River nutrient water and sediment measurements inform on nutrient retention, with implications for eutrophication
- Dalu, Tatenda, Wasserman, Ryan J, Magoro, Mandla L, Froneman, P William, Weyl, Olaf, L F
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Magoro, Mandla L , Froneman, P William , Weyl, Olaf, L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467222 , vital:76841 , https://doi.org/10.1016/j.scitotenv.2019.05.167
- Description: The consideration of nutrients in pollution dynamics is important for environmental management and conservation. Developing countries are yet to appreciate the aquatic ecosystem pollution impacts on their economies and as such, information on water pollution dynamics is limited. This study assessed the spatio-temporal dynamics of nutrient loading and retention in stream water and sediments in the Bloukrans River system, Eastern Cape province, South Africa over the course of the wet and dry season. Sediment and water samples were analysed for total phosphorus (TP) and nitrogen (TN) concentrations, and were used in combination with river flow discharge, to determine nutrient loads. The study results highlight that river discharge plays a significant role in temporal differences in sediment and water column nutrient concentrations.
- Full Text:
- Date Issued: 2019
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Magoro, Mandla L , Froneman, P William , Weyl, Olaf, L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467222 , vital:76841 , https://doi.org/10.1016/j.scitotenv.2019.05.167
- Description: The consideration of nutrients in pollution dynamics is important for environmental management and conservation. Developing countries are yet to appreciate the aquatic ecosystem pollution impacts on their economies and as such, information on water pollution dynamics is limited. This study assessed the spatio-temporal dynamics of nutrient loading and retention in stream water and sediments in the Bloukrans River system, Eastern Cape province, South Africa over the course of the wet and dry season. Sediment and water samples were analysed for total phosphorus (TP) and nitrogen (TN) concentrations, and were used in combination with river flow discharge, to determine nutrient loads. The study results highlight that river discharge plays a significant role in temporal differences in sediment and water column nutrient concentrations.
- Full Text:
- Date Issued: 2019
Sacrificial males the potential role of copulation and predation in contributing to copepod sex-skewed ratios
- Wasserman, Ryan J, Weston, Mark, Weyl, Olaf, L F, Froneman, P William, Welch, Rebecca J, Vink, Tim J F, Dalu, Tatenda
- Authors: Wasserman, Ryan J , Weston, Mark , Weyl, Olaf, L F , Froneman, P William , Welch, Rebecca J , Vink, Tim J F , Dalu, Tatenda
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467233 , vital:76843 , https://doi.org/10.1111/oik.04832
- Description: Predation is thought to play a selective role in the emergence of behavioural traits in prey. Differences in behaviour between prey demographics may, therefore, be driven by predation with select components of the population being less vulnerable to predators. While under controlled conditions prey demography has been shown to have consequences for predation success, investigations linking these implications to natural prey population demographics are scarce. Here we assess predator–prey dynamics between notonectid predators (backswimmers) and Lovenula raynerae (Copepoda), key faunal groups in temperate ephemeral pond ecosystems. Using a combination of field and experimental approaches we test for the development and mechanism of predation‐induced sex‐skewed ratios. A natural population of L. raynerae was tracked over time in relation to their predator (notonectid) and prey (Cladocera) numbers. In the laboratory, L. raynerae sex ratios were also assessed over time but in the absence of predation pressure.
- Full Text:
- Date Issued: 2018
- Authors: Wasserman, Ryan J , Weston, Mark , Weyl, Olaf, L F , Froneman, P William , Welch, Rebecca J , Vink, Tim J F , Dalu, Tatenda
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467233 , vital:76843 , https://doi.org/10.1111/oik.04832
- Description: Predation is thought to play a selective role in the emergence of behavioural traits in prey. Differences in behaviour between prey demographics may, therefore, be driven by predation with select components of the population being less vulnerable to predators. While under controlled conditions prey demography has been shown to have consequences for predation success, investigations linking these implications to natural prey population demographics are scarce. Here we assess predator–prey dynamics between notonectid predators (backswimmers) and Lovenula raynerae (Copepoda), key faunal groups in temperate ephemeral pond ecosystems. Using a combination of field and experimental approaches we test for the development and mechanism of predation‐induced sex‐skewed ratios. A natural population of L. raynerae was tracked over time in relation to their predator (notonectid) and prey (Cladocera) numbers. In the laboratory, L. raynerae sex ratios were also assessed over time but in the absence of predation pressure.
- Full Text:
- Date Issued: 2018
Trophic isotopic carbon variation increases with pond’s hydroperiod: evidence from an Austral ephemeral ecosystem
- Dalu, Tatenda, Wasserman, Ryan J, Froneman, P William, Weyl, Olaf, L F
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Froneman, P William , Weyl, Olaf, L F
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467244 , vital:76844 , https://doi.org/10.1038/s41598-017-08026-6
- Description: Trophic variation in food web structure occurs among and within ecosystems. The magnitude of variation, however, differs from system to system. In ephemeral pond ecosystems, temporal dynamics are relatively more important than in many systems given that hydroperiod is the ultimate factor determining the presence of an aquatic state. Here, using stable isotopes we tested for changes in trophic chain length and shape over time in these dynamic aquatic ecosystems. We found that lower and intermediate trophic level structure increased over time. We discuss these findings within the context of temporal environmental stability. The dynamic nature of these ephemeral systems seems to be conducive to greater levels of intermediate and lower trophic level diversity, with omnivorous traits likely being advantageous.
- Full Text:
- Date Issued: 2017
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Froneman, P William , Weyl, Olaf, L F
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467244 , vital:76844 , https://doi.org/10.1038/s41598-017-08026-6
- Description: Trophic variation in food web structure occurs among and within ecosystems. The magnitude of variation, however, differs from system to system. In ephemeral pond ecosystems, temporal dynamics are relatively more important than in many systems given that hydroperiod is the ultimate factor determining the presence of an aquatic state. Here, using stable isotopes we tested for changes in trophic chain length and shape over time in these dynamic aquatic ecosystems. We found that lower and intermediate trophic level structure increased over time. We discuss these findings within the context of temporal environmental stability. The dynamic nature of these ephemeral systems seems to be conducive to greater levels of intermediate and lower trophic level diversity, with omnivorous traits likely being advantageous.
- Full Text:
- Date Issued: 2017
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