Browsing by Subject "ecology"

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    Ecology and ecophysiology of Zostera capensis: responses and acclimation to temperature
    (2020) Lawrence, Cloverley Mercia; Pillay, Deena; Jarre, Astrid; Bolton, John
    This study aimed to understand the ecology of the threatened, habitat-forming seagrass, Zostera capensis in Langebaan Lagoon, a marine protected area that forms part of the West Coast national park, South Africa; and the physiological strategies that allow this habitat to persist in sub- and supra-optimal temperatures. First, the environmental drivers responsible for spatial and temporal variability in Zostera and its associated macro-epifauna were determined. Secondly, the effects of temperature and the role of algal grazing in maintaining seagrass performance under temperature stress were investigated. Seasonal field collections of seagrasses and their associated macro-epifauna were undertaken, along with regular measurements of key environmental variables. Thereafter, mesocosm experiments were performed to measure the responses of Zostera to thermal stress and grazing using morphometry, fluorometry, chromatography and biochemistry. Significant seasonal variability in seagrass distributions with severe diebacks in summer were found, which influenced associated macro-epifauna communities. Populations responded to environmental stress by changing their growth form producing small-leaves in high densities in the high intertidal, while those in low intertidal and subtidal areas produced sparse, large-leaved populations. These distinct populations supported unique faunal diversities, which were dominated by grazing invertebrates. Temperature was a consistent driver of seagrass density and leaf size, while turbidity and exposure were key environmental factors that influenced macro-epifaunal patterns. Macro-epifaunal abundances were highly positively correlated with seagrass leaf width and biomass. Different growth forms displayed different responses to thermal stress, including a higher photosynthetic rate, and accumulations of carbon and nitrogen as phenolic compounds, in small- compared to large-leaved plants. This implies that large-leaved populations are more vulnerable to stress from fouling, which was evident in their larger epiphyte loads, compared to small-leaved populations. In addition, grazers were ineffectual at regulating epiphyte growth which increased under warming conditions. These findings suggest differences in resilience between sub-populations of Zostera, and attest to their capacity to recover from environmental stress. They further emphasise the significance of identifying characteristics and acclimation strategies that allow habitats to persist under climate change, and thus sustain biodiversity and productivity, as well as continue to provide important ecosystem services.
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    An overview of the biology of the desiccation-tolerant resurrection plant Myrothamnus flabellifolia.
    (Oxford University Press, 2007) Moore, John P; Lindsey, George G; Farrant, Jill M; Brandt, Wolf F
    Myrothamnus flabellifolia (Welw.) is a relatively large resurrection plant, a woody shrub between 0.5 m and 1.5 m tall (Sherwin et al., 1998) that grows on rock inselbergs (Porembski and Barthlott, 2000) throughout southern Africa (Weimarck, 1936; Van Wyk et al., 1997; Glen et al., 1999). The plant was first recorded in 1859 by Friedrich Welwitsch, who named the plant Myrothamnus (myron meaning aromatic and thamnos meaning bush) flabellifolia (meaning fan-like leaves) (Puff, 1978a; Glen et al., 1999), the leaves having a balsamic-like odour (Puff, 1978a; Glen et al., 1999). Weiss (1906) was the first to note the ‘miraculous manner’ with which the desiccated plant revived when supplied with water (Fig. 1A, B). Myrothamnus flabellifolia occupies an important position in traditional African folklore and medicine (Watt and Breyer-Brandwijk, 1962; Hutchings, 1996; Van Wyk et al., 1997). The Zulu name for the plant is ‘uvukwaba- file’ (wakes from the dead). The reviving ability is believed to be passed on to the ill person during treatment (Hutchings, 1996; Van Wyk et al., 1997). The plant is a geophyte possessing an extensive root system which extends into the crevices of the rocky slopes upon which it grows (Child, 1960; Glen et al., 1999). Myrothamnus flabellifolia can dehydrate its vegetative tissue, in particular its leaves, to an air-dry state. In this state, the leaves and stem segments curl and change colour from green to dullbrown (Farrant et al., 1999; Glen et al., 1999). When water is provided to the roots the plant re-hydrates its desiccated tissue and returns to its original colour and shape (Glen et al., 1999; Farrant et al., 2003). Since the last review on M. flabellifolia was written many years ago (Puff, 1978a) and since considerable work has been published in the last decade, this review focuses on recent advances in the understanding of the physiology, biochemistry and chemistry of M. flabellifolia.
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    Weaver Birds
    (2014-09-12) Oschadleus, Dieter; Neary, Tim
    In this radio broadcast, Dieter Oschadleus discusses weavers, from nest-building patterns to the different kinds of weavers (masked weaver, widow and bishop birds, and sparrow weavers, scaly-feathered finch, etc.) and their respective habitats. Weaver nest sites also attract a variety of predators (snakes, birds of prey) and obligate nesters such as the pygmy falcon who do not create their own nests, and thus weaver sites create their own ecologies through provision of shade and concentration of droppings. Citizen scientists can get involved by photographs of weaver sites which are then used to build up a database of weaver sites which provide demographic information very useful to avian zoologists. Image provided courtesy of Snowmanradio under a Creative Commons Attribution Share-Alike 2.0 Generic license.