Tolerating climate change: a study on the influence of thermal history on thermal tolerance of Galaxias zebratus in rivers of the Cape Peninsula, South Africa
type: CreativeWork
description: Global climate change models predict a reduction in rainfall and rise in air temperature for the Cape Peninsula of South Africa’s Cape Floristic Region (CFR). The CFR is a biodiversity hotspot renowned for its high level of floral endemism, but the high level of endemism also applies to the region’s freshwater fish assemblage. Whereas the current threats to endemic freshwater fish include habitat modification, water abstraction, pollution and impacts of non-native species, climate change is predicted to further exacerbate negative impacts on fish communities. The endemic CFR fish species, Cape Galaxias, Galaxias zebratus Castelnau, 1861, is widespread throughout the region, and occurs in both non-perennial and perennial rivers, and wetlands. The species is thought to be a relict group of ancient species originating from the break up of Gondwanaland 180 – 135 million years ago. Endemic CFR freshwater fish, like G. zebratus, may be sensitive to the thermal regime of their environment and may thus be influenced by climate warming. The most commonly used experimental approach for determining the effect of elevated temperature on freshwater biota is the Critical Thermal Method (CTM). The CTM determines the upper thermal tolerance limit or critical thermal maximum (CTmax) of a species. Thermal history is the range of temperatures experienced by an organism in its natural habitat over time and this may be an important factor determining the thermal tolerance of species. The aim of this study was to evaluate the influence of thermal history, reflecting a stream’s thermal profile, on upper thermal tolerance limits of G. zebratus. We hypothesised that G. zebratus from warmer sites would have a higher CTmax than individuals at cooler sites. To examine the influence thermal history has on the thermal tolerance of G. zebratus, hourly water temperature data were collected and the CTmax values were determined for fish (n=30 per site) from 10 different sites in rivers of the Cape P…
abstract: Global climate change models predict a reduction in rainfall and rise in air temperature for the Cape Peninsula of South Africa’s Cape Floristic Region (CFR). The CFR is a biodiversity hotspot renowned for its high level of floral endemism, but the high level of endemism also applies to the region’s freshwater fish assemblage. Whereas the current threats to endemic freshwater fish include habitat modification, water abstraction, pollution and impacts of non-native species, climate change is predicted to further exacerbate negative impacts on fish communities. The endemic CFR fish species, Cape Galaxias, Galaxias zebratus Castelnau, 1861, is widespread throughout the region, and occurs in both non-perennial and perennial rivers, and wetlands. The species is thought to be a relict group of ancient species originating from the break up of Gondwanaland 180 – 135 million years ago. Endemic CFR freshwater fish, like G. zebratus, may be sensitive to the thermal regime of their environment and may thus be influenced by climate warming. The most commonly used experimental approach for determining the effect of elevated temperature on freshwater biota is the Critical Thermal Method (CTM). The CTM determines the upper thermal tolerance limit or critical thermal maximum (CTmax) of a species. Thermal history is the range of temperatures experienced by an organism in its natural habitat over time and this may be an important factor determining the thermal tolerance of species. The aim of this study was to evaluate the influence of thermal history, reflecting a stream’s thermal profile, on upper thermal tolerance limits of G. zebratus. We hypothesised that G. zebratus from warmer sites would have a higher CTmax than individuals at cooler sites. To examine the influence thermal history has on the thermal tolerance of G. zebratus, hourly water temperature data were collected and the CTmax values were determined for fish (n=30 per site) from 10 different sites in rivers of the Cape P…
author: Olsen, Toni
language: eng
date published: 2018
date modified: 2026-07-22T22:22:52Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Environmental and Geographical Science

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/29349