Modern supratidal microbialites fed by groundwater: functional drivers, value and trajectories
- Rishworth, Gavin M, Dodd, Carla, Perissinotto, Renzo, Bornman, Thomas G, Adams, Janine B, Anderson, Callum R, Cawthra, Hayley C, Dorrington, Hayley C, du Toit, Hendrik, Edworthy, Carla, Gibb, Ross-Lynne A, Human, Lucienne R D, Isemonger, Eric W, Lemley, David A, Miranda, Nelson A, Peer, Nasreen, Raw, Jacqueline L, Smith, Alan M, Steyn, Paul-Pierre, Strydom, Nadine A, Teske, Peter R, Welman, Peter R
- Authors: Rishworth, Gavin M , Dodd, Carla , Perissinotto, Renzo , Bornman, Thomas G , Adams, Janine B , Anderson, Callum R , Cawthra, Hayley C , Dorrington, Hayley C , du Toit, Hendrik , Edworthy, Carla , Gibb, Ross-Lynne A , Human, Lucienne R D , Isemonger, Eric W , Lemley, David A , Miranda, Nelson A , Peer, Nasreen , Raw, Jacqueline L , Smith, Alan M , Steyn, Paul-Pierre , Strydom, Nadine A , Teske, Peter R , Welman, Peter R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426008 , vital:72306 , xlink:href="https://doi.org/10.1016/j.earscirev.2020.103364"
- Description: Microbial mats were the dominant habitat type in shallow marine environments between the Palaeoarchean and Phanerozoic. Many of these (termed ‘microbialites’) calcified as they grew but such lithified mats are rare along modern coasts for reasons such as unsuitable water chemistry, destructive metazoan influences and competition with other reef-builders such as corals or macroalgae. Nonetheless, extant microbialites occur in unique coastal ecosystems such as the Exuma Cays, Bahamas or Lake Clifton and Hamelin Pool, Australia, where limitations such as calcium carbonate availability or destructive bioturbation are diminished. Along the coast of South Africa, extensive distributions of living microbialites (including layered stromatolites) have been discovered and described since the early 2000s. Unlike the Bahamian and Australian ecosystems, the South African microbialites form exclusively in the supratidal coastal zone at the convergence of emergent groundwater seepage. Similar systems were documented subsequently in southwestern Australia, Northern Ireland and the Scottish Hebrides, as recently as 2018, revealing that supratidal microbialites have a global distribution. This review uses the best-studied formations to contextualise formative drivers and processes of these supratidal ecosystems and highlight their geological, ecological and societal relevance.
- Full Text:
- Date Issued: 2020
- Authors: Rishworth, Gavin M , Dodd, Carla , Perissinotto, Renzo , Bornman, Thomas G , Adams, Janine B , Anderson, Callum R , Cawthra, Hayley C , Dorrington, Hayley C , du Toit, Hendrik , Edworthy, Carla , Gibb, Ross-Lynne A , Human, Lucienne R D , Isemonger, Eric W , Lemley, David A , Miranda, Nelson A , Peer, Nasreen , Raw, Jacqueline L , Smith, Alan M , Steyn, Paul-Pierre , Strydom, Nadine A , Teske, Peter R , Welman, Peter R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426008 , vital:72306 , xlink:href="https://doi.org/10.1016/j.earscirev.2020.103364"
- Description: Microbial mats were the dominant habitat type in shallow marine environments between the Palaeoarchean and Phanerozoic. Many of these (termed ‘microbialites’) calcified as they grew but such lithified mats are rare along modern coasts for reasons such as unsuitable water chemistry, destructive metazoan influences and competition with other reef-builders such as corals or macroalgae. Nonetheless, extant microbialites occur in unique coastal ecosystems such as the Exuma Cays, Bahamas or Lake Clifton and Hamelin Pool, Australia, where limitations such as calcium carbonate availability or destructive bioturbation are diminished. Along the coast of South Africa, extensive distributions of living microbialites (including layered stromatolites) have been discovered and described since the early 2000s. Unlike the Bahamian and Australian ecosystems, the South African microbialites form exclusively in the supratidal coastal zone at the convergence of emergent groundwater seepage. Similar systems were documented subsequently in southwestern Australia, Northern Ireland and the Scottish Hebrides, as recently as 2018, revealing that supratidal microbialites have a global distribution. This review uses the best-studied formations to contextualise formative drivers and processes of these supratidal ecosystems and highlight their geological, ecological and societal relevance.
- Full Text:
- Date Issued: 2020
The nursery role of a sheltered surf-zone in warm-temperate southern Africa
- Rishworth, Gavin M, Strydom, Nadine A, Potts, Warren M
- Authors: Rishworth, Gavin M , Strydom, Nadine A , Potts, Warren M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443651 , vital:74141 , https://hdl.handle.net/10520/EJC177697
- Description: Marine fish nurseries such as surf-zones have usually been classified as nurseries based solely on the density of pre-adult fish, yet the full suite of developmental stages are seldom assessed because of difficulties associated with sampling these habitats. The larval and early juvenile fish assemblage was studied in a sheltered surf-zone (King's Beach, South Africa), where high densities of older juveniles are known to occur. Fishes were collected fortnightly over six months using two modified seine nets. Although the surf composition included typical species for this habitat type, Gobiidae, Gobiesocidae and Haemulidae dominated the larval assemblage, which suggested that the nearby rocky structure and estuaries have an influence on the assemblage. Three species, Liza richardsonii (Mugilidae), Pomadasys olivaceus (Haemulidae) and Diplodus capensis (Sparidae), showed evidence of growth and recruitment into the surf-zone from the late larval stage. The high density of larval and juvenile fishes, the presence of more than one early life history stage and the observed growth of fishes suggests that King's Beach provides a suitable nursery habitat for several fishes.
- Full Text:
- Date Issued: 2015
- Authors: Rishworth, Gavin M , Strydom, Nadine A , Potts, Warren M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443651 , vital:74141 , https://hdl.handle.net/10520/EJC177697
- Description: Marine fish nurseries such as surf-zones have usually been classified as nurseries based solely on the density of pre-adult fish, yet the full suite of developmental stages are seldom assessed because of difficulties associated with sampling these habitats. The larval and early juvenile fish assemblage was studied in a sheltered surf-zone (King's Beach, South Africa), where high densities of older juveniles are known to occur. Fishes were collected fortnightly over six months using two modified seine nets. Although the surf composition included typical species for this habitat type, Gobiidae, Gobiesocidae and Haemulidae dominated the larval assemblage, which suggested that the nearby rocky structure and estuaries have an influence on the assemblage. Three species, Liza richardsonii (Mugilidae), Pomadasys olivaceus (Haemulidae) and Diplodus capensis (Sparidae), showed evidence of growth and recruitment into the surf-zone from the late larval stage. The high density of larval and juvenile fishes, the presence of more than one early life history stage and the observed growth of fishes suggests that King's Beach provides a suitable nursery habitat for several fishes.
- Full Text:
- Date Issued: 2015
Fish utilization of surf-zones: Are they changing A case study of the sheltered, warm-temperate King’s Beach
- Rishworth, Gavin M, Strydom, Nadine A, Potts, Warren M
- Authors: Rishworth, Gavin M , Strydom, Nadine A , Potts, Warren M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443866 , vital:74167 , https://doi.org/10.1080/15627020.2014.11407616
- Description: Surf-zone fish communities and their shifts over time are generally poorly understood. The aim of this study was to compare the current surf-zone fish assemblage at King's Beach, South Africa, to a similar study conducted three decades ago, before the collapse of many exploited shore fishes in the region. Beach seine nets (mesh sizes of 10 and 50 mm) were used to target juvenile and adult fishes bimonthly from February to August 2011 over the high tide around sunset. A total of 14 species were recorded in both the 30 m and 100 m seine nets. The catch in these seine nets was dominated by Pomadasys olivaceus and Liza richardsonii, and this was significantly different to three decades ago, when P. olivaceus, Sarpa salpa and Diplodus capensis dominated the catch. Important linefish species belonging to the Sparidae and Sciaenidae families were significantly smaller and less abundant in this study. Two sparids, S. salpa and Lithognathus mormyrus, which made a large contribution to the surf-zone catch three decades ago were absent during this study. Reasons for the significant shifts in the surf-zone fish community, including overexploitation of the linefish and potential habitat modification, are discussed.
- Full Text:
- Date Issued: 2014
- Authors: Rishworth, Gavin M , Strydom, Nadine A , Potts, Warren M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443866 , vital:74167 , https://doi.org/10.1080/15627020.2014.11407616
- Description: Surf-zone fish communities and their shifts over time are generally poorly understood. The aim of this study was to compare the current surf-zone fish assemblage at King's Beach, South Africa, to a similar study conducted three decades ago, before the collapse of many exploited shore fishes in the region. Beach seine nets (mesh sizes of 10 and 50 mm) were used to target juvenile and adult fishes bimonthly from February to August 2011 over the high tide around sunset. A total of 14 species were recorded in both the 30 m and 100 m seine nets. The catch in these seine nets was dominated by Pomadasys olivaceus and Liza richardsonii, and this was significantly different to three decades ago, when P. olivaceus, Sarpa salpa and Diplodus capensis dominated the catch. Important linefish species belonging to the Sparidae and Sciaenidae families were significantly smaller and less abundant in this study. Two sparids, S. salpa and Lithognathus mormyrus, which made a large contribution to the surf-zone catch three decades ago were absent during this study. Reasons for the significant shifts in the surf-zone fish community, including overexploitation of the linefish and potential habitat modification, are discussed.
- Full Text:
- Date Issued: 2014
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