Environmental Biology

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Physiological and cytological biomarker studies using Perna perna for marine pollution monitoring.
(2009) Rajkumar, Anisha.; Smit, Albertus J.
Urbanised and industrial coastal areas in South Africa are most vulnerable to the effects of marine pollution, and the Kwa-Zulu Natal coastline is particularly at risk. The mussels Perna perna, from a polluted (Isipingo Beach) and unpolluted (Park Rynie) site, and Brachidontes semistriatus were evaluated for their use as potential bioindicator organisms. The mussels were subjected to increasing copper concentration treatments to asses the following biomarker responses: cardiac activity, lysosomal membrane stability, malate dehydrogenase enzyme (MDH) activity and body condition index. Brachidontes semistriatus exhibited significant variations in biomarker responses only when exposed to higher Cu dosages, whereas P. perna from Park Rynie displayed distinct changes in heart rate, lysosomal membrane stability and MDH activity with increasing contaminant exposure. Perna perna from Isipingo Beach displayed significant biomarker variation in cardiac activity and lysosomal membrane stability, however differences in MDH activity were only evident at the highest Cu concentration of 100 mg.L-1. Both species from the different Cu treatments failed to show any significant changes in body condition indices due to the limited time of contaminant exposure. The mussel P. perna was therefore selected as a suitable biomonitoring species, and cardiac activity, lysosomal membrane stability and body condition index were chosen as reliable biomarkers for the study. Native P. perna from KZN responded to a distinct pollution gradient along the coastline by displaying significant bradycardia, reduced lysosomal membrane stability, poor condition indices and high heavy metal tissue concentrations. Durban, Isipingo and Umkomaas were singled out as the most contaminated sites along the coast, and Zinkwazi and Park Rynie as the least polluted. In addition, significant correlations between tissue and sediment metal concentrations suggest that the species is an effective heavy metal bioaccumulator of Cd, Pb, Zn, Cr and Fe. Similar spatial trends in seawater and mussel tissue concentrations in Durban Harbour were identified. Stations in the port located nearest to the freshwater inputs and stormwater drains displayed the highest metal concentrations in tissue and seawater, as well as adverse biomarker responses from transplanted P. perna. These results suggest that Durban Harbour is strongly influenced by tidal exchange and contaminated freshwater inflow entering the harbour. It was also found that reproduction imposes a considerable effect on P. perna body condition as spawning events in winter months result in pronounced body mass loss. The study concluded that P. perna is a highly effective bioindicator species, and cardiac activity, lysosomal membrane stability and body condition index can successfully be employed in marine pollution monitoring programmes.
The development of clone-unspecific micropropagation protocols for three commercially important Eucalyptus hybrids.
(2001) Chetty, Senica.; Watt, Maria Paula Mousaco Deoliveira.
Micropropagation methods are often used to supplement existing clonal programmes for Eucalyptus species. However, genotypic differences among clones require the implementation of clone-specific protocols, an expensive and labour-intensive exercise. Hence, this study aimed at determining high-yielding hybrid-specific rather than clone-specific, micropropagation protocols for E. grandis x nitens (GN), E. grandis x nitens (NH), and E. grandis x urophylla (GU). Different conditions for surface sterilisation, bud-break (3 protocols, 2 media), multiplication (4 media), elongation (2 protocols) and rooting (4 media) were tested. A single successful surface sterilisation approach was possible for all clones of the tested hybrids (0.0-11.8% contamination, 0.0-22.9% necrosis). It involved rinsing nodal explants in a fungicide mixture (lg/l Benlate, 1g/1 boric acid, 0.5ml/1 Bravo, Tween 20) for 15 minutes followed by calcium hypochlorite (10g/l with Tween 20) for three minutes. Results at each culture stage were dependent on genotypes, and results indicated here represent ranges in values among the clones of each hybrid. The highest bud-break values for GN clones (87-90%) and NH clones (17-75%) were achieved on a medium containing MS, 0.1mg/1 biotin, 0.1mg/l calcium pantothenate, 0.04mg/1 NAA, 0.11mg/l BAP and 0.05mg/1 kinetin. In GU clones, bud-break values on this medium (84-97%) were not significantly different to those achieved directly on a multiplication medium (80-91%) (MS, 0.1 mg/l biotin, 0.1 mg/l calcium pantothenate, 0.2mg/l BAP, 0.01mg/1 NAA). Shoot multiplication yields for GN clones (4-13 shoots/bud) and GU clones (2-6 shoots/bud) were achieved on a medium consisting of MS, 0.1mg/1 biotin, 0.1 mg/l calcium pantothenate, 0.2mg/1 BAP and 0.01 mg/l NAA. As genotypic effects were highly significant among NH clones, a single multiplication medium for all clones of this hybrid could not be determined. The best method of elongation for clones of all three hybrids involved culturing shoots on MS, 0.1 mg/l calcium pantothenate, 0.1mg/1 biotin, 0.35mg/1 NAA, 0.1mg/l kinetin and 0.1mg/1 IBA, under photoperiod conditions, rather than total darkness, for 6 weeks. This resulted in 82.3-86.6% elongation and shoot lengths increasing by 22.9-35.2 mm for GN clones, 80.2-82.3 % elongation and an increase in length of 24.7-32.2 mm for NH clones and 70.8-78.1 % elongation, and shoot elongation of 21.6-29.3 mm for GU clones from passage 1-2. For all the above stages, media contained 20/25 g/l sucrose and 3.5g/l Gelrite, and cultures were maintained at 25°C ± 2°C day/ 21°C night with a 16 h light/ 8 h dark photoperiod (PPFD 66µmol/m2/s). In terms of rooting, cultures on different media were initially subjected to a 72 hour period of total darkness at room temperature, then a 16 h light/8 h dark photoperiod (PPFD 37µmol/m2 /s) at 24°C day/ 21°C night for 7 days. This was followed by a 16 h light/ 8 h dark photoperiod (PPFD 66µmol/m2/s) at 25°C ± 2°C day/ 21°C night for 21 days. Tested clones of the three hybrids were all rooted successfully (56-93% rooting in GN clones, 36-76% rooting in NH clones and 46-96% rooting in GU clones) on a medium containing ¼ MS, 0.1 mg/l biotin, 0.1 mg/l calcium pantothenate, 0.1mg/l IBA, 0.22g/1 CaCI2 .2H20, 0.185g/l MgS04.7H2O, 15g/l sucrose and 3.5g/1 Gelrite. Predicted yields from the established protocol are also presented (168-667 plants of E. grandis x nitens (GN), 35- 854 plants of E. grandis x nitens (NH) and 54-349 plants of E. grandis x urophylla from 100 initial nodal explants, depending on the clone). Hence, the established protocols can be used successfully for some of the clones, but the implementation of specific media and methods to obtain high yields may still be necessary for certain clones.
Monitoring ground-level ozone and nitrogen dioxide in parts of KwaZulu-Natal and Mpumalanga (South Africa) by means of chemical and biological techniques.
(1998) Blair, Sharon Ann.; Cooke, John Anthony.
Surface ozone (O3) is one of the most toxic and abundant air pollutants. It has deleterious effects on human and animal respiration processes, and adversely affects plants. Four sites were selected for monitoring ambient O3 in the Durban metropolitan area: Botanic Gardens, University of Natal (UND), top of Kloof Gorge, and Mooi River. At each site tobacco Bel-W3 bioindicators, and NO2 and O3 passive diffusion tubes were placed. An O3 analyser (Dasibi 1108) was situated at the UND site. Monitoring was carried out for four weeks during summer, autumn and winter at each site, and during spring at the UND site. Two weeks of data from the diffusion tubes were collected during spring, from the Nelspruit area, Mpumalanga. Ozone concentrations measured with the Dasibi at the UND site were low in comparison to other urban-industrial areas in the world, with hourly values falling between 5ppb and 10 ppb. The highest hourly mean maximum recorded was 40ppb. A general spring/winter maximum and summer minimum was observed. This is typical of subtropical locations, where subsidence in prevailing anticyclonic circulation occurs. Diurnal characteristics included early morning minima and maxima at 12h00 in spring and summer, and maxima approximately two hours later in autumn and winter. This pattern was typical of that found in polluted environments, the magnitude, however, being lower. An unusual secondary nocturnal peak occurred during autumn, winter and spring. This could have been due to the long-range transport of relatively O3-rich air from a non-urban, high altitude inland area. Ozone concentrations were not strongly influenced by meteorological variables. Diffusion tube data indicated low O3, however, the coefficients of variation were high, implying a lack of precision in this technique. This technique would have to be improved before data obtained could be regarded as valid. Nitrogen dioxide, NO2, one of the precursors to O3, was monitored using diffusion tubes at the same sites. Concentrations were highest closer to the city centre, the highest concentration being 31ppb in autumn. In the Mpumalanga study, NO2 concentrations were higher in the city of Nelspruit than the surrounding areas. No significant differences were found in the O3 concentrations between the Mpumalanga sites. The tobacco plants showed the highest visible leaf injury in winter, corresponding with the higher Dasibi values, but there were no significant differences between the sites, and no significant differences in chlorophyll contents between the sites. In this study, O3-induced injury occurred below the previously established threshold of 40ppb.
Lion spatial socio-ecology : the effect of habitat on lion group dynamics.
(2000) Donkin, Deborah Anne.; Slotow, Robert Hugh.; Mills, Michael Gus L.
Lions are social, territorial animals that form prides of 2-18 individuals and hold territories ranging in size from 20 to 500 square km. My aim was to investigate the effect of ecological processes on lion spatial demography, specifically to determine the effect of habitat structure, prey availability, and rainfall (predictability and variability) on lion group dynamics. I worked with an extensive database of lion observations (approximately -+7000 over 29 years) from the Kruger National Park that had been recorded on monthly predator returns and in ranger diaries. I used the hypothesis of ideal free distribution to explain group dynamics across four physical habitat structures, namely, thickets, woodlands, mountainous areas and open tree savanna. There were larger groups of adults and more sightings than expected in the open tree savanna, while subadult and cub group sizes peaked in the woodlands. Using the resource dispersion hypothesis (RDH) as a base, I investigated lion group dynamics in relation to prey availability, I found agreement with the RDH, in that larger groups formed where their favoured prey species were in greatest abundance. Exclusively adult male and exclusively adult female group sizes increased with increasing buffalo abundance, while groups of adult males and adult females in mixed groups increased with increasing impala abundance. I used the mechanism of risk sensitive foraging to explain the influence of rainfall on lion group dynamics. While group dynamics did not differ significantly across averaged mean annual rainfall regions or across seasons, it did differ between variability regions and between two years of extreme rainfall. The lions exhibited risk-prone behaviour across variability regions, forming larger groups in more variable environments. Finally, I combined the three factors to determine the relative importance of each in determining lion group dynamics across seasons. Wildebeest were important to adult female group dynamics, impala and buffalo to adult males, while buffalo abundance influenced functional group size. In the wet season, larger functional groups occurred in the areas of medium rainfall variability regardless of buffalo abundance. In the dry season, more groups of females than solitary females occurred in more variable environments with this trend reversed for males.
Systematic revision of the golden mole genera : Amblysomus, Chlorotalpa and Calcochloris (Insectivora : Chrysochloromorpha ; Chrysochloridae)
(1995) Bronner, Gary N.; Meester, Jurgens Anthonie Jansen.; Rautenbach, Ignatius Lourens.; Cooke, John Anthony.; Willan, Kenneth Brian Ronald.
Patterns of variation in hyoid morphology, chromosomal properties and craniodental characteristics among ten chrysochlorid species from South Africa were studied to clarify generic relationships among taxa assigned variably to Amblysomus, Chlorotalpa and Calcochloris by previous authors. Intra-specific variation in hyoid morphology was negligible, but inter-specific differences were marked. Similarly, intra-specific karyotypic variation was negligible, except in A. hottentotus, which displayed three cytotypes. These data supported the recognition of Chlorotalpa, Calcochloris and Neamblysomus as taxa distinct from Amblysomus. Only one (presence/absence of M3) of the seven dental traits used by previous authors was consistent enough within species to be taxonomically useful in this work. Dental variability within species appeared to arise from the morphological differences between deciduous and permanent teeth, which may occur together in the same toothrow. Intra-specific craniometric variation in most species involved pronounced sexual size dimorphism, but negligible age-related variation. In the more widespread species, patterns of geographic variation were dominated by divergence in overall size, although subtle differences in cranial shape were also evident. Multivariate analyses confirmed the validity of subspecies in Chlorotalpa sclateri and Calcochloris obtusirostris, and showed that A. hottentotus (as traditionally recognized) includes: four cryptic species; five subspecies (including A. h. iris); and several populations that should be relegated to A. corriae. Inter-specific morphometric variation was dominated by overall size. The species fell into two size groups, and eight phena that differed mainly in skull width, palatal shape, rostrum breadth and claw size. Inter-specific relationships suggested by phenetic analyses of metric and mixed-mode data were, however, incongruent owing to discordance between different data suites. Evolutionary relationships inferred by integrating data suites, using either equal or differential weights, indicated that a strong phylogenetic signal was present in the data. Phylogenetic analyses showed that the differentially weighted treatment was more consilient with character-state distributions. A phylogram based on the differential-weights cladogram was used to derive a revised phylogenetic classification for the Chrysochloridae. Unlike previous treatments, this classification affords Carpitalpa and Neamblysomus generic rank, and assigns C. leucorhina from equatorial Africa to Calcochloris, rather than to Chlorotalpa.
The spatial ecology of lion (Panthera leo) and spotted hyaena (Crocuta crocuta) in Hluhluwe-iMfolozi Park : implications for the African wild dog (Lycaon pictus.
(2008) Graf, Jan Andreas.; Slotow, Robert Hugh.
The ecological role of apex predators in ecosystems is increasingly recognized not only as a result of their affects on prey species, but also on the numbers and behaviour of other predator species within their guilds. In an African context, dominant apex predators such as lions (Panthera leo) and spotted hyaenas (Crocuta crocuta) have been implicated in limiting endangered intraguild species such as wild dogs (Lycaon pictus) via direct intraguild interactions, such as interference and predation. As a result of this it has been predicted that spatial and temporal refugia are critical for wild dogs to co-exist with lions and spotted hyaenas. Whether such refugia are actually present within small protected areas, such as Hluhluwe iMfolozi Park (HiP), within which these three species co-exist, has been questioned. For wild dogs, interference or predation refugia may be equated to areas or periods which contain a relatively low level of encounter probability with spotted hyaenas and lions respectively. By combining well established field research techniques, such as radio telemetry and audio playbacks, with novel geographic information system tools, I investigated the two key drivers of the probability of encounter with spotted hyaenas and lions, namely density and utilization intensity. Results from the analyses showed that substantial spatial and temporal variation existed in the utilization intensity of lions, as well as the density of both lions and spotted hyaenas, at short and intermediate time scales, in HiP. The spatial scale across which these patterns resolved appear to be well suited to the movement capabilities of wild dogs. This indicated that wild dogs may be able to exploit such areas of temporary lower density and/or utilization intensity, suggesting the dynamic nature of refugia involved in the interactions within these two species-pairs. Results from the lion analyses further suggest that groups rather than individuals are the basic units around which intraguild interactions of social predator and prey species should be investigated, and that social grouping in combination with predator territoriality may stabilize intraguild interactions. An important prediction emerging from this work is that wild dogs, or other subordinate African large predator species, may be forced to trade-off safety from hyaena interference vs. safety from lion predation.
Detecting parasites loads in urine diversion toilets.
(2009) Hawksworth, David James.; Smith, Michael Trevor.; Rodda, Nicola Heike.
In an attempt to supply sanitation to the growing communities in rural and peri-urban areas around Durban, the eThekweni Municipality has installed urine diversion (UD) toilets which have been modified to suit local conditions . These toilets are based on the ecological sanitation (EcoSan) system. The future aims are to reuse waste as a composting medium and minimize the use of water but the presence of microorganisms in the faecal waste poses a potential health risk to people in contact with it. Currently the Municipality has not deemed the waste safe for re-use but has suggested that after a one year standing period it should be free of all potential pathogens including Ascaris lumbricoiodes (human roundworm) ova. This study reports on the development of the AMBIC protocol for the recovery of Ascaris ova from the standing vaults of UD toilets. The protocol has been shown to consistently recover over 70% of Ascaris ova and has the added advantage of recovering the ova of other helminth species (Trichuris trichiura and Taenia sp.) present in a UD standing vault sample. Recoveries of Ascaris ova and ova of other parasite species, namely Trichuris and Taenia sp., are reported from waste which has been standing for one year. This is cause for concern as it shows one year is not a sufficient standing period to render the waste free of all microorganisms. Sampling from 124 UD toilet vaults that were in use, showed a high prevalence of both helminth (Ascaris lumbricoiodes, Trichuris trichiura and Taenia sp.) and protozoan (Giardia and Cryptosporidium) parasites.
The development of an open space system for the Queensburgh municipal area.
(1994) Seppings, Kerry Ann.; Cooke, John Anthony.
This project was conducted with the view of extending the Durban Municipal Open Space System into surrounding municipalities. It was aimed at adopting a holistic approach to nature conservation by providing for the needs of the current human population whilst ensuring the long term survival of representative natural biota of the area. A preliminary study was conducted to: provide a basis for a more detailed vegetation survey; to assess the current public open space areas and to determine the land use history of the area. The vegetation was categorised into 14 community types and mapped to provide the basis for more detailed sampling. A survey of public open spaces revealed that most of the public parks were not providing for the needs of the local residents and that nature reserves and sports fields were more popular than conventional public parks. The land use history study revealed that the study area has been utilised for: cultivation; grazing; market gardening and more recently residential and industrial development purposes. A vegetation survey using phytosociological methods revealed that the vegetation in Queensburgh was dominated by alien invasive plant species although pockets of indigenous vegetation did occur. Drawing from the principles of reticular biogeography an open space system was designed using the information gained from the vegetation survey and preliminary study. The design included: 4 core areas where conservation was a priority; 3 corridors linking the core areas and a number of buffer areas. A general management plan was subsequently developed for the system. Management suggestions were concerned with: ecological; economical and sociological aspects. The open space system offers Queensburgh the opportunity to contribute to the national reconstruction and development program (RDP) by upgrading the current standard of living of the local residents without compromising the natural resources available to future generations.
The effects of sediment disturbance on the macrobenthos of the St. Lucia Narrows, Natal.
(1992) Owen, Rodney Kenneth.; Forbes, Anthony Tonks.
Estuarine studies worldwide have shown that sediment disturbance effects on the macrobenthos are reIated to the nature and scale of the disturbance. Decreased species densities, diversity and richness have been found where the substratum and current patterns have been altered either by direct removal or by the creation of channels . Sediment disturbance in the St. Lucia Narrows has occurred through dredging, beam trawling and episodic floods. The Narrows, a meandering tidal channel approximately 21 km long linking the st Lucia Lakes to the sea, were dredged between 1952 and 1971 to provide a greater flow of seawater to the lakes during periods of low lake levels. A canal was cut through land from the Mfolosi River to the Narrows in an attempt to ameliorate hypersaline conditions in the Lakes, but was never commissioned. Beam trawling has formed the basis of a prawn bait fishery since the 1930's. The bait boats trawl on the mudflats over the entire Narrows on a daily basis and often churn the substratum with their propellers. The objectives of this study were to determine the effects of dredging, a once-off large scale disturbance, and beam trawling, a frequent small scale disturbance, on the macrobenthos of the Narrows. Studies in 1983 and 1984 showed that the dredged channel was impoverished compared with the adjacent mudflat, and that the Link Canal was devoid of benthos. In 1988 species densities, especially of polychaetes, were found to be lower in areas open to beam trawling than in adjacent closed areas. The dredged channel during the present study was again impoverished compared with the adjacent mudflats. The three most abundant species occurring on the mudflats, the crab Tylodiplax blephariskios, the amphipod Victoriopsia chilkensis and capitellid polychaetes, were recorded at densities an order of magnitude lower in the channel than on the mudflats. The substratum in the channel was generally sandier than the mudflats, and this condition appeared to be maintained by the scouring action of tidal currents. It was calculated that the creation of the dredged channel had reduced the standing benthic biomass in the Narrows by a minimum of approximately 20%. The Link Canal was colonised by the three major mud flat species , but at densities an order of magnitude lower than the mudflats. Beam trawling of experimental sites at monthly and 6-monthly intervals on muddy and sandy substrata in the Narrows between July 1989 and July 1990 did not appear to have a negative effect on the benthos. The coverage of the bait boats was calculated to be comparable to the trawling effort in this study, and suggested that the bait fishery is not having a detrimental effect on the benthos. It was concluded that the macrobenthos in the Narrows represented a pioneering community characteristic of estuaries, either not affected by, or able to recover from small scale and episodic disturbances provided that there was no long term habitat modification.
DNA restriction fragment length polymorphisms in the identification of clonal variants of eucalyptus.
(1993) Coulson, Mornay.; Huckett, Barbara Isobel.; Watt, Maria Paula Mousaco Deoliveira.
The technique of restriction fragment length polymorphism (RFLP) analysis, of chloroplastic and genomic DNA, was investigated as a means of identifying eucalypt species and cultivars which are morphologically indistinguishable from one another. In order to resolve chloroplast DNA (cpDNA) RFLPs, a method was developed to extract high yields of intact chloroplasts from Eucalyptus grandis S/N M6. Starch contamination was reduced by incubation of saplings in the dark for 48 h prior to extraction and watering with a solution containing 370 mM Na-phosphate and 296 mM KN03. Optimal chloroplast yields (25 ug chlorophyll/g fresh mass) were obtained by chopping leaf material, using a vertical homogenizer, in a buffer containing 350 mM sorbitol, 50 mM tris-HCL and 5 mM EDTA, 0.1 % (w/v) bovine serum albumin, 0.15 % (w/v) 2-mercaptoethanol, 2 mM L-ascorbic acid and 1 mM MgCI2 followed by washing of leaf pieces in a buffer containing only sorbitol, tris-HCL and EDTA. When these chloroplasts were used in an "in-organelle" DNA digestion procedure, polymorphisms were observed between the cpDNA profiles resolved for E. grandis S/N M6 and that of an outgroup species (spinach). However, the developed chloroplast extraction technique could not be used to obtain chloroplasts from various other eucalypt species, probably as a result of variability in the material at an ultrastructural or biochemical level. For the analysis of genomic DNA RFLPs, a DNA extraction procedure was optimized for use with various eucalypt species and cultivars. This included the development of a purifcation technique during which DNA was ammonium acetate-ethanol precipitated and subjected to mini-dialysis. Following Dra I restriction of DNA, the extract was electrophoresed and Southern blotted onto both nylon and nitrocellulose membranes. These were probed with a Hind-III restricted sample of the multilocus plasmid probe pV47-2. This probe was labelled using 32p as well as a non-radioactive labelling substance digoxygenin (DIG). Hybridization conditions, including the composition of the hybridization buffer, were optimized for use with these labels, and DNA RFLPs (fingerprints) were resolved for the eucalypt species E. grandis and E. macarthurii and cultivars of E. grandis (S/N M6, TAG 5 and TAG 14). An average of 8.5 bands were detected with 32p and 5.0 fragments with DIG. All the species and cultivars fingerprinted with the 32P-label could be distinguished from one another. However, as a result of the reduced sensitivity of the DIG system, two of the E. grandis cultivars, S/N M6 and TAG 5, could not be differentiated. It is concluded that the latter system would be most suitable for incorporation into a routine eucalypt screening programme, although it is suggested that the colourimetric detection assay, used in this study to resolve DNA bands, be replaced by a more sensitive one.
The effects of elephant and mesoherbivores on woody vegetation.
(2011) Lagendijk, Daisy Diana Georgette.; Slotow, Robert Hugh.; Page, Bruce Richard.
Herbivores are important drivers and have a longstanding history in shaping our terrestrial environments. However, during the past decades, changes in woody vegetation in savanna and forest systems have been observed in southern Africa. Subsequently, concerns have been raised about the loss of (tall) trees in areas with elephant. The relative effects of browsing herbivores on vegetation and the potential browsing interaction with other herbivore species remain unclear and were examined using vegetation transects and exclosure experiments in savanna woodland and Sand Forest. Rainfall, fire and elephant were important savanna determinants. Especially rainfall positively affected woody densities, which were negatively affected by a longer exposure time to elephant, but not to elephant densities itself. In general, within South Africa’s savannas, tree height classes were absent from the population demography. Different height classes were likely to be impacted by different drivers. For example, seedling and sapling densities were greater with longer fire return periods and increased rainfall. The Sand Forest exclosure experiments showed that forest regeneration was impacted by nyala and both elephant and nyala, as the absence of both species increased tree densities. Both species combined, and individually, also affected tree species assemblages. In contrast, short term elephant access to a savanna area did not affect tree densities or species assemblages. In both savanna and Sand Forest elephant displaced mesoherbivores, and in Sand Forest both elephant and mesoherbivores displaced their smaller counterparts. The presence of competitive displacement also affected recruitment (i.e. seedlings and/or saplings) of woody vegetation both in Sand Forest and savanna. Thus, elephant and mesoherbivores exert direct and indirect (i.e. competitive displacement providing a window for recruitment) impact on vegetation. Active management of the herbivore species assemblage affects both vegetation and other herbivores, which effects potentially cascade into lower trophic levels, jeopardising biodiversity and ecosystem processes. Therefore, the full herbivore assemblage present and their combined and individual browsing effects need to be considered when setting management goals to conserve habitats and biodiversity across all trophic levels. In addition some contrasting results between Sand Forest and savanna emphasise the need for caution when extrapolating results from different areas and ecosystems.
Conserving forests : a biophilosophical analysis of the Durban region.
(1993) Mattson, M. C.; Poynton, John Charles.
Coastal forests are a significant component of the remaining natural vegetation in the greater Durban area. Being closely associated with an historical and rapidly developing urban environment, these forests are invariably small, isolated and variously disturbed. The nature of disturbance as an ecological phenomenon, coupled with unknowable disturbance histories and ongoing disturbance events poses particular challenges to traditional and tradition-bound attempts to understand and manage such forests. The intention of this study was to discuss as deeply as possible the nature of such challenges, while at the same time considering the broader relevance of practising ecology in the urban environment. At a practical level the forests were sampled in an attempt to describe forest communities, to assess the effects of disturbance on them, and to gain insight into the effects of different disturbance histories and regimes on forest physiognomy and floristics with a view to proposing management guidelines. Various descriptive approaches, as well as a multivariate analysis using Detrended Correspondence Analysis were used in an attempt to interpret the data collected. The unsatisfying nature of the data led the thesis to propose a review of the paradigm in which its methods were rooted. Both the data, and the broader issues on which the thesis touched were discussed in terms of biology's rootedness in philosophical assumptions. This led the thesis to a methodological position aligning it both epistemologically and ontologically with a philosophical method of investigation called phenomenology. While other philosophical contentions were touched upon, the main conclusion of the thesis was that phenomenological thinking, while challenging to apply, was relevant to philosophically mature and methodologically appropriate attempts to conserve the forests with which the thesis was concerned.
Micropropagation and in vitro studies of Pinus patula Scheide et Deppe.
(1993) McKellar, David Stuart.; Watt, Maria Paula Mousaco Deoliveira.; Herman, Barri.
For the South African forestry industry, the patula pine (Pinus patula) is the most commercially important softwood species. A pine clonal programme has yet to be fully implemented in this country and at present much effort is being made to establish clonal plantings of selected trees. In order to accomplish this, it is essential that satisfactory commercially viable propagation technologies be developed for this species. This study examined the possibilities and constraints of three different in vitro systems for mass propagation of rare and important P. patula material. Seed germination and sterilisation techniques were developed for adventitious bud and somatic embryogenesis experimentation. Adventitious buds were initiated from excised 'mature P. patula embryos cultured on LM medium containing 5 mg 1-1 BA. Although, between 50 and 60% of the embryo explants produced adventitious buds, only 3-5 buds per explant actually developed further to form distinct shoots. The adventitious shoots elongated slowly (±8 mm in 2 months) on LM medium, containing 10 g 1-1 activated charcoal. Axillary buds were induced on 10 week-old juvenile shoots, after the development of an effective surface sterilisation procedure, using 0.02% HgCL2. The effect of removing the apex and trimming the needles on bud induction was significant. Dwarf shoots elongated at a rate of 25 mm in 5 weeks. Rooting studies conducted on juvenile P. patula shoots indicated that the most effective treatment was wounding the shoot base and placing the shoot in composted bark growing medium, under a greenhouse mist regime. Rooting percentages were low (50%). Included in this study is the first successful production of somatic pro-embryos from mature Pinus patula embryos. Calli were produced on LM induction medium containing 2 mg 1-1 2,4-D. Cultures were first placed in the dark for 4 weeks and then transferred to a 16 h photoperiod for a further 2 weeks, after which Stage 1 embryogenic cells were observed. When calli were placed on LM maturation medium, containing 12 mg 1-1 ABA, for a further 6-8 weeks, pro-embryo structures (maximum of 7 pro-embryos per callus) were detected embedded In the callus mass. Hence, investigations into the development of protocols for the micropropagation of Pinus patula, were undertaken. Two major constraints for applying in vitro techniques to the commercial production of pine were identified: the poor yield of shoots and pro-embryos and the length of time taken for plantlets to be produced. This study, however, provides some fundamental knowledge and background work required by tree breeders who wish to implement biotechnological techniques in the selection and improvement of P. patula genotypes.
A study of some of the inter-relationships between maize and the seed storage fungi as typified by Aspergillus flavus var. columnaris.
(1990) Mycock, David John.; Berjak, Patricia.
The seed storage fungi (xerotolerant) species of the genera Aspergillus and Penicillium} are renowned for their devastating effects on stored grain and grain products. In view of the fact that most of these fungi Iiberate toxins which can be harmful to both man and his livestock this problem is becoming increasingly relevant, particularly in developing countries. The seed storage fungi are said to be saprophytes and opportunistic invaders of dead or naturally dried organic matter, and as such no direct host-pathogen relationship has been ascribed to them. This dissertation reports aspects of an investigation into the modes/pathways utilised by these fungi in their infection of maize caryopses (seeds) and plants. The work involved studies on: the effects of protracted storage on maize seeds; the morphology of storage fungi; extra-cellular enzymes of storage fungi; the pathways utiIised by the storage fungi in invasion of seed tissues; and the effects of the storage fungi on the seeds. Correlations have been made on a species basis between the extent of seed deterioration and fungal aggressiveness. The results of these investigations indicated that apart from affecting seed vigour and viability, these fungi can also affect plant vigour. This latter aspect was further investigated to determine whether a seed storage fungus could infect germinating maize seeds, and remain an internal contaminant of the tissues during plant growth and development. These latter studies revealed that Aspergillus flavus var. columnaris is capable of systemic transmission from one seed generation to the next. This hitherto unrecognised phenomenon apart from indicating that the fungal species is in fact a biotroph as well as a saprophyte, also has implications In control measures.
The sardine run : investigating sardine and predator distribution in relation to environmental conditions using GIS and remotely sensed products.
(2009) O'Donoghue, Sean Henry.; Peddemors, Victor Marten.
The sardine run is a spectacular but poorly understood natural phenomenon. This research aims to broaden scientific knowledge pertaining to sardine, Sardinops sagax, distribution, both in relation to their predators and environmental conditions. Sardine distribution was closely related to sea temperature. Sardines were sighted every year along the Lower Wild Coast, where continental shelf conditions were cooled by the Port Alfred upwelling cell. To the north of Mbashe River, shelf conditions were dominated by the warm Agulhas Current, and sardine distribution varied annually in close relation with sea temperature conditions. Along this coastline sardine abundance always peaked between Waterfall Bluff and Port St Johns with favourable conditions caused by the westward inflection of the coastline and the shelf bathymetry. Topographically-induced upwelling was concluded to be the cause of cooler sea temperatures and elevated chl a concentrations. Although chl a concentration appeared to be associated with east coast sardine distribution, the uncertainty with regards data accuracy hindered their usefulness as a predictor of suitable biological conditions for sardine. Sardine northward movement along the KZN coastline was impeded adjacent to the Durban Eddy, where they were forced shorewards by the warm conditions. This coincided with the peak in beach seine catches. The Cape Gannet, Morus capensis, was very closely associated with sardine along the entire east coast. Their abundance declined substantially adjacent to the Durban Eddy. Prevailing atmospheric conditions affected gannet behaviour: they travelled more frequently during strong alongshore winds and foraged more upon cessation of such winds. Gannets were closely associated with feeding dolphins at both coarse and fine scales, and responded to changes in dolphin behaviour. Common dolphin, Delphinus capensis, abundance and group size peaked between Waterfall Bluff and Port St Johns. Along this stretch of coastline they travelled more slowly, and in pods more perpendicular to the bathymetry of the region. Bottlenose dolphin, Tursiops aduncus, abundance increased during the sardine run with the influx of a migrant stock which reached the KZN Mid South Coast. Humpback Whale, Megaptera novaeangliae, and sardine distributions did not appear to be related.
Aspects of the ecology of sandy beaches along Durban's urbanised coastline.
(2009) Govender, Natasha.; Schoeman, David S.; Smit, Albertus J.; Roberts, Debra Cynthia.
Urban sandy beaches are the primary focus of numerous pressures. Among these are the disruption of sand budgets because of an increasing demand for coastal infrastructure, pollution from landward sources, and recreation and the associated stressors such as trampling and off-road vehicles. More recently, climate change and the manifestations thereof, such as sea-level rise and increased storminess have added to the suite of threats to sandy beach ecosystems. Despite being important natural and economic resources these urban systems have not received adequate research attention and, consequently, the management of sandy beaches has been based on ecologically unsustainably principles. The aims of this study were to provide baseline biodiversity information of urban beaches along the Durban coastline, South Africa, as a step toward the application of improved ecological management procedures for metropolitan beach ecosystems. Macro- and meiofaunal communities of 15 representative beaches along the Durban coastline were quantitatively surveyed using standard sandy beach sampling protocols. This study showed that Durban’s beaches, despite being highly urbanised, harbour rich and abundant faunal communities. This is contrary to previous findings that reported a paucity of life on Durban beaches. A total of 23 macrofauna taxa were identified, with the dissipative Battery Beach having highest diversity with 13 macrofaunal species. La Lucia, a reflective beach, had the highest macrofaunal abundance and was the second most diverse beach, thus departing from global trends that report a poor macrofaunal community of reflective beaches. Twenty higher-level meiofauna taxa were recorded in this study and it was found that meiofauna abundance showed a significant and positive relationship with beach width. Because of the coarse taxonomic resolution, meiofauna diversity may likely be much greater than that recorded in this study. The conventional view that sandy beaches are resilient to exploitation was questioned when it was found that meiofauna assemblages were significantly and negatively impacted by stormwater outlets on two of the sampled beaches, possibly through freshwater intrusion or erosional effects. This raises questions regarding the functioning of beach ecosystems, and the services they provide, when faced with anthropogenic stressors that impact faunal communities. This snapshot survey of aspects of the ecology of Durban’s sandy beaches has provided much needed baseline data for this coastline. These data will be used in conjunction with other available data toward the development of a fine scale systematic conservation plan for Durban to enable the prioritisation of conservation and management efforts. The use of these data will also facilitate the development of guidelines for the integrated ecological management of urban sandy beach ecosystems.
The use of the toxicity identification and evaluation (TIE) protocol in the Port of Durban, South Africa.
(2011) Parsons, Gary Angus.; Vosloo, Andre.; Trotter, Dayle Carey.; Cooke, John Anthony.
The Port of Durban, with its close proximity to industrial, urban and agricultural activities, receives a number of chemical pollutants that settle out and accumulate in sediments. Chemical analysis of these sediments has indicated elevated levels of chemicals that, according to sediment quality guidelines, might cause adverse biological effects. However, elevated concentrations alone do not necessarily imply that chemicals are present in bioavailable concentrations high enough to be harmful to organisms that come into contact with them. Thus, chemical tests alone cannot provide an accurate indication of the potential adverse biological effects of these chemicals. In this regard, toxicity tests of sediment porewaters have been developed using sea urchin gametes to assist in determining the bioavailability of chemicals present in porewaters. Further, procedures such as Toxicity Identification and Evaluation (TIE), which involves the manipulation and/or treatment of toxic porewater, have also been developed to assist in the isolation and identification of chemicals causing porewater toxicity. In this research, on a number of sampling occasions between July 2007 and July 2009, three replicate sediment samples were extracted from a site in the Port of Durban known to contain sediment with potentially toxic porewater. Results of initial toxicity tests, using the sea urchin fertilisation test indicated the presence of toxic porewater although, in some instances, porewater toxicity was highly variable between replicate samples. However, results from TIE procedures performed to reduce potentially toxic concentrations of metals, ammonia and organic compounds did not resolve the primary cause of porewater toxicity. Further research indicated that chemicals including hydrogen sulphide, which can occur naturally in organically enriched sediments, may have been confounding factors that masked the potential toxicity of other chemicals present in the sediment samples. Consequently, a sampling strategy and modified TIE procedure have been recommended. The sampling strategy has been designed to assist with detecting and understanding any sample variability that may occur. The modified TIE procedure, which suggests initial procedures to determine and reduce/remove the possible confounding effects of potential naturally occurring compounds such as hydrogen sulphide from the porewater, could be used in future to understand and evaluate the quality of contaminated sediments from similar environments.
The health-related microbial quality of drinking water from ground tanks, standpipes and community tankers at source and point-of-use in eThekwini Municipality : implications of storage containers, household demographics, socio-economic issues, hygiene and sanitation practices on drinking water quality and health.
(2009) Singh, Urisha.; Smith, Michael Trevor.; Rodda, Nicola Heike.
The aim of this study was to investigate the microbiological quality of drinking water at the source (taps at eThekwini laboratories, standpipes and mobile community tankers) and corresponding point-of-use (storage containers and ground tanks) supplied to peri-urban areas in Durban by eThekwini Municipality. It also aimed to identify factors associated with deterioration in water quality such as storage of water, household demographics, hygiene and sanitation practices. In order to determine the microbial quality of drinking water, the pour plate method (for enumeration of heterotrophic organisms) and the membrane filtration technique (for total coliforms and E. coli enumeration) were used. Conductivity, turbidity, pH and total and residual chlorine levels of drinking water were measured. Microbial and physico-chemical data was collated and statistically analysed with epidemiological data from an associated study to determine the link between microbial quality of drinking water, household demographics, health outcomes, socio-economic status, hygiene and sanitation practices. Findings showed that all point-of-use water was unsafe for human consumption as a result of either poor source water quality, in the case of standpipes, and microbial contamination at the point-of-use, in the case of ground tanks and community tankers. The latter could be attributed to unsanitary environments, poor hygiene practices or poor wateruse behaviour. Households which included children aged 0-5 years and in which open-top containers were used for water storage had the highest rates of diarrhoea and vomiting. Water from ground tanks had the best microbial quality but people in households using this water presented with the highest rate of diarrhoea. Therefore provision of microbially safe drinking water will not reduce the rate of health outcomes if addressed in isolation. In order to reduce water-associated illness, provision of safe and adequate amounts of water, hygiene and sanitation education and education on water-use behaviour should be provided as a package. The provision of improved water delivery systems does not ensure that drinking water is safe for human consumption. Measures, such as point-of-use water treatment should be considered to ensure that drinking water provided at the source and point-of-use is microbially safe for human consumption.
The effect of wastewater works on foraging behaviour and metal content of Neoromicia nana (Family : Vespertilionidae)
(2011) Naidoo, Samantha.; Schoeman, Marthinus Cornelius.; Vosloo, Dalene.; Mackey, Robin L.
Anthropogenic disturbance from urbanization has introduced a range of contaminants into freshwater ecosystems. Wastewater Treatment Works (WWTW) in particular, deposit effluent with high metal concentrations directly into rivers. These pollutants may affect river biota directly or through modifications to habitat and prey. Therefore, the impact of metal pollution through a food chain should be evident in high trophic level predators such as Neoromicia nana. N. nana is a small, insect-eating bat that occurs in forest and riparian habitats in Africa. Most importantly, it is an urban exploiter, i.e. a species that takes advantage of anthropogenic food and habitat resources. I investigated the foraging behaviour and metal content of N. nana at wastewater-polluted sites (WWTW sludge tanks and sites downstream of wastewater discharge into the rivers) and unpolluted sites (sites upstream of wastewater discharge) at three urban rivers in Durban, South Africa, during winter and summer. To assess water quality, I determined cadmium, copper, chromium, iron, nickel, zinc and lead concentrations using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). To investigate the foraging behaviour of N. nana, I quantified relative N. nana abundance, and feeding activity from recorded echolocation calls. Using ICP-OES, I quantified metal concentrations in three tissues (liver, kidney and muscle). My results show that concentrations of most metals were generally lowest upstream, intermediate at downstream sites and highest at the tanks. The relative abundance and feeding activity of N. nana were significantly higher at wastewater-polluted sites than at upstream sites, despite there being significantly more insect orders upstream. However, pollution-tolerant Chironomidae (Diptera), were significantly more abundant at wastewater-polluted sites. Indeed, at wastewater-polluted sites, Diptera represented the highest percentage of insects in the diet of N. nana. Essential metals (copper, zinc and iron) were detected in all tissue samples of N. nana. In contrast, the toxic metals cadmium, chromium and nickel were present in tissue of bats only at wastewater-polluted sites (except one upstream occurrence of cadmium). This suggests that these metals may accumulate in tissue through the ingestion of pollutant-exposed prey. Thus, metal pollution from WWTWs affects not only water quality of rivers, but also the diversity of resident aquatic insects and ultimately the ecology of N. nana populations, which may pose serious long-term health risks for these top predators.
The relative influence of local and landscape processes on the structure of insectivorous bat ensembles in urban nature reserves.
(2012) Moonsamy, Shivani.; Schoeman, Marthinus Cornelius.; Mackey, Robin L.
Urbanization is arguably the most damaging and rapidly expanding threat to biodiversity. The process of urbanization results in the fragmentation of natural habitat into patches that are disjunct and isolated from one another. Biogeography theory predicts that landscape processes, including fragment size and isolation, should predominate in species assembly. However, these predictions have not been tested on African bats in urban landscapes. Bats are important models for urban studies because they comprise more than a fifth of all mammals, and play vital roles as primary, secondary and tertiary consumers that support human-dominated ecosystems. Furthermore, there is evidence that local, biotic processes specifically competition and prey defences are important determinants of species composition patterns. In this study, I investigated the relative influence of local and landscape processes on the species composition patterns of insectivorous bat ensembles in Durban. Using active capture methods and passive monitoring, I sampled the insectivorous bat ensembles of eight nature reserves in Durban between 2008 and 2010. I used multivariate analyses to test predictions from biogeographic and climate hypotheses, and I used null model analyses to test predictions from competition and nestedness hypotheses to determine whether the bat richness patterns were significantly different from patterns expected by chance. Species richness estimators indicated that species inventories for ensembles were fairly complete (i.e. estimated species richness was not much larger than observed species richness). Multiple regression analyses showed that there was a significant parabolic relationship between species evenness and daily maximum temperature, and there was a significant negative relationship between relative activity and reserve shape. However, I found no evidence that competition influenced species composition patterns. Conversely, I found support for the nestedness hypothesis: species in species-poor ensembles were subsets of species in species-rich ensembles. Spearman rank correlation indicated that the degree of nestedness was significantly correlated with maximum temperature. My results suggest that in urban landscapes, abiotic processes operating at the landscape scale may be more important determinants of composition patterns of insectivorous bat species than biotic factors operating at a local scale. Furthermore, bat species that forage in cluttered habitats may not be able to persist in urban landscapes.

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