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Tribute to the late Davadoss

- EIMWU

Authors: EIMWU
Date: 1990
Subjects: Engineering Industrial and Mining Workers Union (EIMWU)
Language: English
Type: text
Identifier: http://hdl.handle.net/10962/162344 , vital:40921
Description: To my knowledge the author of this adage was Brother Davadoss. Better known to many, far and wide, as “DAVVY”. Lesley Davadoss was one of nine children of a working class family. Grew up and spent his formative years in Bokmakierie, Athlone. Devout in his Catholic upbringing, later to be ordained as a Deacon at St. Mary of the Angels. Lesley was a very sincere person who concerned himself with the needs of the Community, which naturally resulted in his involvement at the Company where he worked with the problems of his workmates. Along with other like thinking persons, he formed the E.I.W.U. in the Cape, holding meetings at his home in Kayter Road Crawford. The Branch in Durban, along with the Cape Town Branch formed E.I.W.U.S.A.
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Date Issued: 1990

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Tribute to the late Violet Seboni, 1965-2009

- South African Clothing and Textile Workers' Union

Authors: South African Clothing and Textile Workers' Union
Date: 2009?
Subjects: South African Clothing and Textile Workers' Union , Labour unions -- South Africa
Language: English
Type: text , pamphlet
Identifier: http://hdl.handle.net/10962/110537 , vital:33297
Description: Violet Seboni was born on 18 September 1965. It was to be a turbulent start to life for this young girl who never got to know her father, in a story that started in sadness. And shortly after her birth, it was her mother too that she lost in circumstances that no one should experience. She knew pain and later in life she stood up for those in pain. Young Violet was raised by her grandmother for the first few years of her life, and when her grandmother died, it was her granny’s friend - in a culture where ubuntu requires that we reach out to others - who took on the responsibility to rear the young girl and to become her comforter, her provider, her mother. Violet went to primary school and later to Madibane High School in Diepkloof, where she developed a love for netball and a passion for activism. After high school, she became pregnant and her beloved daughter Lesego was born. She looked for work, and like generations of young, working- class women before her, she turned to the clothing industry, to use her hands, her dexterity and her skill to earn a living to feed her young family. The role the industry plays, to give work, bread and life to those in need, is in itself a reason not to let the industry die simply due to the cold, harsh winds of global competition and indifference or inaction from those who have the power to intervene, to use trade measures and to use industrial policy tools to save jobs and absorb our people into decent work opportunities. The industry that young Violet chose is one whose factories in Joburg grew with the discovery of minerals and the rapid growth of an urban population that needed to be clothed. Violet’s predecessors in the industry were white women sewing machinists, mainly Afrikaners, often the wives and daughters of the Afrikaner mineworkers who as 'by-woners', were like their black brethren, driven off the land and into the cities hungry for labour. Trade unionism took root among the male mineworkers - Die Mynwerkers Unie was their vehicle - and among female garment workers - through the Garment Workers Union. , A new growth path for decent work in the clothing, textile, footwear and leather industry
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Date Issued: 2009?

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Triggering biodegradation of low-density polyethylene films containing biobased additives for ecological applications

- Gada, Abongile

Authors: Gada, Abongile
Date: 2019
Subjects: Refuse and refuse disposal , Plastics industry and trade -- Waste disposal Polyethylene Polyurethanes
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/39796 , vital:35460
Description: The aims of the present study are focused on the investigation of low-density polyethylene (LDPE) films that contain biobased pro-oxidizing additives (CSIR1% and CSIR3% (w/w)) for environmental degradation in different abiotic and biotic conditions in comparison to non-biodegradable commercially available Pick n Pay (PnP) PE grocery bags. In this project, a biobased pro-oxidant additive master batch was prepared in a heat kneader mixer. A mixture of biobased radical reaction initiators and natural polymers were melt processed as a master batch. The biobased pro-oxidant additive master batch CSIR1% and CSIR3% and LDPE components were melt-extruded to form biobased pro-oxidant additive LDPE pellets using a twin screw melt extruder. The pelletized biobased pro-oxidant additive LDPE was blown into a 25 -27 μm thick film using a melt blower machine. The LDPE containing biobased pro-oxidant additive CSIR 1% and 3% test samples and the PnP polyethylene carrier bags were submitted to thermal oxidizing test conditions in a 70°C air ventilated oven and direct sunlight (photo oxidation) for a period of six months (180 days). The thermal and photo-oxidized LDPE film test samples were further subjected to biotic degradation tests in aqueous, soil and compost environments for varying periods of 180 days to 263 days in biodegradation evaluation studies. The oxidation degradation rates of the test samples were monitored and determined by evaluating carbonyl index (COi) using FT-IR spectroscopy; molecular weight determination and distribution of the test materials were analyzed by Gel Permeation Chromatography (GPC); compounds analysis was done by GC-MS; percentage crystallinity (Xc%) was quantified by DSC; thermal stability by TGA and morphological surfaces were examined by SEM analytical techniques. Biodegradation tests simulating marine salt water, burial in soil and compost conditioning methods were used to determine the “potential biodegradability” of the thermally and photo-oxidized test samples after the oxidation period. The oxidation extent and rate of LDPE films containing CSIR3% biobased additives was higher than that of LDPE films containing CSIR1% biobased additives. GPC molecular weight determination and distribution results showed a decrease for all the test samples exposed to oxidation. The molecular weight of LDPE films containing CSIR1% biobased additives decreased from 404K Mw to 111K Mw for sunlight oxidized samples and to 16KMw for the thermally oxidized LDPE samples after 200 days of oxidation exposure. Molecular weight of LDPE films containing CSIR3% biobased additives showed the most reduction from 293K Mw to 22K Mw for sunlight oxidized samples and to 2K Mw for thermally oxidized samples after 100 days of oxidation exposure. DSC analysis showed that crystallinity degree decreased after exposure to thermal and photo-oxidation. TGA results showed a reduction of initial degradation temperature by almost half compared to zero-days untreated CSIR3% samples, with higher degree temperatures observed in samples exposed to thermal oxidation than those exposed to photo-oxidation. GC-MS revealed peaks of carbonyls such as alcohols, aldehydes, ketones, carboxylic and anionic acids, and very short chain alkenes and alkanes. The SEM showed heterogeneous morphological modifications in surfaces of samples even though they were not severe. After 172 days the oxidized LDPE samples containing CSIR3% biobased additives, were investigated for potential biodegradation in aqueous, soil and composting environments. Thermally oxidized and photo-oxidized CSIR3% samples showed a mineralization degree of 10.4% and 10.7% respectively, when oxidized in 181 days aqueous biodegradation, 20% and 7.7% respectively, when oxidized in 233 days of soil burial, and 52.6% and 62% respectively, oxidized in 263 days of compost. The obtained results confirmed the abiotic oxidation step as the initiation step for PE degradation, succeeded by assimilation, by action of microorganisms (ultimate biodegradation), of lower weight molecular compounds of oxidized LDPE samples in aqueous medium, soil and composting conditions to final end products of CO2, H2O and new microbial cell biomass.
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Date Issued: 2019

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Triggering physics lecturers' reflections on the instructional affordance of their use of representations: a design-based study

- Lombard, Elsa Helena

Authors: Lombard, Elsa Helena
Date: 2014
Subjects: Physics -- Study and teaching , Physics -- Research
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/2899 , vital:20361
Description: There is growing awareness in the physics education research community about the importance of using representations in physics teaching and the need for lecturers to reflect on their practice. This research study adopted a design-based research approach in an attempt to design a reliable, valid and practically useful artefact (framework/strategy) that could be used to trigger introductory physics lecturers’ reflections on their instructional use of representations. The artefact, which was instantiated with physics lecturers, comprised an observation protocol, an accompanying definitions key, a communication platform, and an instrument to assess the outcome (the levels of reflection). The video-data of lecturer practice were analysed using a priori codes to generate profiles of teaching practice. The resulting profiles were used to trigger individual video-stimulated reflection. The levels of reflection were assessed using a purpose-designed ‘Expectations of Reflection’ taxonomy. Thereafter a set of design guidelines and design principles were generated to guide further similar design-based educational studies. The process was validated via interview data but, while it was deemed a valid and reliable solution to the research problem, there were varying levels of perceived value of the artefact among the participating lecturers.
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Date Issued: 2014

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Triggers and barriers to youth entrepreneurship in the Eastern Cape South Africa

- Chindoga, Lynety

Authors: Chindoga, Lynety
Date: 2011
Subjects: Youth development -- South Africa , Entrepreneurship -- South Africa -- Eastern Cape , Young adults -- Employment -- South Africa
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10353/25948 , vital:64636
Description: To realise the dream of the African Renaissance and a better life for all South Africans, the entrepreneurial energies of all people, including children, should be harnessed to contribute towards economic development, job creation and poverty alleviation. Entrepreneurship creates wealth and results in economic prosperity for a country. However, in South Africa, entrepreneurship still remains a dream yet to be realised. This is supported by the findings of Maas and Herrington (2006), who identified entrepreneurial activity in South Africa to be very weak as evidenced by a low Total Entrepreneurial Activity (TEA) rate. Youths are not engaging in entrepreneurial activity and are making the bulk of the unemployed in South Africa. The primary objective of this study was to investigate the perceived triggers and barriers to youth entrepreneurship in South Africa. Two sets of questionnaires were self- administered to high school students and university students. The respondents which consisted of three hundred and twenty three university students and two hundred and fifty six high school students, were selected using simple random sampling method. Five point Likert scale was used to measure the responses. Descriptive as well as inferential statistics were used to analyse the data. The results indicated that youth entrepreneurial intention is low in South Africa. The results also indicated that students perceived mainly extrinsic rewards, market opportunities as well as intrinsic rewards as the three top triggers towards entrepreneurial intention. Independence/autonomy and capital were also regarded as triggers to entrepreneurial intentions. The barriers to youth entrepreneurship included lack of capital, skill and support as well as lack of market opportunities and risk. The study recommends that in order to encourage youth entrepreneurial intentions, government and all stakeholders should ensure that all the perceived triggers are made available. In addition, the barriers to youth entrepreneurship should be minimised. , Thesis (MCom) -- Faculty of Management and Commerce, 2011
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Date Issued: 2011

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Tripping over our own feet : a critical discussion of Trade Related Intellectual Property Rights (TRIPS) with specific reference to their impact on South Africa's ability to combat HIV and AIDS

- Brennan, Jade

Authors: Brennan, Jade
Date: 2008
Subjects: Agreement on Trade-Related Aspects of Intellectual Property Rights, (1994) Trade regulation -- South Africa Intellectual property -- South Africa HIV (Viruses) -- South Africa AIDS (Disease) -- South Africa Patients -- Civil rights -- South Africa Human rights -- South Africa
Language: English
Type: Thesis , Masters , MA
Identifier: vital:2850 , http://hdl.handle.net/10962/d1006316
Description: This thesis aims to look at the agreement on Trade Related Intellectual Property Rights (TRIPS) with specific reference to their impact on South Africa's ability to combat HIV and AIDS. It begins by looking at the history of patents and intellectual property rights and illustrates why and how the TRIPS Agreement came into existence. The TRIPS Agreement exemplifies the disparities between developed and developing countries and this can clearly be seen with regard to the provision of anti-HIV and AIDS drugs. The developing world deals with the bulk of the HIV and AIDS epidemic whilst the developed world holds most of the patents on the medication needed to treat those living with HIV and AIDS. This situation lends itself to a rift between patient rights on the one hand, and patent rights on the other. Traditionally the state has been the provider of rights such as health, but TRIPS alters this to include strong patent protection that is in line with neo liberal doctrine. The thesis examines these tensions with specific reference to South Africa's ability successfully to implement programmes to combat HIV and AIDS.
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Date Issued: 2008

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Tronkvoël: An exploration of the intersection of personal experiences and identities, concerning depression

- Kramer, Brunn David

Authors: Kramer, Brunn David
Date: 2021-10-29
Subjects: Mental illness in art , Art, South African 21st century , Metaphor in art , Depression, Mental , Prisons in art , Identity (Philosophical concept) in art , Gender identity in art , Intersectionality (Sociology)
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10962/191647 , vital:45129
Description: My diagnosis of Major Depressive Disorder in 2018 led to my experience of a terrible loneliness and a peculiar isolation that triggered a feeling of imprisonment. The work thus engages with the idea of prison as a metaphor for depression, and is influenced by earlier work that centred around prisons and ex-prisoners. I explore the intersection of gender-based issues, homophobia, racism and religious prejudice that is based on my experiences and identities, in an attempt to understand the depression and communicate the complex prejudices I face in my daily life. The work is based on my lived experience, through which depression can feel like a self-constructed prison. Thus, by visually communicating my lived experiences with depression as a coloured, queer body, I also aim to encourage dialogue and open up conversations around mental illness, as it is all too is often seen as taboo, particularly in communities of colour. I harness old family photographs as a departure point to investigate personal memory, as well as recently captured selfies to explore my narrative of self-imprisonment. I also integrate objects from childhood games such as glass marbles, with prison objects like paper mache dice and shivs all presented in the form of an installation. My invisible prison is visually communicated further through incorporating visual language of the prison – including tattoos, prison slang, and ‘shifts and shanks’ (makeshift weapons). I use a variety of mediums, including charcoal, photographic transfers, paint and linocuts, with a combination of burning and smoking techniques, made by using candle soot, as a primary feature throughout my work. In this mini-thesis I reflect on memories from my childhood and the way they have informed my experience of depression as a self-constructed prison. I position my practice in relation to the work of South African artist Tsoku Maela who navigates similar concerns in his own artworks. , Thesis (MFA) -- Faculty of Humanities, Fine Art, 2021
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Date Issued: 2021-10-29

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Trophic ecology of breeding northern rockhopper penguins, Eudyptes Moseleyi, at Tristan da Cunha, South Atlantic Ocean

- Booth, Jenny Marie

Authors: Booth, Jenny Marie
Date: 2012
Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
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Date Issued: 2012

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Trophic importance of kelp-derived suspended particulate matter in a through-flow sub-Antarctic system

- Kaehler, Sven, Pakhomov, E A, Kalin, R M, Davis, S

Authors: Kaehler, Sven , Pakhomov, E A , Kalin, R M , Davis, S
Date: 2006
Language: English
Type: Article
Identifier: vital:6876 , http://hdl.handle.net/10962/d1011624
Description: Spatial dynamics of surface chlorophyll concentrations, diatom abundance and carbon and nitrogen stable isotope signatures of surface suspended particulate matter (SPM) were investigated during a bloom event observed in March 2003 in the vicinity of the sub-Antarctic Prince Edward Islands. The surface water composition was studied to estimate the overall importance and spatial extent of kelp derived SPM in the water column of the islands. It was observed that high chlorophyll concentrations (up to 2 mg m–3) between and downstream of the islands could not be explained by the development of the diatom bloom. Instead, microscopic and stable isotope analyses suggested that the chlorophyll signal was largely derived from the residual chlorophyll in fresh and decaying particles of small fragments of the kelp Macrocystis laevis, an endemic kelp species abundant along the shoreline of the islands. The findings of this study suggest that the dietary subsidy of kelp-derived carbon and nitrogen to benthic communities and possibly the plankton is not limited to the vicinity of kelp beds, but rather is a widespread phenomenon between the islands. Due to the dominating unidirectional Antarctic Circumpolar Current, large quantities of kelp-derived SPM may be transported and utilised tens of kilometres downstream of the islands.
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Date Issued: 2006

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Trophic interactions in an austral temperate ephemeral pond inferred using stable isotope analysis

- Dalu, Tatenda, Weyl, Olaf L F, Froneman, P William, Wasserman, Ryan J

Authors: Dalu, Tatenda , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J
Date: 2016
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/68022 , vital:29185 , https://doi.org/10.1007/s10750-015-2533-5
Description: Publisher version , Ephemeral ponds are vulnerable aquatic habitats which are difficult to protect given their dynamic nature and sensitivity to degradation during dry periods. Little information is available on these habitats in austral regions, with almost no information on food-web structure and complexity. The study aimed to assess trophic interactions among dominant organisms in an ephemeral pond food web, and investigate the importance of autochthonous and allochthonous carbon, using 13C and 15N isotopes. Results of the investigation suggest that the food web comprised four trophic levels, with the top predators being Notonectids (Notonecta sp.) and diving beetles (Cybister tripunctatus (Olivier)). Intermediary trophic levels comprised zooplankton (daphniids and copepodids), macroinvertebrates (e.g. micronectids and molluscs) and tadpoles. Generalist feeders dominated the higher trophic levels (>3) with specialists comprising the lower trophic levels (≤3). The consumers preferred autochthonous fine particulate organic matter, epiphyton and submerged macrophyte organic matter sources over allochthonous sources. Autochthonous organic matter was transferred to the food web via zooplankton and select macroinvertebrates including Micronecta sp. and Physa sp. The food-web structure within the pond appeared to reflect the secondary stage of trophic structural complexity in the evolution of ephemeral ponds over the course of their hydro-period.
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Date Issued: 2016

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Trophic preference of southern African dung beetles (Scarabaeoidea: Scarabaeinae and Aphodiinae) and its influence on bioindicator surveys:

- Tocco, Claudia, Balmer, Jonathan P, Villet, Martin H

Authors: Tocco, Claudia , Balmer, Jonathan P , Villet, Martin H
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/140796 , vital:37919 , DOI: 10.1111/aje.12523
Description: Environmental assessments using bioindicators gain value if the interpretability of the indicator used is high, and it is clear how survey methods affect survey comparisons. Because dung beetles are favoured as bioindicators, we studied the trophic preference of a southern African beetle community and its potential effects on surveys of beetle diversity using manual sampling of droppings and pitfall traps baited with carnivore, ruminant or nonruminant dung. Manual sampling showed no significant differences between dung types in either dung beetles abundance or species richness. Generalised linear mixed models of total and endocoprid abundances, species richness and Real Shannon index of trap samples showed higher dung beetle diversity associated with ruminant than with nonruminant dung, which in turn was significantly preferred over carnivore dung.
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Date Issued: 2018

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Trophic relationships of hake (Merluccius capensis Castelnau, 1851 and M. paradoxus Franca 1960) from the Northern Benguela current ecosystem (Namibia) : inferences from stable isotopes and fatty acids

- Iitembu, Johannes Angala

Authors: Iitembu, Johannes Angala
Date: 2014
Subjects: Hake -- Benguela Current , Merlucciidae -- Benguela Current , Multitrophic interactions (Ecology) , Food chains (Ecology) , Biotic communities -- Benguela Current , Merlucciidae -- Food , Fishery management -- Namibia , Stable isotopes , Fatty acids
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:5944 , http://hdl.handle.net/10962/d1020296
Description: Two species of hake (Merluccius capensis and Merluccius paradoxus) account for most of Namibia’s fisheries catch, and they are important secondary consumers in the Benguela Current ecosystem. Inferences on their trophic relationships have been based mainly on stomach content analyses. However, such data are limited temporally because they represent only snapshots of recent feeding, and are quantitatively biased because of variation in the digestion rates of different prey. The principal aim of the thesis was to understand the trophic relationships of two hake species relative to each other, their known prey and top predators (demersal sharks) in the northern Benguela Current ecosystem (Namibia), using time-integrating trophic biomarkers. By using stable isotope (carbon and nitrogen) and fatty acid signatures of their muscle tissues, my overall objectives were to produce new knowledge about 1) hake ontogenic trophic relationships, 2) the contributions of different prey to hake diets, 3) hake dietary differences, and 4) some aspects of hake’s trophic relationships with demersal sharks. Tissues of hake (n=358), their potential prey (n=455), and demersal sharks (n=42) were collected between 2008 and 2012 during demersal bottom trawl surveys off Namibia, for stable isotope and fatty acid analyses. And more...
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Date Issued: 2014

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Trophodynamics of carnivorous zooplankton in the region of the subtropical convergence within the Indian sector of the Southern Ocean, with particular emphasis on chaetognaths

- Sterley, Jessica Anne

Authors: Sterley, Jessica Anne
Date: 2009
Subjects: Zooplankton -- Antarctic Ocean , Chaetognatha , Euphausiacea , Amphipoda , Predation (Biology)
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:5790 , http://hdl.handle.net/10962/d1005478 , Zooplankton -- Antarctic Ocean , Chaetognatha , Euphausiacea , Amphipoda , Predation (Biology)
Description: Trophodynamics of carnivorous zooplankton in the region of the Subtropical Convergence (STC) in the Indian sector of the Southern Ocean was investigated during austral autumn (April 2007) as part of the first cruise of the Southern Ocean Ecosystem Variability Study. Within the region of the study, the STC was well defined by the 14°C surface isotherm which separated the Agulhas Return Current and Subtropical water in the north from Sub-Antarctic waters to the south. Total average abundance (3.89 ± 5.46ind 100m-3) and biomass (0.14 ± 0.27mg Dwt 100m-3) of carnivorous zooplankton south of the front were significantly higher than the total average abundance (1.33 ± 1.81ind 100m-3) and biomass (0.03 ± 0.05mg Dwt 100m-3) north of the front (p<0.001). There were no significant correlations between the selected physico-chemical (temperature and salinity) and the biological (mesozooplankton abundance and biomass) variables and the total abundance and biomass of the carnivorous zooplankton during the investigation (p>0.05 in all cases). There was no evidence of enhanced biomass and abundance values at stations occupied in the immediate vicinity of the front. Total average carnivorous zooplankton abundance was dominated by chaetognaths (Eukrohnia hamata Möbius 1875, Sagitta gazellae Ritler-Záhony 1909 and S. zetesios Fowler 1905) and euphausiids (Nematoscelis megalops Sars 1883, Euphausia longirostris Hansen 1908 and E. spinifera Sars 1883), which contributed up to 86.58 ± 32.91% of the total counts. The total average biomass was dominated by euphausiids and amphipods (Themisto gaudichaudii Guérin-Méneville 1825, Phronima sedentaria Forsskål 1775 and Vibilia armata Bovallius 1887) which contributed up to 71.45 ± 34.85% of the total counts. In general the populations of both the euphausiids and amphipods were dominated by females while the chaetognaths were dominated by juveniles. Numerical analysis identified two major zooplankton groupings within the survey area which did not coincide with the water masses within the survey area. The SIMPER procedure of the PRIMER package indicated differences between the groups were mainly attributed to changes in the abundance of the numerically dominant species rather than the presence or absence of individual species. The absence of any significant spatial patterns in the distribution of the carnivorous zooplankton suggests that the STC did not act as a biogeographical barrier during the present study. The mean feeding rates of the chaetognaths E. hamata, S. gazellae and S. zetesios were 1.82 ± 0.85prey d-1, 3.63 ± 2.08prey d-1 and 2.18 ± 0.59prey d-1, respectively. These rates correspond to a combined predation impact equivalent to <5% of the mesozooplankton standing stock or <10% of the mesozooplankton secondary production. Mesozooplankton, comprising mainly copepods was the dominant prey in the guts of the three chaetognath species. Total predation impact of the euphausiids, chaetognaths and amphipods, estimated using published daily ration data, on the mesozooplankton standing stock and secondary production ranged from 0.01% to 1.53% and from 0.03% to 30.54%, respectively. Among the carnivorous zooplankton, chaetognaths were generally identified as the dominant predators of mesozooplankton. Low predation impact of selected carnivorous zooplankton suggested that these organisms contributed little to the vertical carbon flux within the region of investigation during the study.
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Date Issued: 2009

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Trophodynamics of mesozooplankton in the the vicinity of the subtropical convergence in the Indian sector of the Southern Ocean

- Daly, Ryan

Authors: Daly, Ryan
Date: 2009
Subjects: Zooplankton -- Antarctic Ocean , Phytoplankton -- Antarctic Ocean
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:5791 , http://hdl.handle.net/10962/d1005479 , Zooplankton -- Antarctic Ocean , Phytoplankton -- Antarctic Ocean
Description: The trophodynamics of the numerically dominant mesozooplankton (200-2000 m) in the vicinity of the Subtropical Convergence (STC) in the Indian sector of the Southern Ocean during austral autumn (April / May) 2007 were investigated as part of the Southern Ocean Ecosystem Variability Study. The survey consisted of six north-south transects each bisecting the STC between 38º to 43ºS and 38º to 41º45’E. In total, 48 stations situated at 30 nautical mile intervals were occupied over a period of ten days. Hydrographic data revealed a well defined surface and sub-surface expression of the STC, which appeared to meander considerably between 41ºS and 41º15’S. Surface chlorophyll-a (chla) concentrations were low, ranging between 0.08 and 0.68 mg chl-a.m-3 and were generally dominated by the picophytoplankton (<2 m) which made up 66.6% (SD±17.6) of the total pigment. Chl-a concentrations integrated over the top 150m of the water column ranged between 11.97 and 40.07 mg chl-a.m-2 and showed no significant spatial patterns (p>0.05). Total integrated mesozooplankton abundance and biomass during the study ranged between 3934.9 and 308521.4 ind.m-2 (mean = 47198.19; SD±62411.4 ind.m-2) and between 239.8 and 4614.3 mg Dwt.m-2 (mean = 1338.58; SD ±1060.5), respectively. Again, there were no significant spatial patterns in the total mesozooplankton abundance or biomass within the region of study (p>0.05). No significant correlations were found between biological (chlorophyll-a concentrations and zooplankton abundance) and physico-chemical variables (temperature and salinity) (p>0.05). The total mesozooplankton community was numerically dominated by copepods of the genera Pleuromamma, Calanus, Oncaea and Oithona. Other important representatives of the mesozooplankton community included the tunicate, Salpa thompsoni, and the pteropod, Limacina retroversa. At the 40% similarity level, numerical analysis identified five distinct mesozooplankton groupings within the survey area. Differences between the groupings were associated with changes in the relative contribution of numerically dominant species rather than the presence or absence of individual species. No groupings were associated with any specific feature of the front within the survey area. The feeding rates of the six most numerically abundant mesozooplankton species (Calanus simillimus, Limacina retroversa, Pleuromamma abdominalis, Clausocalanus breviceps, Oncaea conifera, Salpa thompsoni) accounting for on average 39% of the total mesozooplankton counts, were investigated using the gut fluorescence technique. For all species, the total gut pigment contents during the night time were significantly higher than the daytime values (p<0.05 for all species). The gut evacuation rates (k) for selected mesozooplankton ranged between 0.14 and 0.81 h-1. The ingestion rates ranged between 147.8 and 5495.4 ng(pigm)ind-1.day-1 which corresponded to a daily ration of between 2.4 and 10.9% body carbon. The combined grazing impact of the selected species on the daily phytoplankton standing stock was highly variable and ranged between 1.2 and 174.1% with an average of 27.3% (SD±38.78%) within the survey area. The highest grazing impact (>60%) was typically associated with those stations where the pteropod, L. retroversa, and the tunicate, S. thompsoni, contributed more than 5% of the total mesozooplankton counts. No significant differences were found in the grazing impact of any or all selected species situated either north, south or in the immediate vicinity of the front (p>0.05 in all cases). The lack of defined spatial patterns in the mesozooplankton abundance and community structure suggests that the STC did not act as a significant biogeographic barrier to the distribution of mesozooplankton during the study. It is presumed that the large scale mixing event caused by a storm prior to this study was responsible for the observed lack of elevated biological activity within the region of the STC.
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Date Issued: 2009

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