecology for the Third Environmental Assessment of the Mara River(2009) Tamatamah, Rashid A.WWF-Eastern Africa Regional Programme Office (WWF-EARPO), through its freshwater programme, began the task of establishing the Reserve flows for Mara River in 2006. The first two site assessments covering three sites were conducted in March and July 2007 by a team of specialists comprising a geomorphologist, hydrologist, hydraulic engineer, aquatic ecologist, riparian ecologist, water quality specialists, and socioeconomist. The first Reserve flows for the river were prescribed in October 2007 during the EFA workshop held in Narok, Kenya. At this workshop it was also agreed that continued monitoring of the river’s flow levels and ecological status is critical to improve the accuracy of the prescribed flows. The present work reports on the results of a fish sampling exercise conducted in February 2009 during the third assessment for the Mara River. The assessment covered one additional site in the Nyangores River and coincided with the period of low flows in the Mara River.Item Securing Water for the Environment in the Mara River of Lake Victoria Catchment, Kenya and Tanzania(2008-06) McClain, Michael; Ayieko, Joseph; Melesse, Assefa; Ndomba, Praxedis; O’Keeffe, Jay; Onyango, Leah; Tamatamah, Rashid A.; Wasonga, Victor D.The Mara River basin encompasses some of the world’s most unique ecosystems and human communities, tightly linked by their dependence on water from the Mara River. From its headwaters in Kenya, the Mara River flows through a mosaic of forests, tea fields, and croplands before entering Maasai pastoral lands. In this semi-arid landscape, human demands for water – especially for livestock and agriculture – run high and surface flows of the Mara River system are essential to meeting demands.Item Study on the Water Quality Parameters in Semi-Intensive Coastal Shrimp Culture System in Mafia Island, Tanzania(2015-01) Mateka, Hassan A.; Tamatamah, Rashid A.; Kyewalyanga, MargaretThis study was conducted to understand the effect of coastal shrimp farming on water quality properties in the surrounding area of a semi-intensive culture system in Mafia Island, Tanzania. Monthly water samples were collected from six stations located within culture ponds, inlet creek and outlet/effluent creek, from June, 2008 to May, 2009, and November, 2009 to March, 2010. The samples were used for the analysis of the selected water quality parameters following the standard procedures. The data obtained was analyzed using one way ANOVA and significant differences accepted at p ≤ 0.05. Post Hoc Turkeys’ test was used to determine the specific stations which were sources of differences. Correlation co-efficient (r) was performed to establish the relation between independent and dependent parameters. Results showed that DO, salinity, NH4-N, NO2-N and PO4-P were significantly (p<0.05) higher in sampling stations inside culture ponds. NO3-N had significantly (p<0.05) higher mean values at the stations along the effluent creek. No significant differences (p>0.05) were recorded between the stations in terms of temperature, EC and chlorophyll-a. High positive correlations (r = 0.646–0.927) between EC and dissolved nutrients is an indication of common origin of these parameters that is, mineralization of organic materials. In general, concentrations of all analysed parameters were within the desirable and acceptable limits for marine ecosystems. To sustain the present conditions it is being recommended to adopt better farm husbandry as well as treating effluent materials before discharging them to the marine water medium. The study would provide essential information on which further studies can be carried out to evaluate the environmental impacts of marine aquaculture and, supports protection and decision making for sustainable development in the coastal areas.