What does the movement of the Phloem-mobile symplastic tracer, 5,6-carboxyfluorescein in shoots of Pisum Sativum L. Indicate - the existence of a symplastic transport system? - a bid to answer some puzzling questions
- Ade-Ademilua, Omobolanle Elizabeth, Botha, Christiaan E J
- Authors: Ade-Ademilua, Omobolanle Elizabeth , Botha, Christiaan E J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6492 , http://hdl.handle.net/10962/d1004475 , http://dx.doi.org/10.3923/ajpp.2006.127.131
- Description: Like other members of the Fabaceae, the minor veins of Pisum are categorized as a closed system termed type 2 minor vein configuration due to the presence of few or no plasmodesmal connections between the sieve element-transfer cell complex (SE-TCC) and the adjacent cells (Gamalei, 1989; van Bel and Gamalei, 1991) Pisum is classified further into the category of type 2 b minor vein configuration due to the presence of transfer cells with the characteristic wall ingrowths in the minor vein phloem (Gamalei, 1989). According to van Bel et al. (1992), there is a correlation between minor vein configuration and phloem loading. However, by reason of low plasmodesmal frequency, the pathway of the flow of assimilates in plants with type 2 minor vein configuration is considered to be apoplasmic (Gamalei, 1989; van Bel and Gamalei, 1991). Therefore, present reports on the movement of phloem-mobile 5,6-carboxyfluorescein, a known symplamically transported compound between pea leaflets raises some doubts on the accession that transport within the phloem in pea is strictly apoplasmic. In this study we look at different points of arguments and try to offer our explanation and conclusions on the transport pathways that are likely to exist in Pisum.
- Full Text: false
- Authors: Ade-Ademilua, Omobolanle Elizabeth , Botha, Christiaan E J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6492 , http://hdl.handle.net/10962/d1004475 , http://dx.doi.org/10.3923/ajpp.2006.127.131
- Description: Like other members of the Fabaceae, the minor veins of Pisum are categorized as a closed system termed type 2 minor vein configuration due to the presence of few or no plasmodesmal connections between the sieve element-transfer cell complex (SE-TCC) and the adjacent cells (Gamalei, 1989; van Bel and Gamalei, 1991) Pisum is classified further into the category of type 2 b minor vein configuration due to the presence of transfer cells with the characteristic wall ingrowths in the minor vein phloem (Gamalei, 1989). According to van Bel et al. (1992), there is a correlation between minor vein configuration and phloem loading. However, by reason of low plasmodesmal frequency, the pathway of the flow of assimilates in plants with type 2 minor vein configuration is considered to be apoplasmic (Gamalei, 1989; van Bel and Gamalei, 1991). Therefore, present reports on the movement of phloem-mobile 5,6-carboxyfluorescein, a known symplamically transported compound between pea leaflets raises some doubts on the accession that transport within the phloem in pea is strictly apoplasmic. In this study we look at different points of arguments and try to offer our explanation and conclusions on the transport pathways that are likely to exist in Pisum.
- Full Text: false
Converts and conservatives: missionary representations of African rulers in the Northern Transvaal, c. 1870-1900
- Authors: Kirkaldy, Alan , Kriel, Lize
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6146 , http://hdl.handle.net/10962/d1003715 , http://www2.unil.ch/lefaitmissionnaire/pages/tables_publi/lfm18_tbl.htm
- Description: During the second half of the nineteenth century, the Berlin Mission Society made strenuous efforts to convert the rulers of the people in whose areas they worked in the Northern Transvaal. In this they were largely unsuccessful. This raises questions about what forces influenced success and failure, and how the missionaries interpreted this. In this article, we interrogate the Berlin Missions Society’s accounts of the life and death of August Makhahane, a ruler of the Vhavenda who converted to Christianity, against the background of the accounts dealing with Matsiokwane Leboho, a ruler of the Bahananwa who did not convert. Through such a comparison, we aim at exploring the contrasted ways in which the Berlin missionaries reported about the two rulers.
- Full Text:
- Authors: Kirkaldy, Alan , Kriel, Lize
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6146 , http://hdl.handle.net/10962/d1003715 , http://www2.unil.ch/lefaitmissionnaire/pages/tables_publi/lfm18_tbl.htm
- Description: During the second half of the nineteenth century, the Berlin Mission Society made strenuous efforts to convert the rulers of the people in whose areas they worked in the Northern Transvaal. In this they were largely unsuccessful. This raises questions about what forces influenced success and failure, and how the missionaries interpreted this. In this article, we interrogate the Berlin Missions Society’s accounts of the life and death of August Makhahane, a ruler of the Vhavenda who converted to Christianity, against the background of the accounts dealing with Matsiokwane Leboho, a ruler of the Bahananwa who did not convert. Through such a comparison, we aim at exploring the contrasted ways in which the Berlin missionaries reported about the two rulers.
- Full Text:
Oceanographic environment of the Sodwana Bay coelacanths (Latimeria chalumnae), South Africa
- Roberts, M J, Ribbink, A J, Morris, T
- Authors: Roberts, M J , Ribbink, A J , Morris, T
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7126 , http://hdl.handle.net/10962/d1010633
- Description: Trimix scuba divers discovered coelacanths in Jesser Canyon at a depth of 104 m on the northern KwaZulu-Natal (KZN) coast (Sodwana Bay) in October 2000. The existence of these animals at such a shallow depth and in the swift and powerful Agulhas Current led to a suggestion that this might be an isolated group swept well away from the main population in the Comoros, where they live at depths of 200–350 m with little current. Subsequent observations from three manned submersible surveys and one remotely operated vehicle expedition together with recreational diver observations indicate that the South African population of coelacanths has at least 26 individuals, mostly occupying the depth range of 104–140 m in canyons. Seventeen CTD sections collected during four cruises in 2002 and 2003 indicate the temperature range in this habitat to be similar to that found in the Comoros Islands (that is, 15–22°C cf. 15–19°C in the Comoros). However, a 2.5-month-long time series of hourly data collected by a thermistor array deployed near a known coelacanth cave in Wright Canyon indicated greater variation than anticipated, with temperature changes between 16°C and 24°C occurring in a day. Dissolved oxygen levels in this depth zone were found to range between 3.0 ml l[superscript (–1)] and 4.8 ml l[superscript (–1)] compared to 3.5 ml l[superscript (–1)] in the Comoros. The low oxygen values along this coast are a result of the shallow oxygen minimum, which becomes shallower in the southwest Indian Ocean, particularly in the Agulhas Current, than in tropical latitudes. Current velocities measured using a ship-borne ADCP in the depth range 100–140 m at Sodwana were considerably higher than those measured in the Comoros habitat (20–60 cm s[superscript (–1)] cf. 3–4 cm s[superscript (–1)]) and may be an important factor explaining the coelacanths’ occupation of the canyons found along the northern KZN shelf-break.
- Full Text:
- Authors: Roberts, M J , Ribbink, A J , Morris, T
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7126 , http://hdl.handle.net/10962/d1010633
- Description: Trimix scuba divers discovered coelacanths in Jesser Canyon at a depth of 104 m on the northern KwaZulu-Natal (KZN) coast (Sodwana Bay) in October 2000. The existence of these animals at such a shallow depth and in the swift and powerful Agulhas Current led to a suggestion that this might be an isolated group swept well away from the main population in the Comoros, where they live at depths of 200–350 m with little current. Subsequent observations from three manned submersible surveys and one remotely operated vehicle expedition together with recreational diver observations indicate that the South African population of coelacanths has at least 26 individuals, mostly occupying the depth range of 104–140 m in canyons. Seventeen CTD sections collected during four cruises in 2002 and 2003 indicate the temperature range in this habitat to be similar to that found in the Comoros Islands (that is, 15–22°C cf. 15–19°C in the Comoros). However, a 2.5-month-long time series of hourly data collected by a thermistor array deployed near a known coelacanth cave in Wright Canyon indicated greater variation than anticipated, with temperature changes between 16°C and 24°C occurring in a day. Dissolved oxygen levels in this depth zone were found to range between 3.0 ml l[superscript (–1)] and 4.8 ml l[superscript (–1)] compared to 3.5 ml l[superscript (–1)] in the Comoros. The low oxygen values along this coast are a result of the shallow oxygen minimum, which becomes shallower in the southwest Indian Ocean, particularly in the Agulhas Current, than in tropical latitudes. Current velocities measured using a ship-borne ADCP in the depth range 100–140 m at Sodwana were considerably higher than those measured in the Comoros habitat (20–60 cm s[superscript (–1)] cf. 3–4 cm s[superscript (–1)]) and may be an important factor explaining the coelacanths’ occupation of the canyons found along the northern KZN shelf-break.
- Full Text:
Academic Library Consortia in South Africa : where we come from and where we are heading
- Authors: Thomas, G M E , Fourie, I
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6987 , http://hdl.handle.net/10962/d1012410
- Description: The purpose of this article is to give an overview of the establishment of the five academic library consortia in South Africa, their status quo, and a summary of their successes and plans for the future. Although useful information can be found from the consortia Web sites, much of it is no longer current. Similarly, there is limited published literature on the academic library consortia in South Africa. Apart from the sources referenced, the authors therefore relied heavily on an unpublished conference paper by Thomas[reference 1], which included findings gathered during a short survey among the five academic library consortia. In addition, Rowley and Slack[reference 2] and Sekabembe[reference 3] provide useful overviews of the library consortia in South Africa at the time of publication. Further information is available in published and unpublished sources.
- Full Text:
- Authors: Thomas, G M E , Fourie, I
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6987 , http://hdl.handle.net/10962/d1012410
- Description: The purpose of this article is to give an overview of the establishment of the five academic library consortia in South Africa, their status quo, and a summary of their successes and plans for the future. Although useful information can be found from the consortia Web sites, much of it is no longer current. Similarly, there is limited published literature on the academic library consortia in South Africa. Apart from the sources referenced, the authors therefore relied heavily on an unpublished conference paper by Thomas[reference 1], which included findings gathered during a short survey among the five academic library consortia. In addition, Rowley and Slack[reference 2] and Sekabembe[reference 3] provide useful overviews of the library consortia in South Africa at the time of publication. Further information is available in published and unpublished sources.
- Full Text:
Critical media literacy: a design for the future
- Authors: Prinsloo, Jeanne
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6331 , http://hdl.handle.net/10962/d1008476
- Description: [From OPENSPACE Editor Alice Kanengoni's editorial]: Professor Jeanne Prinsloo notes in her article that "In fact, it has been argued that the significance of the media in people’s lives has increased to the extent that it has been described as their primary curriculum, thereby recasting formal education as the secondary curriculum." This therefore requires an incestment in media literacy; people's ability to to understand the world around them, as represented in the media. Thus, Professor Prinsloo argues for critical media literacy, citing the role that the media played in fuelling the genocide in Rwanda, as an illustrative case in point. She states that "While we can not attribute all blame in the Rwandan scenario to the radio use, it is clear that the media mattered." She indicates that "media representations and engagements play a significant role in the way we understand the world, its people and events, and ourselves therein." As such, societies should invest in building a critical citizenry that can read and deconstruct the various ideologies that are often carries in and through the media.
- Full Text:
- Authors: Prinsloo, Jeanne
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6331 , http://hdl.handle.net/10962/d1008476
- Description: [From OPENSPACE Editor Alice Kanengoni's editorial]: Professor Jeanne Prinsloo notes in her article that "In fact, it has been argued that the significance of the media in people’s lives has increased to the extent that it has been described as their primary curriculum, thereby recasting formal education as the secondary curriculum." This therefore requires an incestment in media literacy; people's ability to to understand the world around them, as represented in the media. Thus, Professor Prinsloo argues for critical media literacy, citing the role that the media played in fuelling the genocide in Rwanda, as an illustrative case in point. She states that "While we can not attribute all blame in the Rwandan scenario to the radio use, it is clear that the media mattered." She indicates that "media representations and engagements play a significant role in the way we understand the world, its people and events, and ourselves therein." As such, societies should invest in building a critical citizenry that can read and deconstruct the various ideologies that are often carries in and through the media.
- Full Text:
The effectiveness of schools-based National Arbor Week activities in greening of urban homesteads : a case study of Grahamstown, South Africa
- Parkin, Fiona, Shackleton, Charlie M, Schudel, Ingrid J
- Authors: Parkin, Fiona , Shackleton, Charlie M , Schudel, Ingrid J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6645 , http://hdl.handle.net/10962/d1006885
- Description: Arbor Day, or Week, is a well-established greening initiative worldwide, focusing on tree planting and the benefits thereof. Frequently most effort is targeted at institutions such as schools and community groups. Yet there has been limited assessment of the success of Arbor Day, or Week, activities both at the schools, or the wider dissemination in neighbouring communities and suburbs. The objective of this study was to determine the influence of school-based Arbor Week activities on learners’ home-based practices regarding tree planting and urban forestry. Learners from three schools in Grahamstown, South Africa, with good Arbor Week participation, were assessed on their tree planting knowledge. The learners’ parents were also interviewed to determine whether the information obtained by the learners at school was taken home. A control group consisting of people with no children or very young children was also assessed. This study found that Arbor Week activities were, for the most part, successfully taught in the case study schools, and most of the learners stated that their knowledge of trees and their benefits came from their school activities. However, many learners could not remember the activities in which their schools partook the previous year. Whilst most learners were aware of the importance of trees, few had encouraged tree planting at home. However, over one-fifth of adults claimed that their knowledge of the benefits of trees was as a consequence of Arbor Day activities when they were young. Numerous constraints to tree planting were provided by learners and both the adult groups, the two most frequent being limited space and falling leaves making their yards untidy. External organisations should become more actively involved and provide much needed support systems if greening initiatives are to reach the wider community.
- Full Text:
- Authors: Parkin, Fiona , Shackleton, Charlie M , Schudel, Ingrid J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6645 , http://hdl.handle.net/10962/d1006885
- Description: Arbor Day, or Week, is a well-established greening initiative worldwide, focusing on tree planting and the benefits thereof. Frequently most effort is targeted at institutions such as schools and community groups. Yet there has been limited assessment of the success of Arbor Day, or Week, activities both at the schools, or the wider dissemination in neighbouring communities and suburbs. The objective of this study was to determine the influence of school-based Arbor Week activities on learners’ home-based practices regarding tree planting and urban forestry. Learners from three schools in Grahamstown, South Africa, with good Arbor Week participation, were assessed on their tree planting knowledge. The learners’ parents were also interviewed to determine whether the information obtained by the learners at school was taken home. A control group consisting of people with no children or very young children was also assessed. This study found that Arbor Week activities were, for the most part, successfully taught in the case study schools, and most of the learners stated that their knowledge of trees and their benefits came from their school activities. However, many learners could not remember the activities in which their schools partook the previous year. Whilst most learners were aware of the importance of trees, few had encouraged tree planting at home. However, over one-fifth of adults claimed that their knowledge of the benefits of trees was as a consequence of Arbor Day activities when they were young. Numerous constraints to tree planting were provided by learners and both the adult groups, the two most frequent being limited space and falling leaves making their yards untidy. External organisations should become more actively involved and provide much needed support systems if greening initiatives are to reach the wider community.
- Full Text:
Codeswitching, borrowing and mixing in a corpus of Xhosa English
- Authors: De Klerk, Vivian A
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6130 , http://hdl.handle.net/10962/d1011582
- Description: The paper analyses selected aspects of the codeswitching behaviour in a spoken corpus of the English of 326 people, all of them mother-tongue speakers of Xhosa (a local African language in South Africa), and all of whom would see themselves as Xhosa/English bilinguals. The corpus comprises approximately 550,000 transcribed words of spontaneous, relaxed, oral discourse in English between pairs of Xhosaspeaking interlocutors, discussing a wide range of topics. While the usual pattern in bilingual speech is to use the L1 as matrix language and the L2 as embedded language, in this corpus the opposite is the case, as interlocutors were interviewed in English (the L2). The corpus therefore offers a ‘mirror image’, in a sense, of normal codeswitching behaviour. Using Wordsmith (a concordancer programme), all incidences of codeswitching into Xhosa during these conversations were identified and analysed in an effort to reveal underlying patterns. Examination of the amount and nature of codeswitching in the corpus promised to throw some light on the extent to which participants are genuinely bilingual, in terms of their ability to converse comfortably in English.
- Full Text:
- Authors: De Klerk, Vivian A
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6130 , http://hdl.handle.net/10962/d1011582
- Description: The paper analyses selected aspects of the codeswitching behaviour in a spoken corpus of the English of 326 people, all of them mother-tongue speakers of Xhosa (a local African language in South Africa), and all of whom would see themselves as Xhosa/English bilinguals. The corpus comprises approximately 550,000 transcribed words of spontaneous, relaxed, oral discourse in English between pairs of Xhosaspeaking interlocutors, discussing a wide range of topics. While the usual pattern in bilingual speech is to use the L1 as matrix language and the L2 as embedded language, in this corpus the opposite is the case, as interlocutors were interviewed in English (the L2). The corpus therefore offers a ‘mirror image’, in a sense, of normal codeswitching behaviour. Using Wordsmith (a concordancer programme), all incidences of codeswitching into Xhosa during these conversations were identified and analysed in an effort to reveal underlying patterns. Examination of the amount and nature of codeswitching in the corpus promised to throw some light on the extent to which participants are genuinely bilingual, in terms of their ability to converse comfortably in English.
- Full Text:
Professionalism and training for mass communication: challenges and opportunities for Southern Africa
- Authors: Berger, Guy
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6332 , http://hdl.handle.net/10962/d1008477
- Description: [From OPENSPACE Editor Alice Kanengoni's editorial]: Closely linked to a critical media citizenry that can demand better of the media, is the challenge of professionalism and training in the region. Professor Guy Berger illuminates the challenges that the region faces in this regard, a key one being the ability to to match the inputs with the outcomes ... where measuring whether the quality of media products is directly linked to the inputs in training needs to be explored further.
- Full Text:
- Authors: Berger, Guy
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6332 , http://hdl.handle.net/10962/d1008477
- Description: [From OPENSPACE Editor Alice Kanengoni's editorial]: Closely linked to a critical media citizenry that can demand better of the media, is the challenge of professionalism and training in the region. Professor Guy Berger illuminates the challenges that the region faces in this regard, a key one being the ability to to match the inputs with the outcomes ... where measuring whether the quality of media products is directly linked to the inputs in training needs to be explored further.
- Full Text:
Application of reverse-flow micellar electrokinetic chromatography for the simultaneous determination of flavonols and terpene trilactones in Ginkgo biloba dosage forms
- Dubber, Mary-Jean, Kanfer, Isadore
- Authors: Dubber, Mary-Jean , Kanfer, Isadore
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6357 , http://hdl.handle.net/10962/d1006049
- Description:
A reverse-flow micellar electrokinetic chromatographic (RF-MEKC) method was developed for the simultaneous qualitative determination of 10 components consisting of the flavonol glycosides, rutin and quercitrin, the flavonol aglycones, isorhamnetin, kaempferol and quercetin, the terpene trilactones, ginkgolides A, B, C and J and the sesquiterpene, bilobalide. This method was used to fingerprint Ginkgo biloba solid oral dosage forms and validated for the quantitation of the marker compounds, rutin and quercetin in some commercial products. In addition to the usual variables, the influence of some essential background electrolyte (BGE) components such as sodium dodecyl sulphate (SDS) and
-cyclodextrin concentrations were investigated. A polyimide fused-silica square capillary column (75 μm I.D. × 360 μm O.D.) with a total length of 60.0 cm and effective length of 45.0 cm was used for the separation. The final BGE consisted of 20 mM phosphoric acid, 40 mM SDS and 12 mM -cyclodextrin (pH 2.2) using reverse polarity with a voltage of −17.5 kV. Samples were injected electrokinetically at −5 kV for 3 s for the qualitative analysis and hydrodynamically at 20 mbar for 0.6 s for the quantitative assay. The total run time was 22 min and the limits of detection were 3.13 μg/ml and 1.88 μg/ml for rutin and quercetin, respectively. Fingerprint profiles of the solid oral dosage forms and the results of the quantitative analysis indicated that there were major discrepancies in the marker content between products and illustrates the value of this method for use as a procedure to assess product quality of commercially available Ginkgo biloba products. - Full Text:
- Authors: Dubber, Mary-Jean , Kanfer, Isadore
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6357 , http://hdl.handle.net/10962/d1006049
- Description:
A reverse-flow micellar electrokinetic chromatographic (RF-MEKC) method was developed for the simultaneous qualitative determination of 10 components consisting of the flavonol glycosides, rutin and quercitrin, the flavonol aglycones, isorhamnetin, kaempferol and quercetin, the terpene trilactones, ginkgolides A, B, C and J and the sesquiterpene, bilobalide. This method was used to fingerprint Ginkgo biloba solid oral dosage forms and validated for the quantitation of the marker compounds, rutin and quercetin in some commercial products. In addition to the usual variables, the influence of some essential background electrolyte (BGE) components such as sodium dodecyl sulphate (SDS) and
-cyclodextrin concentrations were investigated. A polyimide fused-silica square capillary column (75 μm I.D. × 360 μm O.D.) with a total length of 60.0 cm and effective length of 45.0 cm was used for the separation. The final BGE consisted of 20 mM phosphoric acid, 40 mM SDS and 12 mM -cyclodextrin (pH 2.2) using reverse polarity with a voltage of −17.5 kV. Samples were injected electrokinetically at −5 kV for 3 s for the qualitative analysis and hydrodynamically at 20 mbar for 0.6 s for the quantitative assay. The total run time was 22 min and the limits of detection were 3.13 μg/ml and 1.88 μg/ml for rutin and quercetin, respectively. Fingerprint profiles of the solid oral dosage forms and the results of the quantitative analysis indicated that there were major discrepancies in the marker content between products and illustrates the value of this method for use as a procedure to assess product quality of commercially available Ginkgo biloba products. - Full Text:
Ameliorating poverty in South Africa through natural resource commercialisation : how can NGO's make a difference?
- Authors: Shackleton, Sheona E
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6615 , http://hdl.handle.net/10962/d1016222
- Description: [From Introduction] Some of the poorest rural people in South Africa are turning to the natural resource base for income generation. Using traditional skills they are converting a variety of wild resources into commodities that are sold in the market place. Wood and woven craft, medicines, fresh and processed wild foods, alcoholic beverages, building materials, fuelwood, dried mopane worms, cultural artefacts and brooms are just some examples of the array of natural resource products increasingly seen for sale in local and external markets. Many of the participants in this trade have minimal education, few assets to draw on, and little access to alternative sources of income or jobs. A significant proportion are women, with more than half heading their own households. Many come from households devastated by HIV/AIDS. The cash earned from selling natural resource products, however modest, is of critical importance to the households involved, preventing them from slipping deeper into poverty. “Since I have been making brooms my children no longer go to bed crying of hunger” observed one broom producer. NGOs, particularly those involved in rural development, can play an important role in assisting producers overcome some of the obstacles they face and in enhancing the opportunities to grow this informal sector. , This policy brief is based on the original brief made available for a workshop in August 2006. It draws on, amongst other sources, the results of several case studies of natural resource commercialisation undertaken across South Africa. The project was funded by the South Africa-Netherlands Programme on Alternatives in Development (SANPAD), BP South Africa and the National Research Foundation (NRF). The Center for International Forestry Research, with support from SIDA, provided the funding to share these findings with key stakeholders including government policy and decision makers.
- Full Text:
- Authors: Shackleton, Sheona E
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6615 , http://hdl.handle.net/10962/d1016222
- Description: [From Introduction] Some of the poorest rural people in South Africa are turning to the natural resource base for income generation. Using traditional skills they are converting a variety of wild resources into commodities that are sold in the market place. Wood and woven craft, medicines, fresh and processed wild foods, alcoholic beverages, building materials, fuelwood, dried mopane worms, cultural artefacts and brooms are just some examples of the array of natural resource products increasingly seen for sale in local and external markets. Many of the participants in this trade have minimal education, few assets to draw on, and little access to alternative sources of income or jobs. A significant proportion are women, with more than half heading their own households. Many come from households devastated by HIV/AIDS. The cash earned from selling natural resource products, however modest, is of critical importance to the households involved, preventing them from slipping deeper into poverty. “Since I have been making brooms my children no longer go to bed crying of hunger” observed one broom producer. NGOs, particularly those involved in rural development, can play an important role in assisting producers overcome some of the obstacles they face and in enhancing the opportunities to grow this informal sector. , This policy brief is based on the original brief made available for a workshop in August 2006. It draws on, amongst other sources, the results of several case studies of natural resource commercialisation undertaken across South Africa. The project was funded by the South Africa-Netherlands Programme on Alternatives in Development (SANPAD), BP South Africa and the National Research Foundation (NRF). The Center for International Forestry Research, with support from SIDA, provided the funding to share these findings with key stakeholders including government policy and decision makers.
- Full Text:
Ameliorating poverty in South Africa through natural resource commercialisation
- Authors: Shackleton, Sheona E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6651 , http://hdl.handle.net/10962/d1007062
- Description: This short policy brief advocates for more attention to be paid to the potential of natural resource commercialisation as a means to livelihood security and poverty alleviation in rural South Africa. It is one of a set of four policy briefs based on the findings of several case studies across the country.
- Full Text:
- Authors: Shackleton, Sheona E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6651 , http://hdl.handle.net/10962/d1007062
- Description: This short policy brief advocates for more attention to be paid to the potential of natural resource commercialisation as a means to livelihood security and poverty alleviation in rural South Africa. It is one of a set of four policy briefs based on the findings of several case studies across the country.
- Full Text:
Maximum likelihood and Bayesian approaches to stock assessment when data are questionable
- Booth, Anthony J, Quinn II, T J
- Authors: Booth, Anthony J , Quinn II, T J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6764 , http://hdl.handle.net/10962/d1007962
- Description: This study examines the use of age-structured maximum likelihood and Bayesian approaches for stock assessment of the Namibian monkfish, Lophius vomerinus, resource with questionable data, in which time series are short, abundance indices are variable, and research data conflict with commercial data. Bayesian approaches with both noninformative and informative priors are investigated to determine if they enhance estimation stability. Three data scenarios are assessed: commercial and research survey data, research survey data only, and commercial data only. Both statistical approaches show that resource abundance has decreased with exploitable biomass estimated at approximately 44% of pristine levels. The maximum likelihood and the Bayesian approach with noninformative priors result in similar estimates. As the abundance data contained little information pertaining to possible density dependence within the stock–recruit relationship, only a Bayesian approach with informative priors reduces uncertainty in the steepness parameter h. Estimated management quantities are sensitive both to the set of data sources and whether prior information was informative or not. The strengths of the Bayesian approach include the integration of prior information with uncertain data, the exploration of data conflicts, and the ability to show the uncertainty in estimates of management parameters. Its weakness is that estimation stability is dependent on the choice of priors, which alters some posterior distributions of management quantities.
- Full Text:
- Authors: Booth, Anthony J , Quinn II, T J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6764 , http://hdl.handle.net/10962/d1007962
- Description: This study examines the use of age-structured maximum likelihood and Bayesian approaches for stock assessment of the Namibian monkfish, Lophius vomerinus, resource with questionable data, in which time series are short, abundance indices are variable, and research data conflict with commercial data. Bayesian approaches with both noninformative and informative priors are investigated to determine if they enhance estimation stability. Three data scenarios are assessed: commercial and research survey data, research survey data only, and commercial data only. Both statistical approaches show that resource abundance has decreased with exploitable biomass estimated at approximately 44% of pristine levels. The maximum likelihood and the Bayesian approach with noninformative priors result in similar estimates. As the abundance data contained little information pertaining to possible density dependence within the stock–recruit relationship, only a Bayesian approach with informative priors reduces uncertainty in the steepness parameter h. Estimated management quantities are sensitive both to the set of data sources and whether prior information was informative or not. The strengths of the Bayesian approach include the integration of prior information with uncertain data, the exploration of data conflicts, and the ability to show the uncertainty in estimates of management parameters. Its weakness is that estimation stability is dependent on the choice of priors, which alters some posterior distributions of management quantities.
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Spatio-temporal patterns in maturation of the chokka squid (Loligo vulgaris reynaudii) off the coast of South Africa
- Olyott, L J H, Sauer, Warwick H H, Booth, Anthony J
- Authors: Olyott, L J H , Sauer, Warwick H H , Booth, Anthony J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6763 , http://hdl.handle.net/10962/d1007930
- Description: Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.
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- Authors: Olyott, L J H , Sauer, Warwick H H , Booth, Anthony J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6763 , http://hdl.handle.net/10962/d1007930
- Description: Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.
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Medicines information and adherence in HIV/AIDS patients
- Mansoor, Leila E, Dowse, Roslind
- Authors: Mansoor, Leila E , Dowse, Roslind
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6395 , http://hdl.handle.net/10962/d1006319
- Description: Background: Providing written medicines information is being legislated in an increasing number of countries worldwide, with the patient information leaflet (PIL) being the most widely used method for conveying health information. The impact of providing such information on adherence to therapy is reportedly unpredictable. Therapy for human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) and related opportunistic infections usually involves polytherapy and complex regimens, both of which are risk factors for non-adherence. The objective of this study was to assess the impact of medicines information on adherence to chronic co-trimoxazole therapy in low-literate HIV/AIDS patients. Methods: Two different PILs were designed for co-trimoxazole tablets and were available in both English and isiXhosa. Participants were randomly allocated to a control group (receiving no PIL), group A (receiving a 'complex PIL') and group B (receiving a 'simple PIL' incorporating pictograms). At the first interview, demographic data were collected and the time, date and day that the participant would take his/her first tablet of the month's course was also documented. In a follow-up interview adherence to therapy was assessed using two methods; self-report and tablet count. Results: The medicines information materials incorporating simple text and pictograms resulted in significantly improved adherence to therapy in the short term, whereas a non-significant increase in adherence was associated with the availability of the more complex information. This was shown by both the self-reported assessment as well as the tablet count. Conclusion: This research suggests that appropriately designed written material can have a positive impact in improving adherence and, together with verbal consultation, are essential for enabling patients to make appropriate decisions about their medicine taking.
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- Authors: Mansoor, Leila E , Dowse, Roslind
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6395 , http://hdl.handle.net/10962/d1006319
- Description: Background: Providing written medicines information is being legislated in an increasing number of countries worldwide, with the patient information leaflet (PIL) being the most widely used method for conveying health information. The impact of providing such information on adherence to therapy is reportedly unpredictable. Therapy for human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) and related opportunistic infections usually involves polytherapy and complex regimens, both of which are risk factors for non-adherence. The objective of this study was to assess the impact of medicines information on adherence to chronic co-trimoxazole therapy in low-literate HIV/AIDS patients. Methods: Two different PILs were designed for co-trimoxazole tablets and were available in both English and isiXhosa. Participants were randomly allocated to a control group (receiving no PIL), group A (receiving a 'complex PIL') and group B (receiving a 'simple PIL' incorporating pictograms). At the first interview, demographic data were collected and the time, date and day that the participant would take his/her first tablet of the month's course was also documented. In a follow-up interview adherence to therapy was assessed using two methods; self-report and tablet count. Results: The medicines information materials incorporating simple text and pictograms resulted in significantly improved adherence to therapy in the short term, whereas a non-significant increase in adherence was associated with the availability of the more complex information. This was shown by both the self-reported assessment as well as the tablet count. Conclusion: This research suggests that appropriately designed written material can have a positive impact in improving adherence and, together with verbal consultation, are essential for enabling patients to make appropriate decisions about their medicine taking.
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Evaluation of Bacillus thuringiensis Berliner as an alternative control of small hive beetles, Aethina tumida Murray (Coleoptera: Nitidulidae)
- Buchholz, S, Neumann, Peter, Neumann, K, Hepburn, H Randall
- Authors: Buchholz, S , Neumann, Peter , Neumann, K , Hepburn, H Randall
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6929 , http://hdl.handle.net/10962/d1011945
- Description: Small hive beetles, Aethina tumida Murray, are parasites and scavengers of honeybee colonies, Apis mellifera L., and have become an invasive species that can cause considerable damage in its new distribution areas. An effective subspecies of Bacillus thuringiensis Berliner (=Bt) would provide an alternative to chemical control of this pest. Therefore, we tested three different Bt strains [B. thuringiensis, var. aizawai (B401®), B. thuringiensis var. kurstaki (Novodor®) and B. thuringiensis var. San Diego tenebrionis (Jackpot®)] and Perizin® (3.2% coumaphos), each applied on combs with a pollen diet fed to pairs of adult beetles. This evaluates the products for the suppression of successful small hive beetle reproduction. While none of the tested Bt strains showed a significant effect on the number of produced wandering larvae, we could confirm the efficacy of coumaphos for the control of small hive beetles. We further show that it is also efficient when applied with a lower concentration as a liquid on the combs. We suggest the continued search for efficient Bt strains naturally infesting small hive beetles in its endemic and new ranges, which may become a part of the integrated management of this pest.
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- Authors: Buchholz, S , Neumann, Peter , Neumann, K , Hepburn, H Randall
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6929 , http://hdl.handle.net/10962/d1011945
- Description: Small hive beetles, Aethina tumida Murray, are parasites and scavengers of honeybee colonies, Apis mellifera L., and have become an invasive species that can cause considerable damage in its new distribution areas. An effective subspecies of Bacillus thuringiensis Berliner (=Bt) would provide an alternative to chemical control of this pest. Therefore, we tested three different Bt strains [B. thuringiensis, var. aizawai (B401®), B. thuringiensis var. kurstaki (Novodor®) and B. thuringiensis var. San Diego tenebrionis (Jackpot®)] and Perizin® (3.2% coumaphos), each applied on combs with a pollen diet fed to pairs of adult beetles. This evaluates the products for the suppression of successful small hive beetle reproduction. While none of the tested Bt strains showed a significant effect on the number of produced wandering larvae, we could confirm the efficacy of coumaphos for the control of small hive beetles. We further show that it is also efficient when applied with a lower concentration as a liquid on the combs. We suggest the continued search for efficient Bt strains naturally infesting small hive beetles in its endemic and new ranges, which may become a part of the integrated management of this pest.
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The use of archaeological and ethnographical information to supplement the historical record of the distribution of large mammalian herbivores in South Africa
- Bernard, Ric T F, Parker, Daniel M
- Authors: Bernard, Ric T F , Parker, Daniel M
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6914 , http://hdl.handle.net/10962/d1011877
- Description: Introduction: The introduction of animal taxa to areas where they do not naturally occur has the potential to damage severely the native fauna and flora. Introductions, both accidental and intentional, to Australia, New Zealand, Marion Island and other oceanic islands provide spectacular examples of this.1,2 Non-native mammalian herbivores often become invasive in the absence of their natural predators2 and their impact on vegetation, which may include alterations to plant species composition, structure and diversity, is exaggerated, especially if the vegetation has evolved in the absence of similar herbivores.3,4 This influence is not limited to the direct consequence for the vegetation and there may be a cascade effect on ecosystem functioning through, for example, a decline in the amount of available forage for indigenous herbivores,3 a reduction in the breeding efficiency of birds that rely on the vegetation,5,6 and a negative effect on carbon storage by transforming stands of dense vegetative cover to open savannah like systems.7 Nor are these outcomes restricted to non-native herbivores; the re-introduction of a species, such as the elephant (Loxodonta africana), to areas from which it has been absent for many years may have similar consequences.8–11 Additional problems associated with the uncontrolled movement of large mammals include the transmission of disease, such as brucellosis in the United States,3 and a threat to the genetic integrity of a species through hybridization.12 It is thus clear that deliberate introductions of herbivores to areas where they do not naturally occur may not be sound conservation practice.
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- Authors: Bernard, Ric T F , Parker, Daniel M
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6914 , http://hdl.handle.net/10962/d1011877
- Description: Introduction: The introduction of animal taxa to areas where they do not naturally occur has the potential to damage severely the native fauna and flora. Introductions, both accidental and intentional, to Australia, New Zealand, Marion Island and other oceanic islands provide spectacular examples of this.1,2 Non-native mammalian herbivores often become invasive in the absence of their natural predators2 and their impact on vegetation, which may include alterations to plant species composition, structure and diversity, is exaggerated, especially if the vegetation has evolved in the absence of similar herbivores.3,4 This influence is not limited to the direct consequence for the vegetation and there may be a cascade effect on ecosystem functioning through, for example, a decline in the amount of available forage for indigenous herbivores,3 a reduction in the breeding efficiency of birds that rely on the vegetation,5,6 and a negative effect on carbon storage by transforming stands of dense vegetative cover to open savannah like systems.7 Nor are these outcomes restricted to non-native herbivores; the re-introduction of a species, such as the elephant (Loxodonta africana), to areas from which it has been absent for many years may have similar consequences.8–11 Additional problems associated with the uncontrolled movement of large mammals include the transmission of disease, such as brucellosis in the United States,3 and a threat to the genetic integrity of a species through hybridization.12 It is thus clear that deliberate introductions of herbivores to areas where they do not naturally occur may not be sound conservation practice.
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Sand stress as a non-determinant of habitat segregation of indigenous (Perna perna) and invasive (Mytilus galloprovincialis) mussels in South Africa
- Zardi, Gerardo I, Nicastro, Katy R, Porri, Francesca, McQuaid, Christopher D
- Authors: Zardi, Gerardo I , Nicastro, Katy R , Porri, Francesca , McQuaid, Christopher D
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6946 , http://hdl.handle.net/10962/d1011974
- Description: Periodical sand inundation influences diversity and distribution of intertidal species throughout the world. This study investigates the effect of sand stress on survival and on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. P. perna occupies a lower intertidal zone which, monthly surveys over 1.5 years showed, is covered by sand for longer periods than the higher M. galloprovincialis zone. Despite this, when buried under sand, P. perna mortality rates were significantly higher than those of M. galloprovincialis in both laboratory and in field experiments. Under anoxic condition, P. perna mortality rates were still significantly higher than those for M. galloprovincialis, but both species died later than when exposed to sand burial, underlining the importance of the physical action of sand on mussel internal organs. When buried, both species accumulate sediments within the shell valves while still alive, but the quantities are much greater for P. perna. This suggests that P. perna gills are more severely damaged by sand abrasion and could explain its higher mortality rates. M. galloprovincialis has longer labial palps than P. perna, indicating a higher particle sorting ability and consequently explaining its lower mortality rates when exposed to sand in suspension. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. Although sand stress strongly affects the survival of the two species, it does not explain their vertical zonation. Contrary to our expectations, the species that is less well adapted to cope with sand stress maintains dominance in a habitat where such stress is high.
- Full Text:
- Authors: Zardi, Gerardo I , Nicastro, Katy R , Porri, Francesca , McQuaid, Christopher D
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6946 , http://hdl.handle.net/10962/d1011974
- Description: Periodical sand inundation influences diversity and distribution of intertidal species throughout the world. This study investigates the effect of sand stress on survival and on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. P. perna occupies a lower intertidal zone which, monthly surveys over 1.5 years showed, is covered by sand for longer periods than the higher M. galloprovincialis zone. Despite this, when buried under sand, P. perna mortality rates were significantly higher than those of M. galloprovincialis in both laboratory and in field experiments. Under anoxic condition, P. perna mortality rates were still significantly higher than those for M. galloprovincialis, but both species died later than when exposed to sand burial, underlining the importance of the physical action of sand on mussel internal organs. When buried, both species accumulate sediments within the shell valves while still alive, but the quantities are much greater for P. perna. This suggests that P. perna gills are more severely damaged by sand abrasion and could explain its higher mortality rates. M. galloprovincialis has longer labial palps than P. perna, indicating a higher particle sorting ability and consequently explaining its lower mortality rates when exposed to sand in suspension. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. Although sand stress strongly affects the survival of the two species, it does not explain their vertical zonation. Contrary to our expectations, the species that is less well adapted to cope with sand stress maintains dominance in a habitat where such stress is high.
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Biogeographic and nearshore–offshore trends in isotope ratios of intertidal mussels and their food sources around the coast of southern Africa
- Hill, Jaclyn M, McQuaid, Christopher D, Kaehler, Sven
- Authors: Hill, Jaclyn M , McQuaid, Christopher D , Kaehler, Sven
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6878 , http://hdl.handle.net/10962/d1011633
- Description: There are broad differences in oceanography and primary production around the southern African coast that are likely to give rise to major differences in trophic pathways. Stable isotope ratios provide integrated information on trophic relationships, yet there has been limited research on geographic variation in isotopic composition of marine consumers and their food. In this study, δ13C and δ15N of suspended particulate matter (SPM), intertidal mussels and common macroalgae along the southern African coastline were explored. Nearshore–offshore isotope trends as well as biogeographic and temporal patterns in isotopic ratios of mussel tissue, macroalgae and SPM were investigated at 12 sites along the coast from Namibia to the Mozambique border. SPM exhibited overall trends of nearshore 13C depletion from south-west to north-east along the coastline and from nearshore (0 km) to offshore (10 km) waters, in both cases suggesting a shift from a nearshore signature strongly influenced by macroalgal detritus to one more representative of oceanic phytoplankton. With one exception it was possible, using discriminant analysis, to categorize mussel populations into 4 geographic groups, on the basis of both carbon and nitrogen signatures: the east coast, the south-east coast, the south-west coast and the west coast. Macroalgae showed no consistent biogeographic trends and need to be examined in greater detail to relate nearshore SPM values to living macroalgal signatures. A linear mixing model indicated that mussels along the entire coastline generally demonstrated more than 50% dependence on nearshore carbon and nitrogen, emphasizing the importance of nearshore primary production to intertidal consumers.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D , Kaehler, Sven
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6878 , http://hdl.handle.net/10962/d1011633
- Description: There are broad differences in oceanography and primary production around the southern African coast that are likely to give rise to major differences in trophic pathways. Stable isotope ratios provide integrated information on trophic relationships, yet there has been limited research on geographic variation in isotopic composition of marine consumers and their food. In this study, δ13C and δ15N of suspended particulate matter (SPM), intertidal mussels and common macroalgae along the southern African coastline were explored. Nearshore–offshore isotope trends as well as biogeographic and temporal patterns in isotopic ratios of mussel tissue, macroalgae and SPM were investigated at 12 sites along the coast from Namibia to the Mozambique border. SPM exhibited overall trends of nearshore 13C depletion from south-west to north-east along the coastline and from nearshore (0 km) to offshore (10 km) waters, in both cases suggesting a shift from a nearshore signature strongly influenced by macroalgal detritus to one more representative of oceanic phytoplankton. With one exception it was possible, using discriminant analysis, to categorize mussel populations into 4 geographic groups, on the basis of both carbon and nitrogen signatures: the east coast, the south-east coast, the south-west coast and the west coast. Macroalgae showed no consistent biogeographic trends and need to be examined in greater detail to relate nearshore SPM values to living macroalgal signatures. A linear mixing model indicated that mussels along the entire coastline generally demonstrated more than 50% dependence on nearshore carbon and nitrogen, emphasizing the importance of nearshore primary production to intertidal consumers.
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Spatio-temporal variability of larval abundance and settlement of Perna perna: differential delivery of mussels
- Porri, Francesca, McQuaid, Christopher D, Radloff, Sarah E
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6877 , http://hdl.handle.net/10962/d1011625 , http://dx.doi.org/10.3354/meps315141
- Description: We examined larval availability and settlement of the intertidal mussel Perna perna simultaneously at different spatial and temporal scales using a nested design at 2 sites, 3 km apart on the south coast of South Africa. Each site had 3 locations (300 m apart) where 5 artificial settler collectors were placed about 20 cm apart. Collectors were replaced on temporal scales varying from fortnightly (for 16 mo) to daily (2 series of 15 to 20 d). Each intertidal location was paired with an inshore location (these too were 300 m apart) within 500 m of the shore, where larval availability was measured by 3 vertical plankton hauls collected on the same dates as for settler sampling. There was strong temporal variation in abundances of larvae and settlers, and no correlation (r always < 0.14) was found between the two. Larvae were abundant only at the start of sampling and rare for the rest of the study, while distinct peaks in settler numbers occurred later. No spatial effect was detected for larval availability, while there was strong spatial variation in settlement at the location level. These results indicate that, on scales of 100s of m to km, delivery of larvae from the nearshore water column onto the shore is strongly differential, with some locations consistently receiving more settlers than others. We conclude that, at these sites, the patchiness in settlement observed on scales of 100s of m depends on differential delivery, rather than differential offshore distribution of larvae. We suggest that differential delivery is due to the effect of nearshore bottom topography on local hydrodynamics.
- Full Text:
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6877 , http://hdl.handle.net/10962/d1011625 , http://dx.doi.org/10.3354/meps315141
- Description: We examined larval availability and settlement of the intertidal mussel Perna perna simultaneously at different spatial and temporal scales using a nested design at 2 sites, 3 km apart on the south coast of South Africa. Each site had 3 locations (300 m apart) where 5 artificial settler collectors were placed about 20 cm apart. Collectors were replaced on temporal scales varying from fortnightly (for 16 mo) to daily (2 series of 15 to 20 d). Each intertidal location was paired with an inshore location (these too were 300 m apart) within 500 m of the shore, where larval availability was measured by 3 vertical plankton hauls collected on the same dates as for settler sampling. There was strong temporal variation in abundances of larvae and settlers, and no correlation (r always < 0.14) was found between the two. Larvae were abundant only at the start of sampling and rare for the rest of the study, while distinct peaks in settler numbers occurred later. No spatial effect was detected for larval availability, while there was strong spatial variation in settlement at the location level. These results indicate that, on scales of 100s of m to km, delivery of larvae from the nearshore water column onto the shore is strongly differential, with some locations consistently receiving more settlers than others. We conclude that, at these sites, the patchiness in settlement observed on scales of 100s of m depends on differential delivery, rather than differential offshore distribution of larvae. We suggest that differential delivery is due to the effect of nearshore bottom topography on local hydrodynamics.
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Temporal scales of variation in settlement and recruitment of the mussel Perna perna (Linnaeus, 1758)
- Porri, Francesca, McQuaid, Christopher D, Radloff, Sarah E
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6963 , http://hdl.handle.net/10962/d1012026 , http://dx.doi.org/10.1016/j.jembe.2005.11.008
- Description: Population dynamics of many intertidal organisms are strongly affected by the abundance and distribution of larvae arriving on the shore. In particular, not only absolute numbers of settlers but also the degree of synchronisation of settlement can have a strong influence on whether density-dependent or density-independent processes shape adult shape populations. Temporal variation in rates of settlement and recruitment of the mussel Perna perna on the south coast of South Africa was investigated using a nested spatial design at different temporal scales. Variability in settlement at spring tides was examined at two temporal scales: lunar (to investigate the effect of state of the moon on settlement) and tidal (to investigate the influence of state of the tide on mussel settlement). Recruitment over neap tides was examined at one temporal scale, fortnight (to investigate the effect of date on mussel recruitment). Strong temporal variation was evident for both settlement and recruitment, but not at all time scales. Distinct peaks of settler/recruit abundance were observed during the lunar and neap tide studies. Recruitment intensity differed over the course of the year, and pulsing of recruitment was generally synchronised among locations. However, the strength of pulsing differed dramatically among locations, giving a significant interaction between fortnight and location. The finest temporal scale, investigated in the tidal study, did not reveal a significant effect of the state of the tide on settlement. The state of the moon (new or full) was not significant as a main factor (p = 0.052), although generally more settlers arrived on the shore during new moon. Phase of the moon appeared to have an effect on settler abundances, but only when and where densities were high.
- Full Text:
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6963 , http://hdl.handle.net/10962/d1012026 , http://dx.doi.org/10.1016/j.jembe.2005.11.008
- Description: Population dynamics of many intertidal organisms are strongly affected by the abundance and distribution of larvae arriving on the shore. In particular, not only absolute numbers of settlers but also the degree of synchronisation of settlement can have a strong influence on whether density-dependent or density-independent processes shape adult shape populations. Temporal variation in rates of settlement and recruitment of the mussel Perna perna on the south coast of South Africa was investigated using a nested spatial design at different temporal scales. Variability in settlement at spring tides was examined at two temporal scales: lunar (to investigate the effect of state of the moon on settlement) and tidal (to investigate the influence of state of the tide on mussel settlement). Recruitment over neap tides was examined at one temporal scale, fortnight (to investigate the effect of date on mussel recruitment). Strong temporal variation was evident for both settlement and recruitment, but not at all time scales. Distinct peaks of settler/recruit abundance were observed during the lunar and neap tide studies. Recruitment intensity differed over the course of the year, and pulsing of recruitment was generally synchronised among locations. However, the strength of pulsing differed dramatically among locations, giving a significant interaction between fortnight and location. The finest temporal scale, investigated in the tidal study, did not reveal a significant effect of the state of the tide on settlement. The state of the moon (new or full) was not significant as a main factor (p = 0.052), although generally more settlers arrived on the shore during new moon. Phase of the moon appeared to have an effect on settler abundances, but only when and where densities were high.
- Full Text: