Showing papers in "Journal of the Limnological Society of Southern Africa in 1979"
TL;DR: The differences found between the two species indicate that Myxus capensis is more specialized for a catadromous life history in an unstable riverine environment.
Abstract: SUMMARY Data on the relative abundance, penetration and breeding biology of the freshwater mullet Mugil cephalus and the flathead mullet Mugil cephalus in the freshwater reaches of some Eastern Cape coastal rivers are described. The differences found between the two species indicate that Myxus capensis is more specialized for a catadromous life history in an unstable riverine environment. Evidence showing the importance of the freshwater phase for the latter species is given and the disastrous effects of the erection of barriers to fish movement are stressed.
49 citations
TL;DR: In this article, the water quality of the upper Hennops River was determined by applying the method of Lange-Bertalot (1978; 1979), which was based on groups of diatom species with similar tolerances towards pollution.
Abstract: SUMMARY The water quality of the upper Hennops River was determined by applying the method of Lange-Bertalot (1978; 1979), which is based on groups of diatom species with similar tolerances towards pollution. A definite improvement in the water quality was indicated between the upper reaches of the river, which receives secondary treated sewage effluent discharges, and Rietvlei Dam, some 25 km downstream. According to the water quality classification of Lange-Bertalot, this represented an improvement from class III – IV (α-meso- to polysaprobic) to class II – III (α- to β-mesosaprobic). These results were in general agreement with chemical analyses, which suggests that Lange-Bertalot's method for classifying the quality of running waters can be adapted, to South African conditions. The pollution tolerances of some species not included in Lange-bertalot's classification are suggested.
36 citations
TL;DR: The Orange River was the major source of dissolved chemicals and suspended sediments, while the Caledon River contributed 24 and 30% respectively, and the Kraai River 9 and 8% respectively as mentioned in this paper.
Abstract: SUMMARY A four year pre-impoundment study of the catchment of the Hendrik Verwoerd Dam was conducted. The Orange River was the major source of dissolved chemicals and suspended sediments, while the Caledon River contributed 24 and 30% respectively, and the Kraai River 9 and 8% respectively. The upper reaches of the Orange River catchment contributed mainly to the dissolved chemical and sediment loads, in contrast to the minimal contribution of the lower reaches. This was in spite of the relatively stable geological formations in the upper reaches and the erodable formations in the lower reaches. Dry-wet seasonal variations occurred in nutrient and sediment concentrations and loads, except for the Bell River where constant values were measured. The water was characterized by magnesium and bicarbonate dominance. Adsorption by the suspended sediments was dominated by calcium (potassium in the Bell River) and zinc among the trace elements. Due to its low salinity and sodium adsorption ratio, the water was sui...
27 citations
TL;DR: During a survey of freshwater nematodes in South Africa, six species of Tobrilus Andrassy, 1959 were encountered, four of which are new to science, are described and figured.
Abstract: SUMMARY During a survey of freshwater nematodes in South Africa, six species of Tobrilus Andrassy, 1959 were encountered. The six species, four of which are new to science, are described and figured, viz. Tobrilus annetteae, n.sp.; T. heptapapillatus n.sp.; T. stefanskii (Micoletzky, 1925) Andrassy, 1959; T. diversipapillatus (Daday, 1905) Andrassy, 1959; T. ampiei n.sp. and T. floridensis n.sp.
8 citations
TL;DR: The modified BG 11 growth medium used in this study has a poor buffer ability and large pH changes occurred during growth of Microcystis, and inhibition of growth in cultures grown at stress light intensity could be ascribed to depletion of the total inorganic carbon content of the medium.
Abstract: SUMMARY The modified BG 11 growth medium used in this study has a poor buffer ability and large pH changes occurred during growth of Microcystis. Inhibition of growth in cultures grown at stress light intensity (26 μEinst m−2 sec−1) could be ascribed to depletion of the total inorganic carbon content of the medium rather than to light intensity per se, pH or high O2 concentration. In cell suspensions grown under stress light intensity an unfavourably low CO2: O2 concentration ratio developed due to rapid photosynthesis and insufficient replenishment of CO2 by diffusion from air which may have induced oxygenation instead of carboxylation by ribulose diphosphate carboxylase.
7 citations
TL;DR: A limnological survey of the Buffelspoort Dam and its catchment between 1973 and 1975 showed that the water of the area contained extremely low concentrations of dissolved minerals and that there was no point source of nutrient supply to the dam as discussed by the authors.
Abstract: SUMMARY A limnological survey of the Buffelspoort Dam and its catchment between 1973 and 1975 showed that the water of the area contained extremely low concentrations of dissolved minerals and that there was no point source of nutrient supply to the dam. The anion and cation dominance in the catchment water may be summarized as HCO3 >Cl >SO4NO3 and Na+ >Mg++ >Ca++ >K+, respectively, and this water may be classified as soft bicarbonate water. The impoundment was warm monomictic and had an extensive anaerobic hypolimnion during summer stratification. Changes in water transparency were related to the seasonal fluctuation in water content and the hydrological cycle. Nutrient concentrations in the dam displayed seasonal trends which were related to stratification, hydrological events and phytoplankton activity. On the basis of its nutrient content and chlorophyll a concentrations the impoundment can be classified as mesotrophic. The further development of holiday resorts in the catchment poses a cutrophication...
6 citations
TL;DR: After the initial decrease, centroplasmic polyphosphate bodies increased to about half of the maximum numbers stored in cells grown in the presence of phosphate, suggesting that translocation of phosphorus...
Abstract: SUMMARY Microcystis aeruginosa toxic strain UV-006 stored a fixed amount of polyphosphate in spherical granules located in the centroplasm. Twenty four hours of phosphate starvation induced use of stored polyphosphate, manifested by reduction in granule numbers. Reintroduction of 2, 4 or 8 mg l−1 K2HPO4 resulted in redeposition of polyphosphate in a critical number of centroplasmic polyphosphate granules. Growth rate was unaffected by phosphate concentrations, although the final cell yield was slightly lower at 8 mg l −1 Continued starvation decreased photosynthetic rate and growth ceased. Cells appeared senescent. Cyanophycin and polyglucoside reserves apparently increased in these cells, whilst thylakoids were reduced in number and reorientated away from. the cell wall and polyhedral bodies were lost. After the initial decrease, centroplasmic polyphosphate bodies increased to about half of the maximum numbers stored in cells grown in the presence of phosphate, suggesting that translocation of phosphorus...
6 citations
TL;DR: In this paper, the volume of sediment in the Bulbergfontein Dam was computed after mapping the area of the dam and ascertaining the depth of the sediment by digging and augering.
Abstract: SUMMARY The volume of sediment in the Bulbergfontein Dam was computed after mapping the area of the dam and ascertaining the depth of the sediment by digging and augering. The watershed of the impoundment had been delimited by means of aerial photographs and field work. The catchment has a mean slope of 1,9° which is mostly covered by perennial grasses and xerophytic shrublets. Approximately 75 per cent of the area is natural pasture and the rest under maize and wheat cultivation. The mean annual rainfall is 471 mm. The fortuitous presence of a fine sand layer (marker) in the sediments made it possible to compute not only the total accumulation of sediment, but also the accumulation since 1971. From these figures the rates of erosion were found to be 27,5 mm 10−3 years for the period 1942 to 1971 and 34,6 mm 10−3 year for the period 1972 to 1978.
6 citations
TL;DR: In this article, the anaesthetic effects of various concentrations of benzocaine hydrochloride were tested on Liza macrolepis and Sarotherodor mossambicus in sea water and diluted sea water, respectively.
Abstract: SUMMARY The anaesthetic effects of various concentrations of benzocaine hydrochloride were tested on Liza macrolepis and Sarotherodor mossambicus in sea water and diluted sea water, respectively. Induction time for anaesthesia was negatively correlated with increasing anaesthetic concentrations in L. macrolepis. In S. mossambicus, however, operculum clamping appeared to be responsible-f or induction times increasing with increased anaesthetic concentration. The tranquillizing effects of low concentrations of benzocaine hydrochloride on L. macrolepis was also studied.
6 citations
TL;DR: In this article, the amount of reactive phosphorus entering the lake has been greatly reduced since the commencement of irrigation with municipal waste water, and that phosphorus entering Lake McIlwaine from the rivers is being removed from the water column by an unspecified mechanism (s).
Abstract: SUMMARY Between November 1976 and September 1977, samples were taken on a fortnightly basis from a representative station in Lake McIlwaine. In addition an intensive study of the riverine input of reactive phosphorus was conducted. Samples were analysed for total reactive phosphorus, conductivity, pH, dissolved oxygen, phytopigments, suspended and dissolved solids, secchi disc light penetration, and temperature, when possible. River flow was obtained from gauging weirs on the major rivers entering the lake. The study to date has indicated two important conclusions, namely, that the amount of reactive phosphorus entering the lake has been greatly reduced since the commencement of irrigation with municipal waste water, and that phosphorus entering Lake McIlwaine from the rivers is being removed from the water column by an unspecified mechanism (s). However, further reduction of the phosphorus loading will be required to return the lake to a mesotrophic state.
5 citations
TL;DR: The extensive weed beds which surround the upper reaches of Swartvlei may be a major source of acetate and glucose in the pelagic water column.
Abstract: SUMMARY The utilization of dissolved organic compounds in Swartvlei was measured by the addition of single concentrations of 14C-labelled acetate and glucose to water samples, The results indicated acetate uptake was greatest in the aerobic zone while glucose was predominantly utilized in the anaerobic zone. With the exception of two months, integral glucose uptake was usually greater than the uptake of acetate. In August and September 1971 acetate was indicated as being utilized predominantly by flagellates and in December 1971 by dinoflagellates. During the remainder of the study, bacteria were assumed to be responsible for the uptake of acetate. The extensive weed beds which surround the upper reaches of Swartvlei may be a major source of acetate and glucose in the pelagic water column.
TL;DR: Sediment samples collected from Jan Smuts Park Dam in Brakpan, Transvaal during winter months were incubated in culture medium in the laboratory and found to contain viable Microcystis aeruginosa Kutz, indicating that the alga may be able to withstand adverse winter conditions in the bottom sediments of the pan.
Abstract: SUMMARY Sediment samples, collected from Jan Smuts Park Dam in Brakpan, Transvaal, during winter months were incubated in culture medium in the laboratory and found to contain viable Microcystis aeruginosa Kutz. emend. Elenkin colonies. The results obtained, indicate that the alga may be able to withstand adverse winter conditions in the bottom sediments of the pan.
TL;DR: Since the bacteria which were studied probably belong to the zymogenous group of Winogradsky (1949), attention should be paid to the presence of autochthonous and/or oligocarbophilic species in the impoundment.
Abstract: SUMMARY Seventy one heterotrophic bacterial isolates were obtained from Wuras Dam, phenotypically characterized and clustered with the unweighted-pair group method. Three groups were obtained of which the first contained 59 members in several clusters. Overall this group was characterized by a lack of positive characteristics (< 21%) e.g. a low fermentative ability. The second group contained three members exhibiting more positive characteristics (53%) and the third group nine members with 56,7% positive characteristics. Evaluations of the groups and clusters did not suggest any distinct spatial or temporal variations within the groups. Since the bacteria which were studied probably belong to the zymogenous group of Winogradsky (1949), attention should be paid to the presence of autochthonous and/or oligocarbophilic species in the impoundment.
TL;DR: The distribution of Knevia auriculata in the upper reaches of the Crocodile River (Incomati River System) was determined and it was found that this fish shows a preference for cold mountain streams with calm pools.
Abstract: SUMMARY The distribution of Kneria auriculata in the upper reaches of the Crocodile River (Incomati River System) was determined. Knevia auriculata shows a preference for cold mountain streams with calm pools. Five isolated populations exist in such streams. Although no accurate technique for the precise determination of the status of this species is possible, there appears to be a total of more than 90 000 individuals in the five habitats. The presence of trout in their presently low numbers is apparently not a threat to all populations of Knevia auriculata, but has seriously limited the range of one population. In addition the incursion of exotic plants such as black wattle (Acacia spp.) and poplar (Populus spp.) on the banks of most of the streams in which this fish occurs, do not have a noticeable detrimental effect on any of the five populations. However, erosion of the stream banks is visible, which may pose a further threat if habitat deterioration is allowed to progress unhindered. The constructio...
TL;DR: In this article, a minimum radiation dose rate of 5 kGy s−1 led to sterilization and no changes in lattice structure or precipitation of the suspensoids were observed.
Abstract: SUMMARY Gamma radiation as an alternative sterilization technique for silt and clay suspensions is evaluated. It is compared to autoclaving in regard to sterility and changes in physical and chemical properties of the suspensions. A minimum radiation dose rate of 5 kGy s−1 led to sterilization and no changes in lattice structure or precipitation of the suspensoids were observed. The adsorbed ionic composition of the silt and clay particles was, however, altered and should be rectified before radiated suspensoids are used. Autoclaving resulted in sterility, but irreversible precipitation of the suspensoids made it less applicable where the colloidal properties of the clay and silt are to be maintained.
TL;DR: The first limnological investigations on three impoundments in the Orange Free State were described in this article, where the waters were turbid and the unfavourable underwater light climate was the major factor limiting algal growth.
Abstract: SUMMARY The first limnological investigations on three impoundments in the Orange Free State are described. No thermal stratification was found and water temperatures below 8,6°C were not measured. The waters were turbid and the unfavourable underwater light climate was the major factor limiting algal growth. The catchment areas influenced the ionic composition of the waters and large quantities of ions were adsorbed onto the suspended silt.
TL;DR: The method uses the Utermohl counting technique but also involves the calculation of the relative density of each species in the association as determined with the ordinary light microscope, which ensures that even the smallest diatoms are accounted for.
Abstract: SUMMARY A method for the quantitative and qualitative determination of planktonic diatoms was developed. The method uses the Utermohl counting technique (in which an inverted microscope is employed) as a basis but also involves the calculation of the relative density of each species in the association (as determined with the ordinary light microscope). A combination of the results thus obtained ensures that even the smallest diatoms (2,5 μm) are accounted for. These often constitute a significant proportion of the population, but are often overlooked or may not even be resolved using Utermohl's method.
TL;DR: The interrelationships between biological parameters such as Biological Growth Potential (BGP), anaerobic fecal and coliform bacteria, Cladocera and Copepoda were established by means of factor and cluster analyses.
Abstract: SUMMARY Seshego Dam, Lebowa, was investigated over a period of 15 months (1974 – 1975). The interrelationships between biological parameters such as Biological Growth Potential (BGP), anaerobic fecal and coliform bacteria, Cladocera and Copepoda were established by means of factor and cluster analyses. Cladocera production is lower than Copepoda production. Parameters which may play a role in Cladocera production are: dissolved oxygen, BOD, PO4−P concentration and N/PO4−P ratios. Probable sources of nutrition for Cladocera are the phytoplankton (of which BGP may serve as an indication) and coliform bacteria. The production of the Copepoda is influenced by temperature, turbidity, conductivity, NO2−N, total nitrogen, SO4 and the N/PO4−P ratio. Food sources of the latter may be anaerobic bacteria and suspended particulate matter. The Cladocera and Copepoda do not appear to compete.
TL;DR: The results indicate that variations in numbers of enteric bacteria are partly caused by man-made changes to the influent water.
Abstract: SUMMARY This study was undertaken to determine the occurrence of faecal bacteria in two trout hatcheries in the Transvaal Province, South Africa. The results indicate that variations in numbers of enteric bacteria are partly caused by man-made changes to the influent water. It was not established whether the bacteria were propogated by the fish, but it was clear that hatcheries can act as reservoirs for allochthonous faecal bacteria.
TL;DR: All patronyms in currently valid species has been established with one exception: Clarias theodorae M. Weber 1897, which was named after a niece of Professor Weber's wife, who accompanied him on his South African visit.
Abstract: SUMMARY Workers revising Southern African freshwater fishes have endeavoured to provide brief information on those persons who have had fish named after them. The provenance of all such patronyms in currently valid species has been established with one exception: Clarias theodorae M. Weber 1897. This was named after a niece of Professor Weber's wife, who accompanied him on his South African visit.