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Water quality in the Okavango Delta
LC Mmualefe, N Torto
Water SA , 2011,
Abstract: The Okavango Delta ecosystem sustains a large number of plant and animal species as well as providing resources for the livelihood of the riparian human population. Despite changes in flow patterns, rainfall and other climatic conditions over the past decades, the system has responded well to maintain low salt-water balances through evapotranspiration and chemical precipitation processes. The electrical conductivity and total dissolved solids are generally low, with values less than 200 êS.cm-1 and averaging 40 mg..-1, respectively. The dissolved oxygen and dissolved organic carbon range from 1.8 to 8.8 and 5 to 15 mg..-1, respectively, while pH ranges from 6.7 to 10.3. Total nitrogen and phosphorus are generally low with maximum concentrations of 1.7 and 1.6 mg..-1, respectively, recorded downstream of the Delta. Even though most of these quality parameters are within limits for potable water, the Deltafs ecosystem needs to be protected from anthropogenic activities. Past use of persistent organic pollutants requires monitoring of impacts of their residues on the plants and animal species within the ecosystem, in order to maintain its rich biodiversity. This review focuses on chemical quality data for water and sediments in the Okavango Delta published between 2000 and 2010. Despite the shortage of published data, it is hoped that this review will provide an overall picture of the status quo of the Deltafs water and will set the direction for future monitoring efforts.
Pteridophytes of the Okavango Delta, Botswana (Southern Africa)  [cached]
Caudales, Rodulio,Vega Hernández, Efrén
Anales del Jardín Botánico de Madrid , 2000,
Abstract: The Okavango Delta in Botswana constitutes one of the larger inland deltas in the world. Fifteen species of fern were found in this ecological system integrated into 10 genera and 9 families. Included in this report are descriptions of each family, genus and species. Also given are artificial keys to the genera, as well as keys for genera and species within the family when necessary. A documented distribution and ecological notes for each species also appears. Se estudian los pterid6fitos del delta del Okavango, uno de los deltas interiores ma's grandes del mundo. Se citan 15 especies, incluidas en 10 generos y 9 familias. Se aportan descripciones, claves de identification, datos sobre la distribucitin y ecologia. y mapas de distribuci6n detallada de cada una de las especies.
Wastewater disposal at safari lodges in the Okavango Delta, Botswana
TS McCarthy, T Gumbricht, RG Stewart, D Brandt, PJ Hancox, J McCarthy, AG Duse
Water SA , 2004,
Abstract: Many safari lodges in the Okavango Delta obtain their water supply from boreholes in near-surface aquifers while disposing of their wastewater via soak-aways, creating a potential risk of contamination of their water supply. Most islands in the Delta contain sites where the groundwater has become salinised as a result of transpiration by island vegetation. This study of wastewater disposal at such a site on Chitabe Island, which involved surveying of the water table, measurement of groundwater salinity, field bacteriological screening and groundwater flow modelling has revealed that although water disposal has created a recharge mound, the depression in the water table induced by transpiration by island vegetation is such that pollutants will remain confined to the region of maximum groundwater depression. Although the soils are sandy, they exhibit significant filtration effects on bacteria. The field assay used in this study was unable to detect coliform and E. coli bacteria in groundwater within a distance of 20 m from the disposal point. Modelling of groundwater flows indicates that boreholes located on the outer fringes of the island are secure from contamination. The study suggests that disposal of wastewater into areas where the groundwater is salinised provides a sustainable solution to the problem of wastewater disposal in the Okavango Delta. Water SA Vol.30(1): 121-128
Deltamethrin in sediment samples of the Okavango Delta, Botswana
PS Daka, VC Obuseng, N Torto, P Huntsman-Mapila
Water SA , 2006,
Abstract: Deltamethrin concentrations were determined in 35 sediment samples collected from three different habitats: channel, lagoon and pool sites from Xakanaxa in the Okavango Delta, NW Botswana. The samples were Soxhlet-extracted in acetone to extract deltamethrin residues and subsequently cleaned-up with silica gel 60. The final determination was carried out with a gas chromatograph equipped with an electron capture detector (GC-ECD). The sample work-up and determination gave deltamethrin recoveries of 54 to 97%, and detection limits of 0.004 mg/kg dw. The concentration of deltamethrin residues in the sediment samples collected from the three sprayed areas in the Okavango delta ranged between 0.013 and 0.291 mg/kg dw, with the highest concentrations observed in samples obtained from the pool sites. Analysis of samples for organic matter content showed percentage total organic carbon (% TOC) ranging between 0.19% and 8.21%, with samples collected from the pool having the highest total organic carbon. The concentrations of deltamethrin residues and the % TOC in sediment samples showed a similar trend with the highest levels recorded in the pool samples. These data confirmed that a simple method based on GC-ECD, after Soxhlet extraction, was robust enough to enable quantification of deltamethrin in the sediments, because comparable results were obtained with a more sophisticated system consisting of a GC coupled to a mass spectrometer with a time of flight (TOF) analyser. Water SA Vol.32 (4) 2006: pp.483-488
Flocking dynamics and roosting behaviour of Meyer’s parrot (Poicephalus meyeri) in the Okavango Delta, Botswana
Rutledge S. Boyes,Michael R. Perrin
African Zoology , 2011,
Abstract: For most of the year, Meyer’s parrots in the Okavango Delta do not form large feeding flocks, and groups larger than two or three are probably the result of opportunistic aggregation at favoured food items after dispersion from communal roosts. Communal roosting likely does not facilitate flocking unless the food resources are close to the roost site, but may function in anti-predator defence. Meyer’s parrots appear to be dependent on riverine forest, Acacia-Combretum marginal woodland and mopane woodland for roost sites in the Okavango Delta. They aggregated more during the breeding season due to their specialist nutritional requirements, and female dependence on food provisioning by the male parrots. Meyer’s parrots may be sedentary in the Okavango Delta, but the possibility of limited local movements in other areas (especially the Zimbabwean highlands) should be investigated.
Contending Claims over Access to Fisheries: A Case Study of the Okavango Delta Panhandle, Botswana  [cached]
Gagoitseope Mmopelwa,Barbara Ntombi Ngwenya,Donald Letsholo Kgathi
Journal of Sustainable Development , 2013, DOI: 10.5539/jsd.v6n3p58
Abstract: Fishing is one of the key livelihood activities in the Okavango Delta in Botswana. Subsistence fishers, commercial fishers and tourist lodge operators derive material and non-material benefits from fishery. However open access fishing has resulted in intergroup conflicts. The objectives of the study were to describe the nature of the fishing conflict and to suggest feasible conflict management strategies. A questionnaire based survey conducted among subsistence fishers, commercial fishers in four villages and among tourist lodge operators in the Panhandle of the Okavango Delta found that fishing in common grounds was the main source of conflict between commercial and recreational fishing. The paper discusses options for managing the conflict to avoid undesired consequences on the fishery resources of the Okavango Delta.
Normal haematology and blood biochemistry of wild Nile crocodiles (Crocodylus niloticus) in the Okavango Delta, Botswana  [cached]
C.J. Lovely,J.M. Pittman,A.J. Leslie
Journal of the South African Veterinary Association , 2012, DOI: 10.4102/jsava.v78i3.305
Abstract: Wild Nile crocodiles (Crocodylus niloticus) of various size classes were captured in the Okavango Delta, Botswana. Blood was collected from the post occipital sinus and used for the determination of a wide range of haematological and biochemical parameters. These values were compared between the sexes and between 3 size classes. The values were also compared with the limited data available from farmed Nile crocodiles, as well as from other wild Nile crocodiles. The Okavango crocodiles were comparatively anaemic, and had comparatively low total protein and blood glucose levels. There was a high prevalence of Hepatozoon pettiti infection, however, there was no significant difference in haematological values between the infected and uninfected crocodiles. The values reported here will be useful in diagnostic investigations in both zoo and farmed Nile crocodiles.
Soil Factors That Influence the Abundance and Distribution of Threatened and Endangered Species in the Okavango Delta; with Particular Emphasis on Eulophia angolensis  [PDF]
Sandra K. Middleton, Kelebogile B. Mfundisi, Naidu Kurugundla
Natural Resources (NR) , 2015, DOI: 10.4236/nr.2015.65033
Abstract: Eulophia angolensis is an endangered plant species found in the Okavango Delta. Generally, there is lack of botanical information on this species in Botswana, which is necessary for its in-situ and ex-situ conservation. The objectives of this research are to map areas where E. angolensis occurs, determine the species that co-exist with it, and establish soil factors that influence its abundance and distribution in the Okavango Delta. A survey of the area where the plant was sighted in 2004 was carried out using recorded GPS points. Soil samples were collected at 0 - 20 cm depth from the floodplain where the species occurred to determine the macronutrients: total nitrogen, phosphorus, potassium (N, P, and K) and soil organic carbon (SOC) contents. The researchers could not find the plant at all GPS locations where the plant was sighted in 2004, but discovered a new unrecorded site for the species. The species was very close to the water channel; approximately 40 cm away, with only one plant about 60 cm away. The mean macronutrients concentrations in the site that contained E. angolensis were total N = 2.61 ± 0.61 mg/L, P = 7.02 ± 0.8 mg/L and K = 14.41 ± 4.28 mg/L. SOC concentration was 40.1 ± 10.28 mg/L. Furthermore, there was K biogeochemical gradient within the E. angolensis habitat, with more concentrations directly around the plant. Therefore, E. angolensis needs critical amounts of N, P, K and SOC, with K, SOC and water requirement being the crucial factors. Frequent monitoring of the endangered species found in the Okavango Delta is required, and ex-situ conservation of the species in the country in the form of a botanical garden should be established for future generations.
Normal intestinal flora of wild Nile crocodiles (Crocodylus niloticus) in the Okavango Delta, Botswana  [cached]
C.J. Lovely,A.J. Leslie
Journal of the South African Veterinary Association , 2012, DOI: 10.4102/jsava.v79i2.246
Abstract: Bacterial and fungal cultures were performed from cloacal swabs collected from 29 wild Nile crocodiles, captured in the Okavango Delta, Botswana. Sixteen species of bacteria and 6 fungal species were cultured. Individual crocodiles yielded 1-4 bacterial species, and 0-2 fungal species. The most commonly isolated bacteria were Microbacterium, Enterococcus faecalis, Aeromonas hydrophila, and Escherichia coli. No salmonellae were cultured. The most commonly occurring fungus was Cladosporium. Several of the bacterial and fungal species isolated have been implicated in cases of septicaemia in crocodilians. Knowledge of the normal intestinal flora will contribute towards the development of a crocodile-specific probiotic for use in farmed crocodiles.
A preliminary disease survey in the wild Nile crocodile (Crocodylus niloticus) population in the Okavango Delta, Botswana  [cached]
A. J. Leslie,C. J. Lovely,J. M. Pittman
Journal of the South African Veterinary Association , 2012, DOI: 10.4102/jsava.v82i3.54
Abstract: The objective of this study was to conduct a preliminary survey of diseases that might be present in the wild Nile crocodile population in the Okavango Delta, Botswana. Blood samples were collected from crocodiles ranging in size from 34.0cmto 463.0cmtotal length. Samples were examined for blood parasites and underwent a haematological analysis. Before release the crocodiles were examined for various clinical abnormalities. Of the 144 crocodiles examined, none were visibly sick or displayed any signs of disease. No antibodies to Mycoplasma crocodyli were detected. Hepatozoon pettiti was present in 55.3 % of blood smears examined, but there was no significant difference in any of the haematological values between the infected and uninfected crocodiles, and a high prevalence of Hepatozoon infection is not uncommon in other species. Only 7.6 % of the examined crocodiles were infested with leeches. Further research is required for several of the crocodilian diseases, in particular to elucidate the role of wild crocodilians as reservoirs of infection.
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