Functional traits and potential physical drivers of offshore benthic epifauna on the west and south coast of South Africa
- Authors: Van Stavel, Jordan , Morris, Tamaryn
- Date: 2023-12
- Subjects: Marine ecology , Marine biology -- South Africa , Oceanography -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62698 , vital:72931
- Description: Offshore benthic ecosystems (> 200 m depth) are challenging to access and remain poorly studied globally. Epifaunal invertebrates comprise a critical trophic level in benthic ecosystems and can serve as indicators of the overall health and functioning. There is limited knowledge of South Africa’s offshore marine environment and benthic ecosystem functioning due to limitations in funding, resources, and the lack of suitable science-based monitoring tools which are vital for sustainable management into the future. The aim of this research was to improve the understanding of epifaunal functioning as well as their potential physical drivers in 13 South African offshore biogeographic ecotypes. The objectives of this study were threefold: 1) to investigate the functional composition of benthic epifauna from 13 biogeographic ecotypes, 2) to quantify the Functional Diversity (FD) associated with epifaunal traits between the different assemblages (i.e. biogeographic ecotypes), and 3) to evaluate the relationship between physical variables and epifaunal functional traits at the biogeographic ecotype level. Biological trait-based approaches were applied to a subset of 80 benthic epifaunal species collected from 909 offshore stations along the west and south coasts of South Africa. Nine biological traits (associated with life history, morphology and behavioural characteristics exhibited by each species) were classified into 39 modalities and weighted with biomass. Community Weighted Means (CWMs) were used to evaluate the benthic epifaunal functional trait composition of the 13 biogeographic ecotypes. Functional composition across the 13 ecotype assemblages on the west and south coast appeared to be dominated by species with similar trait compositions, such as large, long-lived, surface crawling/burrowing/filter-feeding epifauna with medium to no mobility, however, their percentage of contribution to trait expression (CWMs) was higher on the west coast. Functional diversity indices (alpha and beta) showed higher overall FD for west coast ecotypes, with most ecotypes on the continental shelf (except slopes and canyons) being significantly different (p<0.05) from ecotypes on the south coast. The global RLQ (three-table co-inertia) test did not reveal a significant relationship between biomass and physical variables or between biomass and traits (p>0.05). The fourth-corner method was used to test the significance of individual traitenvironment relationships. The fourth-corner results were similar overall to the RLQ analysis, revealing that three physical variables (temperature, depth, and fluorescence) were significantly correlated to two trait modalities belonging to the feeding mode filter-feeders (FM1) and scavengers (FM5). Scavengers were positively correlated with depth and negatively with temperature, while filter-feeders were positively correlated with fluorescence levels. This indicated that the presence of scavenging epifauna increased with a decrease in temperature and an increase in depth. While a positive significant correlation between filter-feeders and fluorescence suggested their potential tolerance or preference for environmental conditions with high levels of fluorescence. This research was the first such study to explore the functional composition and diversity of benthic epifauna and their relationship with potential physical drivers in offshore west and south coast benthic biogeographic ecotypes of South Africa. The application of new tools to quantify the functional diversity of epifauna as indicators of ecosystem health, and their potential physical drivers. This provided a platform on which to advance our understanding of benthic communities and the roles they play in ecosystem functioning under changing environments. Functional trait-based approaches such as those applied in this study can provide us with vital information on the relationship between biodiversity, ecosystem functioning, and physical drivers. Environmental stressors and changing climate patterns threaten to impact marine ecosystems and their functioning. Benthic epifauna are especially sensitive to changes in their environment and these fluctuations could potentially lead to the loss of certain benthic functionality, altering the thresholds these ecosystems have to response to disturbances. This undermines the stability of these ecosystems which can have ripple effects on the health of these ecosystems and their ability to provide the ecosystem services humans dependent on. Having suitable tools to track current and predict future changes will therefore be vital to inform management and conservation strategies for sustainable ocean utilisation. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
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- Date Issued: 2023-12
Integrating state-space modelling and systematic conservation planning to recommend penguin-fishery management zones in Algoa Bay, South Africa
- Authors: Stockdale, Victoria , Goodall, Victoria , Clifford-Holmes, Jia
- Date: 2023-12
- Subjects: Biodiversity conservation -- South Africa -- Port Elizabeth , Natural resource conservation , Marine ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62611 , vital:72828
- Description: Direct anthropogenic impacts on vulnerable marine ecosystems are growing and require effective conservation measures. Integrating the cost impacts of conservation interventions and optimising the spatiotemporal scale of management interventions may improve cohesion between opposing marine users. This study aimed to integrate spatial and temporal models to advise dynamic penguin-fishery management plans in Algoa Bay, off Gqeberha, South Africa, that would maximise penguin foraging success while minimising the impact on the fishing industry. Determining the foraging locations important to breeding penguins is fundamental when understanding the relationship between fisheries and prey availability. Using Global Positioning System (GPS) data gathered from feeding trips of breeding African penguins between 2012 and 2017, and a hidden Markov model, three behavioural states (foraging, commuting, transitioning) were inferred and used as conservation targets in spatial prioritisation using the prioritizr package in R. The cost to the fishery was estimated using the catch of pelagic fish by the fishing industry between 2012 and 2015 as the proxy. The energetic cost to penguins was the distance they travelled from their breeding colony. Nine prioritisation scenarios, varying in levels of conservation for penguins, spatial cohesion and costs to fisheries, were developed using all year’s combined data to explore an ‘optimal’ closure configuration. The optimal closure was determined as an area which met the targets for penguin conservation, with a low cost to the fishery, close to the breeding colony and spatially clumped. The best solution from each scenario was isolated and the solution for the conservation target of 20% foraging habitat, 10% commuting habitat and 10% transitioning habitat and a boundary penalty of 0.01 (a dimensionless value that is used to reduce spatial fragmentation – increasing the value of the parameter signals that it is important to minimise the total exposed boundary of the prioritisation by favouring solutions where units are clumped together) was chosen as the optimal closure. This configuration was used as a static closure and applied to individual fishing seasons to estimate how the cost of a static closure design to the fishery would vary between seasons. Subsequently, a dynamic closure was designed using the same optimal configuration criteria every year, and the cost to the fishing industry was compared seasonally with the cost of a static closure. The cost to fisheries of dynamic closures was consistently lower than that of a static closure and the area required to meet the penguin feeding targets was drastically reduced. While dynamic closure scenarios show promise to minimise costs to the industry while meeting penguin conservation targets, these configurations were designed retrospectively with data collected after the end of the fishery seasons. For efficient management, the closures need to be designed by using data collected at an appropriate temporal scale. For that, the critical missing dimension to this study is the addition of real-time data on pelagic fish positions, areas of fishing intensity and sites of penguin foraging to create appropriate recommendations for up-to-date fishery exclusion zones. Therefore, the priority now is to explore methods of collecting real-time data on pelagic fish abundance, feeding behaviour of penguins at sea, site and mass of pelagic fishery catch, and using these data to delineate real-time, dynamic closures, coupled with a governance and management strategy that can implement dynamic closures. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
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- Date Issued: 2023-12
Exploring and contextualising the predominant coastal and marine environmental worldview orientations of millennial South Africans
- Authors: van Rooyen, Rize Dorothea
- Date: 2022-12
- Subjects: Coastal ecology , Marine ecology , Generation Y -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62484 , vital:72764
- Description: The increase in human activities within the marine and coastal environments has introduced new stressors to the ocean’s ecosystems. Despite the increasing specification of coastal and marine environments within South African management policy and programmes, marine issues as well as ocean and coastal-related environmental inspections still lag behind terrestrial issues. Previous research identified the importance of including contextual factors within the study of environmental worldviews and behaviour. The present study aimed to address the identified needs within South African environmental management frameworks for proactive approaches, with consideration to the values and beliefs of the citizens of South Africa as specified in the National Environmental Management Act. The study specifically explores the coastal and marine environmental worldviews of a sample of South African millennials with reference to the contextual constraints, which influence their environmental perceptions and behaviours. This generation constitutes 26.4% of South Africa’s population and, according to literature, is largely underrepresented within environmental discourse. This exploratory-descriptive study utilised four research phases to contextualise the coastal and marine environmental worldviews of nine millennial South Africans, namely, a systematic review of 1236 academic articles, an observation and analysis of 50 environmentally focused Tweets from South African news media outlets, and the subsequent engagements, the distribution of a compiled coastal and marine environmental worldview scale to a sample of nine millennial South Africans and, finally, a set of phenomenological interviews with nine millennial South Africans to discuss the contextual constraints to pro-environmental behaviours. The findings of the study resulted in the provision of a theoretical model regarding the antecedents to environmental behaviour, which addressed the complexity of antecedent attributes omitted in contemporary theory. Additionally, the findings provided a framework of contextual attributes from which to address South African coastal and marine environmental worldviews. The findings further provided baseline information for proactive, informed, as well as participatory decisions and programmes for policy, development, and conservation. The present study represented a novel contribution to academic knowledge through its provision of a theoretical and contextual framework from which to study the antecedents of environmental behaviour. It further presents a novel contribution to development practice, allowing for proactive approaches to environmental management. , Thesis (D.Phil) -- Faculty of Business and Economic Sciences , School of Economics, Development & Tourism, 2022
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- Date Issued: 2022-12