Estuarine species and habitat :distribution and connectivity
- Veldkornet, Dimitri Allastair
- Authors: Veldkornet, Dimitri Allastair
- Date: 2016
- Subjects: Estuarine ecology -- Research -- South Africa Estuarine fishes -- Speciation -- South Africa , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45388 , vital:38604
- Description: This study explored the distribution of estuarine macrophyte genetic lineages, species and habitats in relation to environmental gradients at various spatial scales. A database was assembled to determine the area and species composition of different estuarine habitats. This can now be used to retrieve information as a baseline for further monitoring and conservation planning. Research has shown that macrophytes occur over a wide range of physiochemical conditions, suggesting that these species have great genetic and phenotypic variation to occupy broad niche ranges. In eight estuaries along the South African coast, sediment and groundwater characteristics were measured in quadrants spanning the salt marsh, ecotone and terrestrial habitats. The results suggested that, in the absence of competition and disturbance at the salt marsh-terrestrial boundary, salt marshes would be unaffected by sea-level rise; and they would migrate landward. However, disturbance at the landward margin of salt marshes has already resulted in changes in species composition and altered environmental conditions. This promotes the encroachment of terrestrial alien invasive plants, leading to a loss of connectivity. A holistic assessment of land-cover changes showed that only 28% of South African estuaries still remain in a natural state. The delineation of all estuaries needs to be consistent and inclusive of all estuarine physical and biological processes, to curb future changes. The research results have been used in national assessments of estuarine health; and they have made a significant contribution to estuary-management plans. In addition, three scientific articles have been published from the thesis; and two more are currently under review.
- Full Text:
- Date Issued: 2016
- Authors: Veldkornet, Dimitri Allastair
- Date: 2016
- Subjects: Estuarine ecology -- Research -- South Africa Estuarine fishes -- Speciation -- South Africa , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45388 , vital:38604
- Description: This study explored the distribution of estuarine macrophyte genetic lineages, species and habitats in relation to environmental gradients at various spatial scales. A database was assembled to determine the area and species composition of different estuarine habitats. This can now be used to retrieve information as a baseline for further monitoring and conservation planning. Research has shown that macrophytes occur over a wide range of physiochemical conditions, suggesting that these species have great genetic and phenotypic variation to occupy broad niche ranges. In eight estuaries along the South African coast, sediment and groundwater characteristics were measured in quadrants spanning the salt marsh, ecotone and terrestrial habitats. The results suggested that, in the absence of competition and disturbance at the salt marsh-terrestrial boundary, salt marshes would be unaffected by sea-level rise; and they would migrate landward. However, disturbance at the landward margin of salt marshes has already resulted in changes in species composition and altered environmental conditions. This promotes the encroachment of terrestrial alien invasive plants, leading to a loss of connectivity. A holistic assessment of land-cover changes showed that only 28% of South African estuaries still remain in a natural state. The delineation of all estuaries needs to be consistent and inclusive of all estuarine physical and biological processes, to curb future changes. The research results have been used in national assessments of estuarine health; and they have made a significant contribution to estuary-management plans. In addition, three scientific articles have been published from the thesis; and two more are currently under review.
- Full Text:
- Date Issued: 2016
Morphological variation and species diversity of South African Estuarine macrophytes
- Veldkornet, Dimitri Allastair
- Authors: Veldkornet, Dimitri Allastair
- Date: 2012
- Subjects: Estuarine ecology -- South Africa , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10635 , http://hdl.handle.net/10948/d1013001
- Description: Studies on morphological variation are important as it can depict the relationship with environmental factors clearly and convey an understanding of the manner, mechanism and factors influencing plant adaptation and evolution. Although many studies have been conducted on South African salt marsh plant physiology and phytosociology there are at present very few morphological studies on estuarine plants. The aim of this study was to compare the morphological variation of estuarine macrophytes in three different estuary types in the warm temperate biogeographic zone of South Africa and to compare characters used in the taxonomic descriptions of species with those measured in the field. Permanently open estuaries investigated were Ngqusi (WC), Kowie (KW) and Swartkops (SW) estuaries. The Knysna Estuary (KN) was the estuarine bay investigated and the temporarily open/ closed estuaries (TOCEs) were the East Kleinemonde (EK) and Great Brak (GB) estuaries. Macrophytes were morphologically different across different estuary types. This suggests that there were different factors operating between these estuary types that would directly influence the morphology of species. The variation of plant height with different estuary types can be attributed to the fact that smaller salt marshes also have smaller habitat ranges compared to larger ones. The variation in morphological characteristics such as plant height can also be attributed to biogeographical range. Most morphological characteristics measured in the field fall within previously published ranges, and so these characters are useful in delimiting species. There were significant relationships between phenotypic variables and multivariate environmental variables. The most important of these variables were soil electrical conductivity, soil organic content and soil water content. Specifically, plant height increased with water content and decreased with salinity, flower stalk length had strong significant positive correlations with moisture content, organic content and pH while there were strong significant correlations with redox potential and electrical conductivity. Salt marshes are considered ideal for studying variation of species due to the explicit environmental gradients and plants occurring in salt marshes are halophytes that exhibit a range of morphological traits that allows for growth and reproduction under the stressful and extreme conditions. Considering recent climate change predictions and the consequent effects on South African estuaries this study provides significant information with regard to the response of species to a changing environment. The study was also aimed at updating the existing botanical database for South African estuaries in terms of species occurrence in South African estuaries, taxonomic name changes of existing species, new species, common names and habitats. Species diversity indices were also calculated for different estuaries, estuary types and biogeographic zones and diagnostic descriptions of the dominant salt marsh species were developed. The objective of this was that these data should provide baseline information for determining habitat richness and plant species diversity of South African estuaries which in turn should be used in determining priority estuaries for conservation and management. The identification key, developed using the DELTA software, would also aid researchers, managers and laymen in identifying salt marsh species. Results showed that the total number of macrophyte species, including intraspecific taxa and macroalgae, was 242 in 53 estuaries that were updated . There was an increase in the number of taxa recorded in the database primarily due to 1) research focus and full taxonomic surveys on larger estuaries and the big research projects has led to the identification of more species, 2) the addition of species that are not characteristically known as estuarine species, 3) the addition of 50 macroalgal taxa and 4) minor changes due to taxonomic revisions of species and the addition of newly described species. The Shannon diversity index showed that greater species diversity was found in the Berg (Groot) Estuary (4.220) and the Uilkraals Estuary (4.025). The cool temperate bioregion was the most diverse in the number of taxa (58) with the highest Shannon index (4.736). Permanently open estuaries were the most diverse in the number of unique taxa (56) with the highest Shannon index (4.867). Estuarine managers need to be aware of the species diversity in different estuarine types as well as the associated impacts on them. Conservation planning must therefore include species. Diagnostic features of INTKEY indicated that all 57 taxa were distinguishable from each other. Contrary to expectations plant height and not floral morphology was the best diagnostic characteristic. Ecological information such as the estuarine habitat, where different life forms occur, was important in delimiting species.
- Full Text:
- Date Issued: 2012
- Authors: Veldkornet, Dimitri Allastair
- Date: 2012
- Subjects: Estuarine ecology -- South Africa , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10635 , http://hdl.handle.net/10948/d1013001
- Description: Studies on morphological variation are important as it can depict the relationship with environmental factors clearly and convey an understanding of the manner, mechanism and factors influencing plant adaptation and evolution. Although many studies have been conducted on South African salt marsh plant physiology and phytosociology there are at present very few morphological studies on estuarine plants. The aim of this study was to compare the morphological variation of estuarine macrophytes in three different estuary types in the warm temperate biogeographic zone of South Africa and to compare characters used in the taxonomic descriptions of species with those measured in the field. Permanently open estuaries investigated were Ngqusi (WC), Kowie (KW) and Swartkops (SW) estuaries. The Knysna Estuary (KN) was the estuarine bay investigated and the temporarily open/ closed estuaries (TOCEs) were the East Kleinemonde (EK) and Great Brak (GB) estuaries. Macrophytes were morphologically different across different estuary types. This suggests that there were different factors operating between these estuary types that would directly influence the morphology of species. The variation of plant height with different estuary types can be attributed to the fact that smaller salt marshes also have smaller habitat ranges compared to larger ones. The variation in morphological characteristics such as plant height can also be attributed to biogeographical range. Most morphological characteristics measured in the field fall within previously published ranges, and so these characters are useful in delimiting species. There were significant relationships between phenotypic variables and multivariate environmental variables. The most important of these variables were soil electrical conductivity, soil organic content and soil water content. Specifically, plant height increased with water content and decreased with salinity, flower stalk length had strong significant positive correlations with moisture content, organic content and pH while there were strong significant correlations with redox potential and electrical conductivity. Salt marshes are considered ideal for studying variation of species due to the explicit environmental gradients and plants occurring in salt marshes are halophytes that exhibit a range of morphological traits that allows for growth and reproduction under the stressful and extreme conditions. Considering recent climate change predictions and the consequent effects on South African estuaries this study provides significant information with regard to the response of species to a changing environment. The study was also aimed at updating the existing botanical database for South African estuaries in terms of species occurrence in South African estuaries, taxonomic name changes of existing species, new species, common names and habitats. Species diversity indices were also calculated for different estuaries, estuary types and biogeographic zones and diagnostic descriptions of the dominant salt marsh species were developed. The objective of this was that these data should provide baseline information for determining habitat richness and plant species diversity of South African estuaries which in turn should be used in determining priority estuaries for conservation and management. The identification key, developed using the DELTA software, would also aid researchers, managers and laymen in identifying salt marsh species. Results showed that the total number of macrophyte species, including intraspecific taxa and macroalgae, was 242 in 53 estuaries that were updated . There was an increase in the number of taxa recorded in the database primarily due to 1) research focus and full taxonomic surveys on larger estuaries and the big research projects has led to the identification of more species, 2) the addition of species that are not characteristically known as estuarine species, 3) the addition of 50 macroalgal taxa and 4) minor changes due to taxonomic revisions of species and the addition of newly described species. The Shannon diversity index showed that greater species diversity was found in the Berg (Groot) Estuary (4.220) and the Uilkraals Estuary (4.025). The cool temperate bioregion was the most diverse in the number of taxa (58) with the highest Shannon index (4.736). Permanently open estuaries were the most diverse in the number of unique taxa (56) with the highest Shannon index (4.867). Estuarine managers need to be aware of the species diversity in different estuarine types as well as the associated impacts on them. Conservation planning must therefore include species. Diagnostic features of INTKEY indicated that all 57 taxa were distinguishable from each other. Contrary to expectations plant height and not floral morphology was the best diagnostic characteristic. Ecological information such as the estuarine habitat, where different life forms occur, was important in delimiting species.
- Full Text:
- Date Issued: 2012
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