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The influence of physical– chemical variables on phytoplankton and lesser flamingo (Phoeniconaias minor) abundances in Lake Natron, Tanzania
(WILEY, 2020) Mgimwa, Emmanuel; John, Jasson; Lugomela, Charles
Soda lakes are alkaline ecosystems characterised by extreme conditions and are one of the most productive aquatic ecosystems. Lesser flamingo, an obligate phytoplankton filter feeder, is widely identified as the flagship species of these saline- alkaline wetlands throughout the African continent. This study, carried out at three lagoons in Lake Natron for ten consecutive months from March 2019, investigated the relationship between Chlorophyll- a and lesser flamingo abundances, and physical– chemical variables and Chlorophyll- a abundance. Lake Natron is the only regular breeding site for the East African population of this specialised species and is known to host thousands of birds year- round. There was a strong correlation between lesser flamingo
and Chlorophyll- a abundances. Chlorophyll- a abundance was significantly influenced by dissolved oxygen, water turbidity, phosphate, nitrate and ammonium. Findings from this study suggest that annual fluctuation in the lesser flamingos numbers in Lake Natron is triggered by phytoplankton abundance whose primary productivity is influenced by physical– chemical variables in the lake waters. In turn, these changes are mainly due to both anthropogenic activities and weather changes within the lake basin and its surroundings. Thus, the conservation and management of this lake require concerted efforts from different stakeholders including those found in Kenya
Biomass and nutritive value of Spirulina (Arthrospira fusiformis) cultivated in a cost-effective medium
(SPRINGER, 2019) Michael, Angelina; Kyewalyanga, Margareth; Charles, Lugomela
Introduction Cultivation of spirulina at commercial-scales relies on analytical grade–based media, which are expensive and so are the product.
Purpose This study assessed the biomass, proximate composition, and other useful compounds in Spirulina (Arthrospira fusiformis) produced with a cost-effective culture medium (LCMA), and the results were compared with those from a standard Zarrouk medium grown spirulina. Methods The LCMA medium was formulated by using a commercial NPK10-20-20 fertilizer as a source of the three major nutrients for spirulina growth, and other three ingredients from Zarrouk medium. The experiment was conducted for 28 days in the glass aquaria under indoor conditions. Standard analytical methods were applied for the determination of proximate composition, chlorophyll, minerals, and vitamins in the spirulina biomass. Result The LCMA medium showed the best growth conditions by accumulating higher chlorophyll content (0.99 ± 0.02%) and dry weight (0.75 ± 0.01 g/100 ml) as well as attaining higher optical density (2.06 at day 15) earlier than the Zarrouk medium. The results of the proximate analysis for spirulina cultured in the LCMA medium were of good quality, with the protein contributing more than 50% of its dry matter. It was further noticed that the LCMA was an ideal medium for optimization of vitamins and some minerals since it recorded a significant amount of most of the analyzed vitamins together with the minerals sodium and potassium compared with the
Zarrouk medium. Conclusion It is suggested that LCMA medium could be used as the alternative and cheap medium for maximization of biomass
and production of useful biochemical compounds in spirulina species
Seasonal patterns of thermal stratification and primary production in the northern parts of Lake Tanganyika
(ELESEVIER, 2018) Prisca, Mziray; Ismael, Kimirei; Peter, Staehr; Charles, Lugomela; William, Perry; Dennis, Trolle; Catherine, O'Reilly; Huruma, Mgana
Thermal stratification in meromictic Lake Tanganyika weakens during the cool, dry and windy season, allowing intrusionsofdeepernutrient richwatersintotheuppermixedlayerenhancingprimaryproductivity.Thecurrent study examined the seasonal influence of thermal structure on the patterns of primary production in Lake Tanganyika. Two sites (Kigoma Bay and Mahale) were sampled on a monthly basis for 1 year. Water temperature and chlorophyll a fluorescence profiles (0–100 m) were measured using a multisonde. Water samples were taken every 20 m (0–100 m)to measuresoluble reactive phosphorus (SRP), chlorophyll a and primary production. Pulse AmplitudeModulatedFluorometrywasusedforthemeasurementsofprimaryproduction.Theresults showthat the dry season coincided with higher wind speeds, elevated SRP and some peaksof chlorophyll a and primary production at both sites. During the wet season, highlevels of chlorophyll a and primary production coincided with an increase in the euphotic depth, a deep chlorophyll maximum (DCM) and a contribution from metalimnetic areal production at both sites. Our results suggest that the vertical distribution of primary production inLakeTanganyika isaffectedbythe lakethermal structure,nutrientavailabilityandtheextentoftheeuphotic zone. In Lake Tanganyika, estimates of areal primary production were significantly affected by DCM and required estimation throughout the entire upper mixed layer and the metalimnion which extended to ~89 m.
Importance of internal and external nutrient loading to the primary productivity of Lake Tanganyika
(ELSEVIER, 2024) Prisca, Mziray; Karsten, Bolding; Anders, Nielsen; Peter, A.U. Staehr; Ismael, Kimirei; Charles, Lugomela; Catherine, O’Reilly; Dennis, Trolle
A coupled hydrodynamic-ecosystem model (GOTM-FABM-ERGOM) was applied to test the hypothesis that primary production in the upper mixed layers of Lake Tanganyika is primarily controlled by internal nutrient inputs. The model was calibrated (data: May 2015–April 2016) and validated (data: May 2016–April 2017) against monthly field data of water temperature, dissolved oxygen, nutrients (nitrate, ammonium, phosphate) and chlorophyll a collected from Kigoma Bay in the northern part of the lake. Data of nutrients and discharge from the rivers (Ruzizi and Malagarasi) and atmospheric dry and wet deposition were derived from the literature. The model generally showed good agreement with the observed data for water temperature, dissolved oxygen and nutrients during the calibration and validation periods. The model satisfactorily reproduced the lake’s seasonal dynamics (dry and wet seasons) induced by the lake’s hydrodynamic processes. We found that both internal and external sources contribute importantly to total nutrient loading in the lake. Our results indicate that nutrient supply from rivers into Lake Tanganyika is more important than previously known. However, we call for further studies to investigate the contribution of other sources of regenerated nutrients (e.g. N primary productivity of Lake Tanganyika. 2-fixation) to the overall
Viral Pathogens Threatening Cage-Cultured Nile Tilapia in Lake Victoria: Epidemiology, Emerging Risks and Integrated Health Management Strategies
(John Wiley & Sons, 2026-05-08) Komba, Richard; Mwita, Chacha
The rapid expansion of cage culture for Nile tilapia (Oreochromis niloticus) in Lake Victoria is central to food security and profitable development in East Africa. Nevertheless, viral conditions affect the sustainability of this sector, with significant imbalances in livelihood, trade and aquaculture adaptability. This review synthesises current knowledge on five crucial contagions applicable to cage-cultured tilapia in Lake Victoria: tilapia lake virus (TiLV), infectious spleen and kidney necrosis virus (ISKNV), lymphocystis disease virus (LCDV) and two arising pitfalls, tilapia parvovirus (TiPV) and betanodavirus (NNV). We discuss their taxonomy, epidemiology, clinical presentations and possible impacts on aquaculture in the region. The review identifies environmental and functional threat factors, including high stocking density, seed movement, variability in water quality and integration with wild fish. We also speculate issues related to surveillance, molecular characterisation, hatchery biosecurity and vaccine development as critical gaps in aquaculture growth in the region. While none of these contagions are zoonotic, they can dispose of fish to bacterial pathogens with zoonotic potential, emphasising the significance of a One Health approach. Recommendations include region-wide coordinated surveillance, investment in molecular diagnostics, harmonised aquaculture health programmes and vaccine development. Addressing these issues will ameliorate viral complaints, strengthen aquaculture sustainability and guard the livelihoods of communities dependent on Lake Victoria fisheries.