A peaceful revenge: Achieving structural and agential transformation in a South African context using cognitive justice and emancipatory social learning
- Authors: Burt, Jane C , James, Anna
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/392049 , vital:68717 , xlink:href="https://doi.org/10.1080/14767430.2018.1550312"
- Description: This is an account of the emancipatory struggle that faces agents who seek to change the oppressive social structures associated with neo-liberalism. We begin by ‘digging amongst the bones’ of the calls for resistance that have been declared dead or assimilated/co-opted by neoliberal theorists. This leads us to unearth, then utilize, Paulo Freire’s Pedagogy of the Oppressed, Steve Biko’s Black Consciousness and Shiv Visvanathan's ideas; which are examples of Roy Bhaskar’s transformative dialectic. We argue, using examples, that cognitive justice – a concept common to each of our chosen theorists – is vital in enabling emancipatory social learning. By embracing cognitive justice, the agents gained confidence, which led to their increased ability to champion community and non-academic knowledge. It also uncovered structural tensions – attendant in neoliberalism – around privilege. By articulating these tensions, the participants were able to ‘come closer together’. Such processes, initiated by ensuring cognitive justice, are possible steps in achieving universal solidarity; which is likely to be a necessary step along the path of achieving emancipation.
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- Date Issued: 2018
A study of the kinetics of a high temperature thermoluminescence peak in annealed natural quartz
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110007 , vital:33213 , DOI: 10.1016/j.jlumin.2018.08.077
- Description: Thermoluminescence of a high temperature secondary glow-peak in natural quartz annealed at 900 °C is reported. The glow-curve of a sample irradiated to 10 Gy and measured at 1 °C/s shows three peaks; the main peak at 71 °C and two other weaker-intensity peaks at 125 °C and 177 °C. For reference, the peaks are labelled as I, II and III. This study is concerned with the secondary peak at 177 °C (peak III). The electron trap responsible for peak III is stable at ambient temperature as determined by monitoring the peak intensity after various delays between irradiation and measurement. The activation energy and frequency factor of the peak were estimated as ~1.24 eV and ~10¹² s⁻¹ respectively. The dose response of the peak in the range 1–300 Gy is sublinear. The influence of either partial heating or irradiation dose on the peak position suggest that the peak follows non-first-order kinetics.
- Full Text: false
- Date Issued: 2018
A study on the creative industry as a pillar of sustained growth and diversification: the film and music sectors in Jamaica: lessons from case studies of successful firms and ventures
- Authors: Hendrickson, Michael , Stanley Niaah, Sonjah
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/146992 , vital:38583 , https://repositorio.cepal.org/handle/11362/43410
- Description: In 2007 the Caribbean Community (CARICOM) published ‘The Cultural Industries in CARICOM: Trade and Development Challenges’ report, which stated that the film and music industries refer to “aesthetic, identity, and copyrightable goods, services and intellectual property. They represent a wide array of activities that make and circulate sounds, words, and images or a combination of these. It applies to artistic, creative, and copyright works that are for sale, license, commercialisation, or display in some marketplace or public arena.” Using the definition in the CARICOM report, this study will identify the critical success factors that have resulted in the global competitiveness and sustainability of individuals, firms and ventures within the music and film subsectors in Jamaica. To anchor the study of the individual firms and ventures, the study first evaluates the historical evolution and recent trends in the development of the music and film subsectors, including their economic contribution and the main challenges and opportunities for their further development and lessons learned.
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- Date Issued: 2018
Action for increasing energy-saving behaviour in student residences at Rhodes University, South Africa
- Authors: Ancha, Angel , Bulunga, Lindelwa , Thondhlana, Gladman
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67801 , vital:29146 , https://doi.org/10.1108/IJSHE-07-2017-0107
- Description: Publisher version , Purpose: In response to increasing energy demand and financial constraints to invest in green infrastructure, behaviour change energy-saving interventions are increasingly being considered as a tool for encouraging pro-environmental behaviour in campus residences. This paper aims to report on a pilot programme aimed at reducing energy consumption via behaviour change interventions, variably applied in residences at Rhodes University, South Africa. Design/methodology/approach: Data were collected via structured questionnaires, energy consumption records and post-intervention programme focus group discussions. Findings: Participant residences that received a mix of different interventions in the forms of pamphlets, face-to-face discussions, incentives and feedback recorded more energy reductions of up to 9 per cent than residences that received a single or no intervention. In post-experiment discussions, students cited personal, institutional and structural barriers to pro-environmental energy-use behaviour. Practical implications: Overall, the results of this study suggest that information provision of energy-saving tips combined with regular feedback and incentives can result in energy-use reductions in university residences, which may yield environmental and economic benefits for universities, but addressing barriers to pro-environmental behaviour might maximise the results. Originality/value: Given the lack of literature on energy conservation in the global South universities, this study provides the basis for discussing the potential for using behavioural interventions in universities for stirring pathways towards sustainability.
- Full Text: false
- Date Issued: 2018
Acute toxicity study and prevention of Nω-nitro-L-arginine methyl ester-induced hypertension by Osteopermum imbricatum
- Authors: Tata, Charlotte, M , Gwebu, Ephraim, T , Olukayode O Aremu , Nkeh-Chungag, Benedicta, N , Oyedeji, Adebola, O , Oyedeji, Opeopluwa, O , Sewani-Rusike, Constance, R
- Date: June-2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/4915 , vital:44303 , https://www.ajol.info/index.php/tjpr/article/view/174343
- Description: Purpose:To determine the phytochemical content, toxicity and hypertension prevention effects of Osteospermum imbricatum leaf and root extracts.Methods:Phytochemical screening of leaf and root extracts of O. imbricatum was performed by colorimetric procedure. Acute toxicity of leaf and root extracts was conductedin two phases; phase I consisted of three groups of mice (n = 3) for each dose level of 10, 100 and 1000 mg/kg while phase II had three mice that received 1600, 2900 or 5000 mg/kg. Wistar rats were grouped into 7 groups that were co-treated with L-NAME and normal saline or L-NAME and hydroethanolic leaf extract (150 and 300 mg/kg) or L-NAME and hydroethanolic root extract (150 and 300 mg/kg) or L-NAME and amlodipine (5 mg/kg) or normal saline only for 4 weeks. Treatment was carried out via the oral route while blood pressure was measured weeklyfor 4 weeks by non-invasive tail cuff method.Results:The phytochemical profile of the leaf and root extracts revealed the presence of phenols, terpenoids, flavonoids, glycosides, tannins, steroids and saponins. Both the leaf and root extracts were toxic at 5000 mg/kg with an LD50of 3807.89 mg/kg. In the fourth week of the study, only the leaf extract significantly (p less 0.01) prevented the progression of L-NAME induced hypertension; systolic and diastolic blood pressure of the group treated with L-NAME and leaf extract (300 mg/kg) were 183 ± 1 and 140 ± 1 mmHg, respectively, compared to the group that was treated with L-NAME and normal saline which produced systolic and diastolic BP values of 213 ± 3 and 172 ± 4 mmHg, respectively. The extracts, especially OIR300, exhibited diuretic effects in the second and third week of study by promoting excretion of 16 and 19 ml urine, respectively, compared to 11 and 14 ml for LN group.Conclusion:The results suggest that O. imbricatum is moderately toxic at a high dose and contains a wide range of phytochemicals which offer partial protection against the development of nitric oxide deficiency hypertension.
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- Date Issued: June-2018
Adsorptive removal of ciprofloxacin and isoniazid from aqueous solution
- Authors: Dube, Cyril S , Tandlich, Roman , Wilhelmi, Brendan S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76846 , vital:30629 , https://doi.org/10.2478/nbec-2018-0002
- Description: This paper describes study of ciprofloxacin and isoniazid removal from aqueous solutions using coal fly ash (FA), kaolinite, perlite, talc and vermiculite. The adsorptive features of the adsorbents were evaluated for ciprofloxacin and isoniazid with regards to the effects of contact time, pH, the solid/liquid ratio and antibiotic concentration. All adsorbents were sterilised by dry heat before use to avoid the proliferation of antimicrobial resistance by the bacteria present on the adsorbents during experiments. The regression correlation coefficients indicate that the Langmuir model gives the best fit for the sorption of both antibiotics onto FA and talc, ciprofloxacin onto kaolinite, and isoniazid onto perlite and vermiculite with R2 values ranging from 0.908 – 0.999. The Freundlich isotherm best describes the sorption of ciprofloxacin onto vermiculite and isoniazid onto kaolinite with R2 values of 0.999 for both. The Tempkin model best describes the sorption of ciprofloxacin onto perlite with an R2 = 0.997. The values of the Freundlich exponent, 1/n, range from 0.221 – 0.998, indicating a favourable adsorption of ciprofloxacin and isoniazid onto the adsorbents. The heat of sorption, B, calculated from the Temkin plots has values ranging from 0.018 – 10.460 J/mol, indicating a physical adsorption process (physisorption). Adsorption equilibrium was achieved after 30 min for both antibiotics and the kinetic data obtained conforms best to the pseudo-second order equation with R2 values ranging from 0.998 – 0.999. The removal of ciprofloxacin and isoniazid by all adsorbents except FA was strongly influenced by the pH suggesting that electrostatic interactions play a major role in the adsorption processes.
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- Date Issued: 2018
Adult binge drinking: rate, frequency and intensity in Buffalo City Metropolitan Municipality, South Africa
- Authors: Owolabi, Eyitayo Omolara , Goona, Daniel Ter , Adeniyi, Oladele Vincent , Seekoea, Eunice
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/4944 , vital:44305 , https://doi.org/10.1080/20786190.2017.1382970
- Description: This study was conducted to explore views about the execution of powers and functions of the police in the light of related challenges. This study made use of data from a total of 83 adult participants (a survey involving 73 individuals, and 10 in-depth interviews), including males and females of diverse occupational backgrounds from Bindura and Mount Darwin policing districts in Zimbabwe. A closed-ended, mostly Likert-scale-based questionnaire was used to collect data about the prevalent forms of police abuse of powers and functions, while an in-depth interview guide was provided to harvest information qualitatively. Findings reveal that police officers abuse their powers through unlawful arrests, arbitrary search and seizure, excessive use of force, unlawful methods of investigation, and ill treatment of detainees. Though not as prevalent as other forms of abuse, malicious criminal prosecution and partisan policing were also cited.K EYWOR DS: powers, abuse, function, police, Zimbabwe
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- Date Issued: 2018
Afrikanische Entwicklungsalternativen: Ubuntu und die Post-Development-Debatte
- Authors: Matthews, Sally
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142157 , vital:38054 , DOI: 10.3224/peripherie.v38i2.03
- Description: In post-development theory, ubuntu is often cited as an example of an “alternative to development”. This article investigates whether ubuntu can play this role and what to think of the demand for alternatives to development in general. In order to do this, the paper fi rst deals with central aspects of postdevelopment theory and the debate about ubuntu. Although the concept fi ts well into a post-development perspective, the attempts to contrast ubuntu with Western ideas and ways of life are often fueled by the desire to rekindle an original, pre-colonial, authentic African philosophy. Yet discourses on Africa are always embedded in Western discourses, so this opposition reproduces precisely those dichotomies it aims to fi ght. More generally, this also holds true for the idea of “alternatives to development”, which postulate an essential opposition to “development”. This, however, denies claims for equal rights and participation at the root of demands for “development”. The struggle for these claims cannot be fought beyond the existing global order. Instead of engaging in romanticizing projections about an Africa beyond “development”, people’s views and needs should be taken as the starting point for the struggle against injustice and inequality.
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- Date Issued: 2018
Allosteric Modulation of Human Hsp90α Conformational Dynamics:
- Authors: Penkler, David L , Atilgan, Canan , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162936 , vital:40998 , https://doi.org/10.1021/acs.jcim.7b00630
- Description: Central to Hsp90’s biological function is its ability to interconvert between various conformational states. Drug targeting of Hsp90’s regulatory mechanisms, including its modulation by cochaperone association, presents as an attractive therapeutic strategy for Hsp90 associated pathologies. In this study, we utilized homology modeling techniques to calculate full-length structures of human Hsp90α in closed and partially open conformations and used these structures as a basis for several molecular dynamics based analyses aimed at elucidating allosteric mechanisms and modulation sites in human Hsp90α.
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- Date Issued: 2018
Aminoacyl tRNA synthetases as malarial drug targets: a comparative bioinformatics study
- Authors: Nyamai, Dorothy Wavinya , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148368 , vital:38733 , DOI: 10.1101/440891
- Description: Treatment of parasitic diseases has been challenging due to evolution of drug resistant parasites, and thus there is need to identify new class of drugs and drug targets. Protein translation is important for survival of malarial parasite, Plasmodium, and the pathway is present in all of its life cycle stages. Aminoacyl tRNA synthetases are primary enzymes in protein translation as they catalyse amino acid addition to the cognate tRNA. This study sought to understand differences between Plasmodium and human aminoacyl tRNA synthetases through bioinformatics analysis.
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- Date Issued: 2018
An ecosystem service value chain analysis framework: a conceptual paper
- Authors: Rawlins, Jonathan M , De Lange, Willem J , Fraser, Gavin C G
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69321 , vital:29499 , https://doi.org/10.1016/j.ecolecon.2017.12.023
- Description: Modern day societies and economies are becoming increasingly vulnerable to the continued erosion of the stocks and flows of essential ecosystem services. Thus, the management of complex socio-economic systems to effectively provide these essential services has become a global priority policy and academic research area. Understanding how underlying processes and functions contribute towards the provision of final ecosystem services can facilitate improved dissemination of credible, legitimate and salient information to decision-makers. This paper presents an ecosystem service value chain analysis framework that applies basic system dynamics modelling in the form of causal loop diagrams to facilitate an alternative analysis of ecosystem service value chains. A scoping application of the framework is applied to a case study for flood attenuation services in the Baviaanskloof catchment in South Africa. The framework enables the identification of forward linkages and ripple effects in individual value chains of final ecosystem services as well as the identification and assessment of challenges and opportunities within individual causal pathways. Ultimately, providing the potential to advance strategies for improving the efficiency and effectiveness of final ecosystem service provision.
- Full Text: false
- Date Issued: 2018
An endangered seahorse selectively chooses an artificial structure
- Authors: Claassens, Louw , Booth, Anthony J , Hodgson, Alan N
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123718 , vital:35486 , https://doi.10.1007/s10641-018-0732-4
- Description: The development of a residential marina estate within the Knysna estuary, South Africa, introduced Reno mattresses (horizontal wire cages filled with rocks) as a novel habitat for the endangered Knysna seahorse Hippocampus capensis. Consistently high seahorse densities on these artificial structures, despite the availability of seagrass habitat, begged the question of whether this habitat was chosen by the seahorse in preference to natural vegetation. An in situ habitat choice experiment was conducted which focused on the choice made by adult H. capensis between natural vegetation (Zostera capensis) and artificial (Reno mattress) habitat within a choice chamber. Seahorses were significantly more likely to move away from Z. capensis onto a Reno mattress structure or remain on this structure. This study concludes that higher H. capensis densities on Reno mattresses within Thesen Islands Marina are owing to some positive feature of this habitat and the underlying processes responsible for the choice made by this species (additional food, holdfasts, protection) can now be investigated.
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- Date Issued: 2018
An exploratory study of Heads of Departments' responses to student calls for decolonised higher education
- Authors: Grant, Carolyn , Quinn, Lynn , Vorster, Jo-Anne E
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123420 , vital:35436 , https://doi.org/10.17159/2520-9868/i72a05
- Description: Central to the tumultuous student protests of 2015 and 2016 was an urgent call for the decolonisation of South African universities. Existing curricula, including teaching and assessment practices, as well as institutional cultures and structures were challenged. Against this backdrop, in this article we focus on the academic leadership role of Heads of Departments (HoDs) at Rhodes University. In this small-scale project we interrogate how HoDs conceptualised their roles in this uncertain and complex context. From the data analysis a number of tensions emerged in the ways in which they articulated and enacted their roles. The findings indicate that the protests have contributed to the increasing complexity of the role of an HoD. Issues raised during the protests catalysed HoDs at Rhodes University, some for the first time, into considering the implications of the decolonising call from students and into exercising stronger transformative leadership roles.
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- Date Issued: 2018
An illustrated booklet for reinforcing community health worker knowledge of tuberculosis and facilitating patient counselling:
- Authors: Okeyo, Ida L A , Dowse, Roslind
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/156629 , vital:40032 , https://phcfm.org/index.php/phcfm/article/view/1687/2559
- Description: Community health workers (CHWs) have facilitated the move to decentralize tuberculosis (TB) management, but lack access to information appropriate both for personal use and in patient interaction and education. To explore the impact of a pictorial-based TB booklet on reinforcing CHW knowledge and facilitating patient counselling.
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- Date Issued: 2018
An Immersive Audio Control System Using Mobile Devices and Ethernet AVB-Capable Speakers:
- Authors: Foss, Richard , Devonport, Sean
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426745 , vital:72388 , https://www.aes.org/e-lib/browse.cfm?elib=19714
- Description: Immersive Sound is commonly used to create the localization of sound sources above, below, and around listeners. To achieve this immersive goal, sound systems are employing an ever-increasing number of speakers. Given that immersive sound systems have large speaker configurations such as in cinemas, theaters, museums, and home theater installations, there is a need to provide control for these various contexts and also to provide a means of automating this control. An immersive sound system has been created that allows for the real-time control over sound source localization. It is a multi-user client/server system where the client devices are mobile devices, thereby allowing remote control over sound source localization. Touch and orientation capabilities of mobile devices are used for the generation of three-dimensional coordinates. The server receives localization control messages from the client and uses an Ethernet AVB (audio video bridging) network to distribute appropriate mix levels to speakers with built-in signal processing. These localization messages can be recorded by users for later playback.
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- Date Issued: 2018
An integrated framework for assessing coastal community vulnerability across cultures, oceans and scales
- Authors: Aswani, Shankar , Howard, J A E , Gasalla, Maria A , Jennings, Sarah , Malherbe, W , Martins, I M , Salim, Shyam S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123063 , vital:35402 , https://doi.10.1080/17565529.2018.1442795
- Description: Across the globe, many coastal communities rely on marine resources for their food security (FS), income and livelihoods and with predicted trends in human populations, the number of people reliant on these resources is likely to increase (FAO, 2012). However, the effects of climate change including increased variability are already being experienced by coastal communities and appear to be accelerating (Doney et al., 2012). Depending on a range of factors, including location, these changes are having mild to severe impacts on communities both in direct and indirect ways (Miller et al., 2010). Communities in coastal areas, for instance, are particularly at risk due to sea level rise but also through their dependence on marine resources that are impacted by multiple climate change pressures. A change in the availability and condition of marine resources has consequences on the livelihoods of fishing populations or those who depend directly on fishing as a source of food (Badjeck, Allison, Halls, & Dulvy, 2010).
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- Date Issued: 2018
Antibiotic-Resistant Pathogenic Escherichia Coli Isolated from Rooftop Rainwater-Harvesting Tanks in the Eastern Cape, South Africa
- Authors: Malema, Mokaba Shirley , Abia, Akebe Luther King , Tandlich, Roman , Zuma, Bonga , Kahinda, Jean-Marc Mwenge , Ubomba-Jaswa, Eunice
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71729 , vital:29931 , https://doi.org/10.3390/ijerph15050892
- Description: Although many developing countries use harvested rainwater (HRW) for drinking and other household purposes, its quality is seldom monitored. Continuous assessment of the microbial quality of HRW would ensure the safety of users of such water. The current study investigated the prevalence of pathogenic Escherichia coli strains and their antimicrobial resistance patterns in HRW tanks in the Eastern Cape, South Africa. Rainwater samples were collected weekly between June and September 2016 from 11 tanks in various areas of the province. Enumeration of E. coli was performed using the Colilert®18/Quanti-Tray® 2000 method. E. coli isolates were obtained and screened for their virulence potentials using polymerase chain reaction (PCR), and subsequently tested for antibiotic resistance using the disc-diffusion method against 11 antibiotics. The pathotype most detected was the neonatal meningitis E. coli (NMEC) (ibeA 28%) while pathotype enteroaggregative E. coli (EAEC) was not detected. The highest resistance of the E. coli isolates was observed against Cephalothin (76%). All tested pathotypes were susceptible to Gentamicin, and 52% demonstrated multiple-antibiotic resistance (MAR). The results of the current study are of public health concern since the use of untreated harvested rainwater for potable purposes may pose a risk of transmission of pathogenic and antimicrobial-resistant E. coli.
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- Date Issued: 2018
Art topples monuments: artistic practice and colonial/postcolonial relations in the public space of Luanda
- Authors: Siegert, Nadine
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147014 , vital:38585
- Description: Even though there have been very few modern and contemporary artworks in the urban space of Luanda in the years after independence in 1975—and especially after the end of the civil war in 2002—there are two works by Angolan artists that are of particular interest: the sculpture Mitologias II (1984) by António Ole (b. 1951) and the photographic series Redefining the Power (2011) by Kiluanji Kia Henda (b. 1978). Both works address the possibility of using contemporary art as a symbolic form of the replacement of power, since both are built on pedestals that had previously supported monuments of Portuguese colonial power. They might, therefore, be read as a form of substitution for monuments that would commemorate and celebrate independence or the end of colonialism. This article also discusses whether these two artworks can also be regarded as counter-monuments and this contributes to the discourse on the visual and material culture of Lusophone Africa.
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- Date Issued: 2018
Assessment of the likely sensitivity to climate change for the key marine species in the southern Benguela system
- Authors: Ortega-Cisneros, Kelly , Yokwana, Sibusiso , Sauer, Warwick H H , Cochrane, Kevern L , James, Nicola C , Potts, Warren M , Singh, L , Smale, Malcolm J , Wood, A , Pecl, Gretta T
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123211 , vital:35415 , https://doi.10.2989/1814232X.2018.1512526
- Description: Climate change is altering many environmental parameters of coastal waters and open oceans, leading to substantial present-day and projected changes in the distribution, abundance and phenology of marine species. Attempts to assess how each species might respond to climate change can be data-, resource- and time-intensive. Moreover, in many regions of the world, including South Africa, species may be of vital socioeconomic or ecological importance though critical gaps may exist in our basic biological or ecological knowledge of the species. Here, we adapt and apply a trait-based sensitivity assessment for the key marine species in the southern Benguela system to estimate their potential relative sensitivity to the impacts of climate change. For our analysis, 40 priority species were selected based on their socioeconomic, ecological and/or recreational importance in the system. An extensive literature review and consultation with experts was undertaken concerning each species to gather information on their life history, habitat use and potential stressors. Fourteen attributes were used to estimate the selected species’ sensitivity and capacity to respond to climate change. A score ranging from low to high sensitivity was given for each attribute, based on the available information. Similarly, a score was assigned to the type and quality of information used to score each particular attribute, allowing an assessment of data-quality inputs for each species. The analysis identified the white steenbras Lithognathus lithognathus, soupfin shark Galeorhinus galeus, St Joseph Callorhinchus capensis and abalone Haliotis midae as potentially the most sensitive species to climate-change impacts in the southern Benguela system. There were data gaps for larval dispersal and settlement and metamorphosis cues for most of the evaluated species. Our results can be used by resource managers to determine the type of monitoring, intervention and planning that may be required to best respond to climate change, given the limited resources and significant knowledge gaps in many cases.
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- Date Issued: 2018
Baseline isotopic data for Wolffia spp.: another option for tracing N-loading in freshwater systems?
- Authors: Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68721 , vital:29308 , https://0-doi.org.wam.seals.ac.za/10.1086/696126
- Description: δ15N values of aquatic plants can reflect anthropogenic N loading. Recent work suggests the duckweed Spirodela spp. effectively maps N loading in freshwater ecosystems, but its use may be complicated by a cyanobacterium–duckweed symbiosis that could reduce its utility in low-nutrient environments. I aimed to evaluate the potential of a 2nd duckweed species Wolffia spp., which lacks a cyanobacterial symbiosis, for use in pollution monitoring in freshwater ecosystems. I used a series of laboratory experiments to investigate δ15N equilibration rates and concentration-level effects of single-source N solutions in plant tissue over 16 d to provide baseline data for sewage-plume mapping with Wolffia spp. I also tested concentration-level effects in multisource solutions to investigate the effects of mixed-source inputs. Wolffia reflected environmental N sources with a 12- to 16-d isotopic equilibration time and showed enriched and depleted δ15N ratios for manure and KNO3 solutions, respectively, but distinguished poorly between lower concentrations of manure. Fractionations at isotopic equilibrium were opposite to expectations and decreased with increasing [N]. Wolffia showed a consistent preference for NH3 in mixed-source treatments, regardless of the proportion or concentration of NH3 or NO3– available, and a capacity for N storage, which may complicate mapping of N-loading in natural environments. Wolffia is likely to be a less useful bioindicator than the previously tested Spirodela. Future research should focus on field applications of Spirodela spp. to test its capacity for sewage-plume mapping of freshwater ecosystems in a natural environment.
- Full Text: false
- Date Issued: 2018